I see that the AFC controllers are quite popular for forced induction guys to tune the fuel trim for optimal air/fuel ratio and to prevent fuel starvation.

Although it would cause great gain on a Forced Induction, would it be a bang-for-the-buck to do this to a naturally aspirated Fit that has a CAI, exhaust and hotter plugs and to do my own tuning after careful research and learning how? Sure the factory ECU is pretty dialed in, but it's also dialed in for stock parameters. With modification, comes deviation from stock parameters. The computer may "re-learn" some parts, but it will still try the best to revert itself back to as close to stock of a tune as possible, NOT to maximize the potential.

My question is...would the gain be significant, or would it be a meager 1-2 horsepower? I've seen an article on tuning of ECU tuning (ECU Reflashing - Import Tuner Magazine), and although it is referring to a 350Z/G35, I would think the same rule of thumb would apply to our Fits. Any experiences or knowledge shared would be great!

 

Problem being fits ecu is tuned for fuel economy and since vafc or afc modify maf voltage to the ecu to add or subtract fuel by nature the fit will probably adapt to whatever you try and do and eliminate any gains it may show for that short period of time these ecus are a lot smarter then those of a ek or ej for example so.while it might do something for a short time end game.is stock.ecu will relearn around it

 

Can you show me proof of that?

I read a thread Lyon posted in about the ECU "dialing back" gains, and after his stance on it, I would like to see proof from either datalogging or a well-written professional article that has a credible source before I believe that.

I can't find the post now, but his conclusion was that there is no freaking way the stock ECU can effectively "reduce power gains" without changing the ignition timing (which it won't do), and that this myth of "ECU relearning around modifications reducing power" was similar to the placebo effect, as a way to justify paying 300 dollars or more for a modification and only gaining diddly squat. In my own Fit, I have seen a pretty good amount of gain on a 5AT with simply a full CAI/Ram Air set up, IK22 Iridium spark plugs, a full 2.25" exhaust from the cat and back. Throttle response is VERY impressive. Also, my IAT's are always colder than ambient.

If you would ask me (from my limited experience), the only real ways the ECU could "Dial back" your power gains are:

- Through the ignition timing
- through the camshaft timing
- through the VTEC engagement
- through the fuel trim

All of four of which sound unlikely. If it's true that the VAFC and SAFC only tune through the MAF voltage reading, I can understand your point, but surely there are other fuel controllers out there that actually can be programmed through the ECU through either reflashing or otherwise, instead of requiring an iffy standalone.

The ECU is only going to try and reprogram itself for a smooth idle and to run at the air/fuel ratio it's told to try and aim for. However, the issue here is that some manufacturers have proven to make the AFR a little rich or maybe a little lean, and NOT perfectly stoich. That's the point behind the Fuel controller, to be sure it is perfectly stoich (not a specific number, but within the stoichiometric range) in every gear and at every RPM. Is the Fit the same way? I don't know. That's one of the things I want to know before I go down this road.

 

I'm sorry I just had to point out that CAI don't make IAT colder than ambient air, but brings temps down to ambient air temps, even intercoolers don't make it past ambient unless it has some source of cooling. Also stoich is a single number so, perfectly stoich, is redundant, it's a ratio of air to fuel of 14.7:1 so it has specific numbers, unless on some other fuel like ethanol which also has it's own ratio, there is no range

 

Okay, thanks for the input, Tuna. I must have misread the information when I was looking at sensor data when I was reading IAT's, or forgot to double check the ambient air temperature at the same time or something (I'm still kinda new at the technical stuff...)

Good info to know! I like to learn. But, does the stock computer tune to 14.7:1, or does it tune slightly lean or slightly rich?

 

Stock ecu varys on the a/f raitio it.aims for based on load throttle.position air temp etc stock leans out a lot under light throttle cruise for fuel economy and is rich under full load to prevent lean misfires.and.what not I wasnt saying.that if you reflash their will be no gains I'm.saying safc that only modifys maf voltage will have no.gains after extended driving I had a safc tuned on a rsx with basic bolt ons first tune after baseline synod gained 15hp and then after that Evry dyno number got closer to stock until it was exactly where it.was at baseline

 

Your fit still runs off of a map sensor and uses speed density. The maf is only there for idel and steady driving. If you do wot pulls your mainly running off the map sensor. You would have to recal the maf and adjust the map settings to really make power out of our cars but i dont know if there is really anything out on the market for use right now to accomplish all that.

 

The ECU doesn't like to be fucked with except by Hondata and as far as I know, the only way you can get them to do the reflash is to own a GD3 and install a brand new KWSC high boost kit on it... They send an addressed box that you send your ECU to Hondata in and it comes back 2 days later ready to go... According to Oscar Jackson who designed the KWSC kits, lighter wheels and tires is the best way to make your Fit run faster... The reduced rotating mass and unsprung weight improves a car in more ways than I am going to elaborate on since I need to go crawl back into bed.

 

I am sold on that idea! I only dropped about 4 pounds per wheel, but there was a noticeable difference. And I don't think any ECU really likes to be fucked with until someone cracks that sucker's software wide open. :P