Maybe an obvious question but can a dirty air filter lower hp? By how much?

The reason I ask is that I dynoed my G yesterday and only reached about 220hp at the wheels. I did go to a special AWD dynojet here in NJ. The guy that did the pulls owns a sedan. Said he got 235 stock. He wasn't a believer in the Stillen Hi-flow. He didn't notice any gains with the Stillen CAI.

Anyway not to start that war here... but when I went home I removed my Stillen and replaced the stock airbox. The K&N on the Stillen was pretty black all around. After I got the stock airbox in I took a drive and the G felt a little more torque. I just ordered a K&N filter for my stock box. Gotta go back and dyno again soon.

 

I think the quick and easy answer is "maybe" - "but not 15whp" and the same is true of one intake over another, not just a dirty filter.

...Try doing an ECU reset next time before you dyno. I think you'll get a better baseline that way.

 

My Chev. S-10 Blazer was a bit show accelerating, epically at highway speeds such as when passing another vehicle. I threw in a new air filter...now I'm good as new.

 

Xman when you go back do a run with the clean air filter, then do a quick ecu reset and then do another one. I wonder what that will bring us to chew on informationally as I suspect the ecu going granny, the dirty filter and the Stillen airbox are combining to net your loss at 15 HP.

 

Also I wonder if your muffler is good for a small loss as the stock muffler has a variable flap in it that open at certain RPM's. That would explain any torque losses if you experienced them maybe.

 

Here's a couple of pics of the filter. It actually looks a bit worse than the pics portray due to the flash. I'm definitely going back with a clean filter and an ECU reset. Thanks!

 

A while back when I had my Civic dyno'ed, I figured I'd replace the "cone" filter and re-dyno while it was on the dyno.. the filter was way worse than what Xman's looked like.. mine had caked on black crap and the filter was pretty old (not to mention I didnt have the inner fender cover so the filter was pretty much exposed to road grime kicked up from the front tire).. anyhow, after I re-dynoed (in the matter of minutes), I made about 5whp through the whole RPM range..

So I think the answer to the question, like doogie said, is "maybe".. if your filter was as bad as mine (which its not), then I'd say you could easily lose a fair amount of horsepower..