carb conversions

[Patch]

So, I have been meaning to get to this topic for a while and seeing how spring is around the corner, carbs have been sitting, bikes are coming up for sale… Some of us would like to modernise/ improve our bikes… andToo often only by guessing at the physics that for the most part are ignored during the process.

I encourage debate and opinions.

 

A key for me while putting my thoughts together is a post by our daredevil forum grandfather of youth Puc. I haven’t spent a day since Puc’s post of his HD not admiring the discipline of that build. Again I would like to better understand why and how Puc set his targets and what mods were considered thru the induction redesign?

 

As I’ve mentioned I have a couple projects coming up so I have been brushing up on tools used today verses my long ago performance days.

All my targets will be around flow and velocity which will establish the stoichiometric except that the gv which will have the additional influence of range, as she will remain our touring bike.

The order posted is correct because the engines are fist air pumps so, air is to be considered a fluid for measuring flow and achieving targets. Then I expect addition angle changes will be needed.

 

A quick thought on pressures: all low pressure runs must be equal therefor all angles must reflect this fact. That is All Angles absolutely no exception to this rule can make sense when attempting, to maintaining or modifying performance characteristics! That 2 or 4 cylinders.

 

Puc obviously knows this and again Puc I would enjoy reading your targets.

 

Base line pressures such as pistons I’m leaving out with the exception of that we must know what they are and that they are benchmark equal. Once we know sizes and stroke we can apply the math and form our expectations.

 

There is of course another important angle to consider when we mod and that is spark @ crank angles.

 

If we mod without understanding the consequence of angles then we are modifying for a net depreciation in overall performance! I am not making this up nor do I wish experimentation to fail.

 

Fast forwarding to what seems to be a topic these days we’ll jump to where many believe thrust, torque and HP is found thru the carburetor and so I’m jumping too...

Considering a gate valve and as it moves from 178ish to 90* we expect there to be a variance in deflection, pressure and flows before 90* is achieved, between leading and trailing surfaces of the gate/throttle plate/butterfly right? So we absolutely expect change throughout the chamber as well right? This has to include adtional defection (s) again wall surface right?

If we pin our ear to say a hose in such a case with a gate valve midstream we would clearly here the effect and turbulence right there at that gate.

At the other end we would expect to measure a reduction or increase of both flow and velocity by the simple use of a pale, ruler and stopwatch.

Basic easy principals when applied to fluids well, it’s the same for air which is considered a fluid and falls under fluid dynamics/ mechanics.

 

So now let’s mix it say with a pressure washer and soap, where is the inlet or mixing done and why?

The same applies to stochi thru carburetors.

 

We can’t just pick a jackpot conversion and expect performance. Thru all of this I haven’t mentioned torque over HP nor have I applied the rules or effect of rational mass…. Sport verses touring. Or the ultimate gate keeper, the intake valves size, lift and duration.

 

Below is a general link to venture conversions watch the rpms as they jump and stall Listen to the difference in throttle positions as they stall due to turbulence and defection of angle. Watch how some jump then slowly climb as an unexpected low pressure increases slowing piston velocity.

In one of these I can clearly say the pilot is under sized, in all of these I know angle results have been ignored. Also moving to plenum, I can say with certainty the runs are tooooo long and that the plenums are inadequate, inefficient and starved due to gate angles. As a result we would likely view a spotted torque curve and drop of HP over the expected range with a wildish lambda both sides of 1.

 

Yes I’d enjoy a good conversion with flow and dino readings even if they were close to stock, but, the CV carb is a tough puppy to beat providing,, the base lines are maintained of course! Not to say someone won’t get this right after they take everything into consideration. But ,if simply trying to avoid CV carb maintenance is the goal, then expect disappointment!

 

Batters up Puc, spill your build memories.. Beautiful color by the way, did Tippy choose the color? Hmm

 

Also by the way, it’s a day off and only 1 with a slice of orange in people time LMAO when I read in dog.. J

 

https://www.youtube.com/results?search_query=yamaha+venture+single+carb+conversion+

[cowpuc]

So, I have been meaning to get to this topic for a while and seeing how spring is around the corner, carbs have been sitting, bikes are coming up for sale… Some of us would like to modernise/ improve our bikes… andToo often only by guessing at the physics that for the most part are ignored during the process.

I encourage debate and opinions.

 

A key for me while putting my thoughts together is a post by our daredevil forum grandfather of youth Puc. I haven’t spent a day since Puc’s post of his HD not admiring the discipline of that build. Again I would like to better understand why and how Puc set his targets and what mods were considered thru the induction redesign?

 

As I’ve mentioned I have a couple projects coming up so I have been brushing up on tools used today verses my long ago performance days.

All my targets will be around flow and velocity which will establish the stoichiometric except that the gv which will have the additional influence of range, as she will remain our touring bike.

The order posted is correct because the engines are fist air pumps so, air is to be considered a fluid for measuring flow and achieving targets. Then I expect addition angle changes will be needed.

 

A quick thought on pressures: all low pressure runs must be equal therefor all angles must reflect this fact. That is All Angles absolutely no exception to this rule can make sense when attempting, to maintaining or modifying performance characteristics! That 2 or 4 cylinders.

 

Puc obviously knows this and again Puc I would enjoy reading your targets.

 

Base line pressures such as pistons I’m leaving out with the exception of that we must know what they are and that they are benchmark equal. Once we know sizes and stroke we can apply the math and form our expectations.

 

There is of course another important angle to consider when we mod and that is spark @ crank angles.

 

If we mod without understanding the consequence of angles then we are modifying for a net depreciation in overall performance! I am not making this up nor do I wish experimentation to fail.

 

Fast forwarding to what seems to be a topic these days we’ll jump to where many believe thrust, torque and HP is found thru the carburetor and so I’m jumping too...

Considering a gate valve and as it moves from 178ish to 90* we expect there to be a variance in deflection, pressure and flows before 90* is achieved, between leading and trailing surfaces of the gate/throttle plate/butterfly right? So we absolutely expect change throughout the chamber as well right? This has to include adtional defection (s) again wall surface right?

If we pin our ear to say a hose in such a case with a gate valve midstream we would clearly here the effect and turbulence right there at that gate.

At the other end we would expect to measure a reduction or increase of both flow and velocity by the simple use of a pale, ruler and stopwatch.

Basic easy principals when applied to fluids well, it’s the same for air which is considered a fluid and falls under fluid dynamics/ mechanics.

 

So now let’s mix it say with a pressure washer and soap, where is the inlet or mixing done and why?

The same applies to stochi thru carburetors.

 

We can’t just pick a jackpot conversion and expect performance. Thru all of this I haven’t mentioned torque over HP nor have I applied the rules or effect of rational mass…. Sport verses touring. Or the ultimate gate keeper, the intake valves size, lift and duration.

 

Below is a general link to venture conversions watch the rpms as they jump and stall Listen to the difference in throttle positions as they stall due to turbulence and defection of angle. Watch how some jump then slowly climb as an unexpected low pressure increases slowing piston velocity.

