After running an AFE cotton gauze filter for about 25K miles now (first mod to the truck) - I figured it was time for a cleaning. I dropped my stock paper filter back in the stock airbox, last Friday night.

To my surprise, the truck's power "feels" to have changed everywhere but WOT. Throttle responce and power off idle to 2K feels improved. The thing is, I'm not scanning any difference between this filter and the old one. (delivered engine torque, and MAF readings).

I do not believe the differences to be PCM/learning related... I've already driven over 250 miles - everything has been consistant, and my STFT's are not straying any more than normal. (0's and 1's in the frequently visted cells)

So I started to wonder if this engine just likes a little more vacuum in the intake system for better (more accurate) MAF readings or some odd theory like that. I scanned "Manifold Vacuum PSI" last night.

At WOT, I'm seeing as low as 0.23psi (if that's accurate) in the intake system. My short WOT blast from 3,600 - 4,700 had readings of 0.23 to 0.64 psi. Average is 0.40psi

I know every little bit counts in some applications, but is that enough of a restriction to warrant swapping filters, nevermind a complete intake system? (for the sole benefit of getting more airflow) I understand things may be reading different at 6,000rpm.

I would never expect to see "0" psi on a N/A engine without some ram-air system helping.

My little tests here are pretty far from being done - but I was real surprised with what I saw so far.

This weekend I'm planning on making some short WOT runs scanning/comparing the MAF, manifold vacuum, and delivered engine torque with both filters.

Maybe I can find a way to at least run the airbox without the bottom half, to simulate a free flowing intake setup if anyone things the bottom of the airbox is a restriction that's holding everything back.

 

When I had my Silverado, it ran faster at the track with a plain ol Purolator paper filter than a K&N drop in filter by about a tenth. A few Dodge guys have dynoed the K&N drop in filter vs the stock paper filter on the Hemi and the K&N has shown a power loss. I'm not sure the "high flow" filters are all they are cracked up to be.
Jim

 

That's strange... My paper filter had the truck running AWESOME for about a week, and then it just turned pretty lousy. I wonder if it was because I did my little SD tune here with the cotton-gauze in there? I don't know...

I was able to get out and make two little 1st gear runs this weekend. Unfortunately, there were a few variables that came out of it. I'm not sure how conclusive this is, but I'll post the results...

1st "run" was with the paper filter. Full 100% throttle. IAT, 39*F. There was a tickle of KR up top - 0.4*. Max MAF - 40.95 @ 6036rpm. Average timing - 23.32*.

2nd "run" was with the CG filter. For some reason I only saw 98% throttle. IAT, 45*F. No KR. Max MAF also 40.95, but at 5750-5850rpm. Average timing 23.18*.

Runs were from 4,000-6,000 rpm.

The paper filter only allowed me to hit the .84 g/cyl range. The CG filter took the motor up to the .88 g/cyl range.

The KR in the paper filter run actually took the timing down to the same range as the CG filters, because the CG filter was in the next higher g/cyl range which happened to provide less timing.

The vacuum in the manifold during the paper filter run was a tenth or so of a PSI higher throughout the run. average was 0.66psi. CG filger only saw 0.51psi.

Scanned/Calculated "delivered torque" was an average of 10ft/lbs more with the CG filter. (379.23 vs 389.75.)

I do not have any info on the WOT fueling.