K/n 9 inch diameter air cleaner-hp killer
 

I spent alot of time dynoing my 455 lately and just to see what happened we put a K/N 3X9 air cleaner on the motor for a pull. I OFTEN see these on Pontiacs featured in magazine articles, even a few drag cars. Well, on this 455 in back to back testing it whacked a SOLID 35-40 hp off the top end AND sent the AFR's down almost 2 full points. We actually previosuly used this air cleaner on my friend Bob aka "goatasaurus rex" on here's 69 gto at the race track and ran as fast as 11.67's with it and ran 11.80's all the time. We were always going to take it off and see what would happen but without a hood on his car couldn't race without a air cleaner and never bothered bringing a different one, I can only imagine we inadvertently tuned around the restriction it was causing when reading our plugs and jetting the carb. We now know better and I thought I would mention it in case someone else is using the same one, Smitty

so this was just a 3*9 air cleaner? without that xstream lid on?
i would think a motor of this size would need more air coming in
wonder how much a difference a 5*9 would make

when i go to cruise ins, i see some old tri power setups/duals etc... with super small louvered air cleaners
can't imagine how much choking those do

3x9 K/N element on a velocity stack base. We ran the velocity stack base by itself with a thin tie bar on top and it by itself did NOT hurt hp at all. No xtreme flow top on the 3x9, did use one on the 14X3, it DID show a slight hp advantage (about 3-4) over flat lid on 14 x3, made no difference on a 14x4, Smitty

Is it because its a K&N filter or because other variables changed too?

I cant emagine why changing from one filter to another....all other variables being the same...would cause such a problem.

Only variable was the air cleaner size, its NOT the fact that it's a K/N, its the fact that it is 3" tall by 9" in dia. This is a VERY popular size as I see them on many Street and a few race cars. What most people don't realize or think about is that a air filter might NOT meet the requirements that there motor needs as far as air flow which is DIRECTLY proportional to media size. It took ALOT of searching but I stumbled acrossed mention of K/N saying their air filters flow 6 cfm per square inch of filter area, 9" x 3.14=circumference of 28.26" X 3= 84.78 total square inches X 6 cfm per sq inch= 508.68 as the CFM rating, I am not sure if this is at 1.5" of vaccuum or what and air filter WILL flow more than that BUT will create a vaccuum in the filter housing which alters your tune and chokes off your motor. I tried several aircleaners , lids and a extreme top while dynoing so this wasn't just a fluke. I suspected there would be a hp drop with this filter and was anxious to try it, I just didn't think it would kill power so bad, Smitty

Smittyseng, K&N also said that 1/8" top and bottom (1/4" total) should be subtracted for the base material coming up into the filter medium. So 3" becomes an effective 2-3/4" high filter.

Can anyone locate the fill-in-the-blanks screen on the K&N site that was there to help figure necessary filter size? I looked all over for it, but nothing. I remember that when I was doing my calculations on their site that a 3x14 round filter on a 455 (462) was okay until 6,200 RPM (121 square inches). Ran engine on dyno up to 6,500 RPM, and horsepower figures were the same with just the filter base plate in place or the K&N filter and top on also. We lost 10 horsepower when the filter was completely removed.

When I was running the dual quads on the 428 (437), I had calculated out that they would get enough air if I used an 8x12x2-1/2 (141 sq. in.) K&N filter on each carb. Ran on the chassis dyno down at Harry K's, and made a run with the cleaners off and lost 8 horsepower. So in two tests, the old K&N computer was accurate, and even a little conservative on sizing.

I dont think the math is correct since you did not account for the fact that the filter is folded. The filter area is much bigger.;)

Except K&N has taken the folds into account with their stated flow rating of 6CFM per square inch of (exterior) filter medium.

Using the 6CFM figure, my 121 square inch sized round filter would flow 783CFM -- which wouldn't be enough to satisfy the needed 829CFM requirement of the 462 at 6,200 RPM. Since we proved on the dyno that the filter size was sufficient up to 6,500 RPM, I'd say that their estimate is somewhat conservative. That nice even 6CFM number was probably rounded down. I'd say that it would be entirely safe to use the 6CFM figure for figuring minimum filter size.

I avoided splitting hairs and simply installed a 5x14 K&N filter on the drag car. Probably didn't need it, but had the room so why not?

thanx for the info Smitty

i've heard that the xtreme top disrupts airflow which robs HP. anyone have any dyno proof one way or the other?

thanx
Kevin

Please confirm, are you saying that your results showed a 8 hp losss with no air cleaner or a 8 hp loss with the KN air filter. I am very interested in this post because I run the KN 9" v-stacks on my dual quads. What about running there 5" filter instead of the 3" filter, has this been tested?

Were did you get that 6cfm figure from? Is it an approximation for all KN filters or an exact no valid for the 3x9 filter only?

Reason I question this, is the fact that even the foldings on different sizes KN filters are different. I have the KN 3x9 filter were the foldings are 10mm deep and a KN 16x3.5 filter were the foldings are twice as deep 20 mm. Because of this fact, the 6cfm figure cannot be correct for both these filters.

are you still able to test some more?
i have that stack and various size filters/lid

i just personally think the 9" is to small for it to breathe
especially the 3"
i notice an improvement with the filters larger then 3 and then adding the lid
albeit nothing earth shattering, but it did improve

i dont run the shaker (don't have one) so i run the stack out of the hood on the TA

U have big heads! U will need a top end that breathes to compliment those! Air in air out, also make sure u have enough clearance over the airhorn, air coming into the carb doesn't like tight bends to get it into the venturi's

Back in the late 90's I had a 10 second 428 in my T/A that lost .2 with a K & N 14" 3" air cleaner. Even after re-jetting, etc.

My car gained 8 hp when I took my air filter off.
It is a K&N 14x4 with an Extreme top.
I didn't test with a different lid,I wish I did
Next time I will.

Mighty TA runs the 3 x 9 with extreme lid.
He's running low 8's. Doesn't seem to hinder his performance.

Brian

Yea, with a bottle ya don't require an air source. It is it's own power supply. That's what the bottle is for. ;)

I think they are talking N/A results.

We don't need no stinking dyno (in this instance), we have Cliff... :D

I made pulls with a 3x14 w /extreme lid, 4X14 w/extreme lid, both with steel top and the 3x9 with steel top. In my application, the extreme lid did NOT hurt performance, it helped when running the 14X3 slightly BUT remember, I am running efi so no fuel or air bleeds to get disrupted or anything either which is what I hear happens, Smitty

I saw in back to back testing -a 35-40 hp drop in my application plus the afr's dropped from the 13's to 11's. I ran this on a 69 gto that ran 11.60's previously but we inadvertently tuned for it with our jetting and plug reading, Smitty