RICHARD J

iTrader: (4)

Hi all,
Iv got a strange blue smoking issue with my 96STI fully forged engine. Occasionally & only after high boost I get a bad plume of blue smoke from my exhaust. The first time it happened It was so bad I thought my engine had blown. Now it only does it sometimes & seems to be when I lift off after holding high boost. There is no serious oil consumption & car seems to run fine.
My engine builder is going to take a look but he's busy at the moment. He suggested some turbos can do this & it not be a major issue, my turbo is an RCM 400 & has only done about 3000 miles.
Just wondering if anyone has experienced occasional heavy blue smoke immediately after high boost as I'm baffled & quite concerned about it.
Thanks, Richard.

BenGTTurbo

Sounds like turbo oil seals to me but best to get it checked out

RICHARD J

iTrader: (4)

Yes, I thought turbo seals too, only does it sometimes though, goes from no smoke atall at max boost to plumes of blue smoke when I lift. Someone suggested to me that it may be manifold vacuum drawing oil through a worn valve guide or stem seal. Wouldn't turbo seals smoke all the time & mainly on start up?

360ste

iTrader: (1)

I know from previous NA cars a puff of blue smoke from the exhaust when coming off throttle was due to the vacuum produced pulling oil down through the valve stem oil seal.

RICHARD J

iTrader: (4)

This is what I'm thinking, but why would it do it intermittently & not all the time?

andy.downes

iTrader: (1)

Blue smoke on start up = valve stem seals

Blue smoke on boost = turbo seals

Blue smoke on overrun (foot off) = piston rings

That's what I've been told before.

kevin wrx

iTrader: (1)

sounds like turbo seals

RICHARD J

iTrader: (4)

Evryone seems to think piston rings or turbo. I'm not saying they are wrong atall but no one can explain why it only does it occasionally. Took intercooler pipes off & looked fairly dry. Turbos only done 3k since I bought it new & engine has been recently rebuilt too.

WMS

iTrader: (2)

Are your block breathers all clear, could be pressure in the bottom end if they are not breathing properly, are they going to a catch tank? It doesn't take much oil to cause smoking but it has to coming from somewhere. The fact it does it after hard driving would suggest breathers, turbo or rings, what pistons are they, do you now the bore clearances, was it re-bored? It may be worth pulling the down pipe off and check for oil at the hot side of the turbo?

RICHARD J

iTrader: (4)

Thanks WMS. It was rebored, I'm not sure about the clearances but I was told the clearance would be larger than standard to run over 400BHP & high boost. The pistons are Mahle, & it does run a catch tank. I'll try & get the down pipe off & take a look, but a brand new turbo should last more than 3k shouldn't it?

Longshanks

Hi All,
Having a similar issue with mine at the minute, where it started smoking after a bit of hard driving. Pulled the intake pipewoirk off and found a bit of oil pooled infront of the turbo inlet from the breathers. Hopefully it was just this getting sucked in under boost & high revs causing the smoke... Only does it after a spirited drive, and for a short while of idling after it's been been running at high revs / boost for a while.
Got a catch can coming to see if it helps, otherwise it'll be turbo off and full leakdown test time... I'll let you know how it goes!
It's a '93 RA running an RCM engine, RCM induction and exhaust from the ports back, FMIC, 550cc's and a Simtek ECU. Hopefuly it's nothing too major, and doesn't iinvolve pulling the engine!

Also, first post here so hello everyone!

RICHARD J

iTrader: (4)

Hi Longshanks, & welcome, you aren't running an RCM turbo aswell are you?

Longshanks

Hi, no unfortunately, still running a td05 at the minute but have zero shaft play so hoping it's not the turbo...

RICHARD J

iTrader: (4)

Longshanks, I hope in your case it is just a case of not having a catch tank fitted. I already have one, so my problem is more serious. Mine only does it on lift off after high boost, I'm still waiting for my engine builder to take a look. I'm pretty gutted about it as my engine has been out 3 times in 3000 miles & the RCM 400 I bought brand new has only done 3k too. Iv had to cancel a track day as I'm sure something is about to blow up & I daren't use the car now. Im hoping it's nothing major, but my history with this car makes me think otherwise. It's only running about 440 BHP & recently it hasn't even felt close to that, but reliability has become an absolute joke, surely I shouldn't be having all these problems.

Longshanks

Ouch, that doesn't sound too good! Hope it all gets sorted soon and isn't too much grief!

