An interesting problem

[Daley Down Under]

Here's one for all you motor engineers out there.  I was at Combe this morning.  Car was running fine - I opened the bonnet to check the oil level (after two runs) and found both oil catch tanks full with additional oil blown out of the breather into the engine bay (approx a litre in total).  I drained the tanks and found the oil contained a lot of petrol.  I refilled the sump (it needed approx 300ml) and checked the fuel pressure which was fine (regulator working ok).  There was no blue smoke so it rules out piston rings or piston failure.

When the car was built in 2008, it suffered from fuel wash down the bores, which diluted the oil with fuel and filled the catch tanks.  The supercharger pulleys were changed which reduced the boost pressure and cured the problem.  TTS did the work. 

My thoughts - I took the car back out and oil pressure was higher than normal - 105psi at half revs.  I came back in and scratched head.  I then checked the dump valve on the inlet plenum.  It was perhaps a bit sticky.  I took it apart and WD40'd the slide and piston.  When re-assembled, it seemed to cure the problem.  In other words, two more runs and no more oil in the catch tank.

What do you all reckon?

Adrian

['The Gaffer']

Wish I could help Adrian  ,maybe or hopefully you have pinpointed the problem. Keep us updated.

[Hairy Santa]

Here's one for all you motor engineers out there.  I was at Combe this morning.  Car was running fine - I opened the bonnet to check the oil level (after two runs) and found both oil catch tanks full with additional oil blown out of the breather into the engine bay (approx a litre in total).  I drained the tanks and found the oil contained a lot of petrol.  I refilled the sump (it needed approx 300ml) and checked the fuel pressure which was fine (regulator working ok).  There was no blue smoke so it rules out piston rings or piston failure.

When the car was built in 2008, it suffered from fuel wash down the bores, which diluted the oil with fuel and filled the catch tanks.  The supercharger pulleys were changed which reduced the boost pressure and cured the problem.  TTS did the work. 

My thoughts - I took the car back out and oil pressure was higher than normal - 105psi at half revs.  I came back in and scratched head.  I then checked the dump valve on the inlet plenum.  It was perhaps a bit sticky.  I took it apart and WD40'd the slide and piston.  When re-assembled, it seemed to cure the problem.  In other words, two more runs and no more oil in the catch tank.

What do you all reckon?

Adrian

Sounds like you have found the cause, very much like over pressure with a sticky dump valve, almost the same as when you built it, my concern would be the fuel in with the oil, thinning it out to much and reducing it's lub qualities, changed the oil on the hayabusa for the same reason  ( oil level had gone up for some reason)    

[Daley Down Under]

Pete - I agree.  Oil change is on the list for the weekend (prior to run to Stoneleigh).

[David H]

I had this with an old NA engine. The catch tanks were filling. No blue smoke but it ended up a cracked piston and rings.

Yours sounds like you have solved it. Bearing in mind the engine wasn't designed to pump out nearly 300bhp, there's bound to be the occasional hic up.

Sounds like you've got the solution. Just keep checking and defo change oil

[Quarrycars]

I've seen leaky fuel pressure regulators that can dump fuel into the manifold under negative pressure conditions such as decel.

[Daley Down Under]

Car has been out for a good hoon this afternoon.  No oil in the catch tanks.  I've booked the car in for a rolling road session on 6th May to check things like fuel pressure on decel, mixture across the rev range and boost pressure.  Everything seems to be ok again now but cant be too careful with the £'s invested in the engine and supercharger.

Thanks for all your replies.

Adrian

['The Gaffer']

Lets hope you've got to the bottom of it Adrian.