Shane661
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posted June 07, 2009 06:34 AM
 Edited By: Shane661 on 7 Jun 2009 14:35
KLEEN Vacuum Mod/Oil Pressure Revisited
I have been doing some research on PAIR/KLEEN vacuum mods. I am pretty clear on how this mod will reduce crankcase pressure. What I am not clear on is how this could affect oil pressure.
Since the oil pump is a positive displacement pump, is the theory that oil return is somehow being adversely affected? I am curious as to why some people have done the mod without incident, but others have seen the oil light flicker. Not just Karl, but this has also been reported on one of the Suzuki boards.
I am wondering what other contributing factors there may be. Perhaps some other changes to the oiling system in certain cases, such as shimming the pressure relief, may exacerbate an oil return issue?
I am just looking for any thoughts/ideas. It has me a bit baffled.
Shane
  
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Johnnycheese
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posted June 07, 2009 08:17 AM
vacuum on motor it is sucking air and liquid last time i crank a shake through a straw the shake came up throgh the straw.
plus the Kleen vacuum goes away after the pulse from the throttle bodies is reduced.
if you doubt this check a/f with the kleen hooked up and closed at WOT it is the same
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Shane661
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posted June 07, 2009 08:24 AM
But once you remove the vacuum operated switching valve from the system, won't it be drawing a vacuum on each exhaust pulse? The reeds should keep the positive pulses from pressurizing the crankcase, while the negative pulse will draw a vacuum. That is the way it would seem to operate, as far as I can tell.
Regarding the oiling, I am still not clear on why it would hamper oil return. Couldn't it just as easily enhance return?
Shane
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Y2KZX12R
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posted June 07, 2009 10:33 AM
Let me shed some light on this topic.
We dyno engines with evacuated wet and dry sumps on a regular basis. Most of the race engines we build are evacuated dry sump systems.
The suction pulses that open the reeds in the stock system are generated by the low pressure pulses in the primary header tubes. These pulses don't generate enough volume of vacuum to bring the crank case pressure to ambient pressure let alone start to evacuate the crank case.
Its very simple to check this. Use a manometer to monitor crankcase pressure with and without the hose hooked to the crank case. Or if you have a blow-by meter use that to monitor it.
Even if it did evacuate the normal blow-by and actually did lower the crank case pressure to a few inches of water its not nearly enough evacuation to even start to show a HP increase.
You have to pull a lot of vacuum in a crank case to see any hp on a dyno. Most of the benefits are actually from the reduction in windage because of the dry sump in combination with the lower air density in the crank case.
On a typical all out race V8 engine with a dry sump and an evacuated crank case you see about 5-6 hp. That's it !! We have run engines with and with out the vacuum pump running and its not much of a difference 5-6 hp that's it.
On a smaller engine like these bike motors with 1/4 of the piston area you can expect even less of a HP gain. And of course this is assuming that you are pulling the crank case pressure way down with a strong vane pump.
The reason you see a small HP increase when blocking off the fresh air supply to the exhaust port by using those aftermarket block off plates or just blocking off the air supply is because the combustion chamber sees a lower pressure from the exhaust port because the negative pressure pulse from the primary tube of the header is pulling more exhaust out of the combustion chamber sooner and scavenging the combustion chamber better because it cant pull air threw the kleen air system anymore.
You will only see a power increase if the engine likes a little more scavenging of the chamber. And whether the engine likes more scavenging of the chamber depends on among other things, the cam timing.
As far as the issue of the oil pump being effected by lower crank case pressure, yes it can have an effect but again you only see it when using a vane pump pulling a very strong vacuum in the crank case and its only a concern at very low rpms like at an idle. and the simple fix for that is to raise the idle up.
The negative pressure pulses in the primary header tube at an idle are very, very week and cant possibly even begin to effect crankcase pressure, let alone effect the suction performance of the oil pump.
Now some of you guys will say that the drag race V8 guys run a hose and check valve from the COLLECTOR of the headers to the crank case to evacuate the crank case, and that is true. But the collector is a completely different animal than the primary tube. There are 4 primaries dumping into the collector so the suction is more constant, but even then the negative pressure wave timing only evacuates the crank case at certain rpms (pulse timing actually) and doesn't help at any rpms where the wave timing is out of phase. This is why there is a check valve in-line.
