Boost/Injectors...was "MAF..."

[Jason_Leone at amat.com]

<<<Yeah I know about the simple boost controllers, but they can't *lower* your
boost.  Then can only raise and/or accellerate the rise in boost by
restricting the pressure from the compressor outlet from reaching the
wastegate actuator.  i.e.  If it takes 8 lbs of pressure to open the waste
gate, then your boost is limited to 8 lbs.  Bleed off some of the signal
though (say 2 lbs) and you'll be making 10 lbs boost before the wastegate
actuator gets it's 8 lbs and opens.To lower my boost, I'd need to add to the
boost signal.  i.e., add say 2 lbs to the actuator so that at 6 lbs boost, the
actuator would see 8 lbs
and open.  A spring is the only way I know of doing this without changing
to a new actuator.>>>

Dan,

Uh, maybe I'm not fully understanding your wastegate here. The whole purpose of
a boost controller is to have control of the amount of boost pressure allowed in
the system. Nothing more than a controlled bleeder, or pressure relief
controller. The reason for "Fuzzy Logic" controllers is simple. They can learn
the boost curve and capabilities/characteristics of your turbo. After that
calibration run, the controller will calculate exactly when to open the
wastegate, based on your boost setting. Let's say my Garrett T04B and Profec
controller are set to 15psi max boost (~380hp). My Racegate external wastegate
can handle it fine, and there isn't any "boost creep" at all. When I'm in WOT in
3rd gear, let's say the boost spikes up from 8psi-20psi in no time at all. Of
course, 20psi would cause some serious damage right now, but the Profec will
never let the charge air system get there. The fuzzy logic knows how fast the
boost comes on, and how much (from my initial dangerous calibration run). So,
when I hammer it in 3rd gear...the boost shoots upward so fast, that a normal
VBC would be way too slow to open the wastegate when 15psi hits. Result? Let's
say I would have overboosted to 17psi (KABOOM!). The Profec would have
recognized the rising boost rate, and would have opened the wastegate at let's
say 13psi system pressure...so...the actual boost the manifold felt was indeed
15psi. Gotta love technology!

So, a boost controller can't lower the boost coming from the compressor
housing...but it CAN lower the amount of boost the intake manifold will actually
experience. If you wanted, you could set your boost for 3psi, all day long. Your
turbo might be cranking out a whopping 25psi capability, but you're just venting
that pressure out through the wastegate.

Where does that air go? Depends on the car. A lot of factory cars plumb the
wastegate air into the exhaust system (Porsche did it on 944s), or some vent the
air into the intake plumbing. Others vent it to atmosphere (noisy). Ever hear a
GT2 911 on the track? Really terrible sounding. Wastegates farting, etc.

Another thing to consider is having an intake blow-off valve. This is a must
have for turbo reliability. It protects the compressor turbine wheel from
harmful pressure surges that occur during lift throttle conditions (like gear
shifts). Ever hear a GT1 911 "chirp" between gear shifts? That's a blow-off
valve in action. Ideal location is as close to the thottle body as possible. Do
you have one? =)

<<<Yeah, but they will flow like a 31 lb/hr injector at about 67 psi.  The stock
20 lb/hr only flow 30 lb/hr at 90 psi, thus my intention of using the rising
rate FPR and slightly larger injectors to reduce how high I have to raise the
fuel pressure.>>>

90psi?!! I don't think so! That's insane. Most EFI books will tell you how
injectors go "static", or simply put...stay open, when they reach very high
pressures. I can tell you this...I know some Bosch injectors that slam SHUT at
about 70psi! Not open, but they slam shut and stay shut after 70psi. Maybe the
Lucas disc style would fare better than the Bosch pintle style.

<<> than the injector needs, you in the clear. If the flow is below your needs
by
> 5%-40%, you can simply variably increase voltage to the pump until it's output
> is your target fuel delivery.

How would I do this?  I see Kenne Bell has something to do this.  It will
provide up to 16v I think to the pump to boost flow?  Cost a couple hundred $$
though I think.  Is there a circuit diagram you know of that'll show how to
build one?>>>

I have the installation paperwork for the Kenne Bell Boost-A-Pump, which can hop
up the voltage to the fuel pump, and is cockpit adjustable. I can fax the wiring
diagrams to anybody that wants it.

Jason
'93 SLC