In one of these I can clearly say the pilot is under sized, in all of these I know angle results have been ignored. Also moving to plenum, I can say with certainty the runs are tooooo long and that the plenums are inadequate, inefficient and starved due to gate angles. As a result we would likely view a spotted torque curve and drop of HP over the expected range with a wildish lambda both sides of 1.

 

Yes I’d enjoy a good conversion with flow and dino readings even if they were close to stock, but, the CV carb is a tough puppy to beat providing,, the base lines are maintained of course! Not to say someone won’t get this right after they take everything into consideration. But ,if simply trying to avoid CV carb maintenance is the goal, then expect disappointment!

 

Batters up Puc, spill your build memories.. Beautiful color by the way, did Tippy choose the color? Hmm

 

Also by the way, it’s a day off and only 1 with a slice of orange in people time LMAO when I read in dog.. J

 

https://www.youtube.com/results?search_query=yamaha+venture+single+carb+conversion+

 

,, WOWZY WOW WOW WOW,,, that right there is a TON of brain storming activity and most of the storm is wayyyyyy beyond my capabilities (can't wait to hear from the real, engineering lop eared scientific brained varmints on this one) BUT,, seems how "debate" and "opinions" were openly asked for and both mentioned very close to my name,, thought I may jump in and a little..

Couple of things to start off this adventure with though.. I never really considered air to be fluid. The main reason for that is that air is compressable and fluid is not. Now if we were talking Electricity, then I would have to agree. Matter of fact, I have successfully (still alive and didnt start to many electrical fires) gotten thru many electrical nightmares because of I can see where the way my mind see's some fairly close comparisons in their charactoristics. I cant say that my pea brain can do that with air though. The compressability of the stuff (this includes atomized gases and such too) is a huge limiting factor in that .

My target for the Blown HD was actually centered on Torque more than HP. That being due to the fact that I was dealing with a Big Twin (88 inch) which, by its very design charachterisics, was extremely limited in its ability to reliably spin to far above the absolute torque/hp rpm line (5250 R's,, did you know that Torque is always greater than HP until the R's get above 5250 rpm and then they invert? Thats right.. And so being, if the engine is not capable of spinning above that line due to design limitations = you HAVE to build for torque). You mentioned not being to concerned with pistons.. Well, in my mind,, I am always concerned with pistons when doing this stuff.. Most of that concern is wrapped up in Piston Speed..

Hold on Steven,, I just thought of something..

Here,, take a peek at this video and see what you think... It may help you in developing some predicitions of where I am going with all the opinion sharing that YOU invited:

 

 

[cowpuc]

By the way,, I am strickly a wanna be back yard mechanic with much lacking therein and WOWZY, my painting skills are wayyyy behind even that. While I did take an airbrushing class out in Sturgis one year, what I learned was that that art form and even spraying on a base coat is best left to people who know what they are doing. That said, Tip had no input into the color of that 2001 HD. The bikes tin actually came to me in the color you see. A good example of my painting abilities is shown on the 59 Iron Head Chop I built. I did mod the frame on it to hang the 10 over Grass Hopper fairly nicely IMHO BUT, look closely at the tank and think = RATTLE CAN AMATURE!!!!!!

[Flyinfool]

Carbs have always been a compromise at best. They just never seem to be able to have the perfect mixture across their full range. That is alyas why some people tune for top end and some tune for torque and some for HP and some for cruise. That is also why you can not find much of any new vehicle that still has a carb. I was getting close to finishing the design of converting my Venture to EFI so I could have that near perfect air fuel ratio across the board. In order to not mess with the air handling that the engineers so carefully designed into out bike too much. I was going to convert the CV carb into throttle bodies. This way I keep all of the good air handling designed by those that know a whole lot more than I do and just change the way the fuel is metered and added to the air stream.

 

https://www.venturerider.org/forum/showthread.php?128079-EFI-for-the-Ventures

 

I am now permanently bike less due to medical issues so I will never get to finish this project unless someone wants to get in it with me. I was kind of stalled at needing an expensive milling cutter to make one of the cuts on the part the would hold the actual injector. I was getting closer to just making my own cutter. For me the machining is half of the fun. I may have been all wet with my theories But if I am having fun that is half the battle. At least none of the changes that I was making to the carbs were permanent so I could always go back to carbs quickly and easily, don't even have to take them off the bike.

 

To me carbs have always been a lot of blue smoke and mirrors, I have always been more comfortable playing with electrons, they just make more sense to me.

[cowpuc]

Carbs have always been a compromise at best. They just never seem to be able to have the perfect mixture across their full range. That is alyas why some people tune for top end and some tune for torque and some for HP and some for cruise. That is also why you can not find much of any new vehicle that still has a carb. I was getting close to finishing the design of converting my Venture to EFI so I could have that near perfect air fuel ratio across the board. In order to not mess with the air handling that the engineers so carefully designed into out bike too much. I was going to convert the CV carb into throttle bodies. This way I keep all of the good air handling designed by those that know a whole lot more than I do and just change the way the fuel is metered and added to the air stream.

 

https://www.venturerider.org/forum/showthread.php?128079-EFI-for-the-Ventures

 

I am now permanently bike less due to medical issues so I will never get to finish this project unless someone wants to get in it with me. I was kind of stalled at needing an expensive milling cutter to make one of the cuts on the part the would hold the actual injector. I was getting closer to just making my own cutter. For me the machining is half of the fun. I may have been all wet with my theories But if I am having fun that is half the battle. At least none of the changes that I was making to the carbs were permanent so I could always go back to carbs quickly and easily, don't even have to take them off the bike.

 

To me carbs have always been a lot of blue smoke and mirrors, I have always been more comfortable playing with electrons, they just make more sense to me.

 

100000000% agreed Jeff!!! Not to long ago HD was producing, and the general public could purchase right over the counter, a tuner called a "Screaming Eagle Race Tuner". This tuner allowed for complete access to all parameters and was tunable down to 200 rpm increments. The thing was AMAZING, the control it gave the builder/tuner was incredable. I did a couple builds with them and WOW was that fun and VERY rewarding performance eliminating all flat spots commonly associated with Carb builds. Problem was, HD got sued for selling them due to the Guvment green standards and they are no longer available. My understanding is (health has taken me out of it too and its been a while) the "new" wave is the fully automatic tuner that makes its own adjustments - crazy!!!

That said though, and this probably sounds just as crazy,, Steven - I have found that the CV Carb has some similar qualities about it in that - due to its nature of functioning off vacuum, it too makes certain corrections for the user,,, sort of a cheap, back yard version of a full blown EFI set up with a self correcting tuner..

