MAF Delete

**richard head** · 02-28-2008, 03:10 PM

In HPTuners, this yielded me a 30 tq gain (probably mostly from switching from an improperly tuned sensor to the factory VE tables as primary WOT tuning source) and so I thought I'd post it up. I removed my MAF, connecting a piece of dryer duct from the TB to the lid and removed the codes in HPTuners as well as setting the MAF Fail Freq. to 0.

What this does and why to do it: My car has had transmission issues on the highway, it is an automatic and the problems started when I descreened my stocker but did not cease when I replaced it with a functional, screened stock unit. I then ordered an 85mm screenless z06 maf and still had problems; for some reason it was telling the transmission I was making more (or maybe less) torque than I was at highway cruising speed and this caused it to slip frequently. The trannys fine, btw.

The MAF functions in an automatic as the transmission's guide, telling it how much pressure to run under part-throttle conditions and allowing it to cut it close, so to speak, and use low pressure under low torque conditions in order to provide a smooth ride without rough hard shifts (which are actually better for it in the long run). It also serves as the sole input into WOT calculations, though the VE table (volumetric efficiency table, basically it calculates cylinder airmass based on RPM and MAP) is in some cases like mine even more effective.

Removing the MAF made my transmission shift at max pressure all the time, causing it to ride a bit rougher in town but at the same time curing my highway slip issue and it cleared out the airway which should be making a few more ponies while I was at it (just switching to the VE table, historically, makes a pretty big difference).

Anyway, just thought this might be helpful if anyone was having similar issues and I wanted to put it out there in case anybody things it's somehow a horrible idea that will kill my car for some reason that has eluded me.

**Frost** · 02-28-2008, 05:39 PM

Couple things to keep in mind by moving to SD. One is, to get the tranny to stop slamming, disable the the tab under trans diag for the max pressure dtc setting.

Also, you can disable the SES light, but do not disable the fail codes (error reporting) for the MAF in the PCM to ensure it is fully in SD.

Once in SD, unless you are using the custom 1-bar SD OS, you will be running off the low octane table and the horribly low-resolution secondary VE table (if 98-00). If you have HPT you should consider spending the few credits to get the 1-bar SD OS. It's really nice and unless you are a 98, gets you real time tuning with your stock PCM as well!

**richard head** · 02-29-2008, 01:07 PM

UPDATE: I did a bunch of the stuff you recommended, good job tranny shifts softer now but it did slip a bit in the parking lot at idle earlier so I think I'm going to go back to it. Also, MAF is reading .46 for some reason, I killed the DTC's and set the fail high to 0 so i have no idea what's going on with that. Few VE table changes netted me another 10 ft lbs at the crank, it's hitting 385 now according to the pcm and the torque band is insanely flat from 2k-6k rpm. I did a calculation on the 374 foot lbs it was making at 5760 rpm and found that it equated to 410 horsepower (at the crank, or 348.5 at the wheels uncorrected, assuming 15% drivetrain loss in my automatic) !!!!!

My only mods are lid, !maf sensor, ! baffles, tb bypass and tune. Oh and exhaust cutout.

**Frost** · 03-01-2008, 04:05 AM

Originally Posted by richard head

UPDATE: I did a bunch of the stuff you recommended, good job tranny shifts softer now but it did slip a bit in the parking lot at idle earlier so I think I'm going to go back to it. Also, MAF is reading .46 for some reason, I killed the DTC's and set the fail high to 0 so i have no idea what's going on with that. Few VE table changes netted me another 10 ft lbs at the crank, it's hitting 385 now according to the pcm and the torque band is insanely flat from 2k-6k rpm. I did a calculation on the 374 foot lbs it was making at 5760 rpm and found that it equated to 410 horsepower (at the crank, or 348.5 at the wheels uncorrected, assuming 15% drivetrain loss in my automatic) !!!!!

My only mods are lid, !maf sensor, ! baffles, tb bypass and tune. Oh and exhaust cutout.

I don't get it, with those mods, why run SD?

Your MAF is not out of the equation and still screwing up your fueling, that's why you get a reading. Like I mentioned, with the DTC disabled, it won't fail into speed density right. It NEEDS to see the MAF error. You need to set it to fail on first.

The internal trans tq calcs are useless even as a measure (vary by internal trans temp and other things), and serve only to allow you to really tune your shift points and pressures. If you have worked your VE table based on feedback from this PID, I'd put my VE back to stock now that you know. Since your MAF is still feeding you a bogus reading as well, it's more than possible that your VE changes have done nothing unfortunately, since they are not being looked at. If you get "slip" with a stock stall in a parking lot, you have trans problems.... if you are really getting slip.

You need a wideband. People love to say "you can tune with fuel trims!!1111".... and a little bit of that is true, you can tune part throttle with them, but you have to have a wideband for WOT tuning anyway, and since it's tons faster than trim tuning, I just can't see tuning without one.

Best of luck, and have fun with what you are doing.

