smoking on decel ????

[gsxr141]

ok guys, here's another rookie question.....
my car is starting to smoke pretty bad on decel. everyone i've talked to says it's the turbo seals.... i DO have a spare turbo that has no shaft play, so i guess i could swap it out. my question is.... will installing a catch can after the valve covers help? i'm thinking that that extra oil going into the turbo might be part of the problem.
that said...... has anyone installed anything like that? if so, please post some pics so i can get an idea of how to mount everything.
thanks again............. kevin

 

[hvyman]

If it's the turbo a catch can is not going to help.

Could also be valve stem seals or rings.

 

[1988ma70supra]

It does sound like the seals on your turbo are on their way out, but here's how i plumbed my catch can for reference

 

[Nick M]

ok guys, here's another rookie question.....
my car is starting to smoke pretty bad on decel. everyone i've talked to says it's the turbo seals....

Here is some food for thought for you. There are many more cars on the road that are naturally aspirated compared to artificial aspiration. And they smoke on deceleration. Is that from turbo seals when it doesn't have a turbo seal?

 

[1988ma70supra]

Easiest way to deduce if its affiliated with the turbo seals; remove the inlet pipe from the turbo and check for shaft play.

 

[atmperformance]

Here is some food for thought for you. There are many more cars on the road that are naturally aspirated compared to artificial aspiration. And they smoke on deceleration. Is that from turbo seals when it doesn't have a turbo seal?

Physics would say no, but valve steam seals and piston rings can still cause smoking on N/A motors.

 

[Dan_Gyoba]

Physics has nothing to do with it when there's no turbo to have a leaky turbo seal.

My '90 smokes pretty hard on decel, and still does after swapping out the turbo. It's definitely valve stem seals, which I knew beforehand.

 

[Insidious Surmiser]

anything in particular that makes the stem seals give up? one of my cars did this but I didn't get a chance to take it apart before it was stolen. (had head rebuilt and put 10k miles on it) that engine also put a lot of soot on the rear bumper (from the smoking). car I have now only smokes when you floor it (lots of shaft play)

 

[gsxr141]

one of the reasons i was thinking it was the turbo is that i just put a different motor in. it seems to be exactly the same as before. i do have some light oil buildup at the top of the valve covers where the two small hoses are. that's why i thought about putting in a catch can.

 

[scottiedawg66]

Are your plugs oily?

 

[gsxr141]

i'll be changing the plugs tomorrow. i'll find out then.

 

[scottiedawg66]

Do a compression test while you are doing plugs. Hopefully you can rule rings out with good results.

 

[Nick M]

My '90 smokes pretty hard on decel, and still does after swapping out the turbo.

I was going to suggest to the author to look up all the threads with the same symptom, suggestions (false diagnosis) and failure to fix it. Not to indict your work, just a generalization.

 

[atmperformance]

Physics has nothing to do with it when there's no turbo to have a leaky turbo seal.

My '90 smokes pretty hard on decel, and still does after swapping out the turbo. It's definitely valve stem seals, which I knew beforehand.

Physics has everything to do with it, silly uneducated Americans. Your statement speaks for itself "there's no turbo to have a leaky turbo seal". just as your valves can't exist where your pistons are you can't leak passed a turbo seal that doesn't exist.

 

[gsxr141]

well, here's what i found..............
i did a leakdown on the first 3 cylinders and found..... 4.5%, 9.5%, and 15%. i stopped there and added a little oil to cyl 3, and is showed less leakdown.
looks like i'll be tearing this motor down again...... oh well.....

 

[MDCmotorsports]

Physics has everything to do with it, silly uneducated Americans. Your statement speaks for itself "there's no turbo to have a leaky turbo seal". just as your valves can't exist where your pistons are you can't leak passed a turbo seal that doesn't exist.

Say what?? You'd like a ban hammer? Come again?

Valves certainly have seals that leak under vacuum.

 

[gsxr141]

just an update. i ended up getting a catchcan from stmtuned.com. i routed it inline between the throttle body and the intake hose. there has been less smoking so far, but i plan to change the setup again. here's how it is set up for now....

i've searched every thread about the proper way to install a catch can. i've seen everything from the way i did it to just running a hose from the valve covers to the ground. i'm going to cap off the throttle body and the intake hose and route the valve covers to the catch can and use a breather on top.
i also plan on testing out a known good turbo, as i want to upgrade anyway. this will help me rule out the turbo as the cause of the smoking.

 

[Insidious Surmiser]

It's my understanding that you don't want to use a breather.... (thinking about crank-case vacuum) stock pcv didn't have a breather on it.

 

[Insidious Surmiser]

read part of this description of PCV purpose, and function, and you might understand why you don't need to alter your catch-can setup. (you got it right the first time)

"Because of the high cylinder pressures, some of the expanding gases are forced past the piston rings and find their way into the lower crankcase. These gases (commonly referred to as blow-by) consist of fuel vapor, partially burnt hydrocarbons, water vapor, and other nasty by-products of the combustion process. If these gases are not vented from the crankcase, they will eventually be absorbed into the oil and cause damage to bearings and other internal parts of the engine.

The goal of the PCV system is to provide a way to get these gases out of the engine’s crankcase and recycle them into the air/fuel mix"

 

[MDCmotorsports]

It's my understanding that you don't want to use a breather.... (thinking about crank-case vacuum) stock pcv didn't have a breather on it.

correct....you'll want vacuum not atmosphere