I have a question, I was under the impression that you could tickle a few extra HP with the S-AFC if properly adjusted, but doesn't the ECU go to open loop under WOT, totally ignoring signals from the O2 sensor? Doesn't that mean any amount of adjustment of the AFC would be ignored?

Also- is there any way to test the injectors? My car runs like crap, stumbling for a second if you floor it at low RPM's, It has to be something in the fuel system (all new ignition system), and I'd like to test the injectors. Also If you install the bigger 550cc injectors does the ECU compensate automatically for them, or do you need the S-AFC?

 

you can check the resistance of the injectors, specs in the manual if you have it. 12 -16 ohms for 89 + cars I don't remember the pre 89 numbers right now.
If that doesn't satisfy you you can pull the fuel rail and wire the injectors to it. Then turn on the ignition, which will tell you if they're leaking. You can also check operation by getting someone else to turn it over while holding the door in the AFM open and you'll see the spray from the injectors.

 

The S-AFC alters the MAF sensor signal, not the O2 sensor signal to get more or less fuel.

 

This is true, but the way it does it is by the user of the S-AFC leaning out the mixture with the stock injectors. Not very safe.

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Also- is there any way to test the injectors? My car runs like crap, stumbling for a second if you floor it at low RPM's, It has to be something in the fuel system (all new ignition system), and I'd like to test the injectors. Also If you install the bigger 550cc injectors does the ECU compensate automatically for them, or do you need the S-AFC?

How long has it been since you changed your fuel filter? That is one of the symptoms of what you describe. Also, you might want to try to reground your ECU, and rewire your fuel pump if you haven't done so already.

The S-AFC is used to down tune larger injectors when using the stock ECU. It uses the MAF signal to adjust/correct the signal that goes to the ECU. The stock ECU will NOT adjust for anything other than stock injectors. If you have an 86-88 car, go to my website and look through our online FSM for the correct procedures on testing the injectors.

 

so i have the question of asking.. i have a 87 rx7 n/t .. to get more horse power can i just change the secondary injectors to 720cc without any modification to the ecu?

 

aehhmm....no.you would jut be running way rich and down on power.the way i understand it,the ecu has set fuelmaps,wich are used in openloop mode.it specifies a certain duration wich the injectors are open.so,if you get a bigger injector,you get a bunch more gas-runs rich!my .02

 

You will not need bigger injectors in a n/a unless you have some serious mods. The stock injectors on a n/a are capable of supporting 200+ flywheel hp, and most n/a's will never have that much hp without porting.

 

Yeah, the only reason bigger injectors are needed is if your engine is putting out a lot more power, generating a low more air flow, and requiring more fuel intake than the stock injectors can provide.