2nd Generation Specific (1986-1992) 1986-1992 Discussion including performance modifications and technical support sections.
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HKS F-Con Q's

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Old 01-27-04, 12:35 PM
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HKS F-Con Q's

I really could not find what I am looking for..

Does the F-Con fix the Rich/Lean problems that all FC's have? Or do you need to get the GCC to cure that? Whats AFR is it set at? Or shall I say what are you AFRs with the mods you have? Also I assume there is really no need for a Wideband unless you are using the GCC, right?

Lastly what is the typical power gains when just adding the F-con? ( with tht mods you already have, intake, exhuast.....)

I have a SAFC II that has not be installed yet, and I accidently came across the F-con in searchI was doing andI found out that it corrects the fuel curve in both rpm and boost, which I REALLY like....because of that, is it THAT much better than a SAFC II? The only thing I am gonna miss wouldbe monitor the rpms, graphs etc...
Old 01-27-04, 12:54 PM
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The F-CON is a piggyback that plugs in between your stock harness and your stock computer. Basically, it makes the most of your stock fuel system (althought if you are planning a turbo back exhaust a high flow fuel pump like a walbro is ALWAYS recommended). It bumps up the duty cycle of the stock injectors big time while still giving you a car that runs and idles well. Witbh an F-CON and a walbro 255 pump you should be able to run a TII at 11-12psi safely on pump gas with the stock turbo. This makes for a very fun street car with nice power and good response (about 240rwhp). The F-CON should have a couple of mixture adjustments on it but this is for very fine tuning, you can get a GCC for even more flexability and the choice of larger injectors. But for an F-CON on a stock ECU you really need to run the stock turbo as it is not programmed to deal with more CFM's from a decent turbo upgrade that would necessitate more fuel and different timing. You could almost call an F-CON plug and play to safely run an open exhaust and possibly a TID with your stock injectors.
Old 01-27-04, 01:23 PM
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Originally posted by jon88se
Witbh an F-CON and a walbro 255 pump you should be able to run a TII at 11-12psi safely on pump gas with the stock turbo. This makes for a very fun street car with nice power and good response (about 240rwhp).
Wow, who did that?


-Ted
Old 01-27-04, 01:51 PM
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Originally posted by RETed
Wow, who did that?


-Ted
me, i even had a bigger turbo
Old 01-27-04, 03:26 PM
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Wow, I was looking at getting an S-AFC II as well. I guess I never gave the F-CON much thought, as it didn't look very flexible. But I've looked into it more now, and it looks like a good option for me. Does the F-CON take care of the timing as well. I read in the S-AFC section that the timing will be slightly advanced when you add more fuel with the S-AFC II, so this could cause problems, as you would have to retard the timing for high-end, but then it wouldn't be as smooth at low speeds and whatnot.

I'm guessing that boost creep will still be a problem with open exhaust correct? I'm probably going to be pulling the engine and dropping the tranny next month, so having the wastegate ported won't really be a big deal. I'm just making sure that I'll still need it.

Last edited by Tristan Bull; 01-27-04 at 03:28 PM.
Old 01-27-04, 03:29 PM
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Yeah, you can run 11-12psi a few times until you blow your **** up. the F-con doesnt make your turbo stronger.You may be able to run a larger turbo safely, but not the stock one. The f-con makes the car run rich as hell. your better off with an safc. I had a load of trouble with the fcon so i switched to the safc for fine tuning.
Old 01-27-04, 03:45 PM
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Originally posted by Tristan Bull
Wow, I was looking at getting an S-AFC II as well. I guess I never gave the F-CON much thought, as it didn't look very flexible. But I've looked into it more now, and it looks like a good option for me. Does the F-CON take care of the timing as well. I read in the S-AFC section that the timing will be slightly advanced when you add more fuel with the S-AFC II, so this could cause problems, as you would have to retard the timing for high-end, but then it wouldn't be as smooth at low speeds and whatnot.

I'm guessing that boost creep will still be a problem with open exhaust correct? I'm probably going to be pulling the engine and dropping the tranny next month, so having the wastegate ported won't really be a big deal. I'm just making sure that I'll still need it.
the fcon isnt very flexable, it doesnt affect timing at all as it goes after the ecu.
Old 01-27-04, 03:50 PM
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Hmmm... Well second opinions are always good. I'm not really looking for 11-12 psi. Probably 10 or so is what I'm shooting for. I'll probably run open turbo-back exhaust with the stock intake system. I currently am running the stock exhaust with a hollowed out precat. I have a full Greddy PE exhaust in the garage. I just haven't installed it yet, as I haven't got my fuel system sorted.

