I made six passes at the track, on the second and fifth pass I pulled the air filter out to experiment, both times netted the slowest times of the day. Has anyone else observed this? or have an explanation why it would be slower?

 

I'll take an educated guess. I believe the computer tries to make adjustments but didn't have enough "learn" time to adjust for the less restricted flow on those short passes.

 

Are you sure you didn't suck in a bird?

 

No. There's no "adjustment" to make. Removing the air filter should increase air flow very slightly. The increased air flow is directly measured by the MAF sensor, the PCM adds the required amount of fuel.

With the LS1 style hood/air box, the air filter may be providing a smoothing of the flow, reducing the turbulence into the throttle body. Turbulence eats up pressure and reduces flow.

 

I'm not using the hood for air flow. I'm getting air from the bottom with something similar to the SSRA kit except extended all the way to the spoiler under the front of the car.

 

is the MAF still on your car?

 

Yes, it is stock untouched.

 

Well i would think your times should be the same with or without a filter. tha is weired. less restriction more air more power but not always better times. but slowing down is not right at all. the pcm pull timing or fuel is what must be going on

 

Yep on my GTO we took the air filter out and it ran a 13.6 instead of the 13.0 it was always running

 

We need numbers!!! "Freescan" these runs so we can see if the gms of air flow are different and/or the incoming air temp. Or if intake noise differences are affecting PCM retard.

 

I bet it has to do with the air filter missing causing turbulance in the air intake and actually slowing things down a bit.

 

wow...thats a big drop, thank you K&N

 

Immediately after making the dyno pull in my sig (325rwhp), I pulled out my air filter and made another pull, which was down 7hp. To rule out heat soak, I made a third pull which was right back to 325.

I've always wondered why, too. I assume that turbulence is the right answer.

 

Yes- we played around on a dyno one day also- did the same thing, 3 pulls back to back and the hp was down considerably after pulling the air-box. The boys at the dyno shop confirmed that the turbulance disrupted the air-flow into the MAF and thus the car made less power.

I would say that there is plenty of evidence here to support it as well.

 

Everyone thank you for sharing what you observed too. I'm glad it's not just my car.