V7 2.5 Spec C - Blowing Smoke

[grego0o]

Hey guys and girls,

Just trying to do some problem solving so thought I throw a thread in here and get some suggesions...

Okay so the back ground is:

2.5 Semi Closed Deck ( 3000ks in from Brand New with Spec C Heads )

Fully Rebuilt Vf34 (done less than 5kms)

Everything else is standard...

I replaced the Turbo as the car was blowing alot of smoke and burning thru the oil.

Was okay when first started it up after putting the rebuilt turbon on but its getting progressively worse with smoking and oil everywhere...

Smokes black and blue ( oil burning ) out the exhaust and is also pushing oil into the intercooler and out the bov...

Removed the Crank Breather for a few seconds and small puffs of smoke coming thru there too?

I'm about to start taking everything off on Monday to check thru everything...

What can cause these symptoms?

I was thinking:

Blocked Oil Return Line from Turbo?

Block Crank Breath Line?

Blown Head Gasket ( but its not overheating? )

Compresson is good on all 4 so can't be rings or pistons? but maybe a melted piston ring and not showing up on the comp test?

Any help is appreciated.

Thanks

[BC5RA]

Who did the rebuild?

[grego0o]

Rebuild on the turbo was done by Steve Merch.

Motor was a Crate Engine from Subaru

[BC5RA]

Did you run it in?

Could be the piston rings haven't bedded properly.

[Guest]

Who checked the fueling once it was running?

sounds like you may have detted a slug (piston)

[grego0o]

it's been on the dyno @ Shred Industries.

Just got driven down there at low rpm after the turbo got put on.

Was putting out 200kw atw while smoking? ( Vf34 is far too small for the 2.5 so can't make much more power than this )

Fueling was running rich before the reflash.

Wouldn't a stuffed piston show up in the Comp Test and cause further problems with the power run on the dyno??

[grego0o]

 BC5RA said:

Did you run it in?

Could be the piston rings haven't bedded properly.

Not sure as have recently purchased the car...

Wouldn't that show in low comp tho?

[Guest boostin]

Do a leak down test. That will show if its rings or not.

[grego0o]

 boostin said:

Do a leak down test. That will show if its rings or not.

"The neat thing about a leakage test (as opposed to a compression test) is that it's faster and easier to figure out where the pressure is going. If you hear air coming out of the tailpipe, it indicates a leaky exhaust valve. Air coming out of the throttle body or carburetor would point to a leaky intake valve. Air coming out of the breather vent or PCV valve fitting would tell you the rings and/or cylinders are worn. "

might explain the smoking out the breather?

mmm not looking great at this stage... fingers crossed for the best otherwise i've got my work cut out for me before megameet

[Guest]

 grego0o said:

it's been on the dyno @ Shred Industries.

Just got driven down there at low rpm after the turbo got put on.

Was putting out 200kw atw while smoking? ( Vf34 is far too small for the 2.5 so can't make much more power than this )

Fueling was running rich before the reflash.

Wouldn't a stuffed piston show up in the Comp Test and cause further problems with the power run on the dyno??

Sorry missed the part of you orginal post re comp test done..

I'd be looking at breathers, sounds like its pressurising the crankcase

[Optical]

The 257 pistons are pretty fragile, sounds like you've damaged a ring-land on one of the pistons.

Ive seen a few 2.5's smoking out the breathers because of this, including one of my own

hopefully it's a pcv issue as others have said though!

[grego0o]

 Ichi Ban']

[quote name='grego0o said:

it's been on the dyno @ Shred Industries.

Just got driven down there at low rpm after the turbo got put on.

Was putting out 200kw atw while smoking? ( Vf34 is far too small for the 2.5 so can't make much more power than this )

Fueling was running rich before the reflash.

Wouldn't a stuffed piston show up in the Comp Test and cause further problems with the power run on the dyno??

/quote]

Sorry missed the part of you orginal post re comp test done..

I'd be looking at breathers, sounds like its pressurising the crankcase

How do I go about testing these? Should I be running a catch can?

This is my first Piston Engine in a few years and Suby so i'm not too up on the play yet

[grego0o]

 Optical said:

The 257 pistons are pretty fragile, sounds like you've damaged a ring-land on one of the pistons.

Ive seen a few 2.5's smoking out the breathers because of this, including one of my own

hopefully it's a pcv issue as others have said though!

So lets say worse say worst case senario... damaged ring or piston?

Aren't the Sti Pistons mean't to be forged not fagile??

What needs to be done from there?

Pull engine? strip block? Complete Rebuild or just new rings?

Worth while sticking with the 2.5 or would it be better to go back to a 2.0?

mmm not looking forward to this. haha

[Optical]

from the sounds of it it isnt too bad, but these things only get worse. yeah dud piston, they are not factory forged in those motors

if the piston ringland has broken or cracked then hopefully it hasnt scored the bore. Assuming the bore is ok you can take the piston out and replace it.

Best thing to do in that case would be strip the short block, hone the bores and rebuild with some forged pistons

[grego0o]

 Optical said:

from the sounds of it it isnt too bad, but these things only get worse

if the piston ringland has broken or cracked then hopefully it hasnt scored the bore. Assuming the bore is ok you can take the piston out and replace it.

Best thing to do in that case would be strip the short block, hone the bores and rebuild with some forged pistons

Arn't the Sti Piston Forged? or Semi Forged already?

[Optical]

sorry edited above

not forged in those. weak pussy ass cast pistons

[grego0o]

ah okay? it's a v10 2.5 STI? does that make any difference?

[Optical]

no

[grego0o]

sweet, thanks for the help!

Will update once taken apart!

[grego0o]

ah it is as suspected, redid the comp test and turns out 2 out of 4 are stuffed ( must have got a faulty reading the first time round )

Will pull the engine on saturday and see what the damage is.

I will still make it to megameet!!! 1 2/3 Month till d day!

Once everything is stripped back i'll order parts from the u.s on Monday.

Will update post with rebuild details

Greg

[Pappu1]

what did u mean the vf34 is too small for the 2.5 litre - u mean its choking it on the exhaust side? ???

[grego0o]

yeah the turbo can't supply enough air to the engine so starts to run out of chuff at 4500rpm will post up dyno results from the run so you can see it happening.

[Optical]

it's not the supply of air that's the problem, the hot side is too small to get the air out

good commitment

[Guest keltik]

I go back on what i said previously. This motor probably had the **** beaten out of it from day one. I cant say much about the build as i only helped taking the old motor out. To lunch 3 motors in less than 6 months (as the previous owner did) youve gotta be doing something seriously wrong.

[Guest boostin]

 keltik said:

I go back on what i said previously. This motor probably had the **** beaten out of it from day one. I cant say much about the build as i only helped taking the old motor out. To lunch 3 motors in less than 6 months (as the previous owner did) youve gotta be doing something seriously wrong.

Or have a faulty AFM, or the compressions are wrong, or there is something up with the fuelling, or......