Slo_crx1

iTrader: (9)

I'm helping a friend out with his 2g eclipse, and we're going to be using an '03 Evo 8 ecu in place of the original and running in conjunction with a 3.5" gm maf and a maft converter. What I'm wondering though is if there will be an issues with the maft in regards to the barometric pressure sensor that's normally built into the Evo maf? The MAFT setup he bought doesn't really specify settings for an Evo though, and I'm trying to find if there's any special switch settings to be able to use it with the stock Evo maf scalings to be compatible with the ecu, although I do have a modified maf scaling from a 2g eclipse that I might have to use in place of the Evo scalings.

If this setup works out good, I might look into running a gm maf on mine.

Or better yet, anyone know any scalings to run a gm maf directly?

JohnBradley

iTrader: (30)

We just adjust the MAF until the trims are correct and leave the MAF scaling where it is in our applications. On the Gen2 MAFT I think you can set it for Baro compensation if it has a baro, and on the pro it has one built in as long as you use speed density mode.

No direct help though for you...sorry

Slo_crx1

iTrader: (9)

I talked to my friend last night, the MAFT he bought is pretty much the vehicle specific one for his 2g (more specifically the 2.01 model), from my understanding it pretty much makes it a plug and play. Unfortunately he bought it from someone else and not a distributor so there's no instruction manual/cd that would list the settings for lo/mid/hi, so it looks like I'll have to log them in evoscan and adjust the MAFT box accordingly. As for the baro sensor, I think I remember reading somewhere that the MAFT uses a set output voltage at all times, which I guess is ok for where we live seeing that I can tune around it, but once the elevation changes it'll be off again, which to me is a rather crappy way to set it up.

Thanks anyway for the info JB!

Deepnine

iTrader: (4)

GM MAF frequency output should be baro and temp compensated, so there is no need for the ecu to calculate that again.

Slo_crx1

iTrader: (9)

I really hope it is, the only info I could find for the baro portion is that the MAFT uses a fixed baro output. I know the temp is compensated in the GM maf, just wasn't sure about baro...where we live it goes anywhere from 1100ft above sea level to 2800ft in a matter of a couple miles in any direction.

03whitegsr

iTrader: (8)

The GM meter is a true mass airflow meter. The Mitsubishi in comparison is actually a velocity meter with a baro and IAT sensors used to calculate the mass flow rate. The GM sensor measures changes in density directly and the output reflects a "true" mass airflow. The Mitsubishi sensor outputs a frequency based on the air velocity, then the ECU calculates mass flow rate based on baro, intake temp, and MAF frequency. The caveat here is that the GM sensor also is to some extent a humidity meter as well, as humidity also affects the sensor output, where I think humidty only marignally affects the Mitsubishi sensor, if at all.

The issue with locking the baro and IAT sensors is you no longer have baro and IAT trims. While you will compensate for density changes because of these different ambient conditions, you will not get corrections that will adjust fuel and timing to accommodate these different ambient conditions.

On one hand, this SHOULD provide more stable AFRs and timing advance, provided the MAF accurately measures air mass under various ambient conditions. On the other hand, the car will not be tuned to best optimize different ambient conditions.

To take it one step further, it seems like the EVO ECU should be able to accommodate a GM MAF directly. The GM MAF uses a Frequency output. Provided the EVO ECU can accommodate the frequency range of the GM MAF, changing the MAF scaling table to match the GM MAF output should provide reliable fueling. You would want to disable any density compensation within the ECU however, which is seems like has been discovered recently.

If the EVO ECU can handle the GM MAF frequency range, I see no reason why direct GM MAF operation isn't possible? Futher, combining something like a Subaru MAF (hot wire 0-5V) with a voltage to frequency converter could allow a good post turbo MAF sensor solution, as the Subaru MAF has proven to be much more stable in a pressurized enviroment then the GM sensors by the Subaru community.

Also, I think this thread title should be relabeled as something to do with "Direct GM MAF Implementation Discussion," or something similar, as it would probably get a lot more knowledgeable people involved.

Slo_crx1

iTrader: (9)

That's really good info to know...thanks!