coxie
New Member
dont know if this has been posted before but here it goes
http://www.mkiv.com/techarticles/filters_test/2/
http://www.mkiv.com/techarticles/filters_test/2/
air filter test.
- Thread starter coxie
- Start date
theres also this theory:
http://www.autospeed.com/cms/A_2232/article.html
http://www.autospeed.com/cms/A_2232/article.html
very unfair test if i remember rightly as they used a strong vaccum cleaner or something which was said to be nothing like the conditions the filter has in the car and the hks and top filter are oiled and the vaccum pulled so hard it sucked the oil throiugh making the test for those 2 look very black or something but that does show the apexi should be good on teh road
Couple of points to clear the mist and hype...
Air filters have been around a loooong time and there is nothing really that new in their design.
The shalom article is spot on but relates to replacement filters and not induction kits.
I've seen many technical articles in the past and in general, the foam filters give better filtration but poorer air flow. This is normally quite a marginal difference but is a function of their design as you can't really do both effectivley. This is different to gnerating real world horsepower.
The induction affect works in two ways:
1. The shape of the cone causes a venturi affect and accelerates the air and drags more air in behind it. Different manufacturers try subtly different things to improve the effect but they are subtle. This is one of the reasons why the the filters in the coxie article all gave a similar improvement over stock because of the way the test was setup.
2. The longer the pipe the air acclerates down, the faster it goes and the more air it drags in behind it and the more torque you generate. This is offset against engine response and pressure drop and past 19" (told you the information was old) you can start to get negative gains. For a NA engine, the pipe is somewhere between a 6" and 18" from the various manuufacturers. In general, too short a pipe and you lose bottom end torque, too long and you lose top end power. Given a reasonable air filter the induction length is the most critical thing in determing the response of the engine.
Notice I said this was for an NA engine, for forced induction the rules are the same but you are more concerned with the turbo's performance.
In short, for our cars, move your battery and bolt the biggest air filter you can find (and that you like the look of :roll: ) as close to the AFM (or turbo if you are clever and have a MAF etc) as possible. It will reduce your off boost torque but will do wonders for your on boost response and peak power.
HKS/K&N/Blitz is not going to matter that much in the scheme of things.
rant over,
Jim
Air filters have been around a loooong time and there is nothing really that new in their design.
The shalom article is spot on but relates to replacement filters and not induction kits.
I've seen many technical articles in the past and in general, the foam filters give better filtration but poorer air flow. This is normally quite a marginal difference but is a function of their design as you can't really do both effectivley. This is different to gnerating real world horsepower.
The induction affect works in two ways:
1. The shape of the cone causes a venturi affect and accelerates the air and drags more air in behind it. Different manufacturers try subtly different things to improve the effect but they are subtle. This is one of the reasons why the the filters in the coxie article all gave a similar improvement over stock because of the way the test was setup.
2. The longer the pipe the air acclerates down, the faster it goes and the more air it drags in behind it and the more torque you generate. This is offset against engine response and pressure drop and past 19" (told you the information was old) you can start to get negative gains. For a NA engine, the pipe is somewhere between a 6" and 18" from the various manuufacturers. In general, too short a pipe and you lose bottom end torque, too long and you lose top end power. Given a reasonable air filter the induction length is the most critical thing in determing the response of the engine.
Notice I said this was for an NA engine, for forced induction the rules are the same but you are more concerned with the turbo's performance.
In short, for our cars, move your battery and bolt the biggest air filter you can find (and that you like the look of :roll: ) as close to the AFM (or turbo if you are clever and have a MAF etc) as possible. It will reduce your off boost torque but will do wonders for your on boost response and peak power.
HKS/K&N/Blitz is not going to matter that much in the scheme of things.
rant over,
Jim