94 trans am..previous owner replaced the injectors while troubleshooting a no start condition. Replaced the factory 24lb units with Accell 26lb units. I know Accell has a bad rep around here for injectors, regardless of that would I need to have the PCM reprogrammed for this slight change in size? Will the car now run slightly rich or can the PCM handle that change?

 

Go to tunercat.com and download the flash program. If you have a cable like the one from akmcables and a computer/laptop hook it into your OBDI ALDL conector under the dash and "read" the pcm. Once your done shoot me the file over email. israelsummers at msn dot com. I'll take the 1 minute it takes to change the injector constants and shoot it back to you with the updated file. If you do not have the cable or computer/laptop you'l have to send it off to someone who will program the pcm.

 

The yellow accels were bad and even when working caused a slow start condition. The newer ones are fine.

Did you look into the pressure the Accels are rated at? It affects how much they flow in each application.

 

For those INJ the actual flow rating at 43.5 psi is 25.6. That would be the new constant inputed into the constants table for his set up. On a side note yeah I've heard of folks having issues with the accells. Never used them personally. I stick with the Racetronix/Delphi stuff. They are pretty good and even though they don't take care of you when you are sent a faulty injector(have you buy another one while they "test" your old one to see if you actually have a faulty injector instead of replacing it right off the bat. Still haven't gotten the final verdict on that one.) they at least have customer support that stays in contact with you and most of their stuff is realy good for the price. I actually recommend them.

 

You should be OK without reprogramming.

 

Just checked the stock setting for my 95 TA, and the injector flow rate is set at 24.91.

 

The stock programming is 24.9 #/HR, so if the Accels are 25.6 #/HR the difference is negligible, only a 2.8% increase in flow. That's probably less the the tolerance you would epxerience in a set of 8 injectors.

But remember... if they actually do flow 2.8% more than the stock injectors, the PCM will easilly adjust in closed loop, by using the long term fuel corrections (BLM's) to cut the excess fuel. However, when you go WOT, since the PCM was cutting fuel, it will lock the BLM's at 128, and you will be running 2.8% richer than with the stock injectors.

Since the stock tune is already too rich at WOT with the 24.9 rated injectors, its only going to run richer with larger injectors. Whether that 2.8% increase in flow will have a negative affect on performance is a toss up. The typical stock target A/F ratio in PE mode is 11.7:1. With the larger injectors it now produces an 11.4:1 A/F ratio.

 

Thanks for the info guys..reason I ask is because I have gotten the engine running, swapped out the opti with a new GM unit to get it going. Idle seemed a bit choppy and the Block learns (believe that is what it was on the scanner) were both at 128. Could be an aftermarket cam, not sure, throttle response seemed ok.
FWIW I am still not sure why the opti fixed the car, the old "new" opti always had spark but not always ignition, and I thought that if the module was dead I would have neither. Wish there was a way to bench test these things.