Round 2 of testing is finally complete. Round 1 of testing can be found
here. This test included a few more filters and was performed slightly differently from Round 1. Another variable to consider is the ambient temperature, which was a toasty 94* during today's testing. The temperature during Round 1 was much cooler (60's if memory serves correct).
Filters tested: Stock, ITG, K&N, BMC, Helene, BMS
Test Vehicle: 2008 335xi E92 6AT with JB2 and no secondary cats
Test Procedure: Each pull was done in 3rd gear. Repeated 4th gear pulls on this load-bearing dyno causes overheating even with the factory oil cooler installed and plenty of airflow in the dyno cell. RPM sampling range was from 2k to 6.8k. Boost was sampled from the BOV vacuum line, and AFR was sampled at the right-side tailpipe using an Innovate LM-1 wideband. The vehicle was warmed up to the point of the oil temp gauge being 3 hash marks short of 250* for the first run to begin for each filter. After each run, the car was allowed a few minutes of cooldown until the oil temp again read 3 hash marks short of 250*. Four runs were done on each filter. The best run for each filter is shown below compared to the stock filter (stock is the solid line). Underscoring the impact of heat, you'll see that the best run for nearly every filter (save the BMC) was the first run. The other runs, grouped by filter, are also found below. Ambient temperature remained between 91* and 94* during the entire test with humidity at 32%.
Conclusion: Under these conditions, none of the aftermarket filters outperform the stock filter.
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