Re: dry sump engine oil level

Very interesting information here.

Cheers,
Joao



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From: Gordon Griffin <gordon_griffin@...>
To: Bike engined Cars Group <bike-engined-cars@...>
Sent: Saturday, 11 April, 2009 23:29:50
Subject: RE: [bike-engined-cars] dry sump engine oil level






You should have 2 (maybe 3) scavenge stages (rotors) to one pressure stage, and yes all are rotating at the same speed and (usually) pumping the same nominal volume per stage - this means that twice the volume of oil can be sucked out of the engine as is being pumped into it.  In normal runnning therefore you might expect a 50/50 mix of oil and air to be coming out of the scav pumps as they can only pump out the oil that the pressure pump puts in.

The pressure pump will push the oil up into the engine - into the gearbox (in a bike), crank main and big end bearings, and up into the head to lubricate the camshaft and followers.  From there it relies on gravity to find its way down through teh oil galleries back into the sump (often hitting the spinning parts of the motor and gearbox on the way and being flung about).  So, when you switch the engine off there will be a fair amount of oil on its way up or down the engine, and over a minute or 2 most of this will work its way back down into the sump where it will stay until you start the engine again, where the scav pumps should suck it all back out into the tank.

So, the oil level in the sump with the engine running should effectively be 0 (though you cant measure this realistically with a dipstick or sight glass as the whole sump will be full of flying oil drops and vapour stirred up by the whirling crank and gears).  The level in the tank is determined by the amount of oil in the system and the amount of oil trying to find its way down the engine back into the sump (hence the recommendation to measure tank level at a hot fast idle - this should be jsut about the maximum level you will see when running).  Reving the engine with the tank cap off, you should see the level dip slightly as the pressure pump stuffs more oil into the engine which will take time to find its way back to the scav pumps and back to the tank.

Assuming your scav pumps are working properly and you dont have blocked pipes or strainers (some Pace sumps have a small mesh cone where the scav pipe joins the sump, pointing into the sump so it's easy to miss - if these get blocked Bad Things can happen):  The only reason you might have oil in the sump is if the scav inlets are in bad positions and you are pulling a lot of G- for instance if both inlets are at the back of hte sump and you are braking heavily.  This is one reason to be wary of sumps proven in side cars (where the engine is transverse) in a north/south engined kit car.

So in summary, I wouldnt worry about oil in teh sump a minute after the engine is switched off, and I dont think you will find a viable way of measuring the oil level with it running.

G
To: bike-engined- cars@yahoogroups .co.uk
From: guzziart@dsl. pipex.com
Date: Sat, 11 Apr 2009 20:11:02 +0100
Subject: Re: [bike-engined- cars] dry sump engine oil level

Thanks for that Gordon, my main question was, what stops it wet sumping?

and is it a problem that immediately after shutdown there's so much oil in the sump?

Since the oil pumps are working in unison and exactly the same volume is entering

as leaving the engine/tank (or sometime down the road one would be empty) what keeps

it all at the right level?

I see that many people with modified wet sumps run much higher than standard oil levels

in becs, so perhaps the level in the engine isn't a problem anyway.

Being a Blackbird I just thought it best to check.

Steve H

----- Original Message -----

From: Gordon Griffin

To: Bike engined Cars Group

Sent: Friday, April 10, 2009 9:08 PM

Subject: RE: [bike-engined- cars] dry sump engine oil level

The whole point of a dry sump system is that the sump should be, effectively, dry when the engine is running. There are normally at least 2 scavenge stages to 1 pressure stage, so the oil should come out of the engine at least as quick as it goes in. Are you measuring level on a dipstick in the engine case while the engine is running? With the amount of oil splashing around in the engine you'll not see any meaningful reading on that. Without the engine running, all you are measuring is how much oil had been up in the engine waiting to drain down when you turned it off.

With a dry sump system the only meaningful level is the oil level in the tank when the engine is running. The oil level in the tank should usually be just below the top baffle in the tank when at a fast, hot idle. This means that the oil returning to the tank has to run across the top baffle before falling into the main bulk of the oil, which helps de-aereate it.

G

To: bike-engined- cars@yahoogroups .co.uk

From: guzziart@dsl. pipex.com

Date: Fri, 10 Apr 2009 18:22:14 +0000

Subject: [bike-engined- cars] dry sump engine oil level

Hello all. I have finally started up my Blackbird engine with Pace/Nova dry sump system. The question I have is what level of oil should be in the engine? With the oil in the remote tank correct, the engine oil level is 12mm ABOVE the max level on the distick. Oil is being returned to the tank via the oil cooler and 1 of the scavenge lines, (I can't see the 1 going to the PRV in the tank) but as quick as it's being pumped out of course it's being pumped back in...which I'm not complaining about..but what governs the level?

Advice would be appreciated. Thanks

Steve H

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