Anyone tried modifing the obd1 pcm to drive low impedance injectors??? I know their is a convertor box, which I own one, but I would like to simplify the process, by just simply modding the pcm drivers. I know the ECM for the Grand Nationals can be altered to do this, since I have had it done to mine. Thanks...
Jose
Saturated injectors can be used in Peak & Hold systems, but not the other way around. The resistance is too low and the driver (chip) can be damaged due to excess current flow and heat. Now if its a big enough injector to where the duty cycle would be off most of the time it may work ok. Of course you'll have to mod the ECM program...
Replacing the driver transistors is another option or you could limit the current flow in the power bus to the drivers.
Now the big question.. why are you wanting to do this? ;D
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The SyTy guys have been modifiying the 749 for P/H's using new drivers. The part number is a Fairchild Semiconductor HUFA76429P3. Also the ECM1 fuse needs changed to a 15 amp from a 10 amp to handle the additional current. Something I plan to do..sooner or later. cheers, Bob
80 Malibu Cpe&&5.0L/TPI/EatonM90/749ECM/T-10/9inch
cool.. I like part numbers..
but.. a question
why would you want to switch types? The ones I've seen are mechanically alike with the differences being in the coil/solenoid assembly. Is there some advantage I am unaware of?
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It appears that this Fairchild number would most likely work in the OBD1 PCMs:
ISL9N306AD3
Its rated at 30v and 50 amps more so than the replacement for the 749 ecm and in the correct package size to replace the drivers in the PCM presently. Anyone want to try it out?
just to answer my own question ;D
I found that your limited to about 32lb/hr with saturated - p&h go to about 55lb/hr
A problem I'd never run into with a n/a 2.2 lol
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Actually that mod won't work unless you change the current sample resistors. You will just be doing 6/1.44 Amp across 4 injectors.Originally Posted by SATURN5
I remember seeing an all in one IC that did the peak/hold and driver. I think it was made by Cherry Semiconductor.
I'm not even sure if that was discontinued or replaced by a new design. I can't find any info on it. I should have
saved the PDF file.
As for the reason behind switching injector types, it's not just the flow. Low impedance injectors open and close faster.
The injector of choice is quicly becomming the Siemens Deka. It's a toss up for me between them and Multec injectors.
toss me an email. ive built some pretty nice injector driver box's. im getting ready to order parts to do another batch. there opto isolated for protection to the ecm and its 8 chanel so it wil stay a squential system.
for the LS1 LT1 boxs they run about $300 interested ? itll run 8 p/h injector no problem.
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