Electric. Digital. Computerized. Throttle Body Sync

[Patch]

Sorry guys been dealen with....

 

Forum:

The question is (would we not see that in reading the vacuum…) by Saddlebum/trampofnorthernOnt.

1^st. I am writing at the moment without internet access but, have had this post in mind for a while so thought I’d get-r-done! Carl has PM’d wondering why I have stopped or haven’t been picking on grasshopper/Puc? Especially at this time of the year (he said) being the perfect time to catch him off guard,,, with all that cheer stuff and good will blabla Puc preaches… so let’s kick some theory into practice and see if we can perk demthere lopsided pointy ears of Puc our way;)

 

Likely you all know I view any engine from the crank up. Every rotation accrues as a result of energy applied and spent, at the moment she begins to rotate.

Just picking numbers here: let’s say the starter turns driving #1 up to compression @ +/- TDC the plug ignites (more energy spent).

Let’s visualize this stroke segment: say #1 is @ BTC ,,, in order for it to hit TDC it must travel say 3” and then thru house power multiplied by X

(what’s X) the plug electrode jumps to ground and unleashes spark.

 

Under which below will this stroke cause combustion to accrue?

1)The jug is below operating temperature:

2)@ or close to operating temperature:

3)If the bike is fuel injected:

4)The throttle was blipped before pressing the start:

5)The plugs are new and 3) or 4) applies:

6)the engine can only start on this stroke if the engine had been running less than 15 +/- minutes before:

 

B) and related how: would valve position influence the outcome given the above format?

C) “ “ if a valve were to be open at BDC which valve would it be?

 

If you are not sure of the answer take a chance and describe your puzzle. If you know the answer share it and why;)

 

I hopefully will be able to follow-up this weekend or early next week.

Patch

[Patch]

My new English Coach suggests I could conciser less alphabet in my posts, hmm? I had to laugh and mentioned that to my old friend SK who also was an employee for many years lol... He agreed ):

 

So, the vacuum stroke is key to performance - it’s on this stroke that air and gas mix to form the fuel ratios we spend so much coin trying to achieve and burn.

 

When we assume that all is equal we, without doing the math or checking via measurements, that questions and disappoint begin to set in and, we begin the process of compounding mistakes.

 

Before I express my experience and why I feel saddlebum question is one of the best I’ve read in a while is because we naturally assume too much too often. Performance engines do not stay calibrated on their own. This fact is why some folks are better at tuning than others who may be better at building or say applying the given power on track days!

 

I’d like cover something that I know our club demographics can associate to. In the 60s and with Webber setups we began tweaking our jug filling techniques. Many of the English engines were moving more towards bike setups such as 4 and 6 carbs or one per jug. Then the 70s was more focused on plenums and lifts & duration's with quads and a short period of 6 packs. How many of us remember our 1^st kick at those setups? I remember my first heart sinking when I read the vacuum gauge “where the heck did I go wrong”? So next on the street warrior side of the sport we began spending insane amounts of coin on blowers to bring the beast to life, right.

How many of us scrapped heads just porting and polishing! Today’s youth is all about turbos and their mods make no damn sense to me, whether its diesel or gas. They have reversed our experience with intakes and now apply our growing mistakes - to the exhaust ports by modding in dead exhaust flows all the while thinking the turbo will magically force the spent charge down the pipe through a seated intake valve!? Make any sense to yo'll..

 

Back to naturally aspirated engines: So, vacuum balances the crank, how? Well it has to do with input and output and is why the simpler the measure of vacuum is, the quicker the find is to the imbalance!

I always set my throttle plates then read vacuum! Think about that.

Let me spark a thought: Visualize the process of an intake stroke – to do this you need consider time over distance; now lets break this down and for this exercise we will reach a conclusion that can only be attributed to velocity & volume losses due to drag.