WMS

iTrader: (2)

The fact that it does it when you go from high boost to 'off throttle' makes me think it's the front seal on the turbo, turbos have 2 seals on, they look like small piston rings, the one on the compressor side could be leaking and is ok when your on postive (boost) pressure but when you shut the throttle and it goes to vacum it may be pulling oil through, it should show in the inlet/intercooler though?
Mahle pistons have a shoulder where the oil ring sits and it's easy to trap the outer oil ring when they are assembled, I know ive bloody done it once.
I would get the turbo checked first.

RICHARD J

iTrader: (4)

Iv been looking at it again today & although I'm not 100% on the turbo, Iv got far bigger problems now. Compression test showed 155 to 160 psi on all cylinders, I then did a cylinder leakage test which showed about 20% on all cylinders, which I thought was OK. I got the Snap On flexi camera out & had a look in the cylinders & No3 piston is covered in oil, but more worrying than that is a section of piston next to the cylinder wall & above the top ring is missing. Iv only had the car mapped about 4 weeks ago after the engine was rebuilt again following HG failure. Not sure if the oil caused the piston failure or the piston failure caused the oil, but I'm about to start drowning my sorrows. I can't keep carrying on like this with this car it's become a topic of hilarious banter amongst friends, but I'm not very happy atall. I know one or two people running almost the same power on standard internals with no problems, but my fully forged motor likes to s##t itself evry 1000 miles, why?

WMS

iTrader: (2)

Just reading your other thread, if you have a damaged piston the fault lies with the fuel or ignition side of things, fitting a cheap short engine will just end uo with the same problem. the fact you have also had headgasket problems indicates additional heat in the cylinder. I had a similar problem with a Customer car, it was bug sti, I built and fitted a new forged short engine and during running in it started smoking, it had melted a piston. Very long story but eventually we fould a broken wire in the loom, it was from the water temp sensor. The varying signal was enough to cause the fueling to melt the piston. I would get your injectors cleaned and flow checked to start with, mark them up to see if No. 3 has an issue.
Daft question but are you always using the same fuel as you mapped it on?

diggingcontractor

i have exactly the same problem as you mate ive just had mahle pistons fitted and it smokes on let off i had no smoke issues prior to build as my engine never blew so we know stem seals and turbo are ok checked in intercooler pipe a bit mucky but they always are im having the engine out on 9th and were changing rings to mrl performance stroker rings my friend howard at hdc subaru has decided thats what it is

like i say you can put you foot down no smoke then when you let off puff and you kill the driver behind lol

i will let you know if it cures it but ive read quite a few bad reviews on mahles own rings but pistons are great

RICHARD J

iTrader: (4)

Yes always used the correct fuel. Know where you are coming from, but each failure was different. Could the excessive oil in cyl 3 have caused the piston damage? I never had any problem until I upped the power. After the first HG failure I rebuilt it myself & drove it very hard for 3 years, I only rebuilt it as a preventative measure as the piston slap had got worse & it made sense to up the power at the same time & build the engine to a higher spec. Since then it's been a total nightmare.

WMS

iTrader: (2)

Ive used Mahles in loads of engines and the only problem ive had with rings is when an oil ring got twisted as I fitted them (ive mentioned this before). It will be interesting to see if the change of rings resolves it?

The oil in the cylinder is most likely from the damaged piston, very unlikely to be the other way around.

RICHARD J

iTrader: (4)

Ok so it looks like this is an issue with fuelling or ign causing det,& nothing atall to do with the engine build. Im now certain there is an issue with the car which has caused this failure. I'm going to see my engine builder for further advice as to what can be done to fix this.

diggingcontractor

Good look mate hope you get it sorted keep us posted on your resalution

WMS

iTrader: (2)

Yes I would say so, the only reason a good quality piston will fail like that is fuel/ignition issues, when it's stripped you should be able to see whats happened. Having said that I have an engine here that was built by an 'engine builder'. They fitted a set of +0.25mm pistons into a worn std bore they went in but no clearance so cracked around the skirt, they were Cossy pistons.
Keep us informed.

RICHARD J

iTrader: (4)

Thanks WMS, I think my biggest problem now will be finding out why it happened & why my Simtec CEL did not flash to show the det which damaged the engine.

RICHARD J

iTrader: (4)

Turns out the det was a false alarm. My engine builder looked at it today & the det can't be seen now & the piston is dry. What looked like det was infect a shadow & fuel was sat on the piston looking like oil. The engine is good only showing less than 8% leakage, we think the blue smoke is from the turbo, but we have changed the breather set up to the catch tank incase this has effected it.
Very pleased the engine is good & I'll update this when we confirm about the turbo.