First off, I want to thank Modern Automotive Performance for donating the 3 hours of dyno time needed to complete this test. The test was performed on a AWD DynoJet. Peak boost was 29.0 plus/minus .5 psi for each filter. This test takes into account only power produced and in no way tested filtering ability.
CAR USED FOR TESTING
2005 Mitsubishi Evolution VIII GSR SSL
Evo IX turbo w/ported exhaust housing
E85 fuel (winter blend = 70% ethanol)
Buschur TBE w/testpipe
Buschur ported/coated exhaust manifold
Buschur coated SS o2 housing
Buschur Deluxe FMIC with Buschur LICP/UICP
Kelford 272 cams w/ GSC beehive springs
Evo IX BOV
Buschur intake pipe
Buschur ported IM/65mmTB
FIC 1050cc injectors
Walbro 255HP fuel pump
Buschur old air filter (eBay style, dry, no longer available)
Tune with MAF scaling set for the Buschur filter
FILTERS TESTED
Buschur (old style, old and rusty)
Perrin
Amsoil
Vibrant
K&N - FIPK
Apexi (note small filter inlet in 2nd picture)
K&N - small
no filter
RESULTS
Buschur: 378whp/361wtq (old style, no longer available)
Perrin: 376whp/345wtq
Amsoil: 374whp/344wtq
Vibrant: 371whp/351wtq (current style Buschur air filter)
K&N - FIPK: 369whp/355whp (comes with Typhoon intake kit)
Apexi: 367whp/357wtq
K&N - small: 367whp/346wtq (caused more knock than others)
no filter: 375whp/358wtq (not recommended to run filterless!)
CONCLUSION
The car's tune was properly setup and scaled for the old-style Buschur air filter so take those results with a grain of salt. Excluding the Buschur, the Perrin filter showed the highest peak whp which was ~10whp higher than the K&N's which CBRD noted a few months ago (thats the thread that spurred the idea for this filter test). The Amsoil filter was very close on Perrin's heels and considering their claims if being the best filtering air filter and very minimal maintenance (no oil, just blow out with air compressor to clean) it may be a very good choice for a street car. K&N's performance in this test was extremely disappointing especially since that is all they do! Apexi makes a good filter but the small inlet really hurt it in the test; this is their Evo kit and MAF adaptor and its really odd to me that they wouldn't use a filter with a larger flange. The runs without an air filter really go to show that at this power level a good performance air filter poses very little restriction. It is also interesting to note that the owner of this car, Scheides, has already ordered a Perrin air filter and Vibrant MAF adaptor to replace his old rusty Buschur air filter with. I will most likely be running a Perrin on my car, but I am still considering the Amsoil due to its filtering ability. I personally run a Vibrant on my car right now and the inside of my MAS is very dirty leading me to believe it does a very poor job filtering the incoming air.
Pardon the salt and dirt every where; its the middle if winter here in Minnesota and is impossible to keep anything clean.
MAP shop car (white VIII RS) & Scheides's car afterwards for lunch
Threaded Mode