my new custom CAI and MAF

jrb55gh

I have measured the pressure drops across various parts of the stock 370z intake tract at WOT and 7300 rpm to determine where to place the emphasis on reducing restrictions. The engine, intake and exhaust are completely stock except for an EcuTek tune. Your custom cai addresses the most important areas. It would be interesting to know the pressure drop of your cai at the entrance to the throttle body under similar conditions.

The stock intake pressure drops measured are:

1.044” H2O pressure drop of air filter only
2.724” H2O pressure drop of intake duct before the air filter
7.128” H2O pressure drop across stock MAF tube

The major restrictions are in the duct up to the air filter and the MAF sensor. The air filter restriction is small compared to other areas of the intake tract. Even if the filter restriction could be halved the flow gains would be almost negligible compared to the other parts of the intake tract up to the throttle body. The small gain in air filter flow may not be worth the loss of filtering efficiency (% of dust entering the filter that is trapped). Most stock paper air filters have a filtering efficiency of about 99% whereas the oiled gauze low restriction filters have a filtering efficiency of about 96%. Here is a link to an informative air filter test:

K&N Air Filter Review - Debunking the Myths (and why OEM is better)

My conclusion from this is to use high efficiency filters on a low restriction cai and keep dirt out of the engine.