327_TPI_77_Maro

iTrader: (8)

Hi guys, I hope to get into prom burning soon for my MAF 327. I've been following most of the threads on this board for a little while so I have some idea of what to do when I get the aldl link for my laptop. It seems like everyone is using speed density. How does MAF programming compare/contrast with speed density?

11sORbust

Maf doesn't have any fuel tables, period. There is PE adders. But overall if you want to adjust fuel, you'll have to use the maf calibration tables. This is the only way to "trick" a maf computer into adjusting idle/part throttle a/f ratio. The MAF sensor itself is not helping airflow at all. When it goes out, it'll cost $150+. The maf system does run better on modified vehicles with stock computer chips.

Speed density does have main fuel tables/maps. So when adjusting the fuel, you are not screwing with a sensors calibration. The map system is very sesitive to engine modifications. Running a stock chip with SD can create major headaches....

ty1295

Speed density works on mathematical formula based on engine size input, and a volumetric efficiency. (Made simple here)

Typically you will rough it in with the other variables (inj. constant, etc.) then tweak the VE tables.

On MAF (which I have never tuned), you "calibrate" the MAF sensor to actual airflow with a little vodoo in there.

Morley

In the $32b code there is an injector PW vs MAF that can be played with...but you are back to using the CSI.

11sORbust

Not too many choices for an aftermarket intake with that option....

Grim Reaper

I've worked with both and I like both. When working with MAF you are best to think "air flow" when tuning while with SD you must think "Volumetric Efficiency" when tuning.

I wouldn't throw away a perfectly good working MAF system just for the sake of it. But there are times when you may wish to consider converting, such as when you MAF takes a dump or if your ECM dies and you have difficulty on finding a "reasonably priced" used one at a wrecking yard.

Possibly the most difficult thing to tune on a MAF car is "rescaling" the MAF Scalar tables. It has been my experience that a little tweaking of the lower 3 MAF scalar tables is often beneficial to obtaining good driveability, especially if your engine has been modified. However, with a WB, rescaling is a snap and usually cure any driveability issues you may have.

The one thing I haven't seen too much with MAF is running "open loop". Some of the SD guys with more radical engines prefer to have "complete control" and run continuously in "open loop". Open Loop and SD seem to be made for each other. However, all the MAF systems I have played with run "closed loop" with the O2 sensor making the "final decision".

I personally would like to do "more experimentation" with a MAF system and running "open loop" to see if continuously running "open loop" runs as well with a MAF system as it does with SD.

There are times on certain engines that the O2 sensor can be "tricked" when running closed loop, and the only real solution is to go into "open loop".