More CFM needed!!

[undy]

At my last chassis dyno run I found that I was losing nearly 30 HP due to my restrictive air filter. I was/am running the 21" x 10" x 1.8" oval K&N filter. No more room is left to run a taller filter either. I called K&N customer service and got them to pass me off to engineering. In talking with the tech I found that my existing filter is rated at 575 CFM before it starts restricting and causing a significant loss of horsepower. That's not nearly enough to feed my twin 750 Quick Fuel carbs on my KC Pond 482. The tech ran the engine numbers saying I needed around 900 CFM or so.

K&N has a very good site for selecting filters by size and seeing the engineering data WRT flow ratings. I found a 9" x 6" BWM 1000 motorcycle filter rated rated @ 372 CFM. That was my target physical size, perfect for nestling between the top of the 2 carbs in/on the filter lid. The combination of the 2 filters should yield +/- 950 CFM.

The filter is only 1" tall and after I mill the rectangular hole for it in the lid It will sit in the lid with 1/4" up on top and only about .6" protruding down into the air stream. That should provide me with the internal, non-restrictive internal flow I need. The interference fit should hold the filter in well.

Here's a few pics of the filter and it's install location. I ordered another lid from Barry_R so I'll have a non-modified lid for car shows etc. I plan on finishing the mod and hitting the chassis dyno for some before 'n after horsepower readings.

Results to follow...

[Avmaviator]

Sweet. Good luck with the project

*Edit: I apparently didn't understand how the filter was going to go in but I got it after reading Z-link's post.

[Z-linkCobra]

Thats a mistake putting that filter in the top like that. You will actualy create a major turbulance by air coming in from the sides and and the top at the same time. A freind of mine builds limited modified motors for circle track racing...they saw a 12 hp drop on the dyno by running one of K and N's filter tops on a round filter. Stop and think about the way air flows for a minute.

just my 2 cents.

[Hotfingrs]

I've got the K&N filter top, and on the dyno, the numbers with an air cleaner and without one, were the same. So for me the air filter is not a restriction.

[Tom Wells]

undy,

Ran into the same problem with the 521 in the Cobra and the 557 in the Zephyr wagon.

In the Cobra the solution was to increase the height of the scoop by about an inch. That got me enough airflow by allowing another inch of height for the filter. I can understand if you don't want to do that.

In the Zephyr the solution was a drop-base air filter. It allows plenty of flow without too much disturbance. Alas, it resulted in shrouding the float bowls of the 950 carb, creating a percolation problem particularly after the fully warmed up engine is shut off. Still working on that one - may have to let the fans run after the engine stops to solve it.

So your problem is a tough one - if you put enough boundary conditions on a problem you may find you've ruled out all the possible solutions...

One of the potential solutions I have not tried is the dual snorkel filter housing, like this:



Good luck and let us know if your solution works!

Tom

[FWB]

Undy,

have been thinking about the same problem, however my solution is similar but using a different filter top. i want to machine a new top to insert two of the smaller K&N "extreme" filter tops they just fit touching each other.
and then the center holes can be used to hold the top on.


Fred

P.S. the oval air cleaner assembly is very restrictive where you actually have flow numbers i did my own back yard test......3 jet sizes different to get the same plug reading from aircleaner on... to... no aircleaner

[Bernica]

Or, you could try one of my setups!
Several CC members now have them on some big motors!
Contact me if interested. Now comes complete with the modified top and the Quik-Latch installed, similar to this:



Check this link for more info:

PhotoPost Classifieds - 9" FLAT AIR FILTER BASE - Powered by PhotoPost Classifieds

[Barry_R]

I've run the extreme lid K&N on several EMC dyno entries when a 14x3 element was mandated. In all cases it was worth a very small - margin of error - 1-3 point improvement in score. Score is average horsepower and average torque over a 4000 RPM range.

[undy]

Originally Posted by Z-linkCobra

Thats a mistake putting that filter in the top like that. You will actualy create a major turbulance by air coming in from the sides and and the top at the same time. A freind of mine builds limited modified motors for circle track racing...they saw a 12 hp drop on the dyno by running one of K and N's filter tops on a round filter. Stop and think about the way air flows for a minute.

just my 2 cents.

