Smoke during normal deceleration

Furthermore the intake side valve seals are far more likely to leak because the intake valves see strong vacuum (and boost in our cars as well) whereas the exhaust valves don't really see any significant vacuum or pressure.

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Hmm why didn't i think of that? I would probably do intake and exhaust seals anyway. I'll probably order and pull both manifolds to check. If they're needed they go in. Anything else i should be looking for?

I will try the borescope first.

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To answer your question oil seems to be on the center of the piston

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VTMongoose said:
Furthermore the intake side valve seals are far more likely to leak because the intake valves see strong vacuum (and boost in our cars as well) whereas the exhaust valves don't really see any significant vacuum or pressure.

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Now the question is rebuild the whole motor, would need to wait 6 months, or do seals now?

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tmillner said:
Hoping some one on here can help. I've done some research but would like opinions on my specific circumstances.

Car has 78k on it, bnrs4 installed about 10k ago. Running an e30 mix, at 24 to 25psi and Stratified Tune. Recently installed a occ to help with blow by.

Upon deceleration from high speeds, normal deceleration, once you stop you can see a puff of light blueish smoke fly past. Doesn't smoke at idle or during acceleration. Did a compression check all cylinders over 180 psi dry, and 185+ to 210 wet, not sure why the variance.

My research has lead me to believe valve guides on the exhaust side. There is a layer of oil in the hot side IC piping, I haven't checked the rest yet or the turbo. I'm putting a new pcv valve in tomorrow anyway but wondering if anyone had any input before I go any further with a leak down etc.
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Hey man, I have the same turbo and I'm experiencing the same issue. My guess is that with my 3" catless exhaust, oil is being pulled past the turbo seal, mainly during high rpm deceleration due to a lack of back pressure, although I'm not entirely sure.

Smoking at WOT has been greatly reduced ever since I went with a dual vented catch can setup and oil breather cap, but I still have this smoking issue during mid to high rpm deceleration. Whether I go into boost or not prior to decelerating doesn't matter. Did you end up finding a solution to this issue? Thanks :)
 
BuddySpeed3 said:
Hey man, I have the same turbo and I'm experiencing the same issue. My guess is that with my 3" catless exhaust, oil is being pulled past the turbo seal, mainly during high rpm deceleration due to a lack of back pressure, although I'm not entirely sure.

Smoking at WOT has been greatly reduced ever since I went with a dual vented catch can setup and oil breather cap, but I still have this smoking issue during mid to high rpm deceleration. Whether I go into boost or not prior to decelerating doesn't matter. Did you end up finding a solution to this issue? Thanks :)
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Ended up being broken piston ringlands. After I did valve seals ended up spinning a bearing so tore the engine apart that's how I found it
 
tmillner said:
Ended up being broken piston ringlands. After I did valve seals ended up spinning a bearing so tore the engine apart that's how I found it
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Oh so the valve seals didn't fix it eh?
Were you catted at the time?
Did you get to a point where you just decided to live with the smoking on decel?
 
tmillner said:
Yeah, new bearings pistons rods etc
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That's interesting, I was just curious whether the S4 is more susceptible to smoking with a catless exhaust, because I know it is with high crankcase pressure. I did a leak down test a month ago, and with the engine hot each cylinder had less than 3% leakage. This makes me think my ring lands are in good shape. I just gotta figure out why it blows blueish white smoke during mid to high rpm deceleration and then dissipates after a few seconds.
 
BuddySpeed3 said:
That's interesting, I was just curious whether the S4 is more susceptible to smoking with a catless exhaust, because I know it is with high crankcase pressure. I did a leak down test a month ago, and with the engine hot each cylinder had less than 3% leakage. This makes me think my ring lands are in good shape. I just gotta figure out why it blows blueish white smoke during mid to high rpm deceleration and then dissipates after a few seconds.
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Did you ever figure out you’re issue I’m having the exact same smoke on high mid rpm deceleration?
 
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