[DML] Re: roundabout question

["BRUCE BENSON" <delornut@xxxx>]

> Turbo cars are that way in general. The trouble is that the engine, as it
> slows down with the throttle closed, can no longer accept all the air
>that the turbo is blowing. Then pressure builds up and the turbo,
>fighting against it, slows down.
> This is why blow-off valves exist; when the throttle is released the valve
> opens and allows the turbo to blow into the atmosphere. That way no
> pressure builds up and the turbos spin freely. Unfortunately the
> currently available Island turbo kit (which is the only one I know about)
> does not have a blow off valve, to the best of my knowledge.

This statement isn't quite right and needs to be clarified. Actually a blow
off valve is something used in the CART racing series cars. It limits turbo
boost to the CART rules by opening, or blowing off, when a CART driver dials
his boost higher than allowed by the CART rules. When that happens he must
return to the pits to have the blow off valve reset. Our DeLorean turbos
have what's called wastegates. These divert the exhaust gases that drive the
turbo around the impellers when the pre-determined level of boost is
reached. They use spring loaded or linkage activated valves that open at
pre-determined boost levels. The single turbos use a remote wastegate
installed down stream of the turbo and the twins, Islands offering, have
interrogated wastegate, built in to the turbos, to accomplish this. When the
exhaust spins the turbo's impeller to the speed that produces the desired
boost level, the excess exhaust is diverted around the impellers to maintain
the level of boost that the system was designed to produce. None of this
process involves anything that happens when the throttle is closed. Driving
with a turbo requires some practice whereby the driver learns what it takes
to get into the boost area and staying there during the up shift process.

Bruce Benson