Getting the most out of your Apexi S-AFC= Stock MAF honeycomb removal - Page 31 - 3000GT/Stealth International Message Center

Innovator · 09-14-2003, 08:10 PM

Quote:

Originally posted by Multiades
You're reading Karman Vortex frequency through the S-afc, not at the ECU. Obviously there will be a decrease at the stock MAS, but there will be no TOTAL DECREASE after the change at the MAS AND the change at the S-AFC (which, BTW, you can't read w/ the S-AFC).

A datalogger can pick up the change (because it only reads the values that the ECU is seeing), but there is always a cut-off at 1606hz, and you can't use a datalogger on your '95.

-Chris

Chris, the AFC displays the uncorrected HZ reading.

What would be the purpose of it showing the corrected value? It would not be of any use in determining the engines true airflow. The HZ valuse is changed after it is displayed on the AFC.

I'm quite certain of this statement.

wizard · 09-14-2003, 09:52 PM

Update for me:
After about 3 weeks, my car is starting to run like shit...... idunno if its b/c of my entire fuel system causing problems or if it's the gutted MAFT, but the car is hicking up, stumbling, and shaking so vielently at low speed that my head will sometimes almost hit the steering wheel.........

Since my honeycombs are broken already....

Are there ANY drawbacks/problems with the MAFT setups???

boostedVR4 · 09-15-2003, 07:12 AM

Quote:

Originally posted by antero
Update:

I've running on my spare MAF for the last two weeks. I had it tuned very well, but noticed the car got slower. Decided to check my trims, and mid fuel trim shot up to 139. No problem, I'll just retune. Turned the boost down and did my retuning. To my surprise, I'm having a hard time. I'll have it tuned fine for 0.75 bars of boost & zero knock, and then when I increment my boost to 0.80 bars of boost knock skyrockets to 18. Adding or subtracting fuel wouldn't get rid of the knock... strange... this is a first.

I give up. I don't have time to keep retuning the car now that I've enrolled into University. To save time I went back with my original MAF for peace of mind and disconnected the battery (reset ECU). Re-tuned, and no problems. I'm even back at 1.1 bars of boost with no knock..

My original MAF and spare MAF are both gutted (3 honeycombs removed). However, the mitsubishi part numbers differs. Ones from a 93 RT/TT, and the other a 92 VR4. My original MAF has the protrusion screw blocking the air stream, whereas the spare MAF doesn't (both came preset like that from the factory).

I'll keep ya posted if the original MAF does the same thing. I'm hoping not.

Thats funny, its been about 3 weeks for me, and I keep noticing my trims are resetting to 81. I get the car tuned pretty well, then next time I check the trims are back to 81. Can't explain it...

wizard · 09-15-2003, 02:28 PM

81 here as well

TurboBob · 09-15-2003, 02:48 PM

To the "81 trim" guys, which trims? (high, mid, low)

watch the O2 trim, it is also used to control fuel delivery.

81 trims mean the car is tuned rich, and the ECU is trying to lean it out. An 81 trim with the O2 trim near 100 is OK, you are near the end of adjustment range, but have some room. 81 trims with low O2 trims (40-60) means the ECU is removing a lot of fuel. There are some wierd things the ECU does, which get worse the further you get from the middle of the adjustment range.

wizard: The only 'drawbacks' to the MAFT are it's tuning resolution. An AFC takes care of this issue. But I am working on the MAFT stuff to provide finer tuning steps.

Send me a logfile of some driving, be sure to capture all 4 trims, throttle position, MAF hz, injector pulsewidth.

Bob

Gabe92RTTT · 09-16-2003, 03:43 PM

I noticed that my fuel trims were out of whack also. 81,134,118 for low, mid, and hi, respectively. I made logs before and after resetting my ECU. There was no change to the trims nor any difference in power. Kinda strange huh? I haven't used fuel trims to tune with my gutted MAS. As long as I got my o2s to cycle while normal driving I felt it was fine. Is this a wrong approach?

Speaking of o2s, I think mine might be going. In neutral, if I hold the throttle at any RPM point (2000, 3000, etc.) my o2s read completely lean, no matter how much fuel I add. Although, I can hear the difference in the engine note. Yet under cruising conditions, they cycle perfectly. Any thoughts?

TurboBob · 09-16-2003, 08:24 PM

Quote:

Originally posted by Gabe92RTTT
I noticed that my fuel trims were out of whack also. 81,134,118 for low, mid, and hi, respectively. I made logs before and after resetting my ECU. There was no change to the trims nor any difference in power. Kinda strange huh? I haven't used fuel trims to tune with my gutted MAS. As long as I got my o2s to cycle while normal driving I felt it was fine. Is this a wrong approach?

Speaking of o2s, I think mine might be going. In neutral, if I hold the throttle at any RPM point (2000, 3000, etc.) my o2s read completely lean, no matter how much fuel I add. Although, I can hear the difference in the engine note. Yet under cruising conditions, they cycle perfectly. Any thoughts?

You mean when you reset the ECU (unhooked the battery) the trims did not go to 100,100,100? My car will do that unless I unplug the stereo amps. The power supply capacitors in the amps keep the ECU from forgetting....

That neutral lean rev thingy is one of the wierd things the ECU does, that's some kind of coast-down enleanment., or ECU diagnostic action I think. The O2 trim gets 'stuck' at ~79 or 80 when this happens....

Toggling O2's is "ok" but the datalog method is more accurate and will result in a tune that shifts very little day-to-day.

The trims can get 'stuck' occaisionally when tuning. I think if the ECU senses a large change in the feedback (like you tweaked something) it will stop adjusting the trims, like it doesn't believe them any more.....

Just idle thoughts.....

