Better Way For MAF Tuning ?

[finishline]

Well, the auto VE tune is finished and now I need to move on to MAF Tuning. From what I've read many tune their MAP, and MAF seperately. When they turn both of them on togeather the car runs poorly.

My approach will be to run in open loop, with a wide band, log MAF Freq vs GPS and correct the MAF Freq table off the wide band info. I think the key here is I will not be driving the car at all. I'll start at 5000 rpm and hold the pedal steady until i get enough data at each Freq and work my way down the MAF Freq table to idle. Adjust the table and check my work.

I've tuned Buick GN MAF's this way with great success.

The reasoning behind this approach is the MAF on a LS1 is really only being used at a steady throttle below 4000 rpm. If the throttle is moving then the MAP (VE) table is being used in conjunction with the MAF.

Everyone's input pro's and con's on the idea are appreciated. I think we all would like an easier way to tune the MAF, especially for poor idle and tip in problems.

[stigmundfreud]

???

I just did AutoVE OLSD - car ran great

then tuned MAF setting the car to use the maf from 400rpm rather than 4000rmp. Got the MAF table scaled - only took about 3 road runs to get it there. and by that I mean fairly quick runs, the MAF scaled in very quickly once the VE table had been done. Basically I used the Speed Density tune and just plugged the maf in and re-enabled it prior to logging. Reset maf back to 4000rpm afterwards combined the two = car runs great, I just ued the b5001 MAF map in the scan tool.

[dfe1]

For what it's worth, I think screwing with MAF calibrations is the wrong way to go-- unless the MAF has been altered. As far as I can see, somebody at GM or one of their suppliers spent a good deal of time working out the original MAF settings. That being the case, I would assume that they are considerably more accurate than any numbers I could come up with, unless I did a calibration check on a flow bench. That being the case, if you alter the MAF calibration table, all you're doing is using erroneous data to alter fuel flow. I think it makes a lot more sense to do that with the VE table. You're probably going to have to modify it anyhow, so why introduce another set of variables by altering the MAF calibration? Even in full MAF mode, the system still uses the VE table, so altering it will affect fuel flow. With some other MAF-based systems, there's either no VE table, or it's only used in the event of a MAF failure. That's not the case with LS1/LS6 and E40 control systems.

[Bruce Melton]

For what it's worth, I think screwing with MAF calibrations is the wrong way to go-- unless the MAF has been altered. As far as I can see, somebody at GM or one of their suppliers spent a good deal of time working out the original MAF settings. That being the case, I would assume that they are considerably more accurate than any numbers I could come up with, unless I did a calibration check on a flow bench. That being the case, if you alter the MAF calibration table, all you're doing is using erroneous data to alter fuel flow. I think it makes a lot more sense to do that with the VE table. You're probably going to have to modify it anyhow, so why introduce another set of variables by altering the MAF calibration? Even in full MAF mode, the system still uses the VE table, so altering it will affect fuel flow. With some other MAF-based systems, there's either no VE table, or it's only used in the event of a MAF failure. That's not the case with LS1/LS6 and E40 control systems.

I wholeheartedly agree. Just have not had any luck figuring out how to run AutoVE with MAF. IMHO that would give all weather results!

[stigmundfreud]

You could also therefore argue that everything stock is as optimum as possible out of the factory, rather than having to accomodate varying fuel quality, air temp, weather etc.

I can understand what you are saying but again some tuners use the IFR to get the commanded AFR etc. All I know now is my VE is dialed in for running in OLSD but now my maf is scaled in whilst the MAF is working the AFR matches commanded, if the maf was to fail and revert to SD only well then my VE table is dialed in for that.

[voda1]

ttt

[redhardsupra]

if your VE is dead on (i doubt it, because AutoVE method does not account for temperature swings, as it attributes ALL airmass changes to VE) why not map out the VE resulting airflow (DynAir) on the MAF scale? also remember that MAFflow vs MAFhz is a 3rd order polynomial, so use that to shape the MAF curve.

[stigmundfreud]

my head just went

http://www.indierag.com/content/reviews/images/anightmare/nightmare5.jpg

[dfe1]

my head just went

http://www.indierag.com/content/reviews/images/anightmare/nightmare5.jpg
What??? You never used a 3rd order polynomial to reshape a curve????

[2002_z28_six_speed]

Werd! It is just a regression. Man. Math 00000001, infact. Take it easy.

There are many data programs available for free that will do this for you. Just enter the data. Or use a graphing calculator. Even MS Excell will form the regression for you.

I think we have to all remember that the shape of your intake could effect how much the MAF sees. This could skew the data if your intake is different from stock in diameter or angle.

Think about a stock intake having more of the air flowing on one side. You modify the intake and now most of it flows on the other side....

Now for injectors there is little better than factory measurements unless you have a different fuel pressure setting!

[finishline]

Well there are many different ways to skin a cat. This worked very well for my situation. The car was tuned by a big name tuner that will remain anonymous. They really only tuned wide open throttle and the customer didn't want me touching the wide open throttle stuff but the rest of his tune left him stalling, surging and the car was basically undriveable. So he only wanted me to fix the lower half of the VE table and MAF table. The car has manners now. Thanks for all your help.

[zapp168]

Would changing the MAF ends be considered enough of a modification to justify re-tuning the MAF?

[redhardsupra]

Well there are many different ways to skin a cat. This worked very well for my situation. The car was tuned by a big name tuner that will remain anonymous. They really only tuned wide open throttle and the customer didn't want me touching the wide open throttle stuff but the rest of his tune left him stalling, surging and the car was basically undriveable. So he only wanted me to fix the lower half of the VE table and MAF table. The car has manners now. Thanks for all your help.

no, not really, unless you're in a parallel universe with a different set of laws of physics.

MAF is a function, and it should not be adjusted on a cell-by-cell basis. if you have to do that, it means you're making up for something else, probably short pulse adders or offsets on the low end, or the limitations of the fuel system on the high end reflected in IFR dropping off more than your IFR table states.

[zapp168]

I dwell in a bizzaro universe.....I will leave my FAM alone :D

[redhardsupra]

Would changing the MAF ends be considered enough of a modification to justify re-tuning the MAF?

this is a good question actually. there's two camps really when it comes to MAF tuning: one, that i described above, that goes about 'shaping' the MAF curve any way they want, because they accredit all fueling changes to the MAF function, even though there's many other variables involved. the second group (much more quiet as of late though) says that MAF is a calibrated device and you should not touch it, for the same reason you dont change the scale on a thermometer just because you place it somewhere else.

I am my own camp ;) MAF, while is a calibrated sensor, it is a very peculiar device, as it's task is to measure airflow without actually deminishing/disrupting it. This is a difficult task, as that means that the sensor itself has to be tiny, but it should measure flow in the whole intake tract, which has nonlinear flow characteristics across the crosssection of the intake tract piping. So you place one tiny probe somewhere in the middle of a pipe, unsmoothing (is that even a word?) the flow. So if we assume the factory calibration is indeed perfect, it's only perfect only for the exactly stock intake tract, as that's the only way to preserve the flow characteristics for which the sensor placement and the calibration hold true. If the airflow in the pipe was always the same it'd be a different story, MAF would be calibrated once and that's it. but of course that'd be too simple :/

So, unless your intake tract is perfectly stock (yea right, that's the first thing that gets molested by gearheads), your MAF needs to be recalibrated for your custom hardware.

now how you do it, that's a whole different story...