I downloaded some new software for my OBDII scanner so that I can log up to 6 parameters. I did three tests with various stock intake setups to lookk for any potential gains. I measured timing advance, intake temp, rpm, and air flow at the MAF (grams/sec).

My cars mods: Z-pipe and 5/16" spacer

The intake setups:

1) Stock airbox with Z-pipe
2) Modified Powerduct (cut lower lip of Powerduct cover to let more air in)
3) Power Duct cover and over radiator snorkel removed (this setup was to emmulate a POP charger setup). I'll call this the open airbox

Conditions: late night, lower 70s, 50% humidity, 30.0 baro pressure, 1100' elevation.

Test run: Highway, 3rd gear from 3500rpms to 6500rpms. 3rd gear was used to capture as much data as possible because the gear winds out longer.

Runs: two back to back runs with 5 minutes cooling (highway speed) between runs.

Interesting notes:

1) The stock airbox and modded Power Duct cover attain very similiar temps at cruise and at a stop. Both will spike 10-15 degrees over ambient when at a stop for longer than 30 seconds. It takes about 5-10 seconds for the intake air to get near ambient (+5 degrees) after a cruise from stop.

2) The open airbox will spike to 30-45 degrees above ambient when at a stop for longer than 30 seconds. It takes about 20 seconds to cool the air down to near ambient after a cruise from stop.

3) The open airbox is very aggressive sounding. Sub 4000rpm tip-in acceleration and tip-in highway acceleration in MM 5 is negatively impacted. Normal acceleration feels softer. Torque converter lock-up and unlock is much more pronounced and somewhat aburpt. It takes a bit more throttle to achieve the same acceleration compared other two setups. Tip in WOT at 4000-4500rpms feels great and more responsive, snappy. It sounds great too. Brake stall launches feel a bit weaker. The typical 5AT bog on launch is a bit more pronounced. 0-40mph acceleration feels a bit weaker, but sounds much faster.

4) The modded Powerduct setup is fractionally louder (15%) than the stock setup. Part-throttle acceleration is much improved as is off the line, part-throttle and WOT. 4000rpms+ tip-in WOT doesn't feel as snappy, but after 500rpms, there's no discernable difference between this setup and the open airbox, other than noise. TC lock/unlock is far better. The engine at a low rpms cruise feel smoother. The engine is far more responsive to throttle input around town. There is a constant wave of acceleration at medium throttle on the shifts. Under the same situation, the open airbox feels boggy initially after the shift.

5) The stock airbox is obviously quieter. It delivers the best around town driveablity. It delivers the best downshift WOT performance. There is a surge of power on every shift. This setup has the least initial snap on a 4000rpm WOT run.


The WOT test results showed that the timing on all the setups was basicially the same (+/-2 degrees, random). Intake temps were basically the same (+/- degrees). The kicker was the airflow. The stock intake showed the most airflow at the MAF followed by the modded Power Duct and then the open airbox. Max airflow with the stock airbox was 169 gm/sec (ave 142 gm/sec) where as the modded Powerduct saw 162 gm/sec (ave 138 gm/sec) and the open airbox saw 159 gm/sec (ave 136 gm/sec) .