Re: [DML] Re: Turbo PRV.

[Martin Gutkowski <martin@xxxxxxxxxxxxxx>]

David Teitelbaum wrote:

>
>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. 
>
I haven't looked lately but I thought these were safety valves that 
operated in the opposite direction to allow the engine to backfire 
without destroying the throttles. On the Renault engines, where the 
brass bypass screws are used, the throttles don't have these valves.

>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. 
>
Er, no, because they only do anything when the throttles are closed and 
there's a vacuum in the intake manifold. On the Island and BAE kits, the 
whole turbo is in a vacuum so a dump valve will do precisely nothing 
except maybe give a big vacuum leak.

> 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. 
>
Possibly, but on any air-mass metered engine they are a must otherwise 
when you throttle back and the dump valve goes, it'll meter a load of 
air that's not actually going into the engine - consequence, soak the 
bores in fuel. On the legend engine, where the (effective) air mass 
meter is downstream of the turbo, the dump valve would have to be before 
the sensor plate, for exactly this reason. The ideal place for the 
turbos to be on the stock DeLorean engine would be between the sensor 
plate and the throttles. but this is hardly practical!

Martin





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