A properly designed collector system like this may be able to yield a few hp at very high rpms.
If you want to read all about this stuff I recommend getting the book by Gordon P. Blair "The Design and Simulation of 4 Stroke Engines". It goes into all the dirty math and details.
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Shane661
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posted June 07, 2009 10:44 AM
Thanks for that information, Jim. And thanks for the recommended reading as well. 
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almost_les
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posted June 07, 2009 12:39 PM
Edited By: almost_les on 7 Jun 2009 20:42
quick question, knowing what i do about basic physics it seems that oil pressure is regulated by the pressure relief valve and ambient pressure in the case as well. this is because the oil is in its own closed high pressure circuit and pressing against the relief valve. take out the valve and the oil pressure drops to ambient absolute pressure of ~14.7 psi, or 0psi as read on a pressure guage. put the valve back in and draw a large enough vacuum in the crankcase and the valve will start to bleed off early. the only thing holding back the oil is the spring and whatever pressure is in the case. so wouldn't any reduction in crankcase pressure also cause an equal amount of oil pressure reduction?
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kawasakijockey
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posted June 07, 2009 12:57 PM
quote:
quick question, knowing what i do about basic physics it seems that oil pressure is regulated by the pressure relief valve and ambient pressure in the case as well. this is because the oil is in its own closed high pressure circuit and pressing against the relief valve. take out the valve and the oil pressure drops to ambient absolute pressure of ~14.7 psi, or 0psi as read on a pressure guage. put the valve back in and draw a large enough vacuum in the crankcase and the valve will start to bleed off early. the only thing holding back the oil is the spring and whatever pressure is in the case. so wouldn't any reduction in crankcase pressure also cause an equal amount of oil pressure reduction?
It will but will take more than an exhaust vacuum will ever do. From what we found on v8 engines is the negative pressure from a vacuum pump just caused less positive pressure on the oil pump feed if the vac. pump was pulling too much. Evidently, it just flowed less oil causing a drop in pressure. We would pull the oil fill cap to check and the oil pressure would shoot up to normal.
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Shane661
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posted June 07, 2009 01:03 PM
Edited By: Shane661 on 7 Jun 2009 21:04
quote:
The reason you see a small HP increase when blocking off the fresh air supply to the exhaust port by using those aftermarket block off plates or just blocking off the air supply is because the combustion chamber sees a lower pressure from the exhaust port because the negative pressure pulse from the primary tube of the header is pulling more exhaust out of the combustion chamber sooner and scavenging the combustion chamber better because it cant pull air threw the kleen air system anymore.
You will only see a power increase if the engine likes a little more scavenging of the chamber. And whether the engine likes more scavenging of the chamber depends on among other things, the cam timing.
Jim, based on what you have written, I am little unsure of one thing. If you hook the crankcase vent up as described, what will the effect be on scavenging? Will it be more or less effect?
Shane
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dougmeyer
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posted June 07, 2009 01:57 PM
Given that I totally agree with Jim (because you can't argue with physics) you will not see any negative effect on scavenging DUE TO THE REDUCED CASE PRESSURE. You might see a slight increase in scavenge flow due to the reduced case pressure which promotes a reduction in aeration (trapped air, "bubbles" in the oil), but with the negative pressures (vacuum) achievable this is pretty doubtful.
almost_ les--
Well sort of. If you have a pump that has excess flow capacity, like a Weaver or a Jackson gear pump, the pressure relief valve is used to set the maximum pressure that the system allows. It does this as you would expect, by having the system pressure act on a ball or plunger pressed against an orifice by an adjustable spring.
On our bikes, though, the system is a little different. The small geroter pumps in the engine are size matched to flow HOT oil of the correct weight at a rate that falls within the needs of the engine without the relief valve "venting" the oil to reduce the pressure. You can shim the valve all you want and it won't change the operating pressure at all. This is because it is in the system as a relief for excessive pressure which might damage the pump. This pressure is rarely, if ever reached once the engine is up to operating temp.
People continuously "shim their relief valve", but this does nothing to the oil pressure because even in it's stock form, the pressure is not great enough to open the valve.
