smoke when comin off boost

[sleeker162]

st162 with 3sgte, runs nicely, but straight after boosting ie, boost then zero throttle, it pours blue grey smoke out the back, before anyone says its the turbo, i have recently swapped it. so throw me some other ideas guys.
cheers

[.T.]

probably rings are stuffed - vac pulling oil past the rings when not on boost. (rebuild time)

if it becomes smokey when idling for a while it's most likly valve stem seals

T

[sleeker162]

Motor Has Just Been Treated To A Forged Rebuild With Zero Gap Rings. Sorry For Caps

[takai]

Who did the rebuild? And did they account for thermal expansion when installing the rings?
A few times ive seen engines rebuilt and the ring gaps set too low for the heat of a turbocharged engine. Basically this causes the rings to beome elipsoidal under high heat and then give the same characteristics as worn rings.

[sleeker162]

Plr @ Brendale Did It, They're Spose To Be The Ducks Nuts, Can Anyone Suggest A Workshop In Brisbane That Is Good Enough To Diagnose This Problem????

[takai]

Being not in Brisbane I cant suggest a workshop.
However, capitalising every word isnt a very friendly way of getting attention.

[sleeker162]

yeah sorry i keep forgettin the caps, the program i use at work requires all text to be in caps, hence i forget about it.

[Starfire]

I would suggest that you take it back to whoever did the build...

[sleeker162]

motor has only done 400km, and has been runnin like shit for thos kms, one turbo shat itself and timing was up to hell, could it be that that motor just needs to burn off all the crap that is most likely inside it? takin cooler n pipes off this weekend to degrease it, as there was a little oil in ther from when turbo's oil seal died...

[sleeker162]

say it had too much oil in it, would that cause the smoking? by over pressurising the crank case?...., i thought about it went out and looked at the dipstick, the oil level is 20mm over the full line (i'd like to mention at this point that this is the work of a nth brisbane workshop, not me) with that much pressure.... would it be able to force its way past the turbo seal? or the piston rings?

[RWDboy]

If you are asking if It's possible for oil to be forced back up the turbo return line and leak into the housing, then yes it is. Usually this'll only happen if you start pressurising the crank by running very high combustion pressure and flowing larger amounts of air (ie making bigger hp). One possible solution is to improve the crankcase breathing system (larger lines, filter etc).

If your oil rings aren't doing their job this early (ie smokey when you are going hard, not just when you lift off), then you've got problems with whoever did the rebuild. Oil rings don't get *as* hot as compression rings and will generally do their job unless they don't fit properly.

[sleeker162]

180PSI per cylinder too much??? coz thats what it is, dont ask me how it got to that... the motor is a 2nd gen 3sgte, anyone got a figure on what they run per pot stock?

[o_man_ra23]

Being a turbo engine, it should be running zero overlap, or there abouts, which will make the compression reading higher than a high compression aspo motor with lots of overlap. You say you only have 400km on the engine since rebuild. What oil were you using for these 400km?? have you changed this oil yet?? When running in a new engine, you should run a single grade oil, about SAE30 is good, and dump that oil after 400-500km. This should then be replenished with the oil you wish to run the engine on, eg penrite HPR5 etc. In the early stages of running an engine, the rings and bore wont match one another perfectly, so there will be a little bit of blowby during this time. This will be accentuated by using chrome rings rather than plain steel, running high boost (bad idea in the first 1000kms) and revving hard. For this first period, of about 1000km for chrome rings, you should run the car about like the average motorist does, shift gears early(not too early that the engine chuggs after the shift) and utilise loading at the lower end of your rev range to help seat the rings properly. Full throttle acceleration in the high power range of the motor should be avoided like the plauge. After the first 2000km its adviseable to change the oil again. After the initial 1000km, you should gradually introduce more boost, more throttle and more revvs to the engine... dont just go crazy at it as soon as the clock ticks 1000. Using zero ring gap is also a poor idea as it does not count for the heat expansion(as stated by takai). But, seeing as your compression readings are high, then your rings may yet be ok. I would suggest changing the oil first, before anything else, and see what that does after 50km of driving. If you still have problems, take it back.

Cheers, Owen

[thechuckster]

could be that your rings havn't bedded in (and probably wont, given that you've done 400k already) - i'd take make to the workshop and discuss further.

[sleeker162]

yeah taking it easy on the motor, not revin over 4k, boost is kept to min, runnin some sort of hpr atm, changin to hpr15/60 ?? this weeked. unless u can convince me why hpr5 is better? alot of ppl recommend hpr 15