Blue smoke from exhaust - RS Cosworth engine

[danny tattersall]

Hi to all, I’m trying to diagnose a problem with my Mk1 Escort, fitted with a RS Cosworth turbo engine, and would appreciate any suggestions. It has not been used on the road since returning from a rolling road session in October last year, where there was no smoke whatsoever from the exhaust despite undergoing a full power run at over 7000 rpm. I did not start the engine for a couple of months after the rolling road session but since then it now emits a significant amount of blue smoke from the exhaust once fully up to temperature, in particular when the engine revs are increased and then drops back to idle speed. There is no smoke on start-up and there is not as much smoke at idle speed (although the exhaust gases do smell of smoke).

I have tried doing some fault diagnosis myself and started by checking for play in the turbo compressor shaft and oil in the air inlet pipes from the turbo through the intercooler and the inlet plenum. There was very little play in the turbo and no oil whatsoever on the inlet side of the engine so, suspecting a turbo oil seal leak, I proceeded to look at the exhaust side of the turbo. Rather than disconnecting the exhaust downpipe from the turbo I undid the oxygen / lambda sensor blank on the downpipe and once again there was no sign of oil whatsoever. The next step was to do a compression check of the engine which resulted in readings of @ 135psi across all 4 cylinders. These appear a bit on the low side but are even and are probably correct as the engine is fitted with low compression pistons to enable it to run 35 psi of boost. My final check was to run the engine with the oil filler cap off and this revealed the fact that there was no back pressure whatsoever.

The engine is a Cosworth YB200 long stud block fitted and, amongst many other things, is fitted with with accralite custom dish pistons, GT30 roller bearing turbo with TIAL external wastegate, BD16 inlet cams, BD10 exhaust cams etc, Bailey breather system. The engine runs and idles smoothly, and performed well on the rolling road, but seems to have developed the problem ever since. I am at a loss where to start looking next so any suggestions would be welcome.

Thanks in advance,

Danny.

[danny tattersall]

Hi Stevieturbo, good suggestion thanks, I've thought about the breather previously but not checked it yet because I can barely see the thing due how little room there is in the engine compartment! The breather system is an uprated Bailey item and for whatever reason I didn't think that it would be susceptible to blocking. Nothing at all was changed during the lay up and the car has only been started and warmed through periodically. It has not actually been driven on the road since. Maybe checking the breather and giving it a run will sort it out but it isn't currently insured for the road. It is possible that the high rpm run on the rolling road forced some oil through and choked up the breather. Other thoughts include valve stem oil seals, although they would have been replaced during the engine build and I would expect smoke on start up.

Regards,

Danny.

[danny tattersall]

Hi Jontysafe, I've not got the equipment to check the oil pressure to the turbo but it has an oil restrictor in the oil feed line and was fine previously. Am I correct in thinking that it the oil feed pressure is too high, or the drain isn’t working correctly, there should be signs of oil in the exhaust downpipe immediately after the turbo?

Thanks in advance,

Danny.

[danny tattersall]

I haven't looked directly at the turbine wheel but there are no signs of any oil immediately downstream of where the exhaust bolts on to the turbo. It could be that the exhaust is already so hot at that point that it is burning it off immediately?

[danny tattersall]

Thanks for all the suggestions. If the problem was related to the restrictor I would expect it to have been evident from the initial build. As for the valve seals it does seem possible, although I think they would degrade over a longer period of time rather than no smoke whatsoever to significant amounts over a period of a couple of months.



Hi Jontysafe, as far as I know the inlet manifold is from a RS 500 and the exhaust is a 4 x 4 manifold modified to fit an external wastegate within the tight engine bay (Mk1 Escort). The ECU it is a Pectel Super 8 fitted with anti-lag, nitrous and water injection control plus control of the 8 fuel injectors. It was live mapped by Tommy Field Motorsport.

Regards,

Danny.

Edited by danny tattersall on Tuesday 19th August 20:43

[danny tattersall]

Jontysafe,

I'm not 100% sure about the exhaust manifold being a 4x4 item. The engine is 550 BHP without nitrous and 620 BHP with nitrous, although it is currently disconnected as none of the insurers that I approached would insure the car with nitrous fitted. To be honest the car has far more power than is necessary in a shell that is so light and appears to be 'pub bragging rights'. The guy that paid to have the car built went over the top on the specification; for example it is fitted with 4 x Bosch 044 fuel pumps!! If you are interested in seeing a picture of the manifold I can take one and PM you?

Danny.