You can check this (like I have) by threading an aluminum block so it accepts a the relief valve on one side and an air source (and regulator) on the other. Add air until the valve opens- there is your maximum oil pressure. You'll find that the valve pops at a pressure number higher than you ever see in the engine.
Y2 may have seen something different, but that's my view.
Doug
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Y2KZX12R
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posted June 08, 2009 10:34 AM
I've never tested the popping pressure of the relief valve on z zx12r engine. I don't know what it will open at.
I agree thou, its there to save the oil pump from damage.
Like starting the engine when its zero degrees out and immediately revving it to 10 grand. That could damage the oil pump if it didn't have a relief valve, for sure.
But what kind of nitwit would do that? But they do have to plan for nitwits.
Addendum to my previous post:
I was just looking at some data on some evacuated engines.... Some engines like the SB2.2 engines we build for the new Trans-Am class this year we did see 12-14 hp with the crankcase evacuated. But a lot of that was from using a extremely low radial tension ring pack that only works properly with an evacuated crankcase.
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Y2KZX12R
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posted June 08, 2009 10:37 AM
quote:
Jim, based on what you have written, I am little unsure of one thing. If you hook the crankcase vent up as described, what will the effect be on scavenging? Will it be more or less effect?
Shane
Combustion chamber scavenging? Lowering crankcase pressure would have no effect on chamber scavenging.
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Shane661
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posted June 08, 2009 11:06 AM
quote:
quote:
Jim, based on what you have written, I am little unsure of one thing. If you hook the crankcase vent up as described, what will the effect be on scavenging? Will it be more or less effect?
Shane
Combustion chamber scavenging? Lowering crankcase pressure would have no effect on chamber scavenging.
I was more referring to the added pulse into the exhaust from the crankcase pressure. Would that enhance or reduce the scavenging? Does that make sense?
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Fasttimez
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posted June 08, 2009 03:56 PM
What advantage or disadvantage will just venting the crankcase to open air have ? Some people claim to pick up hp by doing this ? Other say that at times oil will come blowing out of there crankcase filter they've installed during a 1/4 mile run...what would cause this ?
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NOX
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posted June 08, 2009 04:43 PM
I have the mod done.......
I have no issues.....
I do know, that when I run the bike for a moment, and try to open the oil fill cap...., there is some suction there......., you can hear the air coming in......, or out or whatever.......
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NOX
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posted June 08, 2009 04:45 PM
quote:
Given that I totally agree with Jim (because you can't argue with physics) you will not see any negative effect on scavenging DUE TO THE REDUCED CASE PRESSURE. You might see a slight increase in scavenge flow due to the reduced case pressure which promotes a reduction in aeration (trapped air, "bubbles" in the oil), but with the negative pressures (vacuum) achievable this is pretty doubtful.
almost_ les--
Well sort of. If you have a pump that has excess flow capacity, like a Weaver or a Jackson gear pump, the pressure relief valve is used to set the maximum pressure that the system allows. It does this as you would expect, by having the system pressure act on a ball or plunger pressed against an orifice by an adjustable spring.
On our bikes, though, the system is a little different. The small geroter pumps in the engine are size matched to flow HOT oil of the correct weight at a rate that falls within the needs of the engine without the relief valve "venting" the oil to reduce the pressure. You can shim the valve all you want and it won't change the operating pressure at all. This is because it is in the system as a relief for excessive pressure which might damage the pump. This pressure is rarely, if ever reached once the engine is up to operating temp.
People continuously "shim their relief valve", but this does nothing to the oil pressure because even in it's stock form, the pressure is not great enough to open the valve.
You can check this (like I have) by threading an aluminum block so it accepts a the relief valve on one side and an air source (and regulator) on the other. Add air until the valve opens- there is your maximum oil pressure. You'll find that the valve pops at a pressure number higher than you ever see in the engine.
Y2 may have seen something different, but that's my view.
Doug
Maybe I read this wrong, but Coby suggests shimming the valve......
I have mine slightly shimmed..., my oil pressure at idle went up about 3 lbs........
