Oil Pressure vs Engine Speeds

[Darryl S]

We are currently running a mechanical scavenge pump but we are thinking of maybe converting to an electrical one. I was just wondering if your oil pressure to the engine should increase as engine speed increases. Or can you keep it at a constant presure? From what i understand, as your engine speed increases, the holes that are supplying oil will be in greater contact with the shafts, requiring a higher pressure to overcome this. Is that a correct analysis?

And also, as a side question, for those of you that are running a dry sump, where do you normally route the relieve valve to? And whats the reason behind it?

Thanks for your help again guys

[Darryl S]

We are currently running a mechanical scavenge pump but we are thinking of maybe converting to an electrical one. I was just wondering if your oil pressure to the engine should increase as engine speed increases. Or can you keep it at a constant presure? From what i understand, as your engine speed increases, the holes that are supplying oil will be in greater contact with the shafts, requiring a higher pressure to overcome this. Is that a correct analysis?

And also, as a side question, for those of you that are running a dry sump, where do you normally route the relieve valve to? And whats the reason behind it?

Thanks for your help again guys

[Chris Allbee]

If I'm not mistaken most oiling systems include a pressure relief valve so that the pressure does not continue to climb throughout the RPM range. It should peak and hold at some point. You just need to identify what that pressure is...

[Dallas Blake]

Darryl,

We run a dry sump here at Queen's and our relef valve bleeds off into the pan, although im sure you could bleed it back to your sump. Chris is correct in stating that the relief valve will maintain your oil pressure regardless of RPM (on the F4 it maintains it at 71PSI). Your scavenging pump is a different story though, last year we ran a single stage scavengine pump and we were exceeding its capacity at higher RPM's and as a result our crankcase vacuum would decrease with RPM. this year with a dual scavenge system we hold a steady 34KPa vacuum (Approximately 5psi)

My engine journal has some information on our dry sump system if your interested

[Mike Flitcraft]

General rule of thumb, from the automotive world at least, is 10 psi per 1000 rpm added to 10 psi at idle.

I.E. 70 PSI= 6000 RPM

Dependant upon clearances and construction obviously, but it's been used for years with good sucess.

As Blake stated, if the pressure maintains at 71 psi, shoot for at least that. 80 might be a bit better for endurance. Many vehicles in the US have a relief valve built into the oil pump itself. Look at small block chevs for a gear setup, and almost anything with a pump driven off the crank for a timing cover 'star' design.

[Darryl S]

Hey Blake,

In regards to your single scavenge problem, have you tried to maybe route the oil from the pressure relieve valve back to the oil tank? I think if you do that then your scavenge points will not need to remove the oil from the relieve valve that is thrown back to the sump, which should prevent the scavenge pump from being overused at high RPMs.

I am really interested with the single stage scavenge as we are really keen to downgauge to a single stage, but there are still some tests to be done to make sure the blowby of the engine does not cause the crankcase to pressurise.

And also, do you have a means to measure the blowby rates of the engine. I was thinking maybe installing a flowmeter on the breather hose of the oil tank. Is that ok?

I am also interested in how you measure the crankcase vacumn in your engine, as stated in your journal, which is quite an interesting read =) Would you mind sharing some information about the whole setup? Thanks

[Dallas Blake]

Darryl,

The problem we were having with our single stage scavenging system was that our pan had four holes that were internally routed to one output line from the pan so under any form of acceleration some of the holes would be drawing air and we would begin to lose capacity of our scavenging pump.

We measure crankcase vacuum by attatching a vacuum gauge to the filler cap and data logging with our dyno data aquisition. I think that this is somewhat indicative of blowby rates and pumping losses. If you are certain your oil pump can susatain pressure at high RPM without causing aeration than a decrease in crankcase vacuum should be indicative of increased pumping losses or blowby at higher RPM.

[Akos]

Having run a single stage dry sump (CBR F4) the problem was with oil buildup while extended cornering.

