silverRS4

I'm a little confused. Peak volumetric efficiency (VE) typically occurs at the engine's torque peak. Its the ability of the engine to completely fill the cylinders on the intake stroke of the piston. Its not uncommon to have 90-100% VE on today's naturally aspirated engines and even over 100% is possible with "ram" affects with intake and exhaust tuning. VCDS data logging a RS4 V8 yields air flow of 120 g/sec around 5500 rpm and 150 g/sec at 7500 rpm. Using 1.1 kg/m^3 dry air density (based on recorded IAT and BP), this yields a VE between 52-56% for one of the most advanced engines on the planet. I know the RS4 engine should have great VE, but an airflow of 150 g/s seems to be more in line with a typical 4 cylinder. What's going on?

silverRS4

Obviously the ECU knows the correct amount. Is there just a simple math error in the software for the output value?

Andy@Ross-Tech

You have two MAF sensors, each one reports only the airflow through its bank of 4 cyl.

silverRS4

<center><img src="http://i299.photobucket.com/albums/mm303/silverRS4/RS4ECMs.jpg"></center><p>I took a closer look at the twin ECM setup along with the sensors. I can only find one mass air sensor (on the diagram and on my car). But it looks like each ECM controls one bank of 4 fuel injectors, rather than the master ECM controlling all eight. Since each ECM is only responsible for one half of the fuel delivery, it would make sense that the airflow reported by either ECM would be one half, rather than all of the flow going thru the single throttle housing. I may not be a perfectly correct, but its good enough for me. Thanks for the help.