[s-cars] Re: 80tq: Opinions wanted

[JShadzi at aol.com]

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[ Picked text/plain from multipart/alternative ]
<<I'm thinking you might have an issue with your blow-off valve.  That, or an
issue with some loss of charge air at high pressure and flow.

While a "leak" is unlikely, the symptoms are very close to what I
experienced at much lower boost levels when I plumbed in my new intercooler.
I had a hose clamp too loose, and the hose slipped at high boost and leaked.
As soon as the boost came down, it "resealed" itself and the car drove fine.
I remember the black smoke and the abruptness of the power loss when the
hose slipped.>>


Interesting, hadn't considered this, but I really doubt it, all clamps are
tight, I've checked them quite a few times, but I'll double check as always.

> <<I'm leaning towards the blow off valve being compromised under high heat
> and
> high boost situations.  Once damaged, it likely lets go more easily now
> than
> the first time.>>

Hadn't considered this either, thing is when it happens I don't hear any
distince hissing or otherwise, boost pressure is pretty stable whent the
cutout occurs, it doesn't feel like a loss of pressure as much as a loss of
power, a cut out of some kind.

> <<The black smoke makes me think rich, which would be consistent with a leak
> or a blow off valve actuating (or ignition cut out).  I would expect white
> (coolant) if the head gasket is blown, or perhaps blue (oil), but I can't
> see black being generated by a head gasket issue.  (If you leaked enough
> coolant to quench combustion, to make rich, you would have other signs of
> the problem.)
>
> It might be interesting to try and rule in or out an ignition event as the
> cause of the problem.  You might consider installing a relay on the main
> wire to the coil, and controlling it with a switch in the cockpit.  Have a
> passenger interrupt the ignition while you power through 5k rpm and see if
> the visceral feel and physical evidence (black smoke) are the same as with
> the on track event.>>

Another interesting idea, thanks for the suggestions, I'll look into them.

Javad