FMU's and AFC's

[DurtySpeed]

We just got my friends 91 si running with 8 lbs. Temporarily(emphasis on this part), we are running a fmu for the fuel. It runs pig rich, but at least it can be driven while we decide what else to do. Anyways, that is the background for my question.

Now, here is what I know... I have always heard not to tune a turbo setup with a afc hack because when you add fuel with it, it advances ignition also, which is the opposite of what you want.

Now, my question... The fmu is a 12:1, it makes the car run very rich, I mean, it makes you dizzy sitting at lights, lol. So, if I use a afc hack to remove fuel, this would retard timing right? I just like this idea better because then I can street tune with a wideband without my laptop and having to remove and reinsert a chip. Someone please explain this to me. I know it is best to use something like turboedit, but for some reason, I am just drawn to the simplicity of the afc hack, that and it always shows me what its doing. I know a set tune is good, but I like to see what its doing, not that its important, I just like it....... :goodjob:


Thanks.

[scttydb411]

when you use a negative correction to remove fuel it moves you backward in your maps and in turn advances your timing=bad.

if you want to keep the afc for a gauge, then get a tuneable ecu with crome so you can tune both fuel and timing. with this then you'll be able to remove the fmu and with the right size injectors have a real tuneable system.

if you insist on keeping fmu and afc (modified hack) then it depends on how much correction you do negative as to how much you should retard your base timing at the distributor, but you still don't have anything to control the timing retard under boost. then you need to buy an msd btm and retard .5deg to .75deg per pound.

thing is, if you do this you're spending more $$ that you could do larger inj and tuneable ecu.

what size injectors do you have that it's running so rich at idle? w/ fmu you use stock inj and it should idle nomal, so it sounds like you already have larger inj already.

[DurtySpeed]

No, its stock injectors, but the fmu is a 12:1. I think the ratio is just to much. I know the fmu is benign at idle but I think it is because there ends up being a lot of raw fuel in the exhaust and it burns it out because if you sit and idle for a minute, it does go away.....

So I was backwards, removing fuel with a hack advances timing. So then adding fuel with it, would retard timing? What if I remove the fmu, get largers injectors, and use the afc to add fuel? Would that fix the timing issues? Hell, I already have a apexi unit, so... by what you say, all I need is a msd btm and the injectors(which I want no matter what tuning I use).

Thanks for trying to help explain this to me.

Also, I thought chrome was obd1? I was thinking of using turboedit if I did anything.

[DSMer]

I think a better approach would to be always taking away fuel. You want to properly size your injectors so that you don't end up with too much negative adjustments on your SAFC. How much power do you want to push? <-- start here

[DurtySpeed]

I think a better approach would to be always taking away fuel. You want to properly size your injectors so that you don't end up with too much negative adjustments on your SAFC. How much power do you want to push? <-- start here

We don't know for sure what the future will hold, but.... I just got done doing some reading on pgmfi.org, some great info. The vafc is now ruled out, lol. For now on this motor(d16y7 with 50k) we just want to run 8psi. According to what I read, the hack is only good for up to about 10 psi. That is no good for us as we want to build another motor on the side and and run 15+ in the future. I would rather go ahead and spend my money on something I can use later also. The only reason I bought the fmu is because we were undecided on what we wanted to do and we were running out of time, so I bought it used for 60 bucks and got some check valves at autozone, it is currently set on 5psi. I will leave this until we get the turboedit and get it tuned then for 8-9 psi.

Thanks for all the help everyone.

[DurtySpeed]

Lol, i just read my post and I used a weird combination of we did and then I did, lol. To verify, I built, installed, and etc. all this on my friends hatch, lol. I am the mastermind, he is the money, lol.


Now I am about to call mainstream to find out about getting some turboedit tuning done.

[DSMer]

We don't know for sure what the future will hold
Well hey its your money or your friends, whatever. The smart thing to do is find out your goal so that you can find the proper sized anything that you will need. How big are the stock injectors? <-- might be able to help you with your baseline tune.

[DurtySpeed]

Well hey its your money or your friends, whatever. The smart thing to do is find out your goal so that you can find the proper sized anything that you will need. How big are the stock injectors? <-- might be able to help you with your baseline tune.


cool, thanks for the advice man, i am just going to take it to a shop, get it tuned and do what they recommend.

[scttydb411]

crome is obd1 and turbo edit is obd0 non-vtec. if you're obd0 i would recommend an obd0-1 conversion harness=appx $110, obd1 dist=appx $100-200, obd1 socketed/chipped ecu=appx $160, and tuning=appx $280.

turbo edit is limited and crome will allow you to go further w/ the goals you stated above.

[DurtySpeed]

crome is obd1 and turbo edit is obd0 non-vtec. if you're obd0 i would recommend an obd0-1 conversion harness=appx $110, obd1 dist=appx $100-200, obd1 socketed/chipped ecu=appx $160, and tuning=appx $280.

turbo edit is limited and crome will allow you to go further w/ the goals you stated above.

Hmm...something to thing about. Me and my friend actually talked about converting to obd1 actually, as we already have a obd1 alt. that I wired for obd0 for another car a while ago. So you say tuning is appx around 280? I can get chrome and install it myself, so, I guess that is something to consider.

Thanks for your advice.