Re: dry sump engine oil level

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> 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@...
> <mailto:bike-engined-cars%40yahoogroups.co.uk>
> From: guzziart@... <mailto:guzziart%40dsl.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@...
> <mailto:bike-engined-cars%40yahoogroups.co.uk>
>
> From: guzziart@... <mailto:guzziart%40dsl.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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