Need your proffesional input on air filter locations - and more importantly why.

Air filter mouted directly to the carb, with some sort of air box and long tube running to the top of the cage to breath clean cool air

or

Tube mounted to the carb routed to the top of the cage with a filter on the end - to breath clean cool air.

Both applications are for race vehicles.
Maximum air flow for power is the goal
Water ingetion is not an issue in either application.
Noise is not an issue
Heat / dust are.

The intake tract on a two stroke is tuned like the exhaust, how much Honda spent on tuning the air box on the Pilots and Odysseys is a mystery to me I know the Pilot runs much better with a slightly modified air box than without a air box, I never been passed or intimidated by any Pilot without the stock air box, the best 'run for the money' I have been given the Pilots were equipped with the stock air box...

The FL250 runs better with a open air filter I suspect Honda didnt spend any time tuning that air box, I never messed with the air box on the 250's simply because most of them I owned came without a air box, I fabricated my own air box for one of the 250's doubling its volume and it ran much better than with the stock one, we swapped mine to my buddys stock 250..

The FL350 stock or modified always runs better with the lid off and with a second snorkel, I have seen a few after market air boxes for the 350 both made the 350 run better. If I owned a FL350 the first thing I would do is try to find one of the after market boxes (good luck) but I doubt you will find one so I would fabricate a 1" spacer to go between the top lid and the bottom of the box, I tested 1" spacing on a friends years ago and it worked great, I used a 1" strip of metal between the top and bottom and held into place with duct tape for testing, with today's rapid developing plastics (hey Massody) I think a slick one could be molded off the stock parts...

The Pilot air box works better with no lid but works much better with more opening area in the lid of the air box, I double the intake surface area for my setup, I tired adding a 3rd opening it ran better but was no worth the the extra bulk, I tried running a 3" opening and a 4" opening again it ran better with the larger opening but not enough to give up my dual intake setup, my dual intake setup offers a more compact installation, if you run the 3 or 4" opening then try to add a prefilter you end up with a real mess with the bulk and trying to get the right surface area, I run the prefilters on the end of the tubes at about the stock location the main reason is because the length of the tube closely matches the intact track length and inside diameter of the stock machine (tuning) and provides a volume reservoir.

I uses the dual intake hoses to tune my Engine for huge ambient temperature changes, this is not a easy task with the larger single inlet hoses, by blocking part of or one of my intake hoses I can change my jetting from bottom to top without changing one jet or turning one screw, I setup my initial jetting with the lid off the air box, get it nice and lean but not sticking the piston to the cylinder lean but a perfect little smoke ring on the bottom of the insulator lean, put the modified lid on with the prefilters and presto you have safe jetting I run this setup from 0' to 6000' 40 degrees to 100 degrees, when its cold and the Engine leans you use a little duct tape to blank off one of the intakes.

The dual prefilters I use have about the right mount of surface area when totally loaded dirt they just start to affect jetting.

The Pilot air box needs more volume but the only way to really achieve this without cutting out and redesigning the bottom (only place their is clearance) and maintaining the stock appearance is to use a heat gun to carefully stretch and move the factory plastic, huge gains can be made in the volume and nobody ever notices the changes (did you?)
running my setup I don't ever recall getting passed by another Pilot, my system worked good enough to fend off even the CR500 Pilots so I never refined my intake setup more, their is plenty more left to be done but IMO why? why learn about intake pumping, air box tuning when you don't need power to keep your buddys behind you away

Their is alot more to be said here for sure... I am sure many will comment and they should, I would like to see performance improvements beyond the work I have done made to the Pilot intake let me know when your done we can compare it to the performance of the intake on my wifes Pilot.

Good topic and just in time because I am getting ready to mod my FL350 air box before I rejet. I am currently running an open box with unifilter and outerware. Seems to run good and will keep up with a stock Pilot although has some guts removed from muffler/pipe. I like the prefilter dual intake set-up but I had a slightly different approach in mind. Here is the prefilter I will be using... http://www.knfilters.com/search/product ... od=RF-1012 . The ID of each opening is 3-1/8". I was planning on running two flex hoses or two hard pipes from the K&N prefilter to the stock air box, mounting the K&N prefilter in place of the stock taillight/air-inlet housing. To attach the two flex hoses or hard pipes(PVC etc.) to the stock airbox, I would install two 3-1/8"OD nipples for the flex hose, or running two hard pipes into the TOP of stock air box, then capping off the inlet on the stock air box. Hoser how does this idea sound,also should I install the 1" spacer ,you spoke of, between the top and bottom of the air box?

