Air Filter Facts Part 7: Performance differences between clean air filters
Average atmospheric pressure at ground level is typical estimated at 101.325 kPa. The difference between no filter and the least flowing clean filter, as measured by the Oak Ridge National Lab, is less than 0.7 kPa. This represents less than 0.7% of atmospherics pressure, although it is over 25% of the increase in pressure drop that is considered characteristic of a clogged filter (increase in pressure drop of 2.5kPa). Is this pressure differential enough to cause differences in performance?
Unfortunately, we have no data on this point from Oak Ridge. Diesel Power Magazine, however, commissioned this test from Westech Performance, which compared K&N (typically measured as the best flowing air filter on the market), Volant, AFE, Airaid, True Flow, and S&B aftermarket air filters on a 2004 1/2 Dodge Ram 2500 equipped with a manual transmission:
Diesel Power Magazine's conclusion: "don't bother trying to tell them apart, the average results of the dyno runs ranged between 308.7 and 310.4 hp, and each filter had at least one run that was in the 309s." Differences of 5 hp or less or typically not statistically significant on dynos, due to the sensitivity of the tool, so the differences in results are not significant.
The test's conclusion, then, is that drop-in air filters do not result in any performance difference when tested clean. Can we get corroborative proof to confirm this conclusion?
Next we look at other supporting evidence on air filters and performance... So come back soon!
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