[cowpuc]

Following up in answering the questions, in my case with the blown 88inch 01 HD, piston speed is/was the limiting factor in deciding to go with the CV carb (I still have other mechanical carbs I could easily gone with). One of the reasons for this being that if the engine by mechanical design cannot run reliably and effectively above 5250 without coming unglued then there is no sense in chasing HP by relying on valve overlap that requires a fuel/air flow scavenging which requires velocity stacks and drag pipes. Mechanical (non CV) carbs (sticking with the posts "carb" theme and getting away from the EFI discussion) are far superior in my experience if chasing HP up into the +5250 range in both performance and yield, albeit they tend to be more finicky in maintaining tune. CV's work AWESOME though if boosting for torque (some folks dont know this but boosting for torque is actually a very common thing = think trucking industry and diesels) because they really do not rely on scavanging which wreaks havoc on vacuum pressures that the the CV's "read" to do their thing.

On a side note here, with the onslaught of big V-Twin engines in motorcycles, I have noticed a continual tendency for the manufacturers to use propaganda in the sales of such behemouths that state things like = with all the torque these bikes have - the need to SHIFT GEARS is greatly reduced. I know I am pretty much still alone in this debate but I still take issue with that thought. It is actually the other way around. If your RPM range is increasable (remember = piston speed is the limiting factor in spinning a Big Twin above a few grand and RPM is RPM) you can use that increase to subsidize the need for multiple gears. I have another set of back yard videos that I did where I tried (and failed = caused a LOT of contraversy that ended up being partially responsible for some threatening phone messages = not fun) demonstrate this but in writing, the best way for me to describe what I am trying to convey is advising you look/listen to a Semi Tractor (high torque, low low low rpm range) going thru the gears and then think about a puny little 1000cc R1 Yamaha with its ability to easily top 100mph in its first gear = all because of its ability to reliably spin up well above that 5250.

So for the HD I sprung for 5 pounds of gear driven boost (LOOKED GREAT IMHO, others too cause SOLD fast) to boost the torque and, YES,, the HP too BUT torque was the target. I chose the CV because of its consistency to right itself even with the boost. I wasn't dealing with turbo lag as Gear driven superchargers are much more lenier in their delivery so that enhanced the air flow stabilities and vacuum variances which also inspired my pea brain to stick with the CV. In the end, my butt dyno (that, because of a few years of playing with this stuff - is not usually wayyy far off) told me that I had probably gained 10 to 20 ft pds and 15 HP in the end. This may not sound like much to a lot of folks BUT, considering that 88 inch was probably in the 60 HP and 70 ft pd range when new and stock,, if my butt numbers were even close I ended up with a very rideable 75ish hp/90 ft pds Big Twin. Which, given the bikes weight that the torque had to move/lift, was PLENTY and a very easy, non lumpy, nice attitude scoot that maintained its "potato, potato" friendly voice..

[Patch]

Thanks for tuning in Puc and giving us or me a peak at the thinking behind the boost and CV.

A couple of points:

I remember the video and by memory as I am catching up here, my summery was then rotation & mass.. I'll go thru it again tho but if memory serves that's my answer?

 

I avoided the pistons covering them as base line. The pistons are the brute end of these efforts, they will respond to what we change above them.

Yes I agree tuning for torque is what thought out tuning hunts for in what ever early range we're after. It is a fleeting curve and a heart breaker at times.

Torque is also a rotational force and as such, angles above the crank are critical to output but as we know, this is a much more entailed conversation.

 

Jeff is bang on with his thinking around jetting... However and I remember the talk at the time around using a CV body conversion to efi - the problem as I viewed it was, it was too much of a compromise to the mapping and so a compensate was needed for injector location. Not only have engines moved away from carbs Jeff but cfi as well.

Texture believe it or not would also be a problem throughout the run to the intake ports. This isn't a hard problem to overcome but is a mind bender if it isn't taken into consideration or known as an issue at the beginning of the conversion.

 

So here is where our conscientious differs Puc, (I learned this thu mopar builds back in the days of long hair) its all about air flows and ratios. Torque and HP come from the heads and, how we flow them! Yep there's a lot of nuts and bolts to flow but that is the heart of the matter.

I can see why you find relation to electric flows Puc, the magic of humans is in part the color we bring to reason.

 

Some questions that should be thought thru: Why do intake and exhaust lengths matter? How can either effect piston velocity? Why alter stochi? Why are intake valves larger than ex valves? Why are 4 smaller valves better than 2 larger valves? Why does scavenging make sense (maturely aspirated)? Why does port velocity matter as much as volume? How has Elderbrock built such a long lasting reputation around flows?

 

The displacement you choose, you choose, so efficiency in output is what we usually target, we then measure the efforts via two curves which also has effect on our "bell curve" which as we know tends to lesson in peak and duration with each tick of a new year;)

 

I completely agree with your comment on rpm and gearing and as a member here (still in good standing?) I was not surprised by the followup comments made by the passerby and, as a matter of that thread I think this forum thru membership & leadership displayed what sets this forum apart from others. Anyways that old news now certainly not a first. I prefer rpm so this stays me in the 4 banger range but rarely on the venture did I need to (relative/subjective) push her past 6500 on the kat tho...

 

A couple more things before I forget: The problem I am seeing with this single carb conversion is that, one it is not thought thru, two is that it is based around a simple adapting to the existing runners,and three is the angles do not make sense to me, in fact I know that they are wrong, and the plenum defeats itself, also the length of the runners will cause separation of charge which makes for wet runners. As for heating the plenum hmm, perhaps this may help condensing but not separation.

 

Motorcycle engines are suppose to be performance engines regardless of displacement, this makes street performance mods less easy to accomplish, it really is a fine balance and and more so if we are running touring rides.

 

Puc did you know there are vtwin running 12k plus

I'm going to link over Jeff and read up or view..

 

ps. my name is not steven so if we bump into one another and I don't answer... it aint cause I'm deaf

Edited February 15, 2019 by Patch

[cowpuc]

Thanks for tuning in Puc and giving us or me a peak at the thinking behind the boost and CV.

A couple of points:

I remember the video and by memory as I am catching up here, my summery was then rotation & mass.. I'll go thru it again tho but if memory serves that's my answer?

 

I avoided the pistons covering them as base line. The pistons are the brute end of these efforts, they will respond to what we change above them.

Yes I agree tuning for torque is what thought out tuning hunts for in what ever early range we're after. It is a fleeting curve and a heart breaker at times.

Torque is also a rotational force and as such, angles above the crank are critical to output but as we know, this is a much more entailed conversation.

 

Jeff is bang on with his thinking around jetting... However and I remember the talk at the time around using a CV body conversion to efi - the problem as I viewed it was, it was too much of a compromise to the mapping and so a compensate was needed for injector location. Not only have engines moved away from carbs Jeff but cfi as well.

Texture believe it or not would also be a problem throughout the run to the intake ports. This isn't a hard problem to overcome but is a mind bender if it isn't taken into consideration or known as an issue at the beginning of the conversion.

 

So here is where our conscientious differs Puc, (I learned this thu mopar builds back in the days of long hair) its all about air flows and ratios. Torque and HP come from the heads and, how we flow them! Yep there's a lot of nuts and bolts to flow but that is the heart of the matter.

I can see why you find relation to electric flows Puc, the magic of humans is in part the color we bring to reason.

