it seems like the answer to the 'fool the afc' trick, adjusting the injector pulse width based on a boost signal. just wondering if anybody tried it yet. it also lets you lean out the mixture in the idle range. looks like it's worth a shot. MSRP $399. i'm sure it's cheaper than that somewhere.

Is this similiar to an ApexI Super AFC? If so, what would be the inherent benefit of using it as opposed to the ApexI unit? I haven't seen anyone using one of the HKS units.

DoN

More tuning points, seperate idle control and A/F correction function. Thats about it. Doesn't have the telemetry and I dont think high/low tuning of the AFC. overboost.com and optauto.com sell it for $320


Stan2gnt
Stan2va@aol.com
95 Talon 420A-Turbo
Former and future nitrous user

what telemetry does the s-afc display that you couldn't live without? sure it looks cool, but anybody that's using it to tune their turbo'd car is going to have a boost gauge and a/f gauge anyway.

the main difference between the two is that the apexi uses throttle position and rpm to determine whether to richen or lean the mixture. the hks uses manifold pressure and rpm (maybe throttle position too, i'm not sure). boost pressure is the whole reason for needing to adjust a/f ratios to start with. boost pressure seems like a more important factor than throttle position anyway when it comes to determining fuel needs. i think the s-afr has the advantage there.

LAST EDITED ON 07-Jun-01 AT 12:03 PM (PST)

I think that the S-AFC can use manifold pressure as a reference as well for tuning. (I may be wrong) But I'm inferring this from the recent developments of Corbin's "Fool the AFC" work. With that, he has developed a Map sensor that READS BOOST. You hook that device to your vacuum lines and it will send a corresponding signal to your S-AFC which will in turn use it to better tune your car.

The problem, of course, beforehand, and still very much present without Corbin's device, is that our map sensors can NOT read boost. As a matter of fact, if they do read any boost, they go nuts (fuel cut) and is why we use that VC-1 or Fuel mapper (or more commonly known as a Fuel Cut defencer).

I have all these things right now, but haven't had the time to hook everything up. I look forward to doing so. I'm hoping by being able to have a map sensor which can now READ BOOST and apply those readings to the S-AFC, I will be able to better and more precisely tune my car both on and off boost. I'm still very surprised that more people have not jumped at this "invention" that Corbin has developed.

http://members.nbci.com/cbehnken/foolafc.html

I certainly can't wait. Especially combined with larger injectors, this will be a awesome tool. Right now for me however, I'm contending with two very high powered fuel pumps(Accel and Walbro), and naturally, my low throttle response suffers from rich conditions.

Jason
98' Eagle Talon ESi-T
Mitsu Super 16g Turbo(HRC)/Custom FMIC


http://springfielddsm.homestead.com/JasonsPics.html

so which is better between the two?



Matt
95 Eclipse GS
my babys stock right now, few months and i should be boostin' with NER!

i'm not sure i agree with everything you've said. i don't think the problem is with the map sensor. i think it's with the ecu. the map sensor 'can' read some boost. i believe the stock map sensors can read up to 2-bar (or 14psi above atmospheric). the problem is that when they do read boost and give a signal to the ecu that's above 4.7 volts or so, the ecu freaks out and cuts the fuel.

i believe what corbin did was take the map sensor output and feed it into the afc's throttle position input. so instead of the afc seeing a low/high throttle position, it's really seeing, low/high manifold pressure. that's basically what the hks s-afr is doing, except it was designed for this.

we'll still need a fuel cut defender either way, cuz no matter what we use to trim the a/f ratio, the ecu cannot be allowed to see a map sensor output of more than 4.7 volts.

add to that the hks s-afr can trim the a/f ratio at idle to greatly improve throttle response and 'streetability'. i'm dieing to try one, but i'm not boosted yet.

no..we have a 1 bar map sensor that can read up to 1 bar of atmospheric pressure...or 0 PSI of boost. It just happens though, that when boost is applied to it, it reads slightly higher than 4.7 volts, which is what freaks the ecu out. On a 1 bar map sensor, 0 PSI = 4.7 volts, on a 2 bar, 14.x PSI = 4.7 volts, and on a 3 bar, 28 or 29 PSI = 4.7 volts...or roughly there of depending on the model or brand of map sensor you use. almost all map sensors though are based on a 5 volt scale, and 4.7 is the highest they like to see.

jason
95 GS Turbo

LAST EDITED ON 07-Jun-01 AT 09:47 PM (PST)

Exactly, Jason.

If one were to have a voltmeter attached to our stock map sensor while at the same time monitoring vacuum/boost, at the moment you hit one pound of boost, you'd see the 4.7 volts from the map sensor that Jason's talking about.

I've never done exactly that, however, I have experienced a by-product from the effects of it when I was first installing my turbo. Because my FCD wasn't hooked in properly, every damn time I boosted, at the very onset of the boost, I experienced a very irritating a jerky sensation as the car became absolutely unfriendly. I unhappily met fuel cut.

However, once the FCD, fuel mapper, VC-1, pentantiometer, or whatever name pleases you, was hooked in correctly and was able to clamp the reading down to 4.7 volts or the corresponding 0-1 psi of boost, the car was happy again. No more onset of boost fuel cut.

