Hi all,

Finally summoned up the balls to compression test my grey ST205 today. The symptoms are occasionally a big grey smoke screen from the exhaust, usually when the car is warm, worse when having been boosting fairly hard and then come back to low revs or near idle. Never smokey on start, but sometimes a little smoke when pulling away from a cold start. The only thing to add is, somewhat strangely, it seems to do it more when going round a left-hand corner? Generally otherwise the engine seems in decent health, it doesn't breathe overly heavily, good power, no smoke from dipstick or oil filler. It's consuming a fair amount of oil but not surprisingly when you see the smoke-screen. The engine is, as far as I can tell, original and is at 90k, but first ~60k in km. Oil is 10W50 fully synth, though I have been topping back up with a generic 10W40 semi as it was all I had.

So the test - on a cold engine, throttle open, EFI fuse pulled

Pot 1 - 170psi
Pot 2 - 165psi
Pot 3 - 155psi
Pot 4 - 170psi

So allowing for some variances in the sealing of the gauge and it being new, number 3 is a maybe 10 PSI down on the other three. However I'd expect this to be down to the usual 50-60psi that seems typical when the ringlands start to go? All the plugs show a nice even burn (light brown colour). The turbo is a very low mileage S148 and the exhaust system is a full 3" downpipe and all the way back. Maybe with the lack of back-pressure the turbo exhaust-side seal is letting some oil past? I was trying to work out if the left-hand bend symptom backs this up, ie. it pools near the turbine and then drops into the exhaust with a bit of G loading?

Informed opinions more than welcome.

Cheers,
Jon

Your compression results don't seem to indicate any ringland problems but maybe low enough to pressurise the crankcase more than normal.

Have you checked to see if there is any oil in the compressor inlet? The 3S-GTE does 'breathe' quite heavily and you often find the large breather on the right hand side of the cam cover (looking at the front of the car) does allow oil mist to pass into the intake hose and the compressor.

Your symptoms don't sound like worn valve guides as that would normally be displayed as exhaust oil smoke when you first start the engine. This should burn off quite quickly and the engine should stop smoking.

If the S148 is low mileage then you shouldn't have any problems with the oil seals even with reduced back-pressure from a 3" downpipe. Worn turbo seals normally result in exhaust smoke when the engine is left to idle.

I run my 130k engine on Shell Helix semi-synthetic as fully synthetic is not going to help on a worn high mileage engine.

_________________
Don
GT4DC Chairman
1994 Toyota Celica GT-Four ST205WRC JDM 269bhp @ 0.9bar
1994 Toyota Celica GT-Four Special GT 590bhp @ 1.8bar
1989 Van Diemen RF88/89 Formula Ford 1600
2008 Nissan Patrol GU 3.0L ZD30DDTi 154bhp

If the car has stood for a long time, it may be a bit of rust on a valve seat or bore, could be a ring a bit gummed up etc.
The results don't indicate a 'failure' at this stage, but keep a check on compressions every so often, and don't try winding the boost up to 'pushing your luck' levels.

May be worth checking crank endfloat if you notice something different going round a corner. One of the classics is chuck it round a right hand bend then declutch and see if the bite point is lower letting it back up.

_________________
If at first you don't suck seed, try drier grain.

Thanks both - yes the car does show signs of having been laid up for long periods, both in Japan and in the UK. Are there any none-'snake oil' fuel treatments that are recommended or just keep running V-power through it?

I'm only running a bar of boost, plenty quick enough on the S148.

Don, can I as what weight of semi-synth you put in yours? I may try a higher quality, but heavier, semi synth on the next change, and see if it helps.

Jon, I use Shell Helix HX7 10W-40

You might find the following link interesting:
http://lubematch.shell.co.uk/gb/en_GB/e ... _EFt8Pe0S8

Everybody has their own preference regarding what oil they use in their GT-Four. I've been using Shell V-Power/Optimax fuel and Helix 10W-40 in my standard road-going Four for over ten years with no problems. If you are running a tuned engine then that's a completely different kettle of fish!

_________________
Don
GT4DC Chairman
1994 Toyota Celica GT-Four ST205WRC JDM 269bhp @ 0.9bar
1994 Toyota Celica GT-Four Special GT 590bhp @ 1.8bar
1989 Van Diemen RF88/89 Formula Ford 1600
2008 Nissan Patrol GU 3.0L ZD30DDTi 154bhp