 

Some questions that should be thought thru: Why do intake and exhaust lengths matter? How can either effect piston velocity? Why alter stochi? Why are intake valves larger than ex valves? Why are 4 smaller valves better than 2 larger valves? Why does scavenging make sense (maturely aspirated)? Why does port velocity matter as much as volume? How has Elderbrock built such a long lasting reputation around flows?

 

The displacement you choose, you choose, so efficiency in output is what we usually target, we then measure the efforts via two curves which also has effect on our "bell curve" which as we know tends to lesson in peak and duration with each tick of a new year;)

 

I completely agree with your comment on rpm and gearing and as a member here (still in good standing?) I was not surprised by the followup comments made by the passerby and, as a matter of that thread I think this forum thru membership & leadership displayed what sets this forum apart from others. Anyways that old news now certainly not a first. I prefer rpm so this stays me in the 4 banger range but rarely on the venture did I need to (relative/subjective) push her past 6500 on the kat tho...

 

A couple more things before I forget: The problem I am seeing with this single carb conversion is that, one it is not thought thru, two is that it is based around a simple adapting to the existing runners,and three is the angles do not make sense to me, in fact I know that they are wrong, and the plenum defeats itself, also the length of the runners will cause separation of charge which makes for wet runners. As for heating the plenum hmm, perhaps this may help condensing but not separation.

 

Motorcycle engines are suppose to be performance engines regardless of displacement, this makes street performance mods less easy to accomplish, it really is a fine balance and and more so if we are running touring rides.

 

Puc did you know there are vtwin running 12k plus

I'm going to link over Jeff and read up or view..

 

ps. my name is not steven so if we bump into one another and I don't answer... it aint cause I'm deaf

 

Oppsss, my bad on having the wrong name associated with you brother. Quick question, did you know that your screen name comes up as "Steven" and, while on the subject, may I ask what you prefer to be called - just in case we do bump into each other and I want to get your attention ?

Yep, I am definitely aware of high revving V-Twins. Matter of fact, I had the honor of riding and working on an Aprilla V-Twin dirtbike that was amazing in its ability to aquire some awesome hp wayyy up there in some high R's. A simple check on bore/stroke for figuring out piston speed associated with those like the Aprilla that do may be helpful in understand how/why they are able to do successfully aquire those R's though. I also know of several longer stroked large V-Twins that spin up pretty far too BUT they are very expensive machines built around big money parts that can handle the pressures associated with those R's. Certainly not your typical run of the mill engines and wayyyyyyyy out of my league both financially and mechanical abilities.

Concerning the fuel gathering in the intake track thoughts. Back in the 80's Honda played around with dual carb arrangements on some of their single cylinder scoots. The design was such as using a low speed carb and high speed secondary (set up operated on similar principles behind a 4 barrel carb on a muscle car = they just used separate carbs in place of secondary "barrels") and they found that they had problems with fuel gathering in the intake track of the secondary carb and then, when the secondary was opened a nasty "bog" would take place. Once the fuel had a chance to clear out after the secondary was opened for a second - the bog cleared BUT - that nasty bog cause many not so good issues on hill sides if a rider wasn't aware to what was about to happen. Those engineers at Honda did something pretty cool to eliminate the situation. They borrowed some design work from the 2 stroke world of the day, they introduced a small reed valve into the intake track of the secondary that would only open with pressure from the secondary, thusly closing that track until needed. Worked fairly well too..

IMHO, the only issue with all of that was that keeping those things operating up to par was a NIGHT MARE. Just getting the carbs out for cleaning was a job and half and, if ya had to replace the reed valve, you had to take the head apart as that is where the reed was located..

[Patch]

Oppsss, my bad on having the wrong name associated with you brother. Quick question, did you know that your screen name comes up as "Steven" and, while on the subject, may I ask what you prefer to be called - just in case we do bump into each other and I want to get your attention ?

 

Well that is a hard one to beat Puc:) Yes I know my name shows Steven G.! Too funny! Patch is my nickname since a boy or as I spelled it Patch's cause I knowed no better;) so those that did know better just called me patch. Remember Jethro he and I had plenty in common;)

 

Concerning the fuel gathering in the intake track thoughts. Back in the 80's Honda played around with dual carb arrangements on some of their single cylinder scoots. The design was such as using a low speed carb and high speed secondary (set up operated on similar principles behind a 4 barrel carb on a muscle car = they just used separate carbs in place of secondary "barrels") and they found that they had problems with fuel gathering in the intake track of the secondary carb and then, when the secondary was opened a nasty "bog" would take place. Once the fuel had a chance to clear out after the secondary was opened for a second - the bog cleared BUT - that nasty bog cause many not so good issues on hill sides if a rider wasn't aware to what was about to happen. Those engineers at Honda did something pretty cool to eliminate the situation. They borrowed some design work from the 2 stroke world of the day, they introduced a small reed valve into the intake track of the secondary that would only open with pressure from the secondary, thusly closing that track until needed. Worked fairly well too..

IMHO, the only issue with all of that was that keeping those things operating up to par was a NIGHT MARE. Just getting the carbs out for cleaning was a job and half and, if ya had to replace the reed valve, you had to take the head apart as that is where the reed was located..

 

No I didn't know that Puc; but it does in today's performance mapping jive with duration cheats; cool to know Honda was trying it but, unfortunate that thy put out a bike unproven.

 

"Concerning the fuel gathering in the intake track thoughts." This is a fairly sharp blade and it is also a complicated issue. I see the blurred lines being dragged thru applications that were once relatively easy to compensate for before the gain in popularity of variable intakes theories. I can relate as I dove head first into it as well!

Lets for the moment deal with just one fluid/air. We know instinctively we can manipulate air but we don't or aren't always able to hold a complete picture in say freeze frame.

So we can squeeze it a little or a lot, we can bend or deflect it without much effort, heat and cool it, we can use it for propulsion or propel somethin thru it. And that is just scratching the surface of its multiple uses, right. We can also count on it for delivering sound or sound travels thru it well. Well sonic pulses or pressure waves are also a fact for both sides of combustion so, we can tune to use it, choose to ignore it or even cancel it but we can't (yet) stop it's existence in a 2 or 4 stroke and it has impact.

Now in this model we concern less with it because we are considering a dry single fluid air transfer/delivery intake up to the head ports.

But...that all changes once we mix 2 fluids air and fuel/gas and, is why when additional tuning for torque via intake - fuel porting lower down as close to the end of run is a far better plan.

A stochi mix is far more sticky then just air and of course heavier. Air is more willing to boogie thru at speed then it is when charged with delivering automatized fuel; they also expand at different rates, add in friction wall surfaces and we can see it would be unwise not to assume losses.

If we only use a fraction of new to us technology then we end up misusing it. Know what I mean

 

So back to the honda dual setup, we can do the same thing squeaking in - during duration with fuel mappings. Why do it? Because the charge shape is moving while fallowing the piston. Now if we add to this with sequential firing we cheat ignition duration while firing closer to TDC so achieve higher efficiencies giving us a guaranteed extra rotation effort on the crank due to increased expansion pressures @ more efficient crank angles!