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dougmeyer
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posted June 08, 2009 05:27 PM
Lots of people suggest shimming it. That doesn't mean it accomplishes anything other than raising the maximum limit of oil pressure allowed, which is what it does. By the way, any amount of oil pressure developed (and the resultant flow) GREATER THAN THAT WHICH IS REQUIRED for safe engine operation will actually cost you power.
As an example, the championship winning (Russell, Chandler, etc) factory 750cc AMA superbike engines that were built at Muzzys in the 90's incorporated special oil pumps that were MUCH smaller than the stock pumps to free up a few more hp. This could be done because the engines were very carefully clearanced, were carefully warmed up, and used specifically chosen oils.
Think about it- if it takes 50-60-70 psi to crack the valve, what possible effect could it have at the 20 or so psi of idle oil pressure.
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Y2KZX12R
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posted June 08, 2009 06:37 PM
How could the oil pressure go up at an idle from shimming the pressure relief valve? If that valve is relieving any oil pressure at an idle then the valve is defective.
You most likely changed the oil when you had the pan down working on the valve, that's what may have raised your oil pressure.
Doug, very true. Lower volume oil pumps have less parasitic drag, we use short rotor pumps in some race engines that are VERY restricted in what you are allowed to do to the engine.
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NOX
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posted June 08, 2009 09:14 PM
Interesting thread......., I did assume that it helped, but I used a very thin shim........
I did not realize that was the way it worked......
So, by shimming it......., you just keep the pressure up just a tad at max......, say stock is 70, (i dont know), it may bump it to 80 before it opens???
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entropy
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posted June 08, 2009 11:10 PM
stock opens at 65-ish on bench, i never logged operation in a running motor.
From oil pressure logs, my shimmed relief valve opens at high 80's over about 8500rpm.
Now & again it will open at 91-92# but quickly settles to high 80's.
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Y2KZX12R
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posted June 09, 2009 03:41 AM
quote:
So, by shimming it......., you just keep the pressure up just a tad at max......, say stock is 70, (i dont know), it may bump it to 80 before it opens???
Exactly
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Shane661
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posted June 09, 2009 05:16 AM
Edited By: Shane661 on 9 Jun 2009 13:26
Let me just throw this out there:
http://www.engineeringtoolbox.com/npsh-net-positive-suction-head-d_634.html
This info was posted on another site....not sure if it is really an issue in this case. Could the modest vacuum we are talking about here really lead to boiling and cavitation?
Shane
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NOX
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posted June 09, 2009 05:36 AM
I doubt it.........
Think what happens with those HUGE vacum pumps the PS bikes use.......
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Shane661
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posted June 09, 2009 06:19 AM
Edited By: Shane661 on 9 Jun 2009 14:20
I have some dialogue going on another site. This is what I "theorized", based on some other input:
Isn't the oil pump rotor above the level of the pick up? We are really talking about the pressure delta between crankcase and the pump suction side, correct? The oil is not pushed into the pump, it is drawn in due to the low pressure on the suction side, correct?
So by lowering the crankcase pressure you are reducing the pressure delta, thereby affecting flow to the pump.
How does that sound? If I am way off...hey, I'm not an engineer! 
Shane
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dougmeyer
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posted June 09, 2009 06:29 AM
Consider this:
Barometric pressure is reduced 1 inch of mercury for every thousand feet you climb above sea level. As you know Sea Level Pressure is roughly 30 in Hg. So if you go up to, say 15,000 feet, the pressure in the crankcase on an aircraft piston engine is 16 " hg. Both dry sump and wet sump oiling systems work just fine in that environment and in fact all the way up to the 30's.
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Shane661
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posted June 09, 2009 06:57 AM
Edited By: Shane661 on 9 Jun 2009 15:01
quote:
Consider this:
Barometric pressure is reduced 1 inch of mercury for every thousand feet you climb above sea level. As you know Sea Level Pressure is roughly 30 in Hg. So if you go up to, say 15,000 feet, the pressure in the crankcase on an aircraft piston engine is 16 " hg. Both dry sump and wet sump oiling systems work just fine in that environment and in fact all the way up to the 30's.
That's pretty interesting stuff. Aviation probably has a lot information/lessons learned as related to our sport.
In the case of drawing a vacuum in the cases, we are well below those pressure levels, though, aren't we?
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