Air/Fuel Controllers. When are they needed?

[Turbo 420a]

I have a 1996 Eclipse RS with the Star Stage 2 kit. I have ordered 310cc injectors and will keep my car at 8-9psi until I get internals in a few months. I was wondering if anybody could tell me when it is a good idea to purchase an AFC and if it will be much needed or beneficial when I am running only 8-9psi.

Also, Apex-i S-AFC or HKS AFR? I've so far heard S-AFC is simpler but works fine and the AFR is more complex but could allow better tuning. These true statements? Thanks a lot for any help.

 

[siueclipse]

honestly, most nt conversions don't run with an afc. i personally don't feel one is needed because there isn't all that much tuning you can do with our cars. you can tune the fuel, but in our situations, we want to run rich just in case

 

[Turbo 420a]

Well that's good. More money towards the other stuff then. Thanks.

 

[hybridGS]

I have a hahn turbo kit with rc440 saturated injectors. Without an afc i am full rich at 18psi, at 8 it barely runs it is chocking so bad on gas. I am installing an afc as soon as I figure out the wireing to the ecu harness.

 

[DSM-ZERO]

You won't need the AFC yet. I personly would not get the S-AFC because it will advance timing if you lean too much with it there are other ways to control your fuel like e-manage or 8inj system all these systems do is allow you to control your fuel. It just deponds on what you want and how much power you want to make.

 

[Kirby]

Hey Hybrid, what FMU are you running? The craptech or the SFMU? IF it's the SFMU you need to change the disk inside to a lower ratio and lean out your fuel curve. See if you just slap an AFC on there and lean down 50%, your timing will advance through the roof and blow that motor. The SAFC in a boosted car is meerly for FINE adjustments. You need to take care of the other things first.

 

[siueclipse]

yeah yeah what he said ^^^

 

[hybridGS]

I am running the one that came from hahn with the turbo kit and that is the one component I know nothing about.(yes the pressure is set way to high for the 440's which is half the problem) I will talk to the guys at the dyno tomorrow and see what they say. I am asuming you are refering to spark timing, I have a Msd dis2 which has controll over spark timing. I will admit that i don't know a damn about actually tuning all of this together, which is why first thing tomorrow I am heading to the dyno to have it all set up now that I have installed all of the new parts. (440s msd and s afc). Hopefully it will all work out and I won't blow the engine

 

[Kirby]

Well before you go I would get rid of your FPR from the kit and pick up an sfmu. Nobody I know uses the Hahn reg for high boost apps. (james are you still on that "stock" hahn reg) With the SAFC, DO NOT USE IT TO LEAN OUT YOUR FUEL CURVE RIGHT NOW. Before you even install it, get the car into the right neighborhood with the FPR alone. Then use the SAFC for MINOR adjustments only. I say this because nobody knows exactly how much the SAFC will advance the timing at different leaning ratios, so it could blow before you have a chance to react. The MSD can retard timing, however it DOES NOT control the timing. Your ECU still has full control of the timing, but you can retard it through the MSD. So thereticly if you knew how much the SAFC would advance the timing, then you could set the retard ahead of time to avoid the problem, however as I said that will not be an option. Secondly if you get it tuned now on the dyno, that regulator may drop your settings from the tuning, and you will be back at square one. That's why I would say to get the SFMU before you have it tuned.

 

[hybridGS]

well it is the cartech (i think) regulator. I went this morning to the dyno, we watched the timing it never went higher than 23 and that was at 18lbs at about 6000rpm. I had to set the fuel pressure down to about 20psi at idle and 50 at full boost. Even then I had to set the safc lean 25% at idle to run 12/1 ratio. I am having other problems now if you care to read this post

http://www.dsmtuners.com/forums/showthread.php?s=&threadid=59219

 

[Kirby]

Well that is more advance than you want at wide open throttle. The real problem is when your driving on the street at partial throttle but still in boost. See when you hit WOT the advance drops, and should be between 17-20 deg of advance at WOT. Now at partial throttle the ECU advances more timing to make more power and smother driving, etc. So if the ECU is advancing lets say 30 degrees at partial throttle and the SAFC makes it advance things to say 35-40 degrees then you might blow it up. Does that make sence? Basicly you need to buy an SFMU to run this stuff on a daily driver, then small adjustments on the safc. I think your cam gears might have saved your behind.