 

So back to carb conversion, if we don't get enough air/fuel in during lift and duration then we are in a real sense wasting effort as the lack of flow alone will act as a coil being stretched out thru the cylinder slowing piston speed! Pressure wants to equalize so yes you could argue that velocity is higher @ & around the valve & blow but at what cost for what gain? Having said this I do believe that if one were to start with a fresh sheet of lines then he/she could build a competitive system.

[cowpuc]

No I didn't know that Puc; but it does in today's performance mapping jive with duration cheats; cool to know Honda was trying it but, unfortunate that thy put out a bike unproven.

 

"Concerning the fuel gathering in the intake track thoughts." This is a fairly sharp blade and it is also a complicated issue. I see the blurred lines being dragged thru applications that were once relatively easy to compensate for before the gain in popularity of variable intakes theories. I can relate as I dove head first into it as well!

Lets for the moment deal with just one fluid/air. We know instinctively we can manipulate air but we don't or aren't always able to hold a complete picture in say freeze frame.

So we can squeeze it a little or a lot, we can bend or deflect it without much effort, heat and cool it, we can use it for propulsion or propel somethin thru it. And that is just scratching the surface of its multiple uses, right. We can also count on it for delivering sound or sound travels thru it well. Well sonic pulses or pressure waves are also a fact for both sides of combustion so, we can tune to use it, choose to ignore it or even cancel it but we can't (yet) stop it's existence in a 2 or 4 stroke and it has impact.

Now in this model we concern less with it because we are considering a dry single fluid air transfer/delivery intake up to the head ports.

But...that all changes once we mix 2 fluids air and fuel/gas and, is why when additional tuning for torque via intake - fuel porting lower down as close to the end of run is a far better plan.

A stochi mix is far more sticky then just air and of course heavier. Air is more willing to boogie thru at speed then it is when charged with delivering automatized fuel; they also expand at different rates, add in friction wall surfaces and we can see it would be unwise not to assume losses.

If we only use a fraction of new to us technology then we end up misusing it. Know what I mean

 

So back to the honda dual setup, we can do the same thing squeaking in - during duration with fuel mappings. Why do it? Because the charge shape is moving while fallowing the piston. Now if we add to this with sequential firing we cheat ignition duration while firing closer to TDC so achieve higher efficiencies giving us a guaranteed extra rotation effort on the crank due to increased expansion pressures @ more efficient crank angles!

 

So back to carb conversion, if we don't get enough air/fuel in during lift and duration then we are in a real sense wasting effort as the lack of flow alone will act as a coil being stretched out thru the cylinder slowing piston speed! Pressure wants to equalize so yes you could argue that velocity is higher @ & around the valve & blow but at what cost for what gain? Having said this I do believe that if one were to start with a fresh sheet of lines then he/she could build a competitive system.

 

Dear ? (please fill in the name) = "Stochi" must be wayyyyyy above my pay grade,, please define.

Thank you

Puc

[Patch]

"Stochi" must be wayyyyyy above my pay grade,, please define.[/quote

 

Sorry guys I shortcut that too often Stoichiometric too use to talking with myself

[cowpuc]

"Stochi" must be wayyyyyy above my pay grade,, please define.[/quote

 

Sorry guys I shortcut that too often Stoichiometric too use to talking with myself

 

and I am speaking to whom?

[Patch]

Dear ? (please fill in the name) = "Stochi" must be wayyyyyy above my pay grade,, please define.

Thank you

Puc

 

 

and I am speaking to whom?

 

Jeez Honey I thought you wanted to call me Dear? I guess its over, already? Aint this just like you old bikers, hit and run.

 

post #9

 

"Oppsss, my bad on having the wrong name associated with you brother. Quick question, did you know that your screen name comes up as "Steven" and, while on the subject, may I ask what you prefer to be called - just in case we do bump into each other and I want to get your attention ?

 

Well that is a hard one to beat Puc Yes I know my name shows Steven G.! Too funny! Patch is my nickname since a boy or as I spelled it Patch's cause I knowed no better so those that did know better just called me patch. Remember Jethro he and I had plenty in common;)"

[cowpuc]

ps. my name is not steven so if we bump into one another and I don't answer... it aint cause I'm deaf

 

 

Jeez Honey I thought you wanted to call me Dear? I guess its over, already? Aint this just like you old bikers, hit and run.

 

post #9

 

"Oppsss, my bad on having the wrong name associated with you brother. Quick question, did you know that your screen name comes up as "Steven" and, while on the subject, may I ask what you prefer to be called - just in case we do bump into each other and I want to get your attention ?

 

Well that is a hard one to beat Puc Yes I know my name shows Steven G.! Too funny! Patch is my nickname since a boy or as I spelled it Patch's cause I knowed no better so those that did know better just called me patch. Remember Jethro he and I had plenty in common;)"

 

Seriously Patch, I was just trying to respond to the statement you made above (seen in red) thinking I was not addressing you properly. The "?" you notice following the "Dear" was a simple question as to what name you preferred when addressed as Steven is not your name. Probably sounds corny in todays day and age but when I write a letter, or an e-mail I usually start it out with "Dear Sirs" or something like that. It was purely an oversight on my part that it was taken as some form of gender reference.

Sorry about that Patch..

Puc

[Patch]

 

Seriously Patch, I was just trying to respond to the statement you made above (seen in red) thinking I was not addressing you properly. The "?" you notice following the "Dear" was a simple question as to what name you preferred when addressed as Steven is not your name. Probably sounds corny in todays day and age but when I write a letter, or an e-mail I usually start it out with "Dear Sirs" or something like that. It was purely an oversight on my part that it was taken as some form of gender reference.

Sorry about that Patch..

Puc

 

Puc lighten up! I promise I won't call you Honey in front of the guys again! It's ok tho if you want to call me Dear or Dear Patch, sweetheart:)

[cowpuc]

 

Puc lighten up! I promise I won't call you Honey in front of the guys again! It's ok tho if you want to call me Dear or Dear Patch, sweetheart:)

 

Consider me lightened up Dear !!

[Patch]

,, WOWZY WOW WOW WOW,,, that right there is a TON of brain storming activity and most of the storm is wayyyyyy beyond my capabilities (can't wait to hear from the real, engineering lop eared scientific brained varmints on this one) BUT,, seems how "debate" and "opinions" were openly asked for and both

Hold on Steven,, I just thought of something..

Here,, take a peek at this video and see what you think... It may help you in developing some predicitions of where I am going with all the opinion sharing that YOU invited:

 

 

 

 

Here's what I think: First off Puc it is easier to say nothing then to make the time to explain.

The basics of your explanation and, that is how I view it, was to explain what you do or know instinctively when you are planning a build or past tense.

Torque is not an easy explain, but without its understanding HP means little.

Does HP carry us over the line yes if your dragging.

