AFM to MAP conversion, and temperature compensation~?

erolit

New member
Hey,

I've just been thinking, most MAP sensor based airflow systems have manfold temperature sensors to compensate for the change in air density throughout the wide temperature range of the compressed intake air.

Most of the alltrac AFM to MAP converstions people seem to be doing these days (SMT6/7, circuit board based ones) dont have any compensation for air temperature short of the pre-intercooler airflow temperature sensor (which most people get rid of when they switch to MAP anyway). When manifold temperatures can swing 50-60 degrees on/off boost you are talking almost 20% difference in air density...?

How is this compensated for? Is it that there is a different pressure at zero degrees vs 80 degrees, and the MAP sensor can detect that? If so, what are the MAT sensors for in cars such as the ST205?

(I'm about to attempt MAP conversion using an old IFT fuel computer by PerfectPower, and i am wondering how i need to go about modifying the signal for temperature.)

Thanks guys,

Elliott
 

OlyST185

Active member
if you want my advise, if you want the perfect mixture first you'll need wideband o2 sensor and a standalone, the to trick to convert AFM to MAP signal has a problem even if you find a way to make the IAT available for the computer:
The afm reads the air just beside the air filter, the MAP reads it in the intake manifold, so thier a difference delay between the signal so theres no way you can have a 100% effective air/fuel mixture, by the way it would be close, like 80-90%.
my 2 cents.
 

ChrisD

New member
It shouldnt vary that much...but the ECU does do corrections, you just need to install the intake temp sensor in your system, which is found in the AFM.
 

erolit

New member
Well hopefully it should be all good for me to attempt the conversion, because before i bought the IFT (a realllly oldschool perfectpower tuning device, 2 fuel maps with corrections for boost and intake temp, 1 ignition map) i bought an ST205 ECU and MAT sensor. I installed the sensor just pre-throttle body and its still there, so i will just use that for temperature correction.

I've got my wideband, 3 channel datalogger and the fuel computer - this sunday i'll give the afm>map conversion a shot. I'll post all the results (i can log MAP and AFM side by side at high resolution), as well as the fuel maps i end up with (the IFT has an almost identical fuel map configuration to the SMT6/7 - that is a 7x16 tuning map with a 1x16 correction map for boost/temperature)

Elliott
 

BriinumsBo

New member
erolit":2zxxjdjc said:
Well hopefully it should be all good for me to attempt the conversion, because before i bought the IFT (a realllly oldschool perfectpower tuning device, 2 fuel maps with corrections for boost and intake temp, 1 ignition map) i bought an ST205 ECU and MAT sensor. I installed the sensor just pre-throttle body and its still there, so i will just use that for temperature correction.

I've got my wideband, 3 channel datalogger and the fuel computer - this sunday i'll give the afm>map conversion a shot. I'll post all the results (i can log MAP and AFM side by side at high resolution), as well as the fuel maps i end up with (the IFT has an almost identical fuel map configuration to the SMT6/7 - that is a 7x16 tuning map with a 1x16 correction map for boost/temperature)

Elliott

4 years later. results? :D
 

built2run

New member
lol the supra guys have the way to do it (7mge ma70 supra) the box costs 400bucks but for a straight accross change over it would be simple to do and cost about 100 bucks but i still need to make a simple board to do this but i just don't know the hardware i'll soon find out and make one for me and if its worth it i'll possibly do a write up

btw it will net you very little gains but it will make the engine bay look cleaner and less cluttered.
 

Simba

New member
If you're contemplating converting to a map setup without a system that can read and adjust for air temperature, quite simply: DON'T.

If you want to do it, do it properly with a standalone EMS or good piggyback that can do it properly like the MAP-ECU.
 

built2run

New member
in a little over a week i will be prototyping a map conversion box that has that is a direct conversion/no adjustments. later it will be retro fitted to a hot wire MAF like those on newer toyotas. let me know your oppinions.
 

built2run

New member
kind of, this first one will be a prototype so it will be pretty crude but it will still be in a box of some sort to keep it protected just not sure if i will mount it in the cabin somwhere or in the engine bay.

i guess to better answer you..... maybe lol
 
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