Here is a post from another board(
http://www.automotivetech.org/forum/index.php), "agressorsol", his opinion:
"Ok, this topic has been beaten like a dead horse, but I keep seeing the SAME question time and again. So, let’s answer the eternal question:
"Where can I put my AFC?"
In a trash can. And that's the final answer folks. Here's why for archival posterity:
An air fuel controller adjusts fuel control, and in some cases VTEC activation. This is GREAT for a DSM (like a 4G63 eclipse/tallon etc...) because that engine uses a MASS AIR FLOW SENSOR. Honda's use MAP sensors (manifold absolute pressure or intake air pressure sensor). What's the difference between the 2 and why will it work for one and not the other??? Simple.
-A Mass Air Flow system adds fuel based on "How much air did I just suck up". MASS AIR IS A REAL VALUE. Real values have a basis, and no further calculation is needed. "X air needs X fuel." Adjusting any values PAST that point in the ECU's equation is OK!!!!! If you add fuel to that mixture (by increasing the injector duration), then the ECU will acknowledge that input and add fuel.
-A MAP sensor style system only sees what the manifold pressure (and other data) is, and then has to CALCULATE in order to figure out "How much air did I just suck up?" This number is NOT a REAL VALUE, but a derived value, and therefore is a variable. "X manifold pressure-times X throttle position-times X RPM-times X intake air temperature-times......." ".....equals how much air I FIGURED OUT that I sucked up." See the difference?? The ECU NEEDS this data in order to come up with a derived number for "X fuel."
So here are ALL the reasons why NOT to mount up your AFC:
1: ALL Correct Sensor Data is NEEDED.
A Honda needs all its sensor data, and needs to receive it CORRECTLY to determine how much air it's getting. It auto adjusts for fuel consumption based on these sensor values. If you're running boost, then you need to TELL THE ECU it's getting it. Unfortunately, a Honda ECU in stock form doesn't have the programming for any manifold pressure ABOVE normal barometric pressure. So, what happens when a Stock ECU sees boost at the MAP sensor??? The ECU doesn't have enough data to calculate the fuel table, so..... "Check Engine." "Please help me, I'm an ECU and I'm dumb, what does 7 psi mean?? I don't have that number in my tables, so I can't calculate. Wait a minute....if I don't have that number, then the MAP sensor must be broken, because if I don't have the number, then it doesn't exist. Please replace the MAP sensor." An AFC won't cure that. ONLY A NEW ROM CHIP WITH BOOST TABLES WILL CURE THAT.
2: The ECU "auto adjusts" itself.
Let’s say you want to tune in 10% more fuel with your AFC. Fine, tell your AFC to add 10% more fuel. No problem right?? Wrong. What happens to the O2 sensor when it's got 10% more fuel?? It tells the ECU that it's running 10% rich. So, the ECU "auto adjusts", and takes 10% out of the mixture. You've added 10% with the AFC, and the ECU has taken 10% back out to get back to stoich. What's the net increase in fuel?? That's right, 0%. NOW...... Lets add fuel until the ECU can NO LONGER adjust (or, you've added so much additional fuel that the ECU doesn't know what's happening, and can't compensate that far). Simple. You run rich. "Hi, I'm the check engine light again. There must be something wrong with my O2 sensor because I've backed the fuel off as far as I can go, and it keeps telling me that I'm still too rich. Please change the O2 sensor for me, because that must be what's wrong with me. Thank you."
3: VTEC engagement point calibration.
VTEC is a combination of 3 different things. 1: The changeover of the cam lobes. 2: The changeover of the fuel MAP. 3: The changeover of the Timing MAP. If these 3 things don't happen all at the same time, what happens?? Simple again, you have a "hole" in the fuel and timing MAPS. If VTEC engages at 3000 RPMS, and the fuel and timing table follow the ECU's instructions and changeover at 5200, then have you added any more fuel and or timing from 3000 until 5200?? No. Therefore, what did you gain?? Nothing. So what, the cam changed over, but you didn't add any fuel to it, or change the timing curve. You got more air, but the ECU didn't know that it was going to get it! So it didn't DO ANYTHING ABOUT IT. Yes, adding more air makes it FEEL like you're making more power sooner, but all you're REALY doing is running lean for a few seconds.
4: An AFC can't tell the ECU what kind/size/style injector you're running.
The ECU is programmed for one particular injector size and style. The one that CAME in your car from the factory. If you change the injectors to a larger size, the ECU MUST be reprogrammed in order to realize this, and take away or add some injector duration. If .013 seconds is the time an injector needs to be open to add fuel at 4600 rpm's at wide open throttle with a 240 cc injector, then how much MORE fuel is added with a 440 cc injector held open for the same amount of time?? Correct. Nearly double. That means you've added 2 times MORE fuel than the ECU thought it added. "Hi, it's me again, Check Engine. Yeah.... Ummm, What the f**k."
NOW. Let's look at the options to an AFC controller.
-An aftermarket ECU (Spoon, Mugen)
-A modified ECU with a programmable ROM, AND additional memory in piggyback form (Hondata)
-A plug and play fully programmable ECU (AEM)
-A totaly programmable blank slate ECU (Halltech)
ANY of these will allow for WHATEVER you decided to program for. Bigger injectors. Boost. Different Cams. Higher shift points. Higher rev limits. Anything you want. You can have ONE of these systems do it for you, and do it correctly.
Some are expensive, some are inexpensive (AEM costs about $1,600.00, and Hondata starts at $295.00). But the bottom line remains, YOU HAVE TO HAVE ONE IF YOU EVER WANT TO ADD MORE FUEL OR TIMING CORRECTLY to a Honda. For what it would cost to get an AFC controller, an MSD system with boost retard, a new set of injectors, etc... "YOU CAN AFFORD TO GET THE CORRECT SYSTEM THAT WILL WORK FOR A HONDA."
So, use this knowledge well, for it will be the LAST time the question is CORRECTY answered for you. Please refer to this article and search sway to your hearts content for it. Many will disagree with these statements, but to those who DO disagree....... Buy an aftermarket ECU and tell me what you think. You'll agree, and admit you were wrong all these years.
