Originally Posted by tscompusa

9653 is a universal rom off an evo that doesn't have a map sensor from the factory so you can just install the map sensor with no modifications to the rom and it will work.. you want an omnipower 4 bar map and just use the fuel temp as iat.. pointless tapping a sensor in after what was discovered by people of the accuracy of an existing sensor on the car.. requires no rewiring of anything.. just buy the map sensor .. plug and play.

Originally Posted by Zakie@TIC

Thanks for the reply, a omni power 4 bar would be nice.....do you sell them? I'm not sure if the EVO5 came with a fuel temp. sensor, whats should be my next option in terms of the IAT . Also would like to have some help in wiring the map senor, pin outs of the ECU etc..

Originally Posted by l2r99gst

I give you an A for effort, but some of your thinking is off. The temp sensor in the MAF isn't there to measure engine bay temp. It's there to measure intake air at the maf sensor.

As you correctly stated, the Mitsu Karman MAF is a volume air sensor. The baro and temp are needed to correct to mass airflow. That's why the baro and temp sensor are directly in the MAF, taking the measurments where the volume air flow is being measured.

As you know, there are many 'loads' in our ECU. The load that is used for most of the fuel and ignition 3D maps is the baro+temp compensated load, meaning it's the mass airflow. So, our maps aren't pressure or volume vs RPM, it's actual mass airflow vs RPM. Of course, there are certain conditions that the ECU uses where it uses an uncompensated load where only volumetric airflow is used (such as using only baro comp load for the ignition maps over IAT of 77F, to disallow too much advance), but in general, the mass airflow is used so that it can calculate the mass of fuel.

It's basic PV=nRT. In an engine, volumetric airflow is:

Airflow (CFM) = PR[RPM*V.E.*Cid/3456]
PR=Pressure ratio=(boost in psi+atmos(psi))/atmos(psi)
RPM = RPM of engine
V.E. = volumetric efficiency at RPM being measured
Cid=cubic inch displacement= 122 for our 2.0L engines

To get mass airflow, you have to multiply that volumetric airflow by P/RT:

Airflow(lb/min)=(Airflow(CFM)*P/RT)*29(g/mol air)
P=atmostpheric pressure in PSI
R=ideal gas constant=10.7316 ft3·psi· °R-1·lb-mol-1
T=temperature in R (F +460)


In terms of SD for the Evo ECU, the IAT sensor needs to know the true air temp after the intercooler. That's the only way it's going to know the true mass airflow. Using the fuel temp sensor isn't telling it the correct info. Of course, you can tune around it, with the 3D maps and the VE maps, but you are simply correcting the mistaken mass airflow that is being reported.

Originally Posted by evilempire76

I'm curious as to how tuning using the fuel temp to mimic an IAT for SD tuning would affect a car running a forward facing turbo setup? Since there really is no intake to speak of on these forward facing turbo setup cars, I would think the temps that the turbo are being subjected to are vastly different then what is going on under the hood of the car.

Also, does elevation affect this type of SD tuning? I remember reading somewhere that is does, but would like some confirmation.

Originally Posted by JohnBradley

Its just changing an ADC address in the ROM...0x03 to 0x0E as I recall.