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, Wed, 14 Sep 2005 19:25:21
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statement applies to drop in filters and to their use with T7 cars like the viggen, so please lets draw the line there...
I my self have never been a big fan of "listen to what bla bla bla felt with his butt" or "every tuner I know sugjests getting rid of the paper" type babbling, since these statements have very little informative value what so ever.
I like seing numbers, somthing that can be measured, like pressure-drop and temperature in the intake. Jak, since your a smart guy with oppinios do you think you could actually point out to us how good these filters are after all? I have my own beliefs and oppions and here are a few numbers you might find to your intrest.
Case Subaru legacy
Pressure drop in subaru intake http://www.subaruclubfinland.net/kuvat/Pete/filter1.gif
rpm point1 point2 point3 point4
4000 12 17 17 20
5000 20 24 26 30
6000 27 32 34 41
7000 36 44 48 60
point1 -in the air box before the filter element
point2 -in the air box after the filter element
point3 -in the air duct after the air-flow meter
point4 -in the air duct after the resonator box
What do these figure mean? Standard air pressure at sea level is 14.7psi which equals 29.92in mercury or 406.9in water. Therefore 1in mercury equals about 0.5psi and 1in water equals about 0.036psi. Clearly, this Subaru has a problem which won't be solved by replacing the filter element. At 7000rpm there is enough flow resistance caused by the air muffler before the air filter to cause a depression of 36in water. That's a restiction of 1.3psi even before you get to the filter! again, at 7000rpm the filter restriction is only 8in water (44- 36 = 8) or 0.29psi. The other major restiction is the little resonator box stuck in the air duct right after the air meter. It is causing a depression of 12in water (60-48 = 12) or 0.43psi. In total the system has a pressure drop of 60in, 2.2psi. Instead of air presure of 14.7psi to force air into the turbo, this car is working with only 12.5psi...
According to my own studies a T7 intake systems with all the componets in palce will have a depression of 1.5psi (this measured from a stage III+ modified viggen in high revs, pushing 220g/s worth of airmass flow, ~290hp).
So lets look into the the filter, what can be achieved there. "BOB the guy"
http://www.bobistheoilguy.com/airfilter/airtest1.htm
has some documented test results posted at his website.
Type Average [psi]
Napa Paper filter 0.249
K&N cotton gauze 0.231
Racing Beat foam 0.236
Jackson Racing foam 0.245
Amsoil foam 0.235
By comparing the best and the worts (0.249-0.231) = 0.018psi
So, with a T7 car and stock filter one will see a depression of 1.5psi and with a drop in "free flow filter" roughly 1.482psi :)
Does this make a difference? IHMO the use of a drop in filter in this case is pure nonsense and waste of money...
And why do tuners recommend drop in free flow filters? I would bet my money on the fact that its good business for them. I would imagine that they purchace a big quantity of these filters at very resonable price from the filter manufacturers and later sell them with good profits...
BTW. Hirsch does uses std paper in thir tuning kits, so there is one "tuner" to whom this does not apply.
my 0.02
posted by 12.119.32...
, Thu, 15 Sep 2005 08:18:48, Wed, 14 Sep 2005 19:25:21, Thu, 15 Sep 2005 08:02:42
, Wed, 14 Sep 2005 07:53:21, Wed, 14 Sep 2005 07:51:53, Wed, 14 Sep 2005 21:19:21
, Thu, 15 Sep 2005 02:35:59, Thu, 15 Sep 2005 03:09:56, Thu, 15 Sep 2005 09:33:00, Wed, 14 Sep 2005 22:37:05, Wed, 14 Sep 2005 10:31:05
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