Rotary Car Club - View Single Post - Turbo on RX-8

scotty305 · 07-26-2008, 03:04 PM

The Lancer Evo and WRX STI include both MAP and MAF sensors. I won't pretend that I know much about how their stock ECUs work, but they are two good examples of modern turbocharged engines. It would be much cheaper to use only one sensor as opposed to two, so that makes me think that there are enough advantages and disadvantages that the OEMs would want to use both.

It's pretty apparent that a MAP sensor alone doesn't tell you how much fuel to inject: for instance the MAP sensor will measure about 10psi on a bone-stock FD3S that makes about 250hp at the crank. I don't have a specific example in mind, but the same MAP sensor could measure 10 psi with an upgraded turbocharger, ported engine, and free-flowing intake and exhaust setups on a car that could be making over 300 hp at the wheels. The more powerful motor will require a lot more fuel, which is a good sign that it's flowing a lot more air. This is one example of how a MAF sensor could be very useful; a properly calibrated MAF sensor can accurately measure how much air is going into the engine (if properly calibrated) and simplify the tuning process (if you know how to use the data from your properly calibrated MAF sensor). Modern MAF sensors are not much more restrictive than an Intake Air Temperature sensor, you can install them in a bung that fits in any diameter of intake pipe (although you may need to re-calibrate the sensor voltage vs. airflow if you change the diameter of the pipe).

Then again, there's more to tuning an engine than just making sure it runs at your desired air/fuel ratio. I don't know how a MAF sensor would help determine the "correct" ignition timing settings for making power.

As with anything else, the most powerful ECU in the world won't do you much good if your tuner can't use it. You will need to find a tuner who is familiar with MAF-based systems or learn it yourself. Part of learning often involves making mistakes, and we all know how costly mistakes can be when turbocharged rotary engines are involved.

By the way, cool site Mazdamaniac, and thanks for sharing a bit about the RX-8 ECU.

Edit: meant to post this in the "MAF vs MAP tuning" thread in the ECU section. Nonetheless, thanks for sharing about the RX-8 turbo setups.

07-26-2008, 03:04 PM	#89
scotty305 Rotary Fan in Training Join Date: Mar 2008 Location: Culver City, CA Posts: 84 Rep Power: 18	The Lancer Evo and WRX STI include both MAP and MAF sensors. I won't pretend that I know much about how their stock ECUs work, but they are two good examples of modern turbocharged engines. It would be much cheaper to use only one sensor as opposed to two, so that makes me think that there are enough advantages and disadvantages that the OEMs would want to use both. It's pretty apparent that a MAP sensor alone doesn't tell you how much fuel to inject: for instance the MAP sensor will measure about 10psi on a bone-stock FD3S that makes about 250hp at the crank. I don't have a specific example in mind, but the same MAP sensor could measure 10 psi with an upgraded turbocharger, ported engine, and free-flowing intake and exhaust setups on a car that could be making over 300 hp at the wheels. The more powerful motor will require a lot more fuel, which is a good sign that it's flowing a lot more air. This is one example of how a MAF sensor could be very useful; a properly calibrated MAF sensor can accurately measure how much air is going into the engine (if properly calibrated) and simplify the tuning process (if you know how to use the data from your properly calibrated MAF sensor). Modern MAF sensors are not much more restrictive than an Intake Air Temperature sensor, you can install them in a bung that fits in any diameter of intake pipe (although you may need to re-calibrate the sensor voltage vs. airflow if you change the diameter of the pipe). Then again, there's more to tuning an engine than just making sure it runs at your desired air/fuel ratio. I don't know how a MAF sensor would help determine the "correct" ignition timing settings for making power. As with anything else, the most powerful ECU in the world won't do you much good if your tuner can't use it. You will need to find a tuner who is familiar with MAF-based systems or learn it yourself. Part of learning often involves making mistakes, and we all know how costly mistakes can be when turbocharged rotary engines are involved. By the way, cool site Mazdamaniac, and thanks for sharing a bit about the RX-8 ECU. Edit: meant to post this in the "MAF vs MAP tuning" thread in the ECU section. Nonetheless, thanks for sharing about the RX-8 turbo setups. Last edited by scotty305; 07-26-2008 at 03:11 PM.