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  #1  
Old 18-08-17, 18:07
schomosport schomosport is offline
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How dry should a dry sump be?

Spiess pumped C20XE Dallara. Single stage pressure pump, single stage scavenge back to the oil tank via the oil cooler. Oil tank breathes into catch tank which then breathes to atmosphere. Crankcase breathes to same catch tank from what would have been the dipstick hole in a standard car. There is a baffle plate at the entry to this breather to stop the splashes in the crankcase going straight up the breather. All standard XE Dallara fit so far as I am aware.

Engine rebored with negligible mileage and satisfactory compression so it isn't blow-by pressuring the crankcase.

Immediately after switch off I removed the sump-to-scavenge stage collector pipe and drained approximately 0.8 litre oil out of the sump. The car also seems to be putting a lot oil into the catch-tank - can't make it do it in the garage but after the last test session I found best part of a litre in there. Scavenge pump gone bad because it has had too many bits of engine through it?

Was this the cause of my collapsing oil pressure and oil leak problems last time out because there was more oil in the sump than in the oil tank?

Frustrated and mystified. All offers of advice / help welcome.
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  #2  
Old 18-08-17, 19:59
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madmax53 madmax53 is offline
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Run basically the same on my XE, However my crankcase breather go's to the oil tank and only one from there to the catch tank and never had any problems.
I would say .8 of a litre in the sump is about right.

How much oil is in your oil tank?
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Old 19-08-17, 07:55
St Eval St Eval is offline
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I would say that 0.8 of a litre is about right, we don't run a crankcase breather the scavenge pump sorts that out. Breather from dry sump tank to catch bottle and the only time we have oil in the bottle is when there is a bit too much in the tank.

Roy
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Old 19-08-17, 08:23
Rob Stevens Rob Stevens is offline
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I did an experiment on my engine (when N/A)by running it with just the scavenge pump and no breather. Fitted a sensor to monitor crank case pressure and quickly found that when under power and anything over 1/2 throttle saw the pressure rise well over ambient.
I'd say talk to owners of similar cars to see if your pipes are configured the same.
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Old 19-08-17, 08:37
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redturner37 redturner37 is offline
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My experience with Pace and Titan dry sump pumps is that the scavenge element in the pump is always larger than the pressure rotor and theoretically there shouldn't be any, or very little oil in the sump after shut down. Depending on how much wear in the pressure rotor, oil will leak back into the sump, which is why you should always check tank level before starting the engine, subject to there being oil visible in the tank. It seems that the scavenge rotor is very badly worn and is not doing its job properly hence the build up.
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Old 19-08-17, 09:47
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wil_ker wil_ker is offline
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I had multiple inputs to my catch tank, when it kept filling up it was impossible to tell the source. As an experiment I installed multiple catch tanks and instantly identified the issue.

I try the above so you'll know if the oil is from the dry sump tank or the crankcase.
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Old 19-08-17, 10:34
No Imagination No Imagination is offline
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My Dallara using Spiess components had the crankcase breather in the cam cover venting to the oil tank - thought it was twin scavenge though.
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Old 19-08-17, 11:22
schomosport schomosport is offline
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Thanks for the responses. A correction - the crankcase breather doesn't go straight to the catch tank, it goes goes to the oil tank along with the scavenge return. The oil tank then breathes to the catch tank.

madmax53 - I put 5 litres in after fitting the engine to give the manual recommended 115mm below the top of the filler hole. Then ran the engine up an re-checked the level and it needed another litre or so to correct for what is in the sump, oil cooler and pipework.

StEval - yes agree, catch tank normally only collects oil when too much in the system in my previous experience. However I am not over-filling this time.

RobStevens - interesting, I thought the point of having a strong scavenge was to try to create a partial vacuum in the crankcase

RedTurner37 - yes that is the conclusion I am coming to, needs a new pump. As amatter of interest I had a Ralt Toyota with a Pace/Titan pump (can't remember) with two scavenge stages. When I ditched the home-brewed sump in favour of an alloy one that had only a single drain outlet, I removed one of the scavenge rotors and blanked off the ports (plumbing 1 into 2 was difficult because of space limitations). It didn't cause any problems at all. The pressure/scavenge stages in the Spiess pump are relatively small compared to that pump. I suspect this is done deliberately to minimise HP loss in an environment (F3) where replacing pumps if there was any doubt as to their performance was routine regardless of £££.

wil ker - I will run crankcase and oil tank breathers to catch pans this afternoon and see what collects what

No Imagination - I think there have been several different Spiess pump arrangements over the years, yours may well have two scavenge stages however mine has only the one.

Thanks everyone. Look like I need to talk to Titan/Pace about a pump.
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  #9  
Old 20-08-17, 00:09
Darvie Darvie is offline
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Bleed back when not running, this is why Gould NIMACs cankover for 12 seconds with all turned off, wait a moment then crank 6 seconds and fire up.
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