Blow off valve vs. By-pass valve (semantics aside)

[Jörgen Karlsson]

> Fuel consumption and environmental/cat destruction aside, what
> are the performance ramifications of the momentary rich condition?

I can say that I not all cars with an air meter responds by giving a to rich
mixtutre.

Why?

For example the 5ktq with cis don't! when you release the throttle to idle
as i upshifts the CIS bypass valve is opened... No rich mixture... or at
least not very rich as the bypass probably cannot flow enough air.

On cars with platinum wire or other heated air meters the meter is very slow
and because of this dont feel any air flow difference during a fast shift
even without a blow off. Because of this the throttle position sensor alone
decides on how much fuel should be injected. No rich mixture during shifts
with a blowoff.

Flapper door air meters are fast enough to respond to a normal shift but
idle position on the throttle often cuts fuel anyway as on the CIS
implementaion.

There are cars that do behave badly to a blowoff and need computer
modification to work with a blowoff, I know that some Nissan Skylines do...
In this case it is a lean condition right after the shift that is the
problem, the engine management overcompensates for the rich o2 reading
during the shift.


> Wouldn't it have less power than if it weren't experiencing that
> temporary rich condition?

No, the right mixture is best for power.

Jörgen