That's exactly why I'm excited by the prospect of using a "wider band" map sensor that can read vacuum AND boost, and smartly send a signal telling the map sensor the true electronic version of manifold pressure. This to me is a sort of breakthrough that evolves past the primitive or "caveman"-like reliance on a mechanical FPR. At least now, something electronic can read the boost and vacuum and fool the ecu into sending orders to the injectors of a pulse width that corresponds with manifold pressure beyond mere vacuum. I think this is a much better alternative than merely upping the fuel pressure when the onset of boost occurs.

Now, one can over-compensate with the FPR and then pull the fuel back accordingly, not by throttle position, rpms, or guess, but by the actual manifold pressure interpreted in electronic form.

For those and other related reasons, I think is why Jason has gone to the extent of purchasing a standalone ECU. He desires a prefectly tuned vehicle. Granted, the "Corbin solution" may not be able to fine tune to the degree of a high-tech standalone ecu, but it's promising and to me sounds like a solid and low-cost alternative.

Jason
98' Eagle Talon ESi-T
Mitsu Super 16g Turbo(HRC)/Custom FMIC


http://springfielddsm.homestead.com/JasonsPics.html

ok, i stand corrected on our stock map sensors. 1-bar it is! :)

i just got off the phone with an HKS dealer/installer and he said it will work in our applications. the best part is, that is uses it's own pressure sensor. just splice into a manifold vacuum line. so you can still use the stock map sensor and FCD as usual.

it has inputs from it's own MAP, TPS and RPM. everything you need to adjust a/f according to boost. seems like none of you guys think this is good though. i dunno, oh well.

LAST EDITED ON 08-Jun-01 AT 09:18 AM (PST)

Hey no worries Hoot. I'm wrong all the time! :-)

On your other point, though, I see how it will be able to adjust according to TPS and RPM, but I still see limitations if your going to use a single bar stock map sensor to adjust your fuel. Once the stock map sensor arrives at that 4.7 volts/0-1 psi of boost, it will no longer be able to send any voltage signal for more fuel at it is now "clamped."

I think it's absolutely imperative if you want a true tuning machine to have a map that will in fact read boost. To me, it sounds as if you can use Corbin's boost reading map sensor by hooking it up to a vacuum line, and allowing the signal to be fed into the corresponding Air fuel converter...whether it be the S-AFC or the S-AFR.

I merely favor the S-AFC because I'm a sucker for shiny blue screens. The S-AFR I'm sure is equally up to task, if not better in itself.


Jason
98' Eagle Talon ESi-T
Mitsu Super 16g Turbo(HRC)/Custom FMIC


http://springfielddsm.homestead.com/JasonsPics.html

LAST EDITED ON 08-Jun-01 AT 11:46 AM (PST)

maybe i didn't explain it right. the afr comes with it's own map sensor that CAN read boost. if you were to use the afr, this is what you'd do. get a VC-1 or FCD from hrc and wire it to your stock map sensor. splice a vacuum line and connect it to the afr's map sensor. tap throttle position and rpm wires. done.

the stock map sensor must still be clamped at 4.7 volts so the ecu doesn't freak, but that's ok cuz the afr isn't using the data from that sensor. it's using it's own (optional type-D sensor according to hks).

BTW -- i like shiney blue blinking lights too, but this just seems like it will tune more accurately without any "fooling" necessary.

Ahhhh...I see...(I'm slow too! ;-) )

Cool, that makes it just like Corbin's setup!

Jason
98' Eagle Talon ESi-T
Mitsu Super 16g Turbo(HRC)/Custom FMIC


http://springfielddsm.homestead.com/JasonsPics.html

Yeah, though there's one thing that sucks about it. I was doing some research on it at the World Import Challenge today. It has a cool feature that corrects grumpy idle from atmospheric BOV's and intercooler pipe leaks, its called EIDS I believe. Well, if you have a speed density setup (map, like ours), you cant use it. Ah well, just have to turn that feature off.





"Yes, thats Shaun shooting the finger"

http://members.home.net/xtatdsm




<<< Yeah, though there's one thing that sucks about it. I was doing some research on it at the World Import Challenge today. It has a cool feature that corrects grumpy idle from atmospheric BOV's and intercooler pipe leaks, its called EIDS I believe. Well, if you have a speed density setup (map, like ours), you cant use it. Ah well, just have to turn that feature off. >>>

umm you don't know why is that :)

we will never have any problems venting the BOV to the atmosphere just for the fact that we have MAP sensor, which means ECU counts the amount of air after it gets into the intake manifold. Cars that come with MAS sensor suffer from venting BOV to atmosphere just because the MAS sensor is right by the air filter, so it counts the aif b4 it reaches the intake manifold. which means you will be venting air that has already been counted by the ECU, therefore they run a bit richer between shifts. let's just say we are lucky :)


Adel

You're exactly right. My head is worn out and I'm sunburned to all hell. Gimme a break ;oP





"Yes, thats Shaun shooting the finger"

http://members.home.net/xtatdsm




it's all good bro :)

Adel

Thanks for answering the "AFC fooling" questions for me! I've been really busy this summer with work, traveling, car, computer, everything else. I don't get to read the board as much as I want. I'm getting a handle on it though...

Thanks

Corbin
'95 ESI-T
HRC + FMIC
http://members.nbci.com/cbehnken/