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Discussion Starter · #1 · (Edited)
Hi,
I started a thread to 'resolve' the airfilter subjectback on 11-20-07 and am reposting the original content along with my latest DIY project airfilter that is not CAI but uses a HUGE replaceable dry factory OEM unit. It makes such a big change over 4krpm that my butt-dyno can feel the difference.

I am also re-posting 3 brands of OEM style used before now and the filter paper differences with mileage stats. Please add your own brand and mileage comparisons. (Dr. Dave gave important input regarding 'silicon levels dropped by a factor of three with the paper over the foam' & oiled filters bleeding their oil into the air intake leaving 'gritty oily deposit on the walls of the intake system' http://www.acura-legend.com/vbulletin/f2/airfilter-comparo-pls-contrib-2-a-113833/)

My new install is a Honeywell/Fram CA/DA8038 with 2970 sq in of surface area which is 5x (500%) what a factory airfilter has (570-583). Also since it is not a remote CAI it has no flow loss from chamber flex (think breathing from a paper bag - but on a small scale - all CAI have a flex tube). It is firmly mounted using a thick ABS flange & 2 aluminum mounting stuts bolted to the tranny.

The ABS flange is a hardware store item called a threaded water closet flange. It just happens to be the exact size needed for the job- neck fits the filter & has a strong flange with bolt holes for the strut supports. The aluminum elbow is bonded in place using foam adhesive. Kinda happy with the results so far.

Before 11-20-07 I was running a 6"X6" 'K&N'-style oiled gauze cone style & shortram from Weapon-R on my '90 G1L coupe 5MT. I can say that when I removed the K&N and short CAI and restored the factory intake using the FRAM OEM, mileage 'jumped' from 19 to 21. The K&N had half the surface area of the FRAM (see next)

FRAM OEM p/nCA6308: 97 pleats X (1.25" pleat depth X 2) X 3" width = 727.5 square inches of area ---- mileage over 6 months had been a steady 21mpg. >>>>But!!! Shocking new discovery from my local parts store (Schucks) is the current FRAM CA6308 they sell has only 76 pleats versus the one I threw away had 97. That's a huge surface area change and I expect a change in its performance.

Then I switched to a BECK/ARNLEY OEM p/n#0421449: 80 pleats X (1.20" pleat depth X 2) X 3" width = 576 square inches of area. **Notice the pleat depth & # difference makes a huge difference in area which might lead to greater flow resistance.

As expected, with less surface area the pumping loss is higher and mileage went down. While there's no way to be 'scientific' outside of a lab, my driving pattern stays pretty consistent even though temps don't. So, after 694 miles & 36.8 gallons, mileage dropped from a consistent 21mpg to 18.8mpg

Then around 2/12/08 I purchased an AC Delco #A1211C and found it has the same paper as the BECK/ARNLEY but has 81 pleats of the same depth and width versus 80 giving it slightly more surface area = 583 sq in. Unfortunately my odo/speedo decided to stop & I can't give mileage numbers, but there was no significant change to my driving & refill pattern.
 

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Hi, missed you on Sunday. I am just thinking out loud here. I am wondering if your fuel mileage numbers may be artificially skewed a little here due to the warm underhood air being drawn in by the filter. The OEM setup draws in air under the fender. I would anticipate good fuel mileage from your cleaver setup. However, I am wondering if you might get a power loss during the warm months from the high IAT (induction air temperature). This is a very real issue in aviation. Even though the engine is injected I would think there is an added benefit in mileage to warm IAT's

I am interested in your study. I am curious what the pressure drop is across the filter. I don't get real tied up with the surface area of the filter. Bigger is better. A simple home-made manometer would give some interesting insight to your mileage improvement. We threw one together with some clear plastic tubing on a clip-board with a piece of graph paper behind it. A little water and red food coloring and the "mano-1000" was born. We were using it in modifying an engine cowling on an experimental airplane that burned up cylinders every 100 hours. We found in flight the pressure difference was less than 1". A good cowling had a 5" pressure drop. In the case of the air filter the lower the drop the better.

I think the engine will want to lean the mixture with higher IAT's. It sounds like your situation is likely pressure drop across the filter. If you can't measure an appreciable difference I would look elsewhere for the mileage change.

How much has your intake noise gone up? I wonder what effect the short run from the filter to the throttle body has. There is no place to smooth out the airflow. Remember the days of velocity stacks?

Keep me in the loop on your data.

