Air Filter's

[Trancendental]

Does the shape of your replacement Filter make a difference to Performance? Furthermore, are certain shapes more suitable for a specific vehicle?
Or is it just a sound thing?

http://www.knfilters.com/universal/universal.htm


After talking with Oldschool at the ACE Cafe I've been thinking hard and am comtemplating going back to my original Airbox.

Anyone got any input or suggestions?

 

[dhugg9]

Yes,

Air filters size and shape matters.
Even filters between pertol and diesel cars are different.
You need to be specific when you ask for one.

dhug

 

[Oldschool]

When you speak about air filters in this respect you to specify what air filter means.

If it is the filter element only then size is much more crucial than shape. Genrally the bigger a filter is the more it can flow. But this also depends on the filter medium. Foam filters are the worst filters when it comes to flowing needing between twice and three times the surface area of cotton gauze or a well flowing paper filter.

Shape is important within reason. The less edges (in total length) a filter element has, the less area is needed to flow the same amount of air.

If you relate to the induction as a whole the same principles apply. Additionally you have to find the right balance between gasspeed and total amount of air flowing. You also want to have fairly long inlet tracts in order to have an added advantage of the gasspeed and want to achieve engine specific volumes.

Important is obviously too that the induction doesn't draw any air that is above ambient temperature. An important fact that is often overlooked is the quality of tubing. Tubing that is not smooth (rough surfaces, rippled) or has got sharp bends or poorly designed bends or steps will adversly affect airflow and consequently lead to power loss.

Even if the induction is placed in a rather cool location under the bonnet and having an cold air feed it is not guaranteed that the revised induction will work better than standard. The hydrodynamic paradoxan is often hitting here too, which does not become appearant on the rolling road. But it will show starvation out on the road once the car is moving. And the faster it gets the effect becomes more dramatic.

 

[PNL]

Nice thread old school sooo your bassically saying that by just replacing the original panel filter with say a k&n or green cotten panel filter would be better than those nasty straw sucking performance filter that are everywhere please explain which is the better and why

 

[Oldschool]

Within a given induction setup the most important thing is that the filter medium is flowing well. And it should not be very much different than the paper filter element when it comes to the shape.

If you want to go for a bolt on after market kit it should be a real kit and not just a bolt on filter. The worst you can do for torque is to just put an mushroom type filter on the top of the throttle body. At very high rpm, which is way out of what you will get to with the standard engine, you will see a power improvement over the longe induction tracts. This is why in a lot of performance cars you have a variable inlet track length.

Generally aftermarket cone filters etc are not bad when designed properly. The rather cheap Taiwanese twin cone filters, which you can pick up for some £25 flow better than the BMC or Green twin cone filters. They are not copies of anything. They were designed by people who do know what they are doing.

But even when you have the best flowing filter physics does apply. The reason why the GSR induction kits work well is because it was taken a lot of care just to make sure that minimal flow losses will be achieved by trying to cut down on turbulences whereever possible and to increase the effects of the inertia. You can achieve this only by designing an induction system. It is not possible to have one single solution for many cars as some of the manufacturers suggest with their product range.

The same goes for anything else on the inlet and all the way out with one exception on the exhaust where you want to hae a step between manifold and exhaust ports.

Even with a good filter success is not guaranteed. Recently I was called to a rolling road because a Bravo 20v couldn't be remapped after having had done extensive head work. The engine got stuck at 167bhp with a BMC CDA fitted as BMC recommends. The CDA is quite good but it has to be fitted quite a bit better than with the aluminium hose supplied or a hack off job. It was down on power against the standard airbox by 5bhp. After revising the induction the car could be remapped.

 

[PNL]

Thanks a bunch oldschool very informative and simply put that clears the air a gteat deal pun not intended