Oil pressure question....

[PGunn]

Has anyone looked into replacing the oil pressure relief spring with one that would hold the oil pressure at a bit higher level than what is currently used or is this a bad idea all the way around for these bikes (RSV). I know when I was building Buick V6 engines a long time back I would increase the pressure by swapping out the relief spring for one slightly stronger which would run the idle pressure up a few pounds. This running at 8 - 10 psi is crazy only because by the time you see it's off the gauge it's way too late. I was thinking of somewhere around 20 - 25 psi would be nice and a top cruse pressure of around 40 psi hot.

[frankd]

A heavier oil pressure relief spring will not increase idle oil pressure. It may help a little at cruise RPM, but these bikes don't seem to need more oil pressure. I've got a gauge on my 83, and on a cold start the oil pressure goes up to 90-100 psig. However, at very hot idle, it's only about 6-8 psig. This bike has 140,000 miles on it and I'd think if it needed more oil pressure we'd know by now.

[cecdoo]

If it aint broke, dont fix it:think: Someone much smarter then me would always repeat these words.

 

Craig

[PGunn]

I was leaning that way (increase) but I am still sitting on the fence and I also have the gauge installed. I really am not happy with the idle pressure being that low even though it has not been an issue on any bike to date. 8 lbs is really low.....

[V7Goose]

Has anyone looked into replacing the oil pressure relief spring with one that would hold the oil pressure at a bit higher level than what is currently used or is this a bad idea all the way around for these bikes (RSV). I know when I was building Buick V6 engines a long time back I would increase the pressure by swapping out the relief spring for one slightly stronger which would run the idle pressure up a few pounds. This running at 8 - 10 psi is crazy only because by the time you see it's off the gauge it's way too late. I was thinking of somewhere around 20 - 25 psi would be nice and a top cruse pressure of around 40 psi hot.

I hesitate to cast aspersions on your knowledge and past experience, but most of what you say just does not compute.

 

The specification for this engine is to pump 50 Lbs pressure at 5,000 RPM hot (just going from memory), and it has no problems hitting that - proving that the oil pressure relief setting must be above 50. The ONLY time the pressure is below 10 lbs is when the engine is idling hot, with the oil up to full temp. In this situation, the factors contributing to the low pressure have absolutely nothing to do with any relief valve - it is purely a combination of oil viscosity, bearing clearances, and total number of bearings when combined with pump capacity.

 

Furthermore, the 5-year, unlimited miles warranty, combined with the complete lack of reported problems of engine wear below 300,000+ miles virtually proves that the oiling and cooling capacities of this engine are just fine as manufactured.

 

I will take this opportunity to note that the engine idle spec for this engine is 950-1050 RPM. Although I prefer the way the engine idles down around 700, I firmly believe the spec of 950 is related to the hot idle pressure, so That is the lowest I set..

Goose

[MikeWa]

I hesitate to cast aspersions on your knowledge and past experience, but most of what you say just does not compute.

 

The specification for this engine is to pump 50 Lbs pressure at 5,000 RPM hot (just going from memory), and it has no problems hitting that - proving that the oil pressure relief setting must be above 50. The ONLY time the pressure is below 10 lbs is when the engine is idling hot, with the oil up to full temp. In this situation, the factors contributing to the low pressure have absolutely nothing to do with any relief valve - it is purely a combination of oil viscosity, bearing clearances, and total number of bearings when combined with pump capacity.

 

Furthermore, the 5-year, unlimited miles warranty, combined with the complete lack of reported problems of engine wear below 300,000+ miles virtually proves that the oiling and cooling capacities of this engine are just fine as manufactured.

 

I will take this opportunity to note that the engine idle spec for this engine is 950-1050 RPM. Although I prefer the way the engine idles down around 700, I firmly believe the spec of 950 is related to the hot idle pressure, so That is the lowest I set..

Goose

 

 

+1

 

Mike

[PGunn]

Ok I found the answer and V7Goose is correct.

 

"The real number of concern in engine oil systems is mass flow, not volume. The primary function of engine oil is really cooling, so having the proper mass flow rates to bearings and pistons at all operating conditions is critical. Most engine oil pumps are positive displacement devices, so they tend to have fairly linear flow rates with regards to speed. With these positive displacement pumps, the problem arises due to the fact that they must be over-sized to assure adequate flow rates at low engine speeds and high loads. Thus, the PRV (Pressure Relief Valve) must naturally bypass a large flow volume at high speeds, which is inefficient and hurts fuel economy. As a result, many new engine designs use variable displacement oil pump designs."

 

In other words with the pumps currently in use on the bike the volume of flow is high enough at low rpm's to cover the pressure. High pressure is a no-no on these engines at idle or running in gear.

 

Still it scares me to see 8 psi but knowing the volume is more than enough helps...

Thanks V7Goose......

 

Complete article

http://www.ret-monitor.com/articles/1611/the-oil-pressure-relief-valve-or-when-to-leave-it-alone/

[PGunn]

Oh yea and the reason for rasing the oil pressure in a Buick V6 is because of all the 90 deg bends in the oil gallery (bad design) and when your losing 10 lbs per 90 degree bend the loss adds up fast. Warm up time is longer yes but when your pushing 300hp through an 1/8 mile it's worth the wait.

[wes0778]

I hesitate to cast aspersions on your knowledge and past experience, but most of what you say just does not compute.

 

The specification for this engine is to pump 50 Lbs pressure at 5,000 RPM hot (just going from memory), and it has no problems hitting that - proving that the oil pressure relief setting must be above 50. The ONLY time the pressure is below 10 lbs is when the engine is idling hot, with the oil up to full temp. In this situation, the factors contributing to the low pressure have absolutely nothing to do with any relief valve - it is purely a combination of oil viscosity, bearing clearances, and total number of bearings when combined with pump capacity.

 

Furthermore, the 5-year, unlimited miles warranty, combined with the complete lack of reported problems of engine wear below 300,000+ miles virtually proves that the oiling and cooling capacities of this engine are just fine as manufactured.

 

I will take this opportunity to note that the engine idle spec for this engine is 950-1050 RPM. Although I prefer the way the engine idles down around 700, I firmly believe the spec of 950 is related to the hot idle pressure, so That is the lowest I set..

Goose

 

Yep, in a nut shell, the relief valve in an oil pump is like a "pop off" or safety valve. It keeps the oil pressure from going over what ever the value is. So, increasing the spring is somewhat similar to putting a bigger fuse in an electrical circuit. Pressure is developed by restricting flow. It is a misconception that pumps create pressure,they do not, pumps only create flow. So when the engine is idling, the flow is low and if the engine has little resistance to that flow, there will be little if any pressure. When the engine speed increases, and the resistance in the engine stays pretty much constant, the pressure will increase, maybe up to the relief valve pressure. When it does, the relief valve opens and "dumps" the excess flow so the pressure in the system does not exceed what the engineers deemed as maximum for the engine.

[Kirby]

Dangit Walt, That's twice within a week you've Wowed me!!