RE return to fuel tank

[Greg Hermann]

>Hey Greg
>
>What about wastegate control.  This one is all over the map, like 18 psi +/-
>1 psi, which also effects the fuel press.  I think the bigger the diaphragm
>, the better.  Those elec boost controllers are way too expensive.  Are the
>effective?
>
>TurboDave
>
Two things--

First, using a duty cycle controlled solenoid valve to put a controlled
pressure, rather than just atmospheric on the back side of the diaphram in
the controller is both reasonable in cost and will give the computer some
direct control over boost--things like higher gauge pressure boost at
higher altitude, and lower boost in lower gears, so you don't break as much
stuff.

Second, re-read what I said last night about too big a control valve not
being able to do a decent job of controlling something.

Too small a valve WILL cause boost creep at high revs, regardless of how
you control it, so care is adviseable. But a barely big enough valve with a
larger bypass pipe, or even a (big, but) separate exhaust pipe altogether
for the bypass will do the job far better than a big valve. Restriction at
the valve is VERYnecessary for stable boost control. Restriction downstream
of the open valve is the much more likely culprit in causing boost creep
than valve size--but increasing the bypass pipe size ain't what sells the
bigger, more expensive valves!

Regards, Greg