Thread: Open cone intake clarification

After looking around for a bit on here I've seen a lot of debate on the issue of running an open cone filter vs a cold air intake. My question is about whether an open cone is noticeably better than a K&N drop in filter on a stock intake of a 99 GTP. To be clear I'm talking about basically just a 45 degree elbow on the throttle body with the sensor stuck in it and a 9 inch K&N cone on that. Right now I have just the drop in filter in the stock intake and wanted to know if this type of setup would be an improvement... cause it looks mad easy to do lol.

skip the 45* and find a 22.5* bend. less bends for more flow. pushes the filter toward the fender more too, not that it really helps.

i got a 22.5* 4" elbow, the coupler and clamps from lowes for around $13.

Originally Posted by oneil.GTP

skip the 45* and find a 22.5* bend. less bends for more flow. pushes the filter toward the fender more too, not that it really helps.

i got a 22.5* 4" elbow, the coupler and clamps from lowes for around $13.

Not that it much matters,

According to SlowNA06, the 9" long 4" Dia filter is flowing 227CFM. If we assume that those values as correct, and are for redline RPM, then the 4" tube is flowing 3.78CFS which equates to 43.33ft/sec air speed. This is 29.54MPH air speed through the tube. A 45* elbow shouldn't be too restrictive given that speed.

If I made another intake I would possibly use a 60* elbow instead of a 45* since it would point at the front headlight nicely. I think the 22.5* goes into the pit of the fender though, which is nice.

I got bored and so decided to post this.

ZZP's tests also indicate the following results before adding a filter:

238 CFM on 5" of straight 4" Pipe
220 CFM on 26" of straight 4" Pipe
183 CFM on 26" of straight 4" Pipe + 90* Bend

^I think ZZP needs a new calculator.

Assume a N/A 3800cc engine is running at 6000RPM (GP GT at redline). The engine requires 1800cc of air per revolution. This means the the engine uses 11400 L/min of air, which is 402.59CFM. For supercharged engines, the volumetric flow rate would be higher yet, by quite a bit.

The ZZP specified 227CFM at the filter makes no sense = fail.

^ To me it doesn't make sense. An IC engine is a positive displacement pump. At a given RPM, it will draw the air it needs, for the most part. If it draws less air than the engine capacity, there would be a vacuum created in the cylinders.

^ Now we are getting somewhere. I bet they did this testing on a flow bench, as opposed to on an engine while using a pitot tube. That is the only explanation I can think of.

Originally Posted by Bio248

i believe that they arent trying to disprove what you just said, but to say that certain intakes become a restricting factor, similar to sucking through a straw.

Originally Posted by mechguy

^ Now we are getting somewhere. I bet they did this testing on a flow bench, as opposed to on an engine while using a pitot tube. That is the only explanation I can think of.

Yes, the ran it on a flow bench, where Stock GTP throttlebody with screen rated 107 CFM.

Well I went and did it. I basically followed the write-up for how to do it thats stickied on the forums here. And yeah the blower whines considerably louder lol. Which is totally cool with me. Does the whine get louder and/or higher pitched when dropping pulley sizes?

The CFM flow rating is how much the filter flows before it starts pulling a vacuum.

Originally Posted by darkhorizon

The CFM flow rating is how much the filter flows before it starts pulling a vacuum.

Technically,

Anytime there is fluid flow there is either a vacuum or a pressure rise.

Originally Posted by mechguy

Technically,

Anytime there is fluid flow there is either a vacuum or a pressure rise.

Well, I suppose that I should say "significant" vacuum.

K-N rates their filters at 2 or 3 inches of mercury, which depending on what math you follow could be twice or 3x as much as the zzp test.

The last air filter conundrum I ran into was on a NIC car I was building, where the owner refused to go with my "go to" AEM dryflow filter as it was too large. He ended up buying a bunch of KN stuff that was rated at 800-1000cfm, only to later find out it was causing major KR (wideband stayed the same). Removing the air filter from the system would eliminate up to 4KR in some cases.

So he then looked at the ratings a bit closer via some emails to KN, and found out that the flow ratings were done in situations of IMO high restriction. In theory a filter could flow unlimited amounts of air, but the vacuum, aka restriction, it pulls is going to go up significantly.