So again, it's starting to look like maybe the F-CON isn't a good idea. Ah well.
Old 01-27-04, 04:56 PM
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Well these are the mods I have:

RB Downpipe, midpipe
Feed Sonic HS-R Catback
FD Fuel Pump
Fuel Pump rewire
Ported Wastegate
Blitz Spec R Boost Controller
HKS Intake
HKS FCD

I am not looking to run boost over 10psi with the TMIC, prolly stick inbetween the 7-9psi.. So the F-Con makes the car run rich you say? Hrrmmm, Is there a way to tune/lean that out?

Does the F-con have a built in FCD?
Old 01-27-04, 10:46 PM
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The F-CON just ha a single internal pot that is numbered from 0 to 9.  This adjusts the fuel curve across the RPM band all at the same time.  Someone said that 0 = stock, and you can only adjust the fuel curve *upward* to richen not cut it down to lean - I cannot confirm if this is true.

If you want individual RPM band control *with* the F-CON, you need to get a GCC (Graphic Control Computer).

The F-CON retails around $900.
The GCC retails around $400.

The A'PEXi S-AFC II does this for under HALF the price.
The S-AFC series of fuel computers are proven on the FC's.
The offer individual RPM band control with + or - 50%.
These work very well with upgrade and staggered fuel injectors.

I have always recommended the S-AFC over the F-CON + GCC to all customers.



-Ted
Old 01-27-04, 11:38 PM
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I made 232rwhp at 11 pounds with just the walbro, no fconn or anything else....a/f's were in the mid 11's.
Old 01-28-04, 12:48 AM
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Hmm... Well I would buy it used. I usually see the F-CON going on ebay for around the same price as the S-AFC II. I never really thought the F-CON was an option until I saw this, but I think maybe I should just go with the S-AFC II after reading more opinions.
Old 01-28-04, 05:36 AM
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Originally posted by gsracer
I made 232rwhp at 11 pounds with just the walbro, no fconn or anything else....a/f's were in the mid 11's.
Your sig says you have a TID and downpipe, midpipe and N1 exhaust???
Does that mean you hit 232 without all of those things???


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Old 01-28-04, 09:37 AM
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i heard though that all the FCON does is dump in more fuel, so if your car is already running rich, then you would need an SAFC to tune down the fuel input, which the FCON cannot do, am i correct?
Old 01-28-04, 11:19 AM
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Originally posted by RETed
Your sig says you have a TID and downpipe, midpipe and N1 exhaust???
Does that mean you hit 232 without all of those things???


-Ted
of course it was with full exhuast, I don't even know if you could hit 12 pounds on a completely stock car it's so restrictive. I just thought you believed 232 at only 11 pounds was a wild claim which is why I posted
Old 01-28-04, 01:00 PM
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Hey thanks for the help RETed! I have decided to just stick with the SAFC II, just thought I might look into it a bite, because it reads both boost and rpm, but I guess it is not that great.

To bad there is no **** to set the AFR! Now that would be awesome!!
Old 01-28-04, 01:18 PM
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the SAFC II is a great piece and much improved over the last generation - however, some FCON's can be found at a pretty good buy and for those who are a bit intimidated with tuning it can be a good little unit. I have yet to decide which way to go with my conversion...SAFC's are fantastic for older cars though, many of the newer cars out these days have ECU's that learn around your AFC adjustments after a few days and re-program the car to stock ('02-present WRX, 350Z) unless you are making very very small changes (no more that 5-7% lean or rich). with older cars you can do what you like with much more flexibility. HKS's AFR is also a good piece...good luck w your car!!
Old 01-28-04, 08:40 PM
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Yes. This is why I began looking at the F-CON. It seems to be somewhat cheap on ebay for what you get, and I wouldn't have to have it tuned. However, if it's going to get me 12mpg and bog my engine down from being fed so much fuel, I think I'll pass. I'm not sure how rich it will make me run, but the possibilities aren't very inviting.
Old 01-28-04, 08:50 PM
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Thats really the only reason why I am gonna pass on getting the Fcon, I don't want the car to run any richer..




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