Well, it stands to reason that a open filter would suck in more engine room heat and there-for the engine would make less power. Countless times I've measured IAT temps on differing cars and I've done this on the ranger now several times. (search out some of my other posts) Also, every single time I do this I see the temps cool off to near ambient once rolling 25-30mph. So.. is a shield really worth it? I mean once your rolling and the temps are the same whats the benifiet of a shield?
Well I decided to make a totally inclosed shield for my K&N conical kit after seeing the temp swings this summer while datalogging in traffic. But before I did I wanted to **prove that it would actually make a power difference**. And to be honest my butt-dyno was telling me the open filter was making more power on the top end.
Here is what I did:
1) Made a foam board/duct tape enclosure that sealed everything around the conical filer except The headlight opening. Drove it for a day to work like this. (I like how quiet it is btw)
2) Let the truck fully warm then drove 2 miles to a dead flat road.
3) Made a 3rd gear power pull from 1500-5700rpms
4) Drove 1/4 mile and in 20seconds cut it all off.
5) Drove back to the same flat area and did another power pull.
This is a honest back to back power pull/acceleration and the data points are identically lined with each other too.
I was a little supprised by the top end power! I would have guessed the low end was higher because of the slightly warmer IAT temps. But the top end???!! Hum... I love science.
btw, Don't take these power numbers and compair them to "claimed power by ford". It's a "calculated net TQ" as the convertor/pcm is seeing. Not sure what it would do on a dyno.. but for this test it is a consistant way of measuring power changes. Especially since these two pulls were within 2 minutes of each other.