You going to have room for all your plumbing using the 3" I would make sure you will before you order the filter, then again you can make a reducing bushing for the filter and go smaller?

I would make the 1" spacer for the air box if I owned a FL350, do the math, measure the air box where they connect then add up how many more cubic inches you add to the volume of the box.

Interesting idea, but how will added volume on the air box increase air flow? I understand adding a second inlet on the box surely will, but whats going on with the added volume?

Every intake stroke the Engine takes a gulp of air, more power requires more air, more volume in the box allows for a bigger gulp, your increasing the reservoir size.

Here is a pic of an early 350 lid mod I did. I used a pair of trx250R K&N pods and a Uni filter inside. I really like the power it made.

The other pics are of the water deflector shield removal that will help air flow also.

That looks like less labor than what I was going to do. Will heat be an issue since the pre filters are behind the radiator,head, etc. I am running a water cooled head and my radiator will be in front of the prefilters too if I do your mod. After removing the water deflector shield did you seal off the hole?

So from what I a reading is that a 2 stroke work better with an air box and an inlet hose. Is there a formula for the volume of the air box base upon the cc of the Engine?

Should have clarified what I am working on.
1 - The Staduim Lite (SL350) - currently has a open element filter that gets very dirty very fast. It has / had not air box. If I can get an idea on the air box volume then I will add on an air box with a filter inside.

2 - 266cc Subaru 4 stroke (Trophy Kart) Engine. Does the same concept apply to a 4 stock with an air box?

What I am trying to acheive is maximum airflow while being able to duct in cool clean air.

Going by memory a good starting point is 4.4 times Engine size. 350cc x 4.4 = 1540cc I guess you could cc a stock air box to see what it is, anybody have one off that can test it ?

Lots of info out their if you search long enough in your readings you will run across helmholtz resonator
http://homepage.mac.com/rg500delta/TL10 ... nance.html

http://homepage.mac.com/rg500delta/TL10 ... ssure.html
http://www.snowtechmagazine.com/article ... petemp.php

Hi stix,

I don't remember having any problems with heat. I ran a water cooled head and radiator with that setup also. It worked great at LS Ok for the week the last time there. I did seal the elbow after the deflector removal.

I could send the lid to you for trial/inspection or to compare against what you build. Its in Cheyenne and I won't be back for a couple of weeks. Its on the shelf right now. I am running a tall K&N pod on that 350 right now. If you run a K&N, you must run an oiled foam layer on it too. K&Ns and the prechargers alone just let in too much crap, in my opinion.

Gary

Exactly....

People need to learn how to properly maintain and oil a k&N filter. No argument that they flow more air etc etc.. And I am not saying that oiled foams are no good. But the particles that are showing up in these pics should not be making it past the filter. They are supposed to filter in microns not thousanths of an inch. What are these people cleaning the filters with? Brake clean, parts washer? Do they leave them in the sun to dry or quicken the process up and dry them with a hair dryer? Here are some pics of my K&N's, no prefilters, just an open design with deflectors to keep the heavy mud/debris off, going on 5yrs with these filters and this Engine. No scoring on the piston or carb slide.

Every time I take my K&N prefilters off their is dirt past them, I was told I over oiled mine so I bought 2 new and installed right out of the package same thing they passed dirt/sand, so then people told me I didnt oil them enough so I soaked them and let them drain over night before installing, same thing they pass dirt/sand.

I wash mine at first with the K&N cleaner and used the K&N oil, I let my air dry for at least a week before I oiled them then they went into zip locks until ready to use then lightly oiled again before installing.

Now I use OXY Clean to clean mine the stuff looks smells and works like the K&N stuff but cost hunderds less, my filters are used only for pre filters so the dirt they pass is no big deal for me.

Here is another example this guy been using K&N's on his machines for years, swears by them.

http://www.pilotodyssey.com/K%26N5.htm

Call and ask K&N (I did) they will tell you directly, if your using their filters off road use the foam pre filters but they offer NO flow data with the foam filter installed

My filter setup is the dual airbox bod, K&N filters on the tubes with outerwears and a UNI main filter. Allows for great aireflow and works great for racing in the NW =)

LOL-PROJECT PiLOT ALREADY is being used as a model of what not to do-thats makes me happy!!!

Here is that 350 air box I will looking for .
http://pilotodyssey.com/PO/viewtopic.php?t=573

that's an old kleem research air box lid. I had one on my old fl350 worked great