Stupid Cold Air Filters

[nando]

it's not just air temperature that is important - it's the pressure drop through the airbox.

I get a pretty significant pressure drop over 6000rpm with the stock airbox - about 10-15kpa. The temperature with the open filter was only higher when sitting still, otherwise it was about the same.

anyway, I still got tired of the cone filter - it sounds badass, but it gets dirty really fast, it looks kind of stupid, and there were some really odd harmonics with mine at part throttle that drove me insane. I took the 10hp cut and put the stock airbox back on.

[Threehz]

That's an interesting point. Well maybe I'll see better results then expected.

I do dislike the look of cone filters, but then again it's under the hood. If nothing else I hope that making an enclosure for the stock intake will help a little.

[Roysneon]

It's not going to make the difference people who spend big money on them really want, for the most part. If your car has a shitty intake design, sure, but for the most part on a BMW it's not going to make enough of a difference to worry about it.

[dnguyen1963]

it's not just air temperature that is important - it's the pressure drop through the airbox.

I get a pretty significant pressure drop over 6000rpm with the stock airbox - about 10-15kpa. The temperature with the open filter was only higher when sitting still, otherwise it was about the same.

anyway, I still got tired of the cone filter - it sounds badass, but it gets dirty really fast, it looks kind of stupid, and there were some really odd harmonics with mine at part throttle that drove me insane. I took the 10hp cut and put the stock airbox back on.

This was why GM invested in their RAM AIR tech...

[AwakenNoMore]

One of these days I'll get around to putting the stock box that came in the box-o-parts I got with my E30. That K&N filter out in the open has certainly been a fail point.

[E30 Wagen]

it's not just air temperature that is important - it's the pressure drop through the airbox.

I get a pretty significant pressure drop over 6000rpm with the stock airbox - about 10-15kpa. The temperature with the open filter was only higher when sitting still, otherwise it was about the same.

anyway, I still got tired of the cone filter - it sounds badass, but it gets dirty really fast, it looks kind of stupid, and there were some really odd harmonics with mine at part throttle that drove me insane. I took the 10hp cut and put the stock airbox back on.

How were you able to measure this? I'm curious on finding a way to overcome this problem. Is it the volume of the box that is the cause?

[dnguyen1963]

It is just the fact that the engine has to suck air through the filter; thus, pressure drop after the filter. The selling point behind those cone filters is that air can move freely through the filter. The problem is that many of the cone filter setups pull in too much hot air. If you can prevent that from happening, you can observe some minor improvement in performance.

[nando]

How were you able to measure this? I'm curious on finding a way to overcome this problem. Is it the volume of the box that is the cause?

datalogging with standalone and 2 MAP sensors.

I'm not sure what the cause is. I also saw a pressure drop through the throttle plate of another 5+kpa (at high RPM), but I've pretty much stopped working on this motor.

[TobyB]

this is the fuckin' intake hole right here

hee

t

[Threehz]

Looking at the M42 intake setup in detail yesterday I realized it's really well done. Room for improvement, maybe. I think I'm going to also test out a high-flow filter such as a K&N in the stock box and see what difference that makes.

[nando]

I did a dyno back to back of the stock paper filter and K&N drop in. Any difference could be taken down to statistical error - about 1hp on my stroker M20. and the K&N doesn't filter as well.

[delatlanta1281]

If only we had an airplane and a treadmill....