I was told by a mechanic friend of mine that if you have big injectors on your setup and your alternator is on it's way out, thus not putting out sufficient voltages, it can cause the injectors to not fire properly. Or at least make the AFRs go lean, rich, lean, rich due to the ECU trying to constantly adjust. Does this theory make sense to you?

Btw, I'm aware that I'm probably not explaining the theory properly but maybe you guys can decipher what I mean, lol.

 

it will do that with stock injectors.

 

everything on the car runs on 12v power, not 13 or 14v which is what your alternator puts out, if your alternator goes bad completely, you will run off battery power until your car dies. It will not affect your air fuel ratio or your injectors. And you would know if it was bad because the battery light would stay lit on your dash. You can easily test this theory with a multimeter on your battery with the car running.

You can however have problems running if your battery is faulty to the point where it doesnt hold 12v while the car is running, i have seen this happen, and the only fix is to replace the battery with a new one.

 

If your tuner did not properly tune the battery offset it can and will affect your afr. allot of tuners will just select the provided offset in the tuning software and not fully tune the table. The bigger the injectors the more important it is to have the correct battery correction offset

 

Well that's just it he said he can't tune my idle properly because the alternator was too weak and the car wants to die on idle. Which is true cause the lights dim and everything. I'm going to change the alternator, that's not why I was asking. I'm asking cause the AFRs go leaner, richer, leaner, richer while I'm driving instead of staying in the 14.7 area (holding a constant speed obviously). Nothing else is wrong with the car so my guess is the alternator voltages are affecting this as well.

 

the guy tuning your car is retarded, you havent done anything to test the alternator to show that its bad, it wouldnt cause your car to die on idle because the car doesnt run off of the alternator, it runs off the battery.

 

I alway set the injector battery offset by unhooking the alternator till the voltage drops to 10 volts. You can make your car run much smoother. I had spikes and dips in afr with 880s till i learned to do this. My car would run perfect but if i turned the ac, light, and fan on the afr would be every where. What software you tuning with i could help you.

 

and if battery voltage was low it would cause problems. He did mention the lights going dim, but I think this is more from the rpms dropping too low.

Get out a multimeter and ready battery voltage with the car OFF. Should be around 11.7 or so. Turn on the headlights, not the car, and see how much voltage drops. It should drop some, but not a tremendous amount. This will help remove any surface charge on the battery and give you a more accurate reading. Next, fire up the car and make another voltage reading at the battery. Should be above 12 volts at this point, depending on the state of charge the battery is in. This should help you confirm or rule out the alternator as your problem. This is all things your tuner should know how to do though.

 

My alternator thru a belt, then the battery got low, followed by some really screwed up AFR's on the dyno once... I screwed up a head gasket and the head because of it.

 

Im not sure I see how that helps this thread, but ok.