Smokey Cosworth after overrun.

[Hugh]

I've posted this on the RSOC BB but am more optomistic about getting a good answer on this board.http://www.turbosport.co.uk/images/smilies/smile.gif

I was hoping that the new turbo fitted last week was going to cure all my ailments but alas no.

I drove the car fairly sportily yesterday for about an hour down back roads (never going above 5000rpm though) and after letting the car overrun for a few seconds (whilst going down a hill, foot off the accelerator) at about 3000rpm the very next touch on the throttle unleashes a whopping puff of smoke from the rear.

Please please please can someone tell me why it is doing this as I am now rapidly falling out of love with my car again!
http://www.turbosport.co.uk/images/smilies/sad.gif

Cheers
Hugh

[sean]

I'm suer some one here will have a clue - your mail is almost a challange

[stevedohc16v]

Hi sapphy not sure of the cars spec or what you've had done but an idea would be the valve stem oil seals, cruising with your foot off the accelerator will give you a negative pressure in the cylinders which could pull oil down the valve stems which is then burnt when you accelerate again.

Just an idea to start the ball rolling.

Steve

[Clint]

Hugh this is normally associated with a worn engine BUT new engines can do the same if they havent got the correct breather setup, BUT at 330HP if you engine is the original I would suggest its a bit worn, BUT this isnt too much to worry about.
<br>
<br>The other magor cause of this along witht he breater issue is using a oil that is too thin, I recomend a 10w at the absolute mininum and pref a 15w oil.
<br>
<br>Hope this helps, If you want to call me I can try and diagnose further.

[Hugh]

Thanks chaps, I forgot to give the more detailed information!

The car has done 81k, is running a Stage 1 power engineering chip from Power Engineering and RR at 259bhp. It is all on the original components except the usual stuff like Head Gasket (WRC multilayer), Turbo (Standard Replacement). I have a friend who has a 50k engine and is running 330bhp with no breather system and his is fine without an upgraded breather system.

The smoke only appears after some quite 'high revving' overrun, and 'coughs' out when I next touch the throttle. It is considerably worse once the oil has got up to full operating temperature (30-40mins of driving).

I wondered if the breather system must be cacked as I don't think it can be the rings as blow by would surely occur whilst on-boost?

I had wondered about whether it may be the valve stem seals, is there anyway of checking this without pulling the head off?

Thanks for your number Clint http://www.turbosport.co.uk/images/smilies/smile.gif, it is now stored in my phone. I will ring after I have had a chance to do a bit of further investigation on it this weekend.

Cheers all for your help, keep it comming!
Hugh

[2quick4u]

Not sure Sapphy, but it sounds exactly like the way my 3dr was behaving, before the engine rebuild.
The valve guides were shot in that and I would guess that was causing the bulk of the problem.

[**DONOTDELETE**]

I'm really interested to see if you find the problem. I have the same snag. In order to try and find out what is wrong I have had the head off twice and did the seals first time and the guides second time. Then had the turbo rebuilt with twin oil seals at the back end. I think thicker oil cures it a bit and now use Mobil One Motorsport. Everything on the engine checks Ok and it has now done 88k so I wonder if it is a bit of piston ring bypass when the cylinders go from boost to high vacuum then boost again. Anyone else any good ideas? http://www.turbosport.co.uk/images/smilies/wall.gif

[Ferg]

There is a vent into the inlet manifold from a standard breather system, you can replace it with a grub srew available from GGR for a couple of quid. Your system could be a little blocked (the flame box and non return valve are crap) and forcing some oil into the inlet manifold. Something to investigate anyway. Just a suggestion http://www.turbosport.co.uk/images/smilies/smile.gif

[Hugh]

It was worn bores / rings. It has had a full rebuild since http://www.turbosport.co.uk/images/smilies/smile.gif

[DazC]

Sapphy,

Make sure your intercooler is clean of oil. Remove it and leaving it standing over night (or as long as possible) on one end so any oil can run out of it.

Also check all your breather system for blockages.

[Hugh]

Thanks Daz, but this post was over a year ago! http://www.turbosport.co.uk/images/smilies/smile.gif

[Andycos]

http://www.turbosport.co.uk/images/smilies/jester.gif http://www.turbosport.co.uk/images/smilies/jester.gif http://www.turbosport.co.uk/images/smilies/jester.gif

[DazC]

Nevermind then! http://www.turbosport.co.uk/images/smilies/laugh.gif

I never bothered looking at the date just posted out of habit! http://www.turbosport.co.uk/images/smilies/laugh.gif