Smoking
Turbo Mini Forums

I,m getting well choked with my van engine as it still smokes after a second rebuild.

New Total seal rings (although I could see nothing wrong with the ones that came out ) Valves, guides and stem seals all perfect and the turbo has been rebuilt and has no radial or axial play outside tolerances.

I seem to have a vague recollection that the oil supply to the turbo is restricted in some way ?

The main suspect has to be the turbo, particularly as this engine performed fine when last used 5 years ago.

Any suggestions please ?

Try it NA to eliminate the turbo?

If something is worth doing, it's worth doing half of.

pull off the oil feed to the turbo david ,pop it in the rocker box or in a bucket ,and run the car for a little while on tickover to see if it stops smoking .

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Have you drove it yet? Sometimes they will smoke a little until they bed in

13.95 1/4 mile on a 2.95 fd. Carnt be that hard to beat!

I will try what Robert suggests and I have considered the NA test but it is a bit of a PITA to make a new exhaust to fit the NA manifold.

Yes Eden, good suggestion because on another engine some years ago I got advice on this forum from a certain MR Fenton which ran something like this "Stop fretting about it and get out there and drive it" It worked !

However this engine is smoking much worse than the other. I still have to get a hard pedal on the brakes so then I will drive it (early Sunday morning so no one can see what a poor thing it is)

I still reckon it might be the turbo and I will have to dig out my spare, strip and modify it -frankly after nearly three years I am getting mightily pissed off with the time I am spending in the workshop.

For this reason(and others) I am buying that Magnette and will sort out the logistics afterwards.

SWMBO is not greatly amused as this will be the fourth car in the drive/workshop

What oil pressure you using? Is it a GT1752? I found anything over 60psi passed oil through the seals into the compressor housing .

Edited by alaskanow0 on 4th Jul, 2014.

Class C 3rd Place Avon 2011 14.18 @101mph

That sounds as if it could be my problem then.

It is a GT1752 and it has only run in the workshop and drive, with oil pressure starting out cold at 85psi and steadying around 55 /60 when it warms up a little.

But another thought. The feed is very small diameter so the turbo is not seeing anything like those pressures surely ?

Maybe a restrictor in the oil supply will do it because I am reluctant to drop the oil pressure. My experience is that 50/60 psi in the workshop translates to about 15/20 pisi on idle when fully warmed up ( and I mean FULLY warmed up !)

your max pressure should not really effect idle pressure david , since the bypass valve should be closed .

if it helps , I run 50 psi hot max ,and that equates to around 25 psi hot idle at 900 rpm.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Yes that way too high for the GT1752. This is a known problem on the Saab forums. Turned mine down to 50psi cold & 25psi hot idle. Cruising and boost is normally between 35-45psi. Works a treat.

Edited by alaskanow0 on 4th Jul, 2014.

Class C 3rd Place Avon 2011 14.18 @101mph

shorten the overload spring a tad dave,

Had a variable relief valve on for years,set to 55psi cold,really to help with oil leaking out the midget rear seal,but sounds like it has helped with this problem a well.
You don't say David how the smoking shows up,is it on start or when revving?

'Where does the engine go?'

Steve, it starts up fine and then let it warm a little and the "haze" starts to appear - rev it and it gets a lot worse.

When I had a smoking problem a while back,which was fine on startup but got rapidly worse on warm up it turned out to be oil leaking down the parent bore of one guide.The leak only started when there was enough oil of low enough viscosity sitting in the valve spring pockets. I found the leakage by leaving thin oil sitting overnight in the pockets and checking in the ports.Peter Burgess found the root cause and fixed it by reaming the guide parent bore and fitting a new oversized OD guide.

'Where does the engine go?'

Sorry should also have said that if it's smoking at idle oil pressure is too low to overcome turbo oil seals.

'Where does the engine go?'

Oil pressure at idle when just started is around 80 psi !

Drops quite quickly as the oil starts to warm.

I remember your guide issue but I have done leak checks on the head and it is fine.

Yesterday I thought I had got the brakes fixed and went to drive it -got as far as the gate before I decided they were not right but.... having by then run the engine for longer than before and got it well up to temperature the smoke started to get less. It now only puffs smoke after idling for 30 seconds and then revved so I guess it was just rings getting settled.

Still does not explain why the old rings looked perfect and it was smoking though.

Will have to wait until I can road test to see if the problem was temporary.

Bit disappointed that I am still getting a spot of oil dripping from somewhere !

Thanks to all for advice and suggestions.