 

[hybridGS]

I was under the impression that the cartech regulator that came from hahn was a fmu (it is boost dependent( I don't know much about the manual side of fuel systems).

 

[Kirby]

It is an FMU it is just a crappy one. Also with only 440's at 18psi, you shouldn't be rich enough to need to lean 25% on the SAFC. With the SFMU though you buy a new disk to lower the rise rarte of the regulator. I don't think you can do that with the cartech. If you get an SFMU then you can put a 6:1 disk, 3:1 disk, etc. whatever you need. So if when you hit boost, you only need 3PSI of fuel per pound of boost then you use the 3:1 disk. Basicly the rise rate of the cartech is too high causing you to have to lean with the SAFC.

 

[hybridGS]

actually the cartech is fully adjustable. I am not entirely sure exactly how it works, but i know you can adjust the ratio, and there is a bleed valve that you can adjust to control the rate. Also the injectors are saturated so they have a lower resistance which I supose to in some way or another make them better than unsaturated 440's.

 

[Kirby]

Well if your going to stick with the Hahn REG then I would call them about how to tune this right then.

 

[siueclipse]

the hahn fpr sucks if you change injectors.. the fpr can't tune your fuel after that. get a vortech sfmu

 

[hybridGS]

my fuel curve was just about exact on 12:1 across the rpm range, I don't know why ya'll are so hell bent against it.

 

[DSM-ZERO]

It is just because there is a better unit out there than the hahn frp

 

[Kirby]

I don't know anything about the Hahn FPR from experience, just from what I heard. But I understand that the Hahn unit is a 12:1 rising rate, which is not adjustable. The idle and static fuel pressures are adjustable, however it's rise rate is not. It will always add fuel at a 12:1 ratio AFAIK. The vortech will add fuel at say a 6:1 ratio while still allowing you to adjust the static and idle pressure. See when you have your regulator at 25psi of fuel at idle, the FPR delivers 12 more psi of fuel for every 1 pound of boost. So at 10 psi you would have 145psi of fuel. Now take into account that on 440's that is an ass load of fuel, which is why you have to lean so much with that SAFC. Now if you lowerd your rise rate (which you can with the SFMU) to say 6:1 in the same situation (25psi idle) you would have 85 psi of fuel at 10psi of boost. That way you would be able to lean a lot less with the SAFC to get the right fuel curve, so instead of -50% you could mabye use -25%. Does this make sence?

 

[hybridGS]

actually at idle it is aprox 22psi fuel ( boost is 20 psi vac) and at 0 psi boost, fuel hits 50psi, but stays at 50 through 18psi boost. In which case i am actually running possitive correction on the afc. at high rpms. I do like the idea of a lower ratio so the fuel would be more constant, not spike and need alot of electronic correction

 

[Kirby]

Well why is it staying at 50psi when the car is in boost? The point of the device is to add fuel based on boost, so if it's not doing that then something is wrong. What did the guy's at the dyno do to it? Did they disconnect the vac line to the fpr? All I'm saying is if it is not raising the fuel pressure for each pound of boost then it is not functioning properly in the first place. I would call Hahn before you do anything else and get his opinion. Unless you know why it no longer raises pressure based on boost.

 

[hybridGS]

well it does untill it hits 50psi then it is like it doesn't go higher. The dyno guy was talking about a bleeder valve to control pressure, but i was working on something else at the moment and didn't pay much attention. Ya I should probably figure out how the thing works

 

[Kirby]

I can't stress enough how important a reliable and constant fuel system is to a turbo car. One mistake in fueling will ruin your month. I would find out what is up with that FPR or get the other one we were talking about. There is no way that regulator is supposed to top out at 50 PSI of fuel.

 

[hybridGS]

well it used to top out at 110psi when the idle pressure was 50 psi. For some reason when he turned down the idle pressure to 20psi he either turned down the top end, or it turned itself down. But i am going to try to get the instructions from hahn