**richard head** · 03-01-2008, 11:14 AM

fun it is... and I see your point but man the car is just running so well right now that i have a hard time really believing that what I'm doing is worthless - but I'll change it back and see how that goes.

As far as the trans problems, I guess there is something wrong but i've got a cooler, a tranny full of fluid and perfect WOT shifts. I guess i'll just stop worrying about it

**Frost** · 03-01-2008, 12:26 PM

The butt-o-meter is often influenced by our hopes, the dyno & the track don't care what we hope for at all

I'm not calling your tuning worthless by any means, and this exploration is a great learning tool. Just make sure you see the MAF fail DTC set in the scanner to know you are in SD. The bottom two rows of the VE are the ones that will fuel WOT and PE is a multiplier of their resultant.

Why do you think your trans is slipping in a parking lot? Slippage on shifts is one thing, but for one to slip down low, usually they slip so bad up in higher gears where the real load is that there is no doubt of what is going on.

You aren't feeling the normal converter slip and mistaking it are you?

**richard head** · 03-01-2008, 12:50 PM

Hopefully that's exactly what's going on - this car is a lot more complicated than my v6 ever was so I think I just kind of expect things to break and read into little problems more than I should. The highway slippage from before was no joke though, and that's been cured by this.

Looking back through my logs, when I was running a MAF, MAP never hit anything over 99 and frequently dropped as low as 95 during WOT runs. This directly correlates to the higher tq delivered #s that I was so flattered to see, and to be honest, though they may not be anything like reminiscent of the numbers we'd see on like an engine dyno, much less a dynojet, they seem to be remarkable consistent with each other and I do think that they are probably helpful in some respect just to see if something made it more or less powerful. (I also looked at the trans temps on those logs and it looks like it was the same across the board after I put in the trans cooler - 163*)

I'm gonna get my motor mounts replaced before I test'n'tune it anymore and I want to go dyno this thing with an old, MAF tune that I still have and then with this new SD thing and see once and for all which is better.

I put the stock VE tables back, didn't drive it, and kept the MAF out - more news when I get the motor mounts and hopefully dyno.

**Frost** · 03-01-2008, 01:48 PM

Originally Posted by richard head

....Looking back through my logs, when I was running a MAF, MAP never hit anything over 99 and frequently dropped as low as 95 during WOT runs. This directly correlates to the higher tq delivered #s that I was so flattered to see, and to be honest, though they may not be anything like reminiscent of the numbers we'd see on like an engine dyno, much less a dynojet, they seem to be remarkable consistent with each other and I do think that they are probably helpful in some respect just to see if something made it more or less powerful. (I also looked at the trans temps on those logs and it looks like it was the same across the board after I put in the trans cooler - 163*)
......

Unfortunately if this were true there would be information about it's use all over the place, but it just is not what you are thinking it is. You and NO ONE READING should try and tune their car by the delivered trans tq. PID.

Tell ya what, send me your current file to steve@lsxtune.com and I will get a look at it tonight and see if I can toss in anything that should be useful to ya

**richard head** · 03-01-2008, 02:33 PM

Do you want a log to check out too or just the file? I'll go ahead and send over the file right away, if you want a log just reply to my email. Oh, and thanks a lot man.

**Frost** · 03-01-2008, 02:45 PM

sure shoot a log too if you have it... but it's not super crucial. It will be tonight before I can get in and look at it.

**richard head** · 03-01-2008, 11:32 PM

Good changes. Thanks!

**Frost** · 03-02-2008, 04:15 PM

did you mess with it any today?

**richard head** · 03-02-2008, 05:29 PM

Loaded it up and drove it around a little, seems to run more smoothly. The !LTFT is a good change too, I'm going to fully tune the VE table now I think but it shouldn't need much as stock as my car is. Shifts are great and idle is cleaner. I went ahead and dropped 2* of spark at WOT and it seems to just run better all around.

As far as I can remember, this is the best this car has run so far. I couldn't figure out what you meant about the O2's being set to 350 mv or where that was located but I'm guessing that's what's responsible for the smoothness of the idle and acceleration and all.

I really appreciate the help.

**Frost** · 03-02-2008, 06:31 PM

Originally Posted by richard head

Loaded it up and drove it around a little, seems to run more smoothly. The !LTFT is a good change too, I'm going to fully tune the VE table now I think but it shouldn't need much as stock as my car is. Shifts are great and idle is cleaner. I went ahead and dropped 2* of spark at WOT and it seems to just run better all around.

As far as I can remember, this is the best this car has run so far. I couldn't figure out what you meant about the O2's being set to 350 mv or where that was located but I'm guessing that's what's responsible for the smoothness of the idle and acceleration and all.

I really appreciate the help.

Your airflow modes and O2 rich/lean switch voltages for 3 middle modes was changed. Your rich/lean had been moved from 450-470mV to 350mV which I assumed was from a pseudo lean-cruise attempt (this is do-able this way) but that lean in some areas like can make for stumbling or rough spots.