[DML] Re: Turbo PRV.

["David Teitelbaum" <jtrealty@xxxxxxxxxxx>]

I have to admit I never actually measured this. It could be that it
isn't that big a problem on a Delorean since the turbos are rather
small and would respond quickly. It is still possible though. There
are decel poppet valves on the throttle plates that allow air to pass
even with the throttle plates closed. In any case a blow-off valve
(recirc or not) could only be a further safety item especially if
something happened to the boost control or wastegate. I see no
downside to the installation of a blow-off valve except the cost. I do
not like the recirculating type, they can increase the temperature of
the incoming air charge, better to just dump it. I think the recirc is
used because it is quieter. Because of the known history of engines
damaged by overboost, installation of a blow-off valve can only be
considered insurance against damaging the pistons. BTW the scenario
you call up about running the turbos negative IS hard on the seals in
the turbos and I think is one of the causes of failure. They are not
meant to be subjected to negative pressure. A dashpot on the throttle
linkage to allow the throttle to pass a little air for a second may
also be a good idea. These are just a few of my ideas to improve on
the origional turbo install. I have yet to try them. If you were to
develop a leak on the hoses that control the boost and open the
wastegate you lose all boost control and can overboost the engine. A
blow-off valve will be the only thing that would save the motor. This
system is completely mechanical and can stick or leak. It won't take
much to cause damage. By time you hear the pinging noise it will all
be over. I believe this is why many turbo cars have a lot of positive
pressure in the crankcase. Ask Mark, he has been checking this. There
is some reason why the PRV motors are getting overboosted. They all
can't be set too high, it has to be a momentary condition.
David Teitelbaum
vin 10757


--- In dmcnews@xxxxxxxxxxxxxxx, Martin Gutkowski <martin@xxxx> wrote:
> 
> Hi David
> 
> I'm afraid you're barking up the wrong tree here. Either that, or I've 
> misunderstood how my engine works :-) What you're describing is a
safety 
> device to control overpressure. Not sure what it'd be called but I know 
> that the one on my Turbo-diesel everyday car is also controlled by
the ECU.
> 
> A








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