Does anyone know how to get actual air flow values (as in CFM) from the MAP sensor voltage readings? Anybody know what the conversion is? Any way to get air flow measurements through the intake over the rpm range while the car is on the dyno? This is for the new K series engine. Any info will help, thanks!

 

You need a maf (mass air flow) sensor to measure flow. A map measures vacuum/pressure.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by vtecazo &raquo;</TD></TR><TR><TD CLASS="quote">Does anyone know how to get actual air flow values (as in CFM) from the MAP sensor voltage readings?</TD></TR></TABLE>W = rho(p,t) * (displacement/2) * rpm
(where rho = density, function of pressure & temperature)

Then you have to correct for the pressure drop across the intake ports & valves. This correction depends on the cam profile since the valve isn't 100% open during the ENTIRE intake stroke.

Actually, that's mass flow, in pounds per minute. You'll want mass flow rather than volumetric flow (CFM).

 

but where can I find this conversion function. I plan to read the pressure voltages from the MAP sensor at different RPMs while the car is accelerating on the dynamometer. I am trying to perform an analysis of the engine's efficiency with and w/o a turbo and I need to get accurate values of actual air flow. I'm not looking for an airflow CFM estimation. I need to monitor the CFM or kg/s, etc., while the car is on the dyno. Again, any info is of great use, please help.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by vtecazo &raquo;</TD></TR><TR><TD CLASS="quote">... I'm not looking for an airflow CFM estimation... </TD></TR></TABLE>Well, that's all you can get. Hondas don't measure airflow directly. They measure temperature, pressure, throttle position, and rpm so they can estimate airflow. It's not a conversion function - it's fundamentally different.

If you really need a measurement it'll probably be easier to make your own measurement without using the ECM data.

 

so how does the computer end up calculating air-flow. What equation does it follow? What I had meant was that i wasn't looking for a MAX air flow CFM like when you're trying to select turbo trims.