We did a test with the vehicle idling where one side of the vehicle was lifted off the ground. You could see exactly when the oil started building up the crankcase by watching the oil level drop in the dry sump tank.

Switching to two stage solved all the problems with only a small increase in plumbing.

Pivoting pickup could solve this, but I think 2 stage is simpler.

[Dallas Blake]

Akos,

What brand of pumps are you running? Pace?

[Darryl S]

With regards to few pickup lines connected to a single scavenge stage, will it be better to run one pickup for each of the scavenge stage? or will one sgavenge stage be able to handle multiple pickups?

And what kind of pick up configuration you guys are running (i.e where do you normally place your pickup points in the sump?, front and back, left and right?) We are currently running 3 pickups, one on the front middle, and two on the back left and right and we are thinking of downgauging to 2 pickups, maybe even one. Anyone out there successfully run one pickup?

Akos, with regards to your test, we have quite the opposite result compared to you. When the car is static and flat, the oil level in the tank will continue to drop. But when the car starts doing dynamic runs, which i think is sort of eqvalent to your tilt test, the oil level in the oil tank pretty much stays constant. This is probably due to the three stage scavenge we use compared to your one. But im curious to know how many pickup points are you running, and where did you place it?

Dallas, with regards to your comment about areation at high RPMs, is this areation due to the pickups sucking in air/blowby from the crankcase and getting mixed with the oil at the scavenge pump? Sorry for asking you such a simple question. Still very new to all of this.

Thanks again guys!

[Dallas Blake]

I think that if your careful about you plumbing you can get away with multiple lines to one pick up, however I dont think it can be done with a single stage, maybe some teams have done it, I know our team was successful with a single stage in 2002 but when we used the exact system in 2006 we blew a rod because of lack of lubrication.

With our new system we run two pick ups that are left and right of the pressure inlet and equidistant between the from baffle and the rear of the engine. one is directly under the clutch and one is as far to the left as possible. However, we just got our car rolling so I haven't tested this dynamically and it may call for a few creative baffles if we are finding low oil pressures during high accelerations, time will tell.

When I was mentioning aeration it as because most commercially available pumps are only rated to around 4500-5000RPM which is why so many teams will run them externally with a gear reduction so they run at an adequate speed. Our pump is rated for 5000RPM but we are able to spin it to 6000RPM with synthetic oil without aeration. once again, this is all static, we'll have to log our oil pressures when we get out testing soon.

[Akos]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Darryl S:
With regards to few pickup lines connected to a single scavenge stage, will it be better to run one pickup for each of the scavenge stage? or will one sgavenge stage be able to handle multiple pickups?


&gt;&gt;One scavange stage will never handle multiple pickups. If one pickup has oil in it, the other air, it will only pump air.


And what kind of pick up configuration you guys are running (i.e where do you normally place your pickup points in the sump?, front and back, left and right?) We are currently running 3 pickups, one on the front middle, and two on the back left and right and we are thinking of downgauging to 2 pickups, maybe even one. Anyone out there successfully run one pickup?

Akos, with regards to your test, we have quite the opposite result compared to you. When the car is static and flat, the oil level in the tank will continue to drop. But when the car starts doing dynamic runs, which i think is sort of eqvalent to your tilt test, the oil level in the oil tank pretty much stays constant. This is probably due to the three stage scavenge we use compared to your one. But im curious to know how many pickup points are you running, and where did you place it?


&gt;&gt;If your front stage can't handle the idle oil flow, oil will build up in the case until it gets to the rear pickups. This is is probably why your tank oil level is fine while running. Either way, as long as it works on the track, its good.

The single stager setup had a single pickup approximately in the center of pan, offset to towards the clutch basket. The engine was inclined with a flat plate oil pan, the pickup was near the front of the motor.



Dallas, with regards to your comment about areation at high RPMs, is this areation due to the pickups sucking in air/blowby from the crankcase and getting mixed with the oil at the scavenge pump? Sorry for asking you such a simple question. Still very new to all of this.

Thanks again guys! </div></BLOCKQUOTE>