Burning oil at idle

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Slim
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Location: Pembrokeshire, Wales, Uk
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Burning oil at idle

Post by Slim » Sat May 02, 2015 11:40 am

Hello Guy

Car: Uno Mk2 Turbo sprint car

I've Been getting blue smoke from the exhaust at idle. Normally happens after I have given the turbo a good workout. I believe it's the turbo end seal on the hot side as I can see damp around the core and turbine housing. I spoke to the company that supplied my turbo and they suggested that the crank case pressure may be to high due to blocked breather, in turn causing the turbine end seal to leak. Breather was clear and breathing to catch tank. Compression test showed good even results. Engine was built 6k ago, turbo was fresh then too. Spark plugs do not show signs of burning oil.

Sorry, only happens after I have given the turbo a good workout (ran a sprint or hillclimb), pulled up to let cool before I switch off, idling for 30 secs and the smoke starts, smoke continues for 2-5 mins and then stops, won't see it again until I repete.

I have since altered the breather system. I have now returned the breather system to factory fitment, with the addition of a PCV valve from a Fiat Punto GT in the hope that this would apply a slight vacuum in the crankcase at idle. In theory helping the oil to drain from the turbine core (relieving pressure from turbine end seal).

Prior to testing the new breather system I also turned fuel pressure up to richen the air/fuel mixture due to boost pressure being increased.

The increased fuel pressure caused the idle speed to increase from 850rpm to approx 1200rpm. Following the road test of the new breather system I can report no blue smoke at idle (1200rpm). On my return home I turned the idle screw on inlet manifold to a lower setting of 850-900rpm, walked to the back of the car and the blue smoke started, turned idle back up to 1200rmp and it stopped, lowered it once again to be sure and it came back, adjusted it back to 1200rpm and no more blue smoke?

Could Atmospheric crankcase pressure cause a turbo to have too much back pressure to drain effectively? Personally I doubt it.

My boost gauge reads higher .1 bar vacuum at 1200rpm compared to the lowwer 850rpm. Could this slight vacuum difference really help?

In anticipation of your response.

Liam
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Guy Croft
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Re: Burning oil at idle

Post by Guy Croft » Sat May 02, 2015 7:59 pm

compressor end seals

G
Guy Croft, owner

Slim
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Location: Pembrokeshire, Wales, Uk
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Re: Burning oil at idle

Post by Slim » Sun May 03, 2015 11:18 am

Thought you might say that.

Thanks

Liam
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Slim
Posts: 71
Joined: Wed Aug 07, 2013 10:37 pm
Location: Pembrokeshire, Wales, Uk
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Re: Burning oil at idle

Post by Slim » Mon May 11, 2015 8:09 pm

Just to let you know.

I have now changed the turbo for another and the oil burning problem has cleared. Only problem now is the turbo takes a week to spool as it's got a bigger compressor wheel...next!

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