[Diy_efi] RE: Banjo Dis. Pic

[Grant Beaty]

> Regulating either a draw through OR a blow through throttle in this manner
> would, however, create a situation where the compressor was being run at a
> higher pressure ratio than otherwise necessary at times, thus raising the
> IAT, and obviously , therefore, lowering efficiency. And, in the case of a
> blow through, pushing the compressor closer to, if not into, surge.

Wouldn't the IAC lower as the pressure dropped across the throttle plate?

Grant Beaty

----- Original Message -----
From: "Greg Hermann" <bearbvd at mindspring.com>
To: "List for general do-it-yourself EFI talk" <diy_efi at diy-efi.org>
Sent: Tuesday, January 14, 2003 9:45 AM
Subject: Re: [Diy_efi] RE: Banjo Dis. Pic


> At 7:43 PM 1/14/03, Mike wrote:
> >At 01:51 AM 13/1/2003 -0500, you wrote:
> >
> >>If your talking about controlling boost with the normal butterfly in the
TB,
> >>the turbo would create much more boost in the IC pipes than the intake
> >>manifold, creating a low-airflow high-pressure ratio situation, which
> >>usually means inefficiency or surge. Or am I missing something? Seems
like
> >>you don't want the turbo to do any more work than it has to - after all,
> >>more work requires more exhaust pressure.
> >
> >No. Because throttling the TB reduces exhaust flow which reduces
> >inlet pressure - its a wonderful feedback system in that the
> >effect you are describing is dynamic with a very short delay,
> >if it is a problem then just use a blow-off valve but I doubt
> >it reaches that stage and of course it depends a little to
> >how large the intercooler actually is. I think, we are led into
> >a somewhat false sense of security by virtue of commercial issues
> >when we have a wastegate bypassing flow around the turbine, in
> >general control systems parlance it makes les sense to do it that
> >way - but is justifiable (so far) because we don't have fly by
> >wire in general user
> >
> >rgds
> >
> >mike
> >
> You hardly would need drive by wire to control either a blow through OR a
> draw through throttle in the manner you describe.
>
> Sometime take a peek at the throttle linkage on a Holley 2300G or 4150G
> (governed medium truck carbys).
>
> The accelerator pedal controls maximum throttle position in the usual
> manner on these carbs, but there is an extra spring loaded piece built
into
> the linkage so that a centrifugal vacuum switch (located in the dizzy) can
> closoe the throttles partially to completely--without affecting the feel
or
> position of the accelerator pedal-- when maximum engine speed is reached.
> NO reason this sort of a control could NOT be actuated by boost level,
> leaving no need for drive by wire.
>
> Regulating either a draw through OR a blow through throttle in this manner
> would, however, create a situation where the compressor was being run at a
> higher pressure ratio than otherwise necessary at times, thus raising the
> IAT, and obviously , therefore, lowering efficiency. And, in the case of a
> blow through, pushing the compressor closer to, if not into, surge.
>
> Greg
>
>
>
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