Boost Controllers

["Kaklikian, Gary" <Gary.Kaklikian@Compaq.com>]

Thanks to everyone who responded to my questions on boost controllers. 

The problems I experienced after installing the Profec B on my 4000TQ were:
1.  Unable to set boost level less than 15psig in low boost mode
2. Successively higher boost levels in each gear, with 5th gear reaching the
level  set by the high boost knob
3.  Falling off boost, particularly in the higher gears.

Problem 1 was resolved by reinstalling the stock wastegate spring. Now,
maximum boost in low boost mode is 10psig,  in high boost mode 18psig.

Problem 2 seems to be a limitation due to turbo flow, intercooler pressure
drop, etc. Regardless of how high I set the high boost, 1st and 2nd gears
will not boost above 12psig (only 1psig higher than prior to installation of
Profec B). If I set high boost to 17psig, I will get 17psig in 5th gear,
about 15psig in 4th gear, and about 14 psig in 3rd gear.

Problem 3 is minimal -- boost fall off seems to be on the order of 1-2 psig
in the higher gears.

So in conclusion, I can say that I can attain higher levels of boost in the
higher gears (3rd - 5th) with the Profec B and the boost ramp-up is somewhat
improved.
With the weak ethanol-enriched gas we get here in Colorado in the winter,
the maximum high boost (5th gear) that I feel comfortable running is 15psig.
With good fuel and octane booster (or the half-half racing/pump fuel I run
on the track), 17-18psig is probably realistic.

I'm thinking the only way to get consistent, sustained levels of boost is to
increase the flow of the turbo, probably by putting in a larger compressor
wheel.
So, to anyone else out there considering a 944Turbo intercooler,  do not
even attempt to use it with a K24. Even my stock K26 has problems filling
it.

Gary Kaklikian
86 4kcstq
86 5kcstq