Dave
 

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I am wondering if your fuel mileage numbers may be artificially skewed a little here due to the warm underhood air being drawn in by the filter. The OEM setup draws in air under the fender. I would anticipate good fuel mileage from your cleaver setup. However, I am wondering if you might get a power loss during the warm months from the high IAT (induction air temperature).
I was thinking the same thing.. =/
 

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Discussion Starter · #5 ·
1- I am wondering if you might get a power loss during the warm months from the high IAT (induction air temperature).
2- I don't get real tied up with the surface area of the filter. Bigger is better.
3- I think the engine will want to lean the mixture with higher IAT's.
4- How much has your intake noise gone up? I wonder what effect the short run from the filter to the throttle body has. There is no place to smooth out the airflow. Remember the days of velocity stacks?
A1 - There is no space to 'wrap' the intake but I am looking into installing a 'half-tube' cradle (think heat sheild) below with a CAI pipe leading from the fender that can at least draw cooler air while moving
A2- I mounted the biggest jug I could fit :bigok:
A3- My next emissions inspection is in August - I'll do it in the morning early.
A4- There is a little bit of whoosh with the window open that is barely noticeable closed - I can tell the difference if I rev it up or if the vent is open - and I like it. Regarding smooth airflow - I'm an old aerospace engineer from the F-16 & F-22 programs. One of the bits of reality I learned is about intake turbulence. The intake side on a car is always a pulsing turbulent flow because of valve motion. Aircraft can tune everything for a specific rpm peak performance. What we care about most is the last section length = 10 x valve diameter which is why individual intake runners are best. Before that we care about any lossy details like filter performance, heat, and chamber flex. A long intake runner is a relatively bad idea because the runner leading to the filter suffers from compressibility losses (vacuum & flex) Of course if higher relative pressure can be introduced before the filter we can have lower pressure losses - like a ram air intake - even the fender area CAI might enjoy a bit of higher relative P due to stagnating flow. It looks like that's what Acura tried to create by putting the factory intake horn in the corner by the battery where there is a little round hole leading to the fender. Clever guys they are! My solution is set to avoid the puddle and intake loss problem and trade for the occasional higher IAT - until I get it 'hosed'.
 

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Damn, I didn't know we had such intelligent people on here.
You have quite the background for this haha.
So my question is, what made you decide to use this intake setup as opposed to a CAI? (lamens terms please =p)
 

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not that im wishing anything upon you but im just curious.. what do you think would happen if one of your coolant hoses had a hole and the pressure shot antifreeze into the filter?
 

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If I may...

The coolant would soak the filter. Some antifreeze would go past the filter. It would work it's way past the rings and contaminate the oil. An oil analysis would show high Boron and Sodium. You would change the oil twice to clean all of the residual coolant out. Then you would go about fixing the coolant leak.

Had the exact situation you describe on a sailboat. The problem with seagoing vessels is no intake air filters. The coolant was going right into the intake. Oil analysis caught it. We had a two week period of woory until we flew to Canada where the boat was moored and did a thorough inspection. With a guy in the engine compartment we started the motor and saw a drop of coolant fall off the hose and get ingested right into the air intake.

Without the oil analysis report we would have ruined the bearings in short order. Not the answer you expected.

Dave
 

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you know its funny i was about to buy the same air filter and under take the same task i had actually scouted out Lowe's hardware and come across the same support setup. i opted to go with my SRI and im fairly happy its pictured below, do you think you have more of a gain than my setup?
 

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A long intake runner is a relatively bad idea because the runner leading to the filter suffers from compressibility losses (vacuum & flex)
That compessibility loss is needed sometimes to compensate for intake valve compression leaking at low RPM. That is why Legend has dual length intake runners. At high RPM, this becomes less of an issue because of the camshaft profile and then short intake runners really start helping.

It looks like that's what Acura tried to create by putting the factory intake horn in the corner by the battery where there is a little round hole leading to the fender. Clever guys they are!
Clever, but not clever enough... rectangular opening and very small diameter curvature on the horn make this almost a decorative rather than functional item.
 

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well i have a custum CAI thats in the fender and i got a way to protect it in the rainy seasons. i put clear plastic pieces that covers the fog light hole. And it stills gets air around the front of the rad hole where the rad get air. Theres a little hole that goes around and get the cone. i need to get one of those dryflows but your idea is just stucking hot air i had that before and it sucked. so i got some flex tubing and put it in the fender.
 
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