This new filter actually won't be sitting on top of the carbs like the X-Stream lids do, more so in between. The air currents will be different. I'm going to do some chassis dynoing before and afterwards anyway. If it doesn't work I'll pitch it and scrap that idea.

Originally Posted by Tom Wells

undy,

Ran into the same problem with the 521 in the Cobra and the 557 in the Zephyr wagon.

In the Cobra the solution was to increase the height of the scoop by about an inch. That got me enough airflow by allowing another inch of height for the filter. I can understand if you don't want to do that.

In the Zephyr the solution was a drop-base air filter. It allows plenty of flow without too much disturbance. Alas, it resulted in shrouding the float bowls of the 950 carb, creating a percolation problem particularly after the fully warmed up engine is shut off. Still working on that one - may have to let the fans run after the engine stops to solve it.

So your problem is a tough one - if you put enough boundary conditions on a problem you may find you've ruled out all the possible solutions...

One of the potential solutions I have not tried is the dual snorkel filter housing, like this:



Good luck and let us know if your solution works!

Tom

Sorry Tom, if a run a pair of those I'll need to park with the Subies and Hondas at the local hang-out.. J/K, well maybe not...

Originally Posted by FWB

Undy,

have been thinking about the same problem, however my solution is similar but using a different filter top. i want to machine a new top to insert two of the smaller K&N "extreme" filter tops they just fit touching each other.
and then the center holes can be used to hold the top on.


Fred

P.S. the oval air cleaner assembly is very restrictive where you actually have flow numbers i did my own back yard test......3 jet sizes different to get the same plug reading from aircleaner on... to... no aircleaner

I looked at the x-Stream lid option prior to this. They make them in a 9", 11" and 14". The 9" one is the only one that would fit and there is not much filter media in it. Almost the outer 2" was border and filter frame. I was going to use an 11" filter and only use the center 9" of it for mine. I may still end up going that route anyway, depending what my RWHP numbers show.

Originally Posted by Bernica

Or, you could try one of my setups!
Several CC members now have them on some big motors!
Contact me if interested. Now comes complete with the modified top and the Quik-Latch installed, similar to this:



Check this link for more info:

PhotoPost Classifieds - 9" FLAT AIR FILTER BASE - Powered by PhotoPost Classifieds

My carbs are 8 1/2" apart, center to center. Two 9" filters wouldn't fit.

Originally Posted by Barry_R

I've run the extreme lid K&N on several EMC dyno entries when a 14x3 element was mandated. In all cases it was worth a very small - margin of error - 1-3 point improvement in score. Score is average horsepower and average torque over a 4000 RPM range.

Do you know for a fact that you were originally CFM Challenged? If not, then the results would always be near nill. According to K&N their 14 x 3 is good for 900-950 CFM, which would carry most of your entries pretty well.

[Rick Parker]

Until you have removed the choke tower and radiused all the air flow entries or opted for an HP main body for the carb(s) changing the air filter housing is a mute point.

[Barry_R]

Don't have the numbers in front of me - but the addition of the 14x3 air cleaner always cost a bit of power - maybe 10ish IIRC. The filter lid reduced that by a tiny bit. Once thing is certain - the lid did NOT cost the HP that was referenced when used in 600-750+ HP applications.

I don't hold much stock in published cfm ratings. In order to be an accurate measurement, a cfm rating much have a defined degree of pressure drop. Without a defined amount of restriction you cannot determine flow because you will not know whether you've reached a limit of any degree. Carbs are/were rated a 1.5 drop value - meaning the were a restriction on airflow at that cfm value. Every single EMC entry I have had has picked up power with a larger carb no matter what size the engine.

[ERA Chas]

Originally Posted by undy

My carbs are 8 1/2" apart, center to center. Two 9" filters wouldn't fit.

Not true Dave. Here's how you do it; offset the the center posts. Then build a flat pan with flanges at the throats to clear the adjusters:

[undy]

Originally Posted by Barry_R

Don't have the numbers in front of me - but the addition of the 14x3 air cleaner always cost a bit of power - maybe 10ish IIRC. The filter lid reduced that by a tiny bit. Once thing is certain - the lid did NOT cost the HP that was referenced when used in 600-750+ HP applications.

