Question about Howell conversion.

Bruce Plecan nacelp at bright.net
Sun Apr 4 22:12:26 GMT 1999


----- Original Message -----
From: esc <esc at firstnethou.com>
To: <diy_efi at esl.eng.ohio-state.edu>
Sent: Sunday, April 04, 1999 4:19 PM
Subject: Re: Question about Howell conversion.


> >If your talking about wanting to run a 4 barrel TBI, the only gm ecm I
know
> >of to do that properly is the 1227749 wired as used in a 87 Sunbird
Turbo.
> >  In some testing that I did, I was unhappy with the results of firing
> >injectors wired, in series parrarel.
> >  If you want to run a 4 barrel TBI, my suggestion is to run, a TBI ecm
and
> >then make an injector driver board external to the ecm, to actually fire
the
> >injectors.
> Sounds like a can of worms I'de rather not open.
> >  From what I've heard all the 4 barrels use the same butterflies, but
> >different injector sizes from rating to rating.   So the idea of selling
> >them by CFM is silly, when they all flow about the same CFM, and the
actual
> >difference is gals/hour....
> Mine is the 900CFM..uh, 4 85 lb/hour injectors.  Holley claims it is good
> for 500 HP at 15 PSI.

4x85=340gal/hr     @.5 BMFC = 680 HPx .8  544, min duty cycle...
Trouble would be leaning idle out enough, unless your really making that
much HP..

One other thing I have done was run a 730 memcal+calibration in a 749, to
run a two barrel TBI.  You lose the TCC, and since your's don't sound like a
emission application the lose of the carcoal canister yada yada don't sound
like an issue.
I ran out of time/volunteer on finishing it but, it did seem to be workable.
   While more involved, there is the option of setting your manifold up for
TPI injectors, and use your TBI throttle body with that.  Then, you have all
kinds of ecm options.  Extending from like using a TBI ecm to run TPI to TPI
running TPI.
Then you could use the 808 calibrations in a 1227165 for a very "low" code
ecm.
>
> >  Next item, 4 ninety gal/hr injectors would support about 700 HP.
> >  I run 13s in a 3000#/350 CID car, with 2 two inch butterflies, if you
> >really need that much air (4-2" butterflies), I'd look further than a
TBI...
>
> I want to use my TBI because I put a lot of effort into the ram-air system
> on the car.  If I go with a port injection system (most anyway) I would
> have to scrap my ram-air, and maybe my hood.
>
> >  If your needing that much air, then you have a bunch of cam, and might
do
> >well using a 747 where you can go open loop at idle.
>
> I do have a lot of cam 255 at 0.50 and 0.600 lift.  Would I need the
> external driver board you mentioned earlier to use the 747?

Yep, the 749, is the only ecm to support what ya got, that I know of.
Cheers
Bruce
>
> Eric
> esc at firstnethou.com
> If it breaks, make it stronger.
> If it doesn't, try harder.
> '68 Big Block Bird
> '69 Spitfire
> '82(sort of) Camaro
>




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