Fuel tuning question. How much does .1 ms equal as afr?

[powellds2]

So I'm in the process of tuning my Portfueler. I have Accel 410cc injectors. I was wondering, does anyone know what pulling .1 millisecond will reflect as far as the afr leaning out? Basically, how much fuel can I pull to reflect -.1 afr? I just want to get an idea of what to expect. Right now I'm pretty solid 10.2-10.3 afr all the way through the rpm range. I'm wanting to get 11.5ish across the rpm range. Tia

 

[1996Eclipse420a]

I've never used Portfueler.... I'm working on my build now, but I'm going with a SAFC to start out with, just as it seems to be better than a FMU 12:1 to me. People say they don't work for our cars, but I've seen plenty of people use them, and have a good tune. Specifically 250whp on a stock motor, tuned with SAFC.

As for portfueler, I'd find DSM-ZERO or whatever, and ask him. I'm not quite sure if he uses PF of MS, but I'm sure he could explain it a little bit better.

 

[92 GSR-4]

MS isn't really something that you can give a universal answer for. For instance, XXms on 450cc injectors is a lot different than the same ms on 1450's. So you see that ms is relative to the injector size you are running. The best thing to do in order to lean out your AFR is to gradually pull fuel a few % at the time, doing pulls in between, and record your progress. You'll get the feel for YOUR setup and know about how much of a change in AFR you will see at a given adjustment.

1996Eclipse420A, an AFC is fine, but it works off the airflow signal (either increasing or decreasing it) to make the ECU think there is more or less air coming into the engine, thus increasing or decreasing the amount of fuel it injects. The problem with it is, when using larger injectors, the correction needed throws your "adjusted" airflow WAY off from what actual airflow is and the ECU will be using timing values for a lower airflow value than what is needed. For instance, if you use 1000cc injectors on a stock turbo DSM, you'll be around -50% correction value on the AFC, which means the airflow signal will be reduced by half. So you can see how it throws everything off and can cause problems. For a minor change in the AFC (-20% or so) you won't really have issues.

 

[glowryder]

This is simple.. Every motor is differnt, and since your running on a static pressure, your ms may npt be my ms at the same fuel pressure.. Just remove some fuel from the table.. untill you get where you want.. there wont be a perfect tune using that system b.c your boost fuel wont change for temp etc.. so your going to have condtions where its leaner, thus aiming for the 11.5's is good. Just sayve your tune, then start subtracting very little at atime cross the brd and see how it reacts..GL!

Its not that SAFC doesnt work, it does, its just "tricking" the ecu.. It not "real" tuning.. thats what our complint is about it..

 

[bastarddsm]

You could calculate it out, I won't walk you thru it tho. You'd be best off working in precentages.. So like at 6000rpm and 20psi I am 10.5:1 and it is like 26ms pw. I wanna be 11.5:1 so 10.5/11.5 = 91% So 91% of 26ms is 23.7, I'd be conservative and goto like 24.5ms.

You could actually put your logs in an excel spread sheet, and have it calculate it all for you. I wouldn't get too carried away at getting it perfectly exact, once the afr's are in a decent range, dialing them in perfect is only worth a few hp.