DIY_EFI Digest V2 #328

[Jake]

>      The whole question is silly anyways; I'm sure that if you tried hard 
>      enough you could get equal performance out of Q-Jets or Holley carbs 
>      if they are rated the same CFM and sufficient fuel were supplied.  And 
>      likewise I doubt that "all" hot rodders "couldn't" understand Q-Jets.  

I happen to think that the reason people generally prefer Holley (or
similarly designed edelbrock) carbs is because it takes LESS effort to
make them work. No one said it's IMPOSSIBLE to work a quadrajet, but why
bother with the extra effort if a holley is so much simpler?

> I'm trying to tune a custom EFI system that I've developed and I'm having
> trouble with the cold start.  By cold I mean room temp, which in my garage
> lately has been about 70-80 F.   I've tried many settings from moderately
> rich to "pig" rich and nothing at all happens until I squirt some Carb
> cleaner into the manifold.  Once I do that, the engine will hit and then may
> start (or may not).  One or two shots of Carb cleaner more and it starts and
> runs (at which point my warm up cycle takes over and seems to work OK).

It sounds to me like you might be flooding it with fuel. It's likely that
i'm wrong, but have you tried slowly bringing injection up from 100%
warm-normal curve? Carb cleaner is often the only way to start a flooded
engine, and at that temperature you shouldn't need ANY choke at all.

> Is there any way to upgrade the injector drivers in a GM computer to drive
> the low impedence injectors? I've heard the stockers will burn out driving a
> L Imp. pinjector, but they are so much cheaper than the ACCEL H Imp.
> injectors.
> Tom

speaking of which, does anyone know how I can identify the optimum voltage
of a given injector based on its impedance, and what are some common
voltages? i'm dealing strictly with production stuff, for example, bosch
LH-jetronic injectors. They are 4 VDC, right? what cars use 12V injectors,
and where can i find a good example circuit of how to trigger one?

Jake