[Diy_efi] Accel GEN 6 and blowe

[Dave Dahlgren]

If the Gen 6 has a 'primer' function you will need lots of it with that setup..
You can not start a roots blower type engine with no port injectors lean. It
takes a lot of fuel to wet the system down before any amount of fuel reaches the
engine. Even worse you now have this big blower full of fuel try to NOT back
fire the engine. Better to be too rich than too lean or 'just right'.. Lacking
the primer add what might seem like an inordinate amount of cranking fuel in
whatever way you can. Then back off slightly from there. It is never going to
start cold on the first couple of cranks as the fuel path is very long. A simple
way to prime the blower is to have a separate switch for the ignition system and
shut off the spark for about 5 or 6 turns on a cold engine. Flip the ignition on
while still cranking.. 

As a side note I worked on a couple of these. They have exhibited some major tip
in problems that could only be solved with very large amount of accel fuel and
some driveabilty problems, because of the way the injectors are both positioned
and plumbed. One good fix for the driveability was to blank off one of the 3 bug
catcher butterflies. This helped tip in a lot and made it possible to somewhat
modulate the throttle rather than have a 'toggle switch' from idle to full on. 

On another note. Not for nothing but 1000 hp out a supercharged 557 is not that
much.. I have done a N/A 557 and had 750 hp @ 6200 and 750 ft lbs @ 4500 had 600
ft lbs @ 2500 as well with 10/1 compression and pump gas.. Dart CNC ported heads
and Dart 4500 series intake modified for efi with a Kinsler TBody, progressive
and very driveable. The 1071 blower while 'big' and impressive is probably too
big for a street engine. If you have to run the blower at less that 1 to 1 there
will always be issues. Most times you are better served with a smaller blower
running faster as far as response and driving go. It makes the fuel path
essentially shorter as the rotors are turning faster so what goes in on top gets
to the engine sooner. Yes there is more intake air heat but I suppose you have
to know that going in as a roots is generally only 50% efficient to begin with.

Dave

Phil wrote:
> 
> Noel-
> 
> By the looks of the power level you have achieved, it seems as if you
> already have the combination dialed in, yes? What are the issues with the
> engine when cold or at startup?
> 
> If I recall correctly, you should have the 25lb./hr. Ford injectors that
> came with the kit, yes?
> 
> -Phil
>


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