Vacuum is a result of applied energy, right, it is in fact a bleed off of the preceding combustion stroke lets say off of #2s contribution to the applied torque (forces in rotation) to the crank: (pause, now I know that the math is around 430* so let us just run to jug #4 as #2s energy should be allocate to #3 compression stroke say +/- the * angle shared difference) (it doesn’t help to muddy this exercise with the understanding of crank timing:… )

Now here’s the point: if 90* is a closed throttle plate (it isn’t tho) and 70* is idle and high vacuum and, they are all at 70* then the velocity and volume should be eq. assuming ware is eq. across the board! But if #4 s vacuum is lower, than the tuner will likely set that plate tighter maybe as much as 10*or; if it is higher then he will reverse the angle to get closer to eq. readings, regardless of sync tool used.

Now the complete sync turns into a vacuum balance chase as he rolls thru each carb! By the time he has reach an acceptable balance at say 1200 RPM (that is a leftover from the days of stick syncing) the volumes passing each plate are way too off scale, yet velocity is being driven by the 4 contributions to the crank thru unequal fuel pickup being "vacuumed/siphoned thru jets!

Now lets look at the drag: Vacuum causes drag from TDC to BDC because, it has to be generated by the down travel distance of the piston. The resistance from the air box orifice thru the V. stacks passing the slides, picking up fuel and adding more drag, then past the throttle plate at velocity each of which increase the amount of drag thus slows the piston x 4 "it becomes a matter of time/duration! When all 4 are in sync this provides a smooth balance to the crank! Assuming ignition is solid.

 

Now we still need to consider the ports and the multi valve system design which by the way is not designed for velocity at low rpms, that would be useless to a sport machine!

So, at the very moment you are syncing - the port is under high vacuum but low velocity because it is larger the plate opening, so volume is not considered rather it is assumed!

This means that close attention needs to be paid to whatever the gauges used read at the start of sync because, at higher demands that sync can ruin the power band where velocities and volumes count much more and are hardest to achieve!

One final comment on this parallel: total displacement divided by 4 is only a potential and cannot be achieved thru dohicky tuning and is rarely above 65 – 70 % on naturally aspirated engines so making every tweak count is essential.

 

Let me tie this in:

In gearheads thread which was a confusing one, we can clearly see by the results at the end as more facts came to be known that the premature limit of that engine was reached as result of internet gossip. It was a clear lack of understanding theory and, lack of maintenance at the carb level, period. As a result of over fueling, temperatures dropped, carbon built up, compression number climbed, pre ignition then turned it into a washing machine. Note our exchange over “bench syncing” as the first step!

The mistake and I see it over the net even by “Motorcycle Tech’s” is due to not beginning the sequence correctly. https://www.venturerider.org/forum/showthread.php?141445-87-VR-carb-problem/page2

Post #16

 

Having worked on European sport engines I can tell you 1^st hand that chasing vacuum problems is a nightmare. There is rarely an easy way to simply track them down! Sometimes the best way is to understand the rpm range, track it to throttle position, then determine where to look for the imbalance. Harder than it sounds when you have a module performing compensations resulting from monitor signals and feedback, and yet, it is just a vacuum leak or lack of balance!

 

Not a problem we need to face on these engines in this forum but an example of why following procedures is the correct way to begin.

 

Back to sticks for a moment not my favorite but effective for touring; then again so is a drill bit yet put in the hands of an experience tuner he/she will not know there lies a question below the carbs in need of resolve!. When we cal the sticks off of one manifold then they should be in sync discounting time and heat fluctuation over that period, good enough. But in the hands of a less experienced person the likely first choice will be to compensate, makes sense but incorrect and the follow through won’t be there. They likely won’t know to check throttle positions and, therefore say at WOT when vacuum drops volume will be unequal and that results in a performance issue! That also means ratios are out, combustion temperature is out, imbalance has reached the crank via torque (ignition, duration and expansion – is off even if spark is good and advance is adequate) the crank roll is inconsistent or as they say today unexpected!

 

And so you have these imbalances right through the potential range of output!

A tuner would have to be distracted to make such a mistake, a hobbyist simply does not know and will not grow from the experience unless we share ours!

The more the sync tool dictates to him, or buffers the input readings the less he suspects the need to look further!

So the answer is yes you will see it but will they understand it? Will they follow through and check compression and lash or even the outcome on plate position?

 

And the above is why I chose my VacuumMate!

Patch

 

Right Puc;)

Edited January 11, 2020 by Patch