Bob

Gabe92RTTT · 09-17-2003, 12:36 PM

Thanks for the advice, Bob.

Yeah, I found that odd that the ECU didn't reset the trims back to 100 upon resetting it. I know that it reset because the AC came on at 77. My amps are also directly wired to my battery.

I will try to retune the thing so that I may get my fuel trims closer to 100. The LO trim is easy enough to change, but I can never seem to get my mid and hi trims to change. How do I get these to change?

TurboBob · 09-17-2003, 12:46 PM

reset the ecu first to see where they truly are. You may have to pull the amp fuse. Like I said, sometimes the ECU will not update them if they are too far off. (or so it seems)

The MID trim is used when airflow Hz are between 85 and 180
the high trim is used form 185 and higher (based on analyzing a buncha logfiles) So mid is more light throttle/cruise. High is more highway/accel.

Take a bunch of logs and look to see what the O2 trim does.

Bob

Gabe92RTTT · 09-17-2003, 03:25 PM

Ok, will do. Does it take a particularly long time to see a change in mid & hi trims?

09-14-2003, 09:52 PM	#302 (permalink)
wizard I drive, therefore I am. Join Date: Jun 2003 Location: Van Nuys, CA Drives: 92 Stealth TT Trader Rating: (1)	Update for me: After about 3 weeks, my car is starting to run like shit...... idunno if its b/c of my entire fuel system causing problems or if it's the gutted MAFT, but the car is hicking up, stumbling, and shaking so vielently at low speed that my head will sometimes almost hit the steering wheel......... Since my honeycombs are broken already.... Are there ANY drawbacks/problems with the MAFT setups??? __________________ Mods list: HKS 13g turbos, CC's FMIC, 550ccs Injectors, Walbro 341 high flow (hotwired) pump, Apexi SAFC-II, HKS EVC IV, MAF-T and LS6, Stillen Downpipe, gutted custom exhaust, Greddy Type S BOV, UR pulley, Resistorless NGK Copper plugs, Stillen drilled rotors, EBC red pads, steel braided brake lines, RPS MAX street clutch, Clarion TV/face, 1800watt amp/sub, infinity kappa speakers.

09-16-2003, 03:43 PM	#306 (permalink)
Gabe92RTTT U2SLOW Join Date: Aug 2002 Location: Albuquerque Drives: '92 Dodge Stealth TT Trader Rating: (37)	I noticed that my fuel trims were out of whack also. 81,134,118 for low, mid, and hi, respectively. I made logs before and after resetting my ECU. There was no change to the trims nor any difference in power. Kinda strange huh? I haven't used fuel trims to tune with my gutted MAS. As long as I got my o2s to cycle while normal driving I felt it was fine. Is this a wrong approach? Speaking of o2s, I think mine might be going. In neutral, if I hold the throttle at any RPM point (2000, 3000, etc.) my o2s read completely lean, no matter how much fuel I add. Although, I can hear the difference in the engine note. Yet under cruising conditions, they cycle perfectly. Any thoughts? __________________ Last edited by Gabe92RTTT : 09-16-2003 at 03:48 PM.

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09-15-2003, 02:28 PM	#304 (permalink)
wizard I drive, therefore I am. Join Date: Jun 2003 Location: Van Nuys, CA Drives: 92 Stealth TT Trader Rating: (1)	81 here as well

09-15-2003, 02:48 PM	#305 (permalink)
TurboBob Resident mad scientist Join Date: Jan 2003 Location: Near Detroit Drives: 86 GN 91 RT/TT Trader Rating: (17)	To the "81 trim" guys, which trims? (high, mid, low) watch the O2 trim, it is also used to control fuel delivery. 81 trims mean the car is tuned rich, and the ECU is trying to lean it out. An 81 trim with the O2 trim near 100 is OK, you are near the end of adjustment range, but have some room. 81 trims with low O2 trims (40-60) means the ECU is removing a lot of fuel. There are some wierd things the ECU does, which get worse the further you get from the middle of the adjustment range. wizard: The only 'drawbacks' to the MAFT are it's tuning resolution. An AFC takes care of this issue. But I am working on the MAFT stuff to provide finer tuning steps. Send me a logfile of some driving, be sure to capture all 4 trims, throttle position, MAF hz, injector pulsewidth. Bob

09-17-2003, 12:36 PM	#308 (permalink)
Gabe92RTTT U2SLOW Join Date: Aug 2002 Location: Albuquerque Drives: '92 Dodge Stealth TT Trader Rating: (37)	Thanks for the advice, Bob. Yeah, I found that odd that the ECU didn't reset the trims back to 100 upon resetting it. I know that it reset because the AC came on at 77. My amps are also directly wired to my battery. I will try to retune the thing so that I may get my fuel trims closer to 100. The LO trim is easy enough to change, but I can never seem to get my mid and hi trims to change. How do I get these to change?

09-17-2003, 12:46 PM	#309 (permalink)
TurboBob Resident mad scientist Join Date: Jan 2003 Location: Near Detroit Drives: 86 GN 91 RT/TT Trader Rating: (17)	reset the ecu first to see where they truly are. You may have to pull the amp fuse. Like I said, sometimes the ECU will not update them if they are too far off. (or so it seems) The MID trim is used when airflow Hz are between 85 and 180 the high trim is used form 185 and higher (based on analyzing a buncha logfiles) So mid is more light throttle/cruise. High is more highway/accel. Take a bunch of logs and look to see what the O2 trim does. Bob

09-17-2003, 03:25 PM	#310 (permalink)
Gabe92RTTT U2SLOW Join Date: Aug 2002 Location: Albuquerque Drives: '92 Dodge Stealth TT Trader Rating: (37)	Ok, will do. Does it take a particularly long time to see a change in mid & hi trims?