Turbo problem?

[david hopwood]

Hi all

can anyone help with this one.There appears to be two problems with the car that have developed together and I suspect are related.Firstly,the left hand side exhaust seems to have developed that horrible rasp sound you get when the system is blowing ,you only notice it when you apply lots of throttle but the really strange part is it totally dissapears after a couple of miles warm up.The second problem is as if the car has been fitted with a blow off valve but it dosn't have one,if the roof or window is open I can hear a woosh on high throttle gear changes I have examined the exhaust and joints all appear in order as do the turbo to plenum ducting,I have the alloy wastegate capsules so I know these are holding under pressure.Performance wise things appear to be unaffected,has anyone anything similar to this or could point me to the possible cause of these problems.

cheers dave

[mike_sekinger]

Hi David,

I am struggling to see a connection between these two symtoms as they appear to be associated to both induction and exhaust sides of the engine.

Has there been any recent servicing or changes made?

Cheers,

Mike S

[david hopwood]

Hi Mike,

no nothing at all has changed the car is used everyday,I agree with you though, problems with both induction and exhaust is unlikely.the other thing I find strange is the way the exhaust sound clears after a short warm up .Would a good place to start be to measure each individual turbos boost(can this be done by using the small screw on the alloy induction ducting pipe)?.Can you suggest any other checks I could perform?

cheers dave

[Paula&Marcus]

Dave,

You cannot measure the pressure of both turbos individually, because both are working simultaneously on a shared plenum and furthermore the controlling is also done in a shared way (= one pressure line controls both turbos). BTW, this is the reason why it is necessary to adjust both wastegate-capsules VERY accurately !

IMHO the induction/whosh noise you are hearing during high load/boost gear changes seems to be normal. If you happen to use high flow air filters it will even become more prominent ...

The left side exhaust sound could be a loose or cracked heat shield or you may have a blocked cat and the exhaust is actually blowing ...

Maybe its a good idea to have the backpressure measured on both sides.

Cheers

Marcus

Hi Mike,

no nothing at all has changed the car is used everyday,I agree with you though, problems with both induction and exhaust is unlikely.the other thing I find strange is the way the exhaust sound clears after a short warm up .Would a good place to start be to measure each individual turbos boost(can this be done by using the small screw on the alloy induction ducting pipe)?.Can you suggest any other checks I could perform?

cheers dave

Edited June 2, 2008 by Paula&Marcus

[mike_sekinger]

Hi Dave,

I think that it will be impossible to accurately monitor the boost from each turbo. The boost equalises in the EGR manifold (after the throttle butterflies) so the systems are not seperate.

On the exhaust side, you may have a very small leak on the manifold, that closes-up once there is some heat in it the metal...... you might also check the EGR outlet on the LH exhaust manifold is still secure.

Are you sure that you don

[david hopwood]

Yes I do run with K&N's I washed and oiled them over the weekend as part of the induction inspection,it is quite difficult to check all of the system with everything else in the way and no car lift.The exhaust was custom made by Blueflame with silenced cans and those horrible Saab couplings engineered out so I can rule out a good 75%being to blame.Please,please don't tell me the exhaust manifolds on stock engined V8's go the same way as the 4 pot ones and crack ,as I presume this would be an engine out job.

cheers dave

[mike_sekinger]

No, the exhaust manifold itself is fine - I

[david hopwood]

Hi Mike,

had a good look round the exhaust /manifold last night with a mirror and torch, first thing I noticed is the end stud on the left hand manifold(one next to the egr blanking plate is sheared off?)The egr plate itself is quite corroded, I feel tempted to replace it but feel any attempt to remove the two m6 bolts would result in the heads shearing off,all of the exhaust components appear to be free of any sooty telltale marks indicating blowing.One thing I did find strange is Blueflame have used silicone sealant to joint the pipework together,I would have thought the heat generated by the exhaust system would far exceed the operating range of silicone?you can see some of the cured silicone hanging out of the silencer box flange joints,i'll seperate these joints tonight clean and re-seal,do you think it would be better to use a proper exhaust jointing compound?

cheers dave

[mike_sekinger]

Hi Dave,

If the blanking plate is secure, then I would leave it be. The plate itself is pretty thick and although it may look a bit tatty, if it is tight it is probably sealing well - especially if you can

[Günter]

the advice "never touch the EGR blanking" is good, as i had one with an rusted fixing and one bolt sheared of as i unscrewed it... . really bad work if you have to drill the rusty bits out of the manifold. And Mike, yes they do crack! Mine are cracked with visible black carbon powder marks, and as i oiled my manifolds with 'derust-oil' to dismantle my turbo system i have seen the oil that goes inside the manifolds.

It's simply an fault construction to fit the hot turbos (as additional weight) onto the manifold together with the hot/cold temperature changes in the rear wheel area (especially on wet roads..)

[mike_sekinger]

[quote name='G

[david hopwood]

Gunter,

could the cracks to your manifolds be seen with the engine in place?

[Günter]

Yes! with my head in the wheelarch i can see the cracks. One major crack is near to the Turbo connection, an some of them are between the separate cylinder outlets.

[jeff_hooper]

What sort of money are we talking about with the Zircotec work please Mike?

[mike_sekinger]

Beware - it is not cheap......

For the Esprit V8 manifolds, I was quoted 360GBP for the pair. That will give you the manifolds is the natural white/cream finish. Apparently, that tends to yellow over time, so they also offer additional surface finished (either matt black or matt silver). These equate to a 15% charge on top.

I

Edited June 4, 2008 by mike_sekinger

[Günter]

"..aka vibration machine.." Yes! i know i know- as long as it rattles the engine is still in the car..

So back to the manifould/turbo conection face problem. The gabs get longer , year by year!

It might be there also on RH-side, but access was easier on LH so i show you all this:

*edit* what the f**** , those resizing in board legal dimensions does not work in two of them ?! Moderator - i need help!!

Edited June 3, 2008 by G