ARC2 vs. AFC
08-09-2004, 06:53 PM
#1
Drive-by provocation guy
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ARC2 vs. AFC
Anyone have any pros and cons of the Arc1 or 2 vs. the Apexi AFC 1 or 2??
yes, I know there are others that are much better, but these two can be had in alomst new condition for about half of the cost of PSC or SMT.
yes, I know there are others that are much better, but these two can be had in alomst new condition for about half of the cost of PSC or SMT.
08-10-2004, 02:16 AM
#2
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i have the afc 2 on my car. install was easy. i haven't done any tuning with the afc yet because i was waiting for the guru chips for a base. i got the chips today, and will bring it to the dyno sometime this week hopefully to tune it a bit. i'll let you know how it goes, but i thought the AFC 2 would work better then the arc because it has many more points of adjusatbility for about the same price
08-10-2004, 11:16 AM
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the afc is somewhat universal. when you buy one, make sure you get one with the english manuals. i hear the ebay ones that go for half price only have the japanese manuals. anyway, i posted a while ago how to install it in our cars. you can do a search for something like "wuhu, apexi afc installed" or something like that. the manuals that come with it do not have instructions for installing them in our car, so you will have to use the instructions i provided (basically it is a pinout for where the wires go). the manuals do however tell you what each wire does, and how to set the thing up, which is very important. let me know if you have any other questions. i will try to keep this thing updated with tuning my car, and how that goes.
09-08-2004, 02:56 PM
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09-08-2004, 03:17 PM
#8
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a lot of my friends, and myself, have used the apexi SAFC, its extremely easy to install and set up. I actually have a brand new one that I need to get rid of, if anyone has any questions let me know
09-08-2004, 03:50 PM
#10
I too have used the APEXi AFC (Air Flow Converter), S-AFC (Super Air Flow Converter), and now the new S-AFC2 for years in turbocharged Honduh & Mitsubishi platforms. The biggest issue is when tuners try to compensate for larger injectors solely with the AFC. Granted it works, but with only +/- 50% fuel adjustment, it's a weak patch at best and severely limits your choice of injector sizes.
Fortunately for the 944/951 crowd (among other P-cars) the available chipsets will handle any aftermarket injector flow differences leaving only slight fuel ratio tuning to the AFC. For this, +/- 50% is way more than enough to accommodate any tuner. I don't think I've ever adjusted any fuel curve beyond -15% for a street-driven application.
All-in-all, I love the S-AFC and it's proven itself over & over again in the Japanese market as a reliable fuel management tool.
Fortunately for the 944/951 crowd (among other P-cars) the available chipsets will handle any aftermarket injector flow differences leaving only slight fuel ratio tuning to the AFC. For this, +/- 50% is way more than enough to accommodate any tuner. I don't think I've ever adjusted any fuel curve beyond -15% for a street-driven application.
All-in-all, I love the S-AFC and it's proven itself over & over again in the Japanese market as a reliable fuel management tool.
09-08-2004, 04:06 PM
#11
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I have never understood how these 'piggy back units' really offer good control.
If your ECU is in closed loop in part throttle, then the O2 sensor will correct any
change you make. While at full throttle and open loop, then its a 2-d lookup based on RPM.
How can a signal massager really control much especially once the AFM is maxed out??
Please help me fill in the blanks.
If your ECU is in closed loop in part throttle, then the O2 sensor will correct any
change you make. While at full throttle and open loop, then its a 2-d lookup based on RPM.
How can a signal massager really control much especially once the AFM is maxed out??
Please help me fill in the blanks.
09-08-2004, 04:34 PM
#12
Race Director
The close-loop O2-feedback ONLY works during partial-throttle operations. Even then, the O2-sensor only has a minor correction amount, +/- 6% or so, which means it cannot correct out-of-spec fuel-values larger than that. ALso, once you get over 65-degrees open on the throttle in less than a certain amount of time, the DME drops into the WOT map which completely ignores the O2-sensor.
Now, the S-AFC-2 is the best one out there, and cheap too, around $300. The 2nd generation one is great because it has two RPM-based tables for correction, one low-load and one high-load and it interpolates values in between. What this gives you over the ARC2 is much tigher precision with 3D references similar to a standalone EFI. You can pinpoint LOAD x RPM areas on the 3D map to adjust, something that can't be done with straight volt-in -> volt-out massagers like the ARC2.
Also this is great with MAF systems, and I"m addressing the maxed-out AFM issue here, because it allows you to use the last edge on the chip's fuel-maps that can't be touched by the AFM. The stock AFM maxes out at 4.6v and if you measure a stock system, it never actually reaches that. With larger turbo and high-boost upgrades, yes it will be pegged at 4.6v before redline and signal-massaging won't help because you'll still have a flat-line curve.
However, MAF-sensors are calibrated for 0-5v output and the chip's programming DOES go up to 5.0v. So you can do signal-massaging to increase or decrease the air-flow signal within this range and if you end up in the 4.6-5.0v range, you'll be getting more fuel than can be possible with the stock AFM. You'll also be getting a rising-rate fuel curve if the signal increases linearly from 4.6-5.0v without ever getting clipped at 5.0v. So that's how you can use the S-AFC2 with a MAF to give more precise control over the ARC2.
Although I'm still have the physology that it's best to have a chip mapped precisely to the response curve of a particular MAF sensor, thus no signal-massaging needed. Like the APE MAF kits, which are the best on the market, IMHO.
Now, the S-AFC-2 is the best one out there, and cheap too, around $300. The 2nd generation one is great because it has two RPM-based tables for correction, one low-load and one high-load and it interpolates values in between. What this gives you over the ARC2 is much tigher precision with 3D references similar to a standalone EFI. You can pinpoint LOAD x RPM areas on the 3D map to adjust, something that can't be done with straight volt-in -> volt-out massagers like the ARC2.
