Re: Dump valves (was Max boost)

["Ken Keith" <ken.keith@specialdevices.com>]

Daniel Hussey <GY3WSX@vm.sc.edu> wrote:
> 
>      THE THING I DON'T UNDERSTAND IS why it would create any more of a rich
> condition (off full throttle) than without one!???  I really can't figure out
> why it would!  I mean, that pressure (air) is not entering the intake anyways
> since the throttle plate is closed.  So, why does it matter what happens to
> this back-pressure.  It can just run upstream and cause your turbo to stall
> and create more problems.  And, even if it runs a little rich just off
> throttle (littleraly for only a second) would it creat any problems?  I have
> thought a lot about about it, and can't see why installing a bypass valve
> would create any problems, but I don't actually have one.  Anyone out there
> with a different view or any different thoughts....I'd like to hear them.

(If this has already been discussed, I apologize.  I'm catching up on my 
emails from the weekend.)

It's my understanding that since the fuel is metered by the metering plate, and 
that is based on airflow across it, that if the air flowing across the metering 
plate is more than what makes it into the engine (since the throttle plate is 
closed, and the fuel is entering through the fuel injectors and not the 
throttle body), then you have too much fuel for the air entering the engine.

I guess if there is no blow off valve, then the pressure builds up between the 
turbo and the closed throttle valve (when shifting), which in turn slows the 
air being sucked through the metering valve, reducing the amount of fuel being 
sent to the same place.

You kind of said it yourself, the air pressure is not entering the intake since 
the throttle plate is closed.  But, the fuel is because the metering plate is 
not.

Ken