Getting the most out of your Apexi S-AFC= Stock MAF honeycomb removal

[Innovator]

Yea that's right.

Since I got my FJO wideband I've become pretty brave.

Seriously though...

A lot of people who have removed the two side and lower honeycombs have the same complaint. "The car runs like shit now"

Well of course it does. You've just removed three big restrictions, and the air will follow the path of least resistance. So what in affect happens is that the air bypasses the resistor in the MAF and makes the car run as lean as hell. That's why the car idles so shitty afterwards. It would also make the engine run leaner all throughout the rpms's, causing certain catastrophic failure. Not good.

Here is where the S-AFC earns its stripes. It’s much more than a way to run bigger injectors, folks. It’s a great tool, but it has its limits and problems. The biggest problem I see it that the larger the injector, the more it needs to fool the ECU to run leaner. So, you end up setting the correction factor to -35 or lower. The lower you go, the leaner the engine gets, great but…

This may not be news to many of you, but the more – correction you run, the more advanced the timing gets. This is one of the *big*negative effects of the AFC and high correction factors. You guys are always worried about knocking and detonation. Well, the #1 cause of detonation isn’t just running lean; it’s also , and mainly running too much advanced timing.

Ideally you would want around -20-22 degrees maximum at WOT. But with the AFC cranked to -40 or so, you are likely to be running -28 or more advance at WOT. That’s way the f*ck too much if you want to keep the engine from detonating. Remember that the knock sensor will pull back timing if it senses knock (to a point). But ideally, you don’t want the knock sensor to be constantly doing that, because that makes for one bumpy ass power curve Also, you can’t always depend on the knock sensor to react quickly enough, or pull back the timing enough at all times.. Adding fuel and running rich is a bandaid that ulimately will rob you of power and money for gas.

So, what I did was remove the two sides and lower honeycomb from the stock MAF. This allows you to use lower correction factors because the MAF is seeing less air go past it to begin with. The car naturally ran like ass until I used the AFC to compensate for the leaner condition caused by the honeycomb removal. As a starting point, I went about 10% richer across the board. A little richer that 10% at idle worked great. The car went into closed loop no prob.

So I went from an average of -30 on the low settings (with 550cc injectors) to -20 low. I went from an average of -37-38 on the high settings to -24-27/ That made a big difference in my timing advance. Now the car is maxing out at -21 degrees advance from a scary -28-29 advance. Good deal (Do not assume your car will work well with the same settings! You gotta tune the A/Fproperly!)


But the real kicker was the dyno #’s
The most I was ever able to get out of my car was 425 AWD HP and 410 torque. Today, I went to Philly and dynoed my car on the same dyno, and I made 475 AWD HP and 468 torque at the same 17 PSI and 15G’s.

The car runs perfectly and the throttle response it better than ever. I had to play with the AFC to get the A/F ratio smooth across the board, but in the end I got it to 11.7:1- 12:1 . The car was running 11:1 (very rich) before to keep knock down, but no more! Its kick ass now, and I didn’t need another MAF to do it! It also used a 1/3 less gas on the way home!


I just wanted to share this with you guys, and I hope you can make use of it

[2root4u]

Thanks for the good info! The timing issue has come up time after time without any good resolution except "buy an AEM"

Good job on the research! And your idea has good theory to back it up. Amazing concept. Posts like this are a dying breed on this board.

[AllEyezOnMyVR4]

i was gonna say the same thing rick

[Innovator]

Originally posted by 2root4u
Thanks for the good info! The timing issue has come up time after time without any good resolution except "buy an AEM"

Good job on the research! And your idea has good theory to back it up. Amazing concept. Posts like this are a dying breed on this board.

Thanks man. I also used a timing light to verify my results. The 1995 has no logging capacity to speak of...

[SLguy]

whats the best way to monitor your timing?

[Innovator]

I used a timing light and a white mark on the crank pulley. On a 94 and 95, you can't use a datalogger

It's not the safest way, but it worked for me!

I used saftey goggles and a helmet in case something fragged

[Odin]

Hmmm.....very interesting. This could be the next great thing to happen, lol. Any negative effects to this?

And on my level of mods, what kind of gains do you think I'll see?

I'm always overcautious when considering these...."experiments". did you have any major problems tuning afterwards?

[91vr4n00maxima]

so you were perched on your engine while someone drove your car at WOT


awesome. nice to see someone doing something new

[PrimeUser]

Very interesting!

I just ran mine on the dyno last Sunday too. While I was there I learned from the dyno tech that turbo cars should run about 11.5 A/F ratio for max HP...

That's something I never knew... Before going to the dyno I always thought you should always shoot for 14.7 (perfect stoichiometric ratio) but no, not on a turbo'd engine he said. 11.5 is apparently the magic number to seek for max power...

And I always thought the magic numbers were 12.7 to 12.9:1 for peak torque and 13.0 to 13.2:1 for maximum horsepower.

Well, anyway, like I said, very interesting!

You DO learn something everyday...

Great info tip on the MAF gutting tho!

*EDIT* Ohh, I forgot to post my dyno pic (embarrassing HP but posted anyway so you can see my A/F ratios)

[Innovator]

Originally posted by Odin
Hmmm.....very interesting. This could be the next great thing to happen, lol. Any negative effects to this?

And on my level of mods, what kind of gains do you think I'll see?

I'm always overcautious when considering these...."experiments". did you have any major problems tuning afterwards?

No problem tuning. Feels better than stock IMO, and no drivability problems on the 550 mile trip. I'll report back if I have any more input.