High flow intake design.

[E55er]

Hi all, I am looking to fabricate a high flow intake for my supercharged e55. i will be using 5" aluminum and rubber tubing. my qyestion is will an in-line cone type air filter work well if it were incased within the tubing itself or will it need to be mounted at the end of the tube. K&N makes some cone type filters that have the diamter to fit snug inside 5" tubing but it has a flat top metal covered top versus another manuf.'s open funnel type design. which type is better? also if the base opening is only 3" inside the pipe will this need to be opened to as close to 5" as possible if i go the incased route?

i saw a movie once where they showed old time gold strip miner's tools. one was a pressure washer (not powered obviously) which sent water down piping with reduced diameter piping along the way until it reached the end where it was blasting water to strip earth. can this principal, if it is one be applied to intake or was this because the weight of the water in the holding tank was creating pressure?

thanks for your expert knowledge.

 

[Rob45]

I've got a couple thoughts for you: first, K&N are in the filter selling business. Simply because they sell a product doesn't mean it'll work for you.
You want to do several things: you want to provide clean cool air to your engine, with as little pressure drop as possible because the only driving force for this airflow is atmospheric pressure - seldom more than 14.7 psi. Therefore, you want to minimize flow losses, which doesn't simply mean bigger pipes: you want smooth transitions from one element of the system to another, without any abrupt changes in diameter. Sudden increases in diameter are as disruptive of the flow as are sudden decreases. Thus, you might well find that for example a smooth 4" diameter system could flow considerably more air than a 5" system with several abrupt changes in it.
Next, you want to draw air from outside the engine compartment! The underhood air is almost always considerably hotter and therefore less dense than outside air. Except sometimes here in Texas...
Then, because your airflow is NOT continuous, but is made up of a series of (rapid) individual pulses, even when you're feeding a supercharger, you want the filtering element surface area to be as large as possible, preferably several times larger than the area of the duct it feeds.
And finally, you may well find your car makes some fairly loud noises when you've installed this new intake, noises of the sort that sound strong and manly at first, but become pretty annoying after the first say 300 or 400 miles. This can be the result of your having created a sort of organ pipe, driven by the engine noise, and can require some diagnostic work with a microphone and frequency analyzer.

Good luck,
- R

 

[richdubbya]

The type of filter you describe would be very restrictive IMO. The 3" diameter is unacceptable as are the 2 almost 90 degree turns the air has to follow. It may be the filter area is too small also, I have found the larger the filter area the better even if a smaller filter is rated with enough CFM. I agree with Rob45 that the air should come from outside the engine compartment, this is where intake tubes get 80 to 90% of their gains. I disagree that the diameter of the tube can be too large, in fact i believe a tube matched in diameter to the intake flow will upset intake wave tuning somewhat (although less with a supercharger than NA)and be restrictive because of the length. I think 5" or 6" would work fine, with a bell mouth shape to the supercharger opening which i assume to be much smaller. If the tube is close to the throttle body size, then a tapered section would be more appropriate. It is lots more complicated, but a flat filter that does not change the air direction is the best, if direction must be changed 90 degrees a medium sized plenum area after the filter and a bellmouth entrance to the tube would be best in my experience. I have found air entrances to either side of the radiator work well, not picking up as much debris or water as low ram air type scoops. Under the fenderwheel picks up too much dirt also. When the area between the grill opening and the radiator is sealed well (air not allowed to escape)this is an excellent place to pick up air, unfortunately with newer cars it is very hard to find the necessary room. Make sure you save all the old intake parts as they are required to pass emission inspection in most places, and if there are evaporation lines or sensors in the original design you must include them.