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Dyno Test PROVES Dirty Air Filters Cost Power #946813
07/20/07 05:21 AM
07/20/07 05:21 AM
Joined: Aug 2005
Posts: 4,563
NW Ohio
Jim Allen Offline OP
Jim Allen  Offline OP

Joined: Aug 2005
Posts: 4,563
NW Ohio
Was recently doing some dragstrip and dyno testing on a new model programmer on a Duramax diesel truck. The truck had just been "serviced" and the assumption (what is the acronym for A.S.S.U.M.E. again?) was that the air filter was new or at least checked during the service. Throughout the tests, we just weren't getting the right numbers, either stock or on program. One of us looked at the air filter indicator... it was showing all red! Well, heck! It was on the dyno at the time, so we installed a new filter and ran one test for fun. A solid 5 hp and 15 lbs-ft increase and much less smoke. It wasn't the worst looking dirty filter I have ever seen either.


Jim Allen
Keepin' the Good Old Days of Four Wheeling Alive
Re: Dyno Test PROVES Dirty Air Filters Cost Power [Re: Jim Allen] #946814
07/20/07 06:21 AM
07/20/07 06:21 AM
Joined: Jul 2007
Posts: 747
miami fl
lazaro Offline
lazaro  Offline

Joined: Jul 2007
Posts: 747
miami fl
when I finally removed my cone K&N filter and Tied it to another one and flung it on the power lines for amusment.
I installed a new EAA filter and my milage shot up 4/5 mpg.
I was surprised, I went 15,000 miles and cleaned it with air and it came out clean and It jumped up again in milage, clean air is vital to engine performance


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Re: Dyno Test PROVES Dirty Air Filters Cost Power [Re: lazaro] #946815
07/20/07 09:27 AM
07/20/07 09:27 AM
Joined: May 2002
Posts: 3,845
Terry Offline
Terry  Offline

Joined: May 2002
Posts: 3,845
I have been preaching this for 30+ years and base it on UOA testing. Air filter IS THE MAIN ingredient to better performance and MPG for most engines,spark or diesel. Those that take the change interval for air filter to factory recommended durations will MOST of the time find the leaks in the system and suck dust and or needlessly increase specific fuel consumption.

Had a major racing engine builder argue with me about semantics on this point when our common racing engine customer was running high levels of fuel in the oil and he poopooed my observations because ECU and injection systems correct for restricted air flow. ....Poppycock......

Re: Dyno Test PROVES Dirty Air Filters Cost Power [Re: Terry] #946816
07/21/07 10:16 PM
07/21/07 10:16 PM
Joined: Sep 2002
Posts: 39,806
Pottstown, PA
Gary Allan Offline
Gary Allan  Offline

Joined: Sep 2002
Posts: 39,806
Pottstown, PA
I've pondered this a bit. That doesn't mean that I'm correct here ..but these are my musings on the topic. In olden days, when our carbs had external vents, a clogged air filter meant sucking fuel excessively. When they went to internal vents(at the same atmospheric pressure - inside the filtered air zone) ..the rhetoric (mostly) evaporated from the media arm of the aftermarket as, I suspect, the major impact of the effect.

Now, I imagine, a restrictive air filter adds to throttling losses ..and alters MAP readings. Maybe only in terms of inches of water column at first ..but I'm sure that it's a progressive condition. Once you exceed the parameters of the mapped fuel curve ..a speed density system will just go to the max settings in corrective action. Something we would term in my former instrumentation calibrations as "OUT OF RANGE". I don't necessarily understand the dynamics of it in a racing situation ..but one should reason that you want fractional inches of negative water column across your air filter. Assuming that your OEM designed your plumbing appropriately, that's probably (my speculation, I've never researched it, nor tested it) all you'll see.

In a street piece, I'd say you're looking at some added effort in just getting the air to the engine on top of any alterations to the MAP readings. You're simulating a higher altitude for the engine ..or so I reason

Again, this is just my backburner pondering on the topic. It's not any enlightenment. That, I'd surely welcome from someone who truly knows. I'd also love to have the refined instrumentation to explore this at the end user level ..but that's beyond my means.

Edit: In the terms of a diesel, there is no inherent throttling loss due to no throttle. You are introducing one with a clogged or restrictive filter. Keep in mind when a diesel owner says that they have no "compression braking" ..they really mean vacuum braking. They have all the air and compression that they need 24/7 whenever the engine is turning rpms ..gobs more than any gasser..what they don't have is a butterfly to produce vacuum braking.

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