Also this is great with MAF systems, and I"m addressing the maxed-out AFM issue here, because it allows you to use the last edge on the chip's fuel-maps that can't be touched by the AFM. The stock AFM maxes out at 4.6v and if you measure a stock system, it never actually reaches that. With larger turbo and high-boost upgrades, yes it will be pegged at 4.6v before redline and signal-massaging won't help because you'll still have a flat-line curve.
However, MAF-sensors are calibrated for 0-5v output and the chip's programming DOES go up to 5.0v. So you can do signal-massaging to increase or decrease the air-flow signal within this range and if you end up in the 4.6-5.0v range, you'll be getting more fuel than can be possible with the stock AFM. You'll also be getting a rising-rate fuel curve if the signal increases linearly from 4.6-5.0v without ever getting clipped at 5.0v. So that's how you can use the S-AFC2 with a MAF to give more precise control over the ARC2.
Although I'm still have the physology that it's best to have a chip mapped precisely to the response curve of a particular MAF sensor, thus no signal-massaging needed. Like the APE MAF kits, which are the best on the market, IMHO.
09-08-2004, 04:46 PM
#13
awilson40 -
Well, what you said is mostly true. Yes the car's computer will compensate for air/fuel ratios (AFRs) while in closed loop. Granted you can force a rich or lean condition, but the situations which require such a thing are rare. If you max out your AFM, you've maxed it out. Get out your checkbook, time to upgrade.
The only thing I'd like to point out is that the S-AFC (and S-AFC2) creates a 3-dimensional fuel map. It's not as sexy as a stand-alone map, but it works pretty well. You provide two rpm vs. fuel adjustment graphs, one for 'low throttle' and one for 'high throttle'. You then set the 'low' and 'high' throttle points, usually something like 50% and 100% respectively. This means that at any throttle position of less than or equal to 50%, only the 'low' throttle fuel settings are used. For 100%, only the 'high' settings are used. For any throttle position in-between 'low' and 'high', the S-AFC computes the required fuel to be delivered. For 75% throttle at 5000rpm, the result would be half of the 'low' 5000rpm setting + half of the 'high' 5000rpm setting. For 60% throttle at 5000rpm, the result would be 80% of the 'low' plus 20% of the 'high' since we're closer to 'low' than 'high'. And so on and so on. Make sense? Cheap, but reasonably effective.
But you're missing the true purpose of a piggy-back device: all we really want it to do is slightly 'massage' the wide open throttle AFR.
If you beat on your car for hours at a time such as on a road race course, a (relatively) richer mixture would provide marginally less power with greater safety. If you live a quarter mile at a time, a (relatively) leaner mixture would help squeeze out those last few drops of performance at a greater risk of detonation. Pick your poison.
How can you achieve such AFRs on demand? A piggyback is a fast & easy way. No need to reburn chips, no need for a laptop or other bulky device, all you need is right in front of you inside a plastic box the size of a cigarette pack. Obviously, to do this the RIGHT way requires an AFR sensing device such as a wideband oxygen sensor, available on any reputable dyno or from several vendors who offer in-car models. Simply guessing you need less fuel is a Darwinistic approach to tuning.
That help?
danno -
For what it's worth, the S-AFC also had two maps. The original **** & dial AFC had only one map and very very few adjustment points.
Well, what you said is mostly true. Yes the car's computer will compensate for air/fuel ratios (AFRs) while in closed loop. Granted you can force a rich or lean condition, but the situations which require such a thing are rare. If you max out your AFM, you've maxed it out. Get out your checkbook, time to upgrade.
The only thing I'd like to point out is that the S-AFC (and S-AFC2) creates a 3-dimensional fuel map. It's not as sexy as a stand-alone map, but it works pretty well. You provide two rpm vs. fuel adjustment graphs, one for 'low throttle' and one for 'high throttle'. You then set the 'low' and 'high' throttle points, usually something like 50% and 100% respectively. This means that at any throttle position of less than or equal to 50%, only the 'low' throttle fuel settings are used. For 100%, only the 'high' settings are used. For any throttle position in-between 'low' and 'high', the S-AFC computes the required fuel to be delivered. For 75% throttle at 5000rpm, the result would be half of the 'low' 5000rpm setting + half of the 'high' 5000rpm setting. For 60% throttle at 5000rpm, the result would be 80% of the 'low' plus 20% of the 'high' since we're closer to 'low' than 'high'. And so on and so on. Make sense? Cheap, but reasonably effective.
But you're missing the true purpose of a piggy-back device: all we really want it to do is slightly 'massage' the wide open throttle AFR.
If you beat on your car for hours at a time such as on a road race course, a (relatively) richer mixture would provide marginally less power with greater safety. If you live a quarter mile at a time, a (relatively) leaner mixture would help squeeze out those last few drops of performance at a greater risk of detonation. Pick your poison.
How can you achieve such AFRs on demand? A piggyback is a fast & easy way. No need to reburn chips, no need for a laptop or other bulky device, all you need is right in front of you inside a plastic box the size of a cigarette pack. Obviously, to do this the RIGHT way requires an AFR sensing device such as a wideband oxygen sensor, available on any reputable dyno or from several vendors who offer in-car models. Simply guessing you need less fuel is a Darwinistic approach to tuning.
That help?
danno -
For what it's worth, the S-AFC also had two maps. The original **** & dial AFC had only one map and very very few adjustment points.
Last edited by Dark Lightning; 09-08-2004 at 05:26 PM.
