30# injectors.... not quite what I expected (Mark D please advise)

[MarkD]

Ok so BJL4776 said he has 30# injectors on his M50 and it idled fine. I installed mine tonight and it was surging horribly. I unplugged the battery to let it reset the ECU and then I started it back up, it was a flatter idle. I took it up the street at <2,000 rpm drove it around for a few mins and then the idle was healthier if not perfect. However, if I went over like 3/4 throttle it would misfire and sputter. I think (obviously) it's because too much fuel is entering the combustion chamber. Now, since this is going to be for a supercharged application, I can alleviate that once my mechanic at Bimmers Only calls and says my damned pulley is done and I can install my s/c. Anyway, this was just to test the injectors since no one local wanted to flow-test them cheaply for me. So, yeah all 6 injectors work and work correctly... but unfortunately it looks like they either may not work out for me, or I will need custom software. I am hoping I do not need the software, and simply adding the additional air from the supercharger will help bring things back into range. I didn't even get to install the rising rate fuel pressure regulator, as it is 30# was too much fuel for NA, so no sense in that. So what do you think? Mark, if you're reading this, is there anything you can offer me? So far I've looked into piggyback ecu's b ut that only alters timing, not injector flow. Apexi S-AFC does the same by messing with O2 signal. Standalone is not an option, as I do not have $3,000 for an ecu. What should I do? I am going to run 6.5 psi. Should I just use stock 17# injectors and use the rising rate fuel pressure regulator to force more fuel out of the injectors? Or should I try the 30# again once I have the blower on? HELP.

As you guessed, the 30# injectors are making the motor run too rich @ WOT. They have 76% more flow than stock, so if your fuel pump is able to maintain the right pressure/volume, you would be richening the air/fuel ratio down to around 9.6:1 !

Don't use an AFPR, it's better to correct this all in the chip.
I don't recommend piggyback units either, but I'm sure many people have had success with them.

Ideally, this needs to be tuned on the dyno once you have the system completely installed. I can do that here in Toronto but you are probably far away. If you would like me to make a test chip for those injectors and your supercharger setup, please send me an email. It won't be ideal but should get you going till you log the air/fuel ratio with a wideband.


Mark

[Jon K]

As you guessed, the 30# injectors are making the motor run too rich @ WOT. They have 76% more flow than stock, so if your fuel pump is able to maintain the right pressure/volume, you would be richening the air/fuel ratio down to around 9.6:1 !

Don't use an AFPR, it's better to correct this all in the chip.
I don't recommend piggyback units either, but I'm sure many people have had success with them.

Ideally, this needs to be tuned on the dyno once you have the system completely installed. I can do that here in Toronto but you are probably far away. If you would like me to make a test chip for those injectors and your supercharger setup, please send me an email. It won't be ideal but should get you going till you log the air/fuel ratio with a wideband.


Mark

I will be writing you an e-mail soon mark.

[emw525E34]

Jon,

Does seem that those 30# injectors are way too big for your application. I would suspect 21 # would be a better fit. Even if you run 6.5 psi on SC, your fuel pressure might need to go about 50 psi as opposed to stock 43 psi. An adjustable FPR will do the trick.

Good luck.