I don't hold much stock in published cfm ratings. In order to be an accurate measurement, a cfm rating much have a defined degree of pressure drop. Without a defined amount of restriction you cannot determine flow because you will not know whether you've reached a limit of any degree. Carbs are/were rated a 1.5 drop value - meaning the were a restriction on airflow at that cfm value. Every single EMC entry I have had has picked up power with a larger carb no matter what size the engine.

They rate their filters at a negative 1.5" water column too... K&N actually has some good tech data on their site, nice linear charts of each filter's pressure drops (at least the published ones).

Originally Posted by Rick Parker

Until you have removed the choke tower and radiused all the air flow entries or opted for an HP main body for the carb(s) changing the air filter housing is a mute point.

Originally Posted by ERA Chas

Not true Dave. Here's how you do it; offset the the center posts. Then build a flat pan with flanges at the throats to clear the adjusters:]

Dunno Chas, think I'll still head down this path until it fizzles. Then, maybe a twin filter setup. That's pretty trick how you set that up though...

Dave

[ERA Chas]

Originally Posted by undy

Dunno Chas, think I'll still head down this path until it fizzles. Then, maybe a twin filter setup. That's pretty trick how you set that up though...
Dave

Thanks Dave. I know it gets spendy buying filters for R&D work but this would be easy to mock-up for dyno testing...
I realize you might not care for the look but I'm feeding 1305 CFM with this to your 1500. Maybe the flow math would work.
If we were neighbors, I'd lend it to you for testing-and waive my usual Licensing Fee...

[FFR428]

Dave sent you a email.

G.

[undy]

Well.... I picked up the modified air cleaner lid from the machine shop with the 2010-11 Chevy Malibu V6 K&N air filter in it. I also did some mods to the base to lower it and fit a 2.25" tall S&B filter in it. That replace the 1 3/4" tall K&N.

I took it for a test drive today and SOTP says it's definitely quicker. Both sets of vacuum secondaries snap open much sooner and much quicker. The Dyno will tell the though...

Here's the old setup...


Here's the modified base, it allowed for almost 1/4" drop.


Here's the new lid with the embedded filter.


Here's the bottom of the filter lid.


The finished product.


Good or bad, I'll post the results of the dyno session.

[FWB]

Hmmmmm, with a plain lid that might not look bad.......i'll wait to see what the dyno says. before i make chips out of my lid.....

[ERA Chas]

Dave,
Your project reflects your excellent fab skills and logical thinking. In an effort to make a complete ass of myself and exhibit my kindergarten graphic skills, I've tried to expand it to the next (and probably ridiculous) level.
I'm sure that for the mere cost of your firstborn's eye teeth, K&N would custom make an 'H' shaped unit to the size you specify after you mill the crap out of your 'real' top plate. Or fab a simpler one.
Aesthetics aside, it WOULD add CFM. Whether worth the cost and trouble-your call. Maybe it'll just inspire you to a better, more professional job than this.
Mea culpa...

PS- If this does catch-on and you sell 1000's of 'em, I will NOT waive my licensing fee...

[undy]

I hit the chassis dyno today... All runs were kept with the same amount of cool down and other similarities

The numbers weren't kind to me. In fact, I think the corrected numbers are low as the operator wasn't sensing temp and humidity at the carbs. This is a topic for another discussion though.

Run #1 was open carbs, no filters at all.

Run #2 was with the old restrictive filter.

Run #3 was with the new filter setup.

Here's the SAE corrected graph.



Here's the STD graph.



It appears that open carbs tends to generate some inlet air turbulence, at least that would be my explanation of it being the lowest number.

The run with the new filter indicates marginal, although measurable gains. Given the hot dyno operation I would imagine the gains becoming more marked with the open road's cooler (and denser) temps.

Those who say the "unsealed" hood scoop actually blows air out instead of sucking it in is mistaken, at least in my case. After a 10 minute 60 mph jaunt down the road during 78 deg temps I opened the hood to feel the air cleaner top. It felt like it was very cool, around outside ambient temp. I then tried it at 35 mph with the same results. This puppy sucks outside air going down the road.

All in all, I would call new intake a minor success. Cooler temps will tell me just how minor of an improvement it is.

[patrickt]

Well, it's a damn fine looking filter, regardless.