I'm currently installing a set of 36lb injectors in my SC'd LT1. I have LT1 edit and have reprogrammed the injector size. Can the PCM now accomodate the fuel if I remove the FMU, or does it require more programming? I'll get it dyno tuned eventually, but I was wondering if this would fix it up enough until then.

 

That should do it I would recommend running a scanning device for a while just to make sure.

 

You should be fine, as long as you are running less than 8 psi of boost. Quite a lot depends on your altitude, the higher up you are the less likely you are to max out your MAF. That said, from what information you gave about your car, you are not likely to max out the MAF.

All in all the computer in these cars is very adaptable. You should of course get your car on a wide band dyno so you can do a little fine tuning. End of the day I think you are looking for a 12:1 air/fuel ratio.

Hope this helps

LWM

 

The injectors are installed and I ran it with the FMU still on, everything seems to run good. I'm at 7000' and the drag strip is at 5300', so altitude isn't a problem, and the cars runs with 6lbs of boost (Vortech SC w/ aftercooler). I think I've only triggered the MAF out of range code once or twice the whole time I've had it, and it's been a long while since it has. I may remove it tomorrow and see how it runs. And also call the dyno shop and try to weasel my way in. I've called three times, left messages and had no reply.

Thanks for the info.

 

This is the same thing I am doing. However, I feel safer by waiting until I can get it on the dyno before I put in the injectors and yank the fmu. I am not sure that the stock tuning fuel curve is sufficient for the supercharger's requirements.

Also, if you are still using the fmu, you should be running very rich at wot.

 

I removed the FMU and took the car out for a test drive. The A/F gauge in the car read stoich to rich under boost, but I don't know how accurate the gauge is. I can hook up my code reader, it will tell me the voltages from the oxygen sensors, but I don't know what voltages are safe. Anybody know?

 

I "think" you can use the voltages if you had them referenced to a wide band reading but if you don't, you are probably just guessing. Like if you had it on a wide band and saw the wide band reading "x"=O2 voltage "y", you could use the voltage later without the wide band to determine a/f.

I am sorry if that is not understandable. I tried

 

I was wondering this also. I am getting a 10 PSI Vortec on my 383. it has 8.5:1 Compression and I am running a warblo 255LPH intank FP and 50# injectors. do I need a FMU?

Thanks
Matt

 

The only time you "need" an fmu is if your injectors can't supply the fuel under the operating psi of the pump.

I don't know if the 255 can keep up with your combo, or if the injectors can. I don't know the formulas off the top of my head.