Torque is leverage over C of the crank so yep length matters mass matters but, there is zip without expansion of charge. And this is my tuning passion.

In your reference to maximums that is a very broad statement because it opens arguments to application (s), we are consistently rewriting limits so... But Puc you could refer to crank and mains as an example 2 verses 4 bolt mains as a common easy to understand requirement?

 

I post only here now so I don't know or have experienced the pressures of utube comments. But I do know a couple of things about posting, getting it right or not requires stepping out onto the field and swinging at that fast or curve balls; also that with experience comes a lack of shelve space, and in my case at least I sometimes have to go looking in forgotten files for things I once knew well or snapped right up on demand. Now this is the tough one for me at least, there are times we all know here I get my tongue so tied up in alphabet soup I just need to take a break. Sometimes thru our best intentions we just fork it up or mix our threads, its not surgery and someone can jump in, its a forum and a good one at that, and Puc it is because we get up and bat, right on's, excellent's, close but, or foul balls all happen because we choose to get involved and share.

You often say "this might be a dumb or stupid question, yet your generation hammered home that there was no such thing.!?

One tragedy can rune a forum, experience not shared or kept to ones self, of that Puc you can not be accused!

If we listen when others talk then we speak on topic, if we disagree well we can still grow from this as well

 

You asked

[cowpuc]

Here's what I think: First off Puc it is easier to say nothing then to make the time to explain.

The basics of your explanation and, that is how I view it, was to explain what you do or know instinctively when you are planning a build or past tense.

Torque is not an easy explain, but without its understanding HP means little.

Does HP carry us over the line yes if your dragging.

Torque is leverage over C of the crank so yep length matters mass matters but, there is zip without expansion of charge. And this is my tuning passion.

In your reference to maximums that is a very broad statement because it opens arguments to application (s), we are consistently rewriting limits so... But Puc you could refer to crank and mains as an example 2 verses 4 bolt mains as a common easy to understand requirement?

 

I post only here now so I don't know or have experienced the pressures of utube comments. But I do know a couple of things about posting, getting it right or not requires stepping out onto the field and swinging at that fast or curve balls; also that with experience comes a lack of shelve space, and in my case at least I sometimes have to go looking in forgotten files for things I once knew well or snapped right up on demand. Now this is the tough one for me at least, there are times we all know here I get my tongue so tied up in alphabet soup I just need to take a break. Sometimes thru our best intentions we just fork it up or mix our threads, its not surgery and someone can jump in, its a forum and a good one at that, and Puc it is because we get up and bat, right on's, excellent's, close but, or foul balls all happen because we choose to get involved and share.

You often say "this might be a dumb or stupid question, yet your generation hammered home that there was no such thing.!?

One tragedy can rune a forum, experience not shared or kept to ones self, of that Puc you can not be accused!

If we listen when others talk then we speak on topic, if we disagree well we can still grow from this as well

 

You asked

 

,, well put my friend ...

 

I gotta ask,, are we in agreement that on any and all dyno charts, as applied to all internal combustion engines, that there is an absolute given that the torque curve stays above the horsepower curve until exactly 5250 rpm's and at that point they intersect and then at 5251 rpm's and above that horse power stays above the torque curve?

[Patch]

Wow Puc how about an easy one?

I am assuming that we are talking modified street averages, naturally aspirated and pump gas.

I get why you limit @ 5000ish but to just agree or disagree stunts growth. Mach 1 was also thought unachievable.

If the question is solely based on should the torque curve be above the HP curve? Then yes, but, I am uncomfortable with the limit!

I am not going to comment on catastrophic failures of components because, this usually has more to do with the bottom line more so then possibilities. Then or as described in the vid..

 

So regarding curves, where can we find a 25% equalizer? That’s not gain but equalizer of such curves?

I’m going to leave this with you and the guys.

So if I want to leap over for bragging rights on a Saturday at the dino and coffee shops then I have to ask, where is my ceiling limitation (s) why? Then how do I chase the HP curve further up increasing both during the event?

 

Where we divide again: I am going to study my flows; I have to start with air flows and velocities.

No one can change this basic thinking that freight trains thru my mind. This is regardless of displacement. The higher these benchmarks are set the high and longer my torque will play.

 

My opinion for what it is worth Puc is we are limited by efficiency. The higher we achieve then the further torque goes. Therefore it is possible in my mind to beat out any limits placed by common rules of thumb. HP is a combined result of…

 

Now change how we measure these 2 curves and don’t point at the crank output efforts for what the wheels are or aren’t producing and, maybe you will realize better numbers for the time and investment spent?

 

Late 70s I build a sleeper which was my trip; I kept it streetable and could run on high test. I had rebuilt for me by a custom shop a 727 modified 2 speed out of a failed dragster project and, was running stock 273 at the wheels intending to up to 311. Doggonit I had to keep it in second all the time; my stall was 11 or 1200? Man if I shifted down that 383 would lose her mind. That old 71 NY would be scaring the bricks out people’s!

Where did I go right, air flows for my mildish cam crane .525. I tuned flows to the very tips of her sweet-talkers!

 

So is there an rpm range when admiring the sexy curves of a cam? Hmmm Are there impacts to torque?

 

I read something the other day all about communication: Honey;) I just got home, the Mrs. Texted her hubby; she goes on to say: windows froze I can’t open up…!? Hubby text back: boil some water, poor over and around the insides and sharply rap with butt end of hammer… ! 15 minutes later Mrs. Texted back; OH honey I think the laptop is really screwed now

 

In your video you demonstrated using an 80oz in one corner & a light weight in the other corner. Now I don’t wish to launch a protest your way but I’m thinking more like 32oz! I don’t mind if you cheat a bit because in the end it means the same thing, tho with different results.

Then the hammer must representing charge expansion right!?

Well what if I trim the tails of the bottom of all cylinders so I can see the pistons skirts? Hmmm

And lets say cause I have all this extra open area I increase lever and angles?

Because I can let’s just toss those ashtrays and install shorter ones, then what?

 

Would my hammer now have reached it full potential? Yes the cheat would work, providing my flows could keep up! If they can’t then I likely experience losses throughout the 2 curves but lets not forget I’ve also increased mechanical advantage so I should see or measure a result right?

 

So I can’t comment on lower end structural stabilities as that is a design issue related but, I can assure one that if you increase charge expansion your torque will increase; and if you increase lever then you are multiplying effects of pressure thru expansion!

Right Puc? Like I said not sure if we can agree or agree to disagree but, speak to Tippy and see if she’ll agree to singing off and funding the experiment. You get the block and I get top end?

[cowpuc]

,, well put my friend ...

 

I gotta ask,, are we in agreement that on any and all dyno charts, as applied to all internal combustion engines, that there is an absolute given that the torque curve stays above the horsepower curve until exactly 5250 rpm's and at that point they intersect and then at 5251 rpm's and above that horse power stays above the torque curve?

 

Wow Puc how about an easy one?

I am assuming that we are talking modified street averages, naturally aspirated and pump gas.

