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      04-05-2006, 07:13 AM   #3

Drives: 2006 330i
Join Date: Mar 2006
Location: San Jose

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Just to do the math on this one:

There's an air-compressor rule of thumb that states 1 HP produces 4 CFM at 100 PSI. Power = (output) airflow * pressure.

Let's look at the cfm at 1 PSI of boost. It would take a 1/2 HP to deliver 200 CFM at +1 PSI. And a HP is 745 watts. No way is a motor drawing a couple of amps @ 12 V (24 watts) going to come even close.

The air consumption of the engine depends entirely on RPM, so any pressure it does produce will fall-off very rapidly with engine RPM as well, since unlike a turbo/super-charger, there is no scaling with engine speed. At 6000rpm, a 3L engine will actually inhale in excess of 300 cfm.

These guys, in contrast, are drawing 60 amps (120 amps for the super version), making their boost claims much more reasonable. This is very much in line with the theoretical power requirements to compress air at these rates and pressures.

Last edited by bos; 04-05-2006 at 08:09 AM.