DIY_EFI Digest V5 #578

[Greg Hermann]

 restrict
>the air going into the s/c and then use the bypass (or a 2nd bypass) to
>give you the required air for the engine.  This way you control the amount
>of boost by varying tha amount of air the s/c can suck.  Only disadvantage
>I can think of is that the air might get quite hot if the s/c is restricted
>too much at high speeds.

Yes, it WILL get quite hot--you are effectively increasing the preessure
ratio across the comprssor. The heat in the air also means that the
bloweeer will be sucking more power via its drive belt.

The one good thing here is that you would not have to restrict (throttle)
the intake to the s/c as much as you might think--because throttling the
intake air to it reduces the density of the intake air, and the compressor
will not make as high a pressure ratio at the same speed on less dense
intake air.

It is possible that you MIGHT be able to just use a venturi in the inlet to
accomplish what you are talking about.

Maybe two smaller blowers compounded--with a venturi in the intake to the
first and a somewhat restrictive interstage intercooler would give a
flatter boost curve. Basically--the compounding would give pretty good
boost at lower engine speeds (and low air flows, where the restrictions
wouldn't matter) and as the engine speeded up, the two restrictions would
keep the boost from getting out of hand. Doing it compound would also keep
the temperature rise and power demand pretty well withing reason.

Greg


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