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

[BlackStealth]

Originally posted by Eric_VR-4
where is this "screw" we can back out... also.. I was thinking of that plastic piece that holds the honeycombs in... I don't see why the car would need that... we could probably leave it out. I'm sure the extra airflow would be completely undetectable though... but it shouldn't hurt.

Look at the bottom of your MAF. You'll see a screw about the size of a dime. The factory has glued?? it in place.
Extra plastic pieces. Yeah, I've been thinking of the same. That's why I'm searching for another MAF to hack. I want to port it really smooth with minimal material, while leaving the actual metered area alone.

Originally posted by VR4blur
Maybe Im wrong, but I thought 550cc injectors were the largest you could run with a SAFC...

I always thought the SAFC could only handle a 50% increase in injector size

An old incorrect theory. 50% increase actually works out to 720cc not 550cc.

[BlackStealth]

Just picked up another stock MAF from a fellow member on the board. To my surprise, the protrusion screw was completely backed out by the factory, where as my other MAF the screw was in there half way obstructing flow. I picked this spare MAF so I could butcher it up err I mean cut out more obstruction material away.

First I had to test if this MAF is any good, so I removed the three honeycombs to match it up to my previous MAF. This setup should run a tad bit leaner cuz the screw is backed out, so for safety sakes I turned the boost down.

Just as I expected, I had some knock from the extra leaness. Adjusted the SAFC and repeated the runs until knock was gone. Increased the boost a little, and repeated everything again. I decided to stop at 1.05 bars, and resume sometime in the near future so my fuel trims have time to adjust.

Here's my findings for WOT:
MAF (5 honeycombs) -23%
MAF (5 honeycombs) & Fuel rewire -27%
MAF (2 honeycombs) & Fuel rewire -19%
MAF (2 honeycombs & screw backed out) & Fuel rewire -14%

I'm really surprised to see a 5% difference with a backed out screw. I acknowledge that the MAF is not the same for the final test, so it may be a contributing factor too. I strongly suggest anyone who has done this mod, should back out the screw too.

Checked out my datalogs. Timing is 2 degrees lower at 5200 rpms when comparing the -27% logs, and -14% logs. Who says this mod doesn't work? The closer we get to 0% correction the closer we are to a normal timing curve.

In the near future, I'm gonna butcher this spare MAF for more unmetered air. And also consider removing my Erik Gross fuel rewire mod. My car is never gonna see 100% injector duty cycle, or any race gas or propane injection so I don't think that mod is necessary for me. The purpose of the removal is to see if my WOT correction factor will get closer to zero. As you can see above, I had to lean my mixture out by 4% when I introduced that mod. I would like to get that back. Does anyone know roughly what amount of duty cycle is safe for 550cc injectors on a supra pump on stock voltages? My car currently runs 80% duty cycle at 16psi.

[BlackStealth]

Forgot to state something in the last post.... the car pulls great! My car doesn't want to drive in a straight line anymore. It now sometimes wanders as the torque kicks in hard. That's something I can live with.

[Innovator]

The only people that say the mod doesn't work are blinded by what logic dictates. All theory and no practice makes some people doubt without giving it a try first.

[boostedVR4]

Originally posted by Innovator
The only people that say the mod doesn't work are blined by what logic dictates. All theory and no practice makes some people doubt without giving it a try first.

Just for an update, I've had this done for a few weeks now, and the car is still driving perfect, fuel trims are still fine. I have since finer tuned the low end from 2k down.

I don't really notice the car pulling any harder, but it does spool up a little faster. But, its free so its worth it.

[Lucky31337]

Originally posted by boostedVR4


Just for an update, I've had this done for a few weeks now, and the car is still driving perfect, fuel trims are still fine. I have since finer tuned the low end from 2k down.

I don't really notice the car pulling any harder, but it does spool up a little faster. But, its free so its worth it.

Thanks for the update.

[Multiades]

Originally posted by antero
Checked out my datalogs. Timing is 2 degrees lower at 5200 rpms when comparing the -27% logs, and -14% logs. Who says this mod doesn't work? The closer we get to 0% correction the closer we are to a normal timing curve.

I've said it before, I'll say it again -- you are still applying the same amount of total correction. Whether or not that correction is done with the AFC makes no difference.

Timing might decrease for a number of reasons (including temperature, etc) -- but the most likely is that you are making more power at the same boost due to less pressure drop through the MAS. You have a higher density ratio at the same boost pressure, simple as that.

Originally posted by antero
The only people that say the mod doesn't work are blined by what logic dictates. All theory and no practice makes some people doubt without giving it a try first.

I never said the mod doesn't "work" -- it should work if your intention is reducing pressure drop from flow loss at the MAS. I stated and maintain that it is impossible for this mod to reduce timing in the claimed way. There is still a total corrected airflow value at the ECU -- whether that correction is done electronically or physically matters not.

Any difference in total timing you may see represents MORE POWER being made due to higher air massflow (at the same boost). You can achieve that same timing reduction without this mod by increasing boost pressure, but knock will probably prevent you from doing so safely.

-Chris

[wizard]

Originally posted by Multiades
I've said it before, I'll say it again -- you are still applying the same amount of total correction. Whether or not that correction is done with the AFC makes no difference.

Timing might decrease for a number of reasons (including temperature, etc) -- but the most likely is that you are making more power at the same boost due to less pressure drop through the MAS. You have a higher density ratio at the same boost pressure, simple as that.

I never said the mod doesn't "work" -- it should work if your intention is reducing pressure drop from flow loss at the MAS. I stated and maintain that it is impossible for this mod to reduce timing in the claimed way. There is still a total corrected airflow value at the ECU -- whether that correction is done electronically or physically matters not.

Any difference in total timing you may see represents MORE POWER being made due to higher air massflow (at the same boost). You can achieve that same timing reduction without this mod by increasing boost pressure, but knock will probably prevent you from doing so safely.

-Chris

im gonna have 2 agree with him on this 1 guys.... if you look at your pocketlogger.... b4 the MAS setup with afc corrections, and after the setup with less afc correction, you'll b looking at the same airflow Hz.
There could b OTHER factors making you less timing, but it can't be b/c of the airflow #'s...

the mas DOES read other values like barometric pressure, temp, and some other crap that we can't even datalog (air volume). that could b the factor, or just purely making more power would also cause the same thing to happen. but its DEFINITLY not from the airflow correction value.

i'm stating this b/c at first, i was thinking the same thing (that the closer to 0 the afc is, the less timing correction) but then i started researching getting the MAF-T b/c my timing was WAY advanced, and realized that it wouldn't change my timing in any way.

[boostedVR4]

Indeed, my HZ levels didn't change at all either. Has anyone tried the Greddy emanage? It has a timing control feature.

This entire timing advance problem is another reason why stand alone ECU's are becoming popular with our cars.

[Innovator]

The HZ level have to change. They will be lower.