I get why you limit @ 5000ish but to just agree or disagree stunts growth. Mach 1 was also thought unachievable.

If the question is solely based on should the torque curve be above the HP curve? Then yes, but, I am uncomfortable with the limit!

I am not going to comment on catastrophic failures of components because, this usually has more to do with the bottom line more so then possibilities. Then or as described in the vid..

 

So regarding curves, where can we find a 25% equalizer? That’s not gain but equalizer of such curves?

I’m going to leave this with you and the guys.

So if I want to leap over for bragging rights on a Saturday at the dino and coffee shops then I have to ask, where is my ceiling limitation (s) why? Then how do I chase the HP curve further up increasing both during the event?

 

Where we divide again: I am going to study my flows; I have to start with air flows and velocities.

No one can change this basic thinking that freight trains thru my mind. This is regardless of displacement. The higher these benchmarks are set the high and longer my torque will play.

 

My opinion for what it is worth Puc is we are limited by efficiency. The higher we achieve then the further torque goes. Therefore it is possible in my mind to beat out any limits placed by common rules of thumb. HP is a combined result of…

 

Now change how we measure these 2 curves and don’t point at the crank output efforts for what the wheels are or aren’t producing and, maybe you will realize better numbers for the time and investment spent?

 

Late 70s I build a sleeper which was my trip; I kept it streetable and could run on high test. I had rebuilt for me by a custom shop a 727 modified 2 speed out of a failed dragster project and, was running stock 273 at the wheels intending to up to 311. Doggonit I had to keep it in second all the time; my stall was 11 or 1200? Man if I shifted down that 383 would lose her mind. That old 71 NY would be scaring the bricks out people’s!

Where did I go right, air flows for my mildish cam crane .525. I tuned flows to the very tips of her sweet-talkers!

 

So is there an rpm range when admiring the sexy curves of a cam? Hmmm Are there impacts to torque?

 

I read something the other day all about communication: Honey;) I just got home, the Mrs. Texted her hubby; she goes on to say: windows froze I can’t open up…!? Hubby text back: boil some water, poor over and around the insides and sharply rap with butt end of hammer… ! 15 minutes later Mrs. Texted back; OH honey I think the laptop is really screwed now

 

In your video you demonstrated using an 80oz in one corner & a light weight in the other corner. Now I don’t wish to launch a protest your way but I’m thinking more like 32oz! I don’t mind if you cheat a bit because in the end it means the same thing, tho with different results.

Then the hammer must representing charge expansion right!?

Well what if I trim the tails of the bottom of all cylinders so I can see the pistons skirts? Hmmm

And lets say cause I have all this extra open area I increase lever and angles?

Because I can let’s just toss those ashtrays and install shorter ones, then what?

 

Would my hammer now have reached it full potential? Yes the cheat would work, providing my flows could keep up! If they can’t then I likely experience losses throughout the 2 curves but lets not forget I’ve also increased mechanical advantage so I should see or measure a result right?

 

So I can’t comment on lower end structural stabilities as that is a design issue related but, I can assure one that if you increase charge expansion your torque will increase; and if you increase lever then you are multiplying effects of pressure thru expansion!

Right Puc? Like I said not sure if we can agree or agree to disagree but, speak to Tippy and see if she’ll agree to singing off and funding the experiment. You get the block and I get top end?

 

The reason that I asked if we could agree on that one fact is that that number (5250) is a baseline for building IMHO. That said, your earlier statement that you limit your revves to 6500 rpm is another baseline in building as it gives a parameter to build around and, if 5250 is where hp becomes the relevant measurement of power and torque becomes a thing of the past at that point, then intake/exhaust flows, carburation, cam options, valve timing all now have a source to build to to obtain effeciency.

Perhaps a short study to determine whether or not the standards of which I have built by thru the years (that 5250 is in fact a hard, unchangeable number) hold any merit BEFORE we continue in figuring out the carb build? What say you?

[Patch]

Right Puc now I see your intent differently/clearer.

Off the cuff here (been a busy day) What I believe is the typical problem is the stripping if energy thru velocities and duration? I say this because torque remains in play ( according to basics laws) we are still dealing with rotation and once established lever is applied then our next thoughts move to stability. So as I've mentioned, what we didn't grow up with was the application of fluid dynamics, rather we patched around via tdc's and angles. Having said this my thinking is that with corrected or available air flow we can deliver enough flow/ratio volume at a loss of velocity of such; (flow over velocity) but piston velocity is our next timing issue as relating to ignition and duration, of what ever makes it past the valve!? So we have the problem of charge & duration, right? (we agree?) That equals efficiency as we will measure loss of pressure returns on combustion strokes which is much differant then active compression numbers (fun but dangerous, ask me how I know)! That falls our torque curve and is why naturally aspirated represents this challenge at higher piston velocities!? But there ar cheats, yes they are limited but still measurable gains. So I covered this briefly in an other post here by cheating duration via sequential injection and spark/ignition,,, think of it as lighting the candle at both ends, duration shortens and therefor higher pressures are a reasonable expectation, @ higher piston speeds! So an interesting conversation is developing!

Give me a few minutes to think of a challenge or asses what I think the challenge is. MT here

[cowpuc]

Hey Patch, I did a little 2 second research into the subject by asking google this: "is there an exact rpm where torque crosses horsepower"

 

And this was the first thing that popped up:

 

Horsepower is a unit of power. ... Going back to the formula: HP = (Torque x RPM) / 5252 we can see that at an engine speed of 5,252 RPM Torque and HP are equal. That's why when we see a graph of Torque / HP we see the lines always cross exactly at 5252 RPM.

 

For me, the reason this is applicable to engine building and tuning is if you know that your build parameters involve staying predominately below 5252 R's (which in your case it does) than Torque becomes the predomenent intent on the build. Now in the case of the carb conversion, it is going to involve some form of intake track/manifold. IMHO, different configurations (length of intakes) of the intakes will have different results in fuel/air mixture effeciency in the combustion chamber. In your case, I am thinking that a plenum with intake tracks tigged inside to achieve desired width and length of travel would work awesome. I have found that longer/narrower intake tubes will move the peek torque on any given engine down = farther away for 5252 R's.

Also, by developing a plenum with inner intake track, one single side mount CV Carb would all of a sudden become an option.

Following me?

[Patch]

Hey Patch, I did a little 2 second research into the subject by asking google this: "is there an exact rpm where torque crosses horsepower"

 

And this was the first thing that popped up:

 

Horsepower is a unit of power. ... Going back to the formula: HP = (Torque x RPM) / 5252 we can see that at an engine speed of 5,252 RPM Torque and HP are equal. That's why when we see a graph of Torque / HP we see the lines always cross exactly at 5252 RPM.

 

For me, the reason this is applicable to engine building and tuning is if you know that your build parameters involve staying predominately below 5252 R's (which in your case it does) than Torque becomes the predomenent intent on the build. Now in the case of the carb conversion, it is going to involve some form of intake track/manifold. IMHO, different configurations (length of intakes) of the intakes will have different results in fuel/air mixture effeciency in the combustion chamber. In your case, I am thinking that a plenum with intake tracks tigged inside to achieve desired width and length of travel would work awesome. I have found that longer/narrower intake tubes will move the peek torque on any given engine down = farther away for 5252 R's.

