In a message dated 96-02-27 07:36:50 EST, you write:
>>>(understatement)..... There are other more sensible ways to reduce turbo
>>>lag....... S4 turbos do it, so do some modified stock turbos, or RS2's,
>>What's the operating principle behind these systems?
>S4s do it with a 'turbo bypass valve' which is, I think, sort of a misnomer,
>as the turbo is not bypassed, it's the closed throttle-plate that is
>'bypassed'. I guess it depends on how you look at the system, semantics,
>etc. Basically, when the throttle slams shut, like between shifts, the
>'bypass valve' opens and allows the output of the turbo's compressor to feed
>back into the compressor inlet -- rather that pushing against the closed
>throttle-plate. This helps to reduce high pressure spikes and also helps to
>keep the turbo spinning for near-instant boost when the throttle-plate is
>reopened after the shift or upon exiting a corner, etc. The valve is a very
>simple vacuum-operated unit, newer Saab use 'em, etc, etc. I plan to add one
>to the KUQEFH when it gets done....sometime soon.....I hope.....
>I don't see how a CPU mod could help keep the turbo spinning.... Scott?
Coupla ways: 1)ignition advance .... 2)look hard at how a WG freq valve
works (vendors here.Stop)
Regarding the Pressure feed to the intake side of the turbo..... How much of
that air actually spins the turbo is prolly insig, what you are allowing the
turbo to do is to free spin as apposed to pressure braking the pressure
side.... When that bypass valve opens the turbo is spinning full tilt,
hardly think that pressured air will have any efffect on the turbo itself,
and in fact prolly creates more turbulence than spin..... Disconnect the
intake side of the bypass valve to atmosphere (Like the ProRally guys) and
you will understand my point, it's a freewheeling concept not a pressure
spin. However, there is a reason, esp on mass air cars, why you want that a
closed loop system. Measured air is before that valve, so to dump it to
atmosphere, you have mixed up the computers estimate of air in the system,
not a good thing, race guys could care less, most run a full rich system
anyhow, with no lambda..... With CIS, since the air is "metered" not Mass,
it's not AS critical, but you can get a rich spike at the motor.