Also, by developing a plenum with inner intake track, one single side mount CV Carb would all of a sudden become an option.

Following me?

 

I too took some time in the wee hours to look for a better way to explain why 5252 is limiting higher targets or goals; and I found some better more direct posts that explain it.

If we set the limit of what we are after and want to measure our progress then we need to apply physics and math to know where we are during/after our efforts.

 

As I mentioned for me it is all based around air flows, below the flows is where our force/pressures become concentrated then distributed via output of the crank! Stability will limit how fast we can spin the crank and is why in the past I've cautioned against higher rpms above design. Just because you can doesn't mean you should; rather what one should consider doing is improving flow characteristics and timing angles, there's no one without the other.

 

My perpetual quest for flows and ratios provides me with a different color and point of view to others that seek just bolt on HP projects and, often find myself at odds with their reasoning; sometimes it is best to just let it pass by because, they might not be ready for harder to understand theories ( hard to appreciate air when it's all around you)

 

So the highlighted sentence is an easy no for me. It is in fact the equivalent of the wrong crank or wrong cam choice; just because it fits does not make it the better choice.

 

We need to remember the purpose of the mod and targets that improve on base line factory and production compromises or we are walking backwards and away from performance.

 

I have taken very pricey variable intakes and opened them up too better understand how and why, going back to 98. Yes a little extreme but I learnt some thru it.

 

We can't expect intake length to answer all our needs. Air is a fluid and when mixed with fuel we slow it, ( a velocity challenge) if we don't then we end up with separation of fluids (or lean to rich alternating ratios). If we could dye mark it then we could time it visually, rather we time thru lift and duration, and measured velocity and flow. Like your view of thinking of air as electricity - run/length has to consider resistance.

 

As I've mentioned I started putzing with carbs pretty young, on my mopar build I had some typical problems of the day like to rich or to lean, also very hard to start cold... It took a bit of figuring but, I took a four barrel direct/mechanical linkage and found the correct mix of jetting which gave me more flows at a wider range of throttle angles. I can tell you that I was the only fool in the junkyard going thu bins of carb castings headed for meltdown. I knew what I needed was not on the shelf so I came up with my on patch.

 

Today it is a much easier process with better yields. Some things to remember as we mod CV carbs are, designed of flows and velocities and how that design will work with re jetting. We could also consider that if you alter flows one way or the other we effect the properties designed into them such as the venturi and its function. Re jetting a CV is a re-balancing of flow but does anybody take into consideration the butterfly angle and turbulence? Sure there's room for change but not much and why pilot? If pilot is chosen as to its constant then it has to be considered as a minimum improvement at larger openings? Sticking with this for a moment, if it does make a noticeable improvement to say transitioning then it also must depreciate in function as pilot? Lean is not always a bad thing and if you are working on a liquid cooled engine @ idle where is the concern?

 

Back to conversions to a single carb, where is the math? We can't arbitrarily pick runner lengths. Nor we can we plenum without considering volume and angles hoping to match or improve performance.

 

Just opinion

I'll post the findings I have regarding 5252 torque and horsepower later.

[cowpuc]

Here is an interesting explanation of why, in all cases, the hp curve crosses the torque curve at 5252. Given, this guy being a math guru and not an engine builder/tuner clearly see's no reason why that fact would make a difference to anyone but none the less (unless you change the 1 to 1 ratio's on a dyno chart), 5252 is an absolute.

 

[Patch]

Hi Puc,

I’m thinking you are mistaking the 5252 as you say from the mathematician?

I have a couple of links below that I think are worth viewing (its short) and the others worth the read. One addresses directly, the others both I think will cause all of us rethink how we consider results.

 

Somewhere around 5000rpms the two curves converse true (not always)but, we aren’t measuring loss we are still in fact measuring gains.

You asked me about tuning for torque instead of HP and if we were in agreement and I said yes, and still agree.

But, until we move past the engine with the mods or the tuning of an engine, dyno is what I think matters, not the measuring of wheel output! This is also where we find the 25% narrowing of Torque equals HP gap and it is to be found at crank shaft output.

I realized during our chat that this line and time over distance;) has become blurred. I think its just one of those parts where time and conversations confused instinct?

Also your days spent building V-twin long winded strokes, influence how you view mods? That doesn’t make you wrong Puc it does upset the 2 curves tho because of volumes in percentage loss over strokes.

 

Put this way, if HP is a result of torque/crank then volume wise twin wins because of stroke (given equal bore dia).. But shorter strokes win higher up the rev range because they complete cycles at faster/shorter stroke times, per revolution! Both have percentage of volume losses around flows and, how flows move thru the engines! When the bottom end is built correctly then increasing volumes above the piston is the next hurtle; one without the other would explain what you allude to in the video for self-destruction of the pistons and crank. Lets not forget that pistons are rocking on a pin while floating between walls, positioned and held by the rings, also floating. If the piston comes off its axis then it will slap increasing heat, increasing expansion and knocking the crank out of balance; which is soon followed by catastrophic failure. Likely you will achieve that fast on a big twin then a four banger because the crank is longer and we can design in compensating strokes! That gets complicated but its there on the four bangers and measured in degrees of the crank levers.

 

I wanted to thank you for forcing me to dig deeper into my off the shelf corners of my experience Puc; I haven’t thought of renovating crankcase area in a very long time, this was a great experience for me to dive further into and express smilingly those very well learned lessons!

 

I didn’t explain my objection to the Variable intake with center carb.

Overlooking angles such as Throttle plate defections and 90* turns , plus valve pressure pluses at either end, there would require one additional butterfly per side per cylinder for the variable intake to be variable.

When closed the air/fuel mix will stall in both high demand intake flow tubes, up till and around peak torque when the butterfly (x2) would open allowing for additional flow through both sides. However the mixture can separate at this stall and fuel will seep past with a likely slightly leaking air flow as the butterfly remains closed before actuated. This will likely cause spotty surging on both cylinders as the fuel makes it way down. (makes sense) is that not what happened to the honda?

Add to this, variable intakes are designed around port injection or direct injection or combos of both. This means that the added wall, floor and ceiling surfaces generate additional friction and flow losses yet increase concentricity but; although average losses are higher, stoichi is not effected yet due to port situated injection and, mapping is a simple compensate, meaning you don't have to go looking for the flow loss it just is what it is! Not so with a carb at the center of the induction.

At least that is how I see it..

 

 

This is in my opinion a good explanation of dyno when used as a build or result tool.

 

 

https://mechanics.stackexchange.com/questions/30142/torque-reduces-gradually-after-certain-rpm

 

This one is a bit longer but read what happens with gear to torque values.

 

https://mechanics.stackexchange.com/questions/25419/what-is-the-difference-between-torque-and-horsepower