TRX250r.org

Author Topic: Anybody ever made a homemade air intake?  (Read 3427 times)

Offline Tbone07

Anybody ever made a homemade air intake?
« Reply #15 on: February 26, 2017, 09:26:34 PM »
So basically...

higher HP engine w/ smaller filter = higher intake velocity = increased suction = decreased air filter effectiveness

higher HP engine w/ larger filter = lower intake velocity = increased intake volume = increased air filter effectiveness
LED Performance 350 Sphynx - XC Machine
Laeger's-Roll-GThunder-HLS-PEP-HiPer-GBC

RIP Laz

Offline Big_Mike

Anybody ever made a homemade air intake?
« Reply #16 on: February 26, 2017, 10:22:40 PM »
In my honest opinion an air intake with a "bell type" velocity stack would be the best design to go with as opposed to a straight pipe leading into the carb..  Such as this, I know BDT and LED have a velocity stack design in their intakes..

Offline Jerry Hall

Anybody ever made a homemade air intake?
« Reply #17 on: February 27, 2017, 12:28:51 AM »
Quote from: Tbone07;71987
So basically...

higher HP engine w/ smaller filter = higher intake velocity = increased suction = decreased air filter effectiveness

higher HP engine w/ larger filter = lower intake velocity = increased intake volume = increased air filter effectiveness


Yes  your right.



Foam filters, K&N filters and paper filters work on entirely different principles

Dry paper filters have extremely small air passageways (pores) for the air to flow through.  There are not many dust particles that are smaller than the pores in a paper filter so the particles are prevented from passing through and stay on the outside of the filter.

The K&N filtering medium is an oiled cotton gauze that is comprised of small fuzzy cotton strings that are woven into a mesh. Dirt particles larger than the string mesh will not pass through the gauze.  Smaller dust particles are suppose to stick to the oil impregnated fuzz that is suppose to overlap the cotton string mesh.  A brand new K&N properly oil filter will do a pretty good job of catching almost anything but most guys ruin a K&N the first time they clean and oil the filter.  A slightly dirt K&N will usually provide better filtering than a freshly serviced filter.

Using a water hose or compressed air hose on a K&N while cleaning will crowd some of the cotton strings closer together.  When some strings are crowded together this will increase the mesh size between parallel strings.  When the mesh size is increased large particles can now pass through the larger mesh holes.  When the mesh size is increased on a properly cleaned filter, the fuzz that surrounds each string will not overlap enough between strings to catch the small stuff.  

A K&N filter must be 100% oil free after it is cleaned for the fuzz that is suppose to surround each string to be present when it dries.  If there is some oily residue remaining in the gauze after cleaning and not 100% dry, the fuzz that normally surrounds each string will stick to the string.  A K&N filter that does not have fuzzy strings, will allow the medium to small particles to pass through the filter.

The oiling technique on a K&N is critical.  If using the K&N spray oil , spray only the outside of the filter and wait a few minutes for the oil to wick all the way through to the inside.  If the oil has not wicked through to the inside after a few minutes, spray the outside again.  Repeat the process until the inside of the fabric has the same color as the inside.  Using this process guarantees the cotton gauze is thoroughly saturated.  Use the K&N oil and do not use ATF of some other imitation air filter oil.  K&N oil is not a petroleum oil but I have heard that it is a vegetable based oil so that it has some very very slight tackiness when exposed to air for a while.  

I like to use the K&N oil that comes in a squeeze bottle.  Use the  squeeze bottle to place a bead of oil down the outside edge of each pleat.  Wait a few minutes and look at the inside of the filter to see if the oil has wicked through to the inside.  If it has not wicked through after a few minutes, make another pass down the outside of each pleat. Repeat the process until the gauze is thoroughly saturated.  It is better to slightly over oil the filter than to under oil it.  Excess oil will eventually drip off the bottom of the filter or the engine will run lousy for a while if the filter is undersized.

Foam filters have many large interconnected air flow passageways that have the inside walls of the passageways coated with a very tacky substance.  The filtering process occurs occurs on the inside surface of the interconnected air flow passageways through the filter.  Very large particles will stick to the outside of the filter and or get wedged into the entrance of the airflow passageways.  The small particles move through the passageways until they encounter and adhere to a sticky surface.  Once all of the sticky surfaces in the interconnected passageways have particles stuck to them,the filter will allow the small particles to pass through the filter unless all of the entrances of the passageways are plugged with large particles.  

Mesh type filters filter better as they get dirty until enough vacuum is present to distort the mesh so that particles wiggle through the mesh.  Foam filters will pass dirt once the tacky surfaces have dirt stuck to them. With any type of air filter that is not substitute for having as much filter surface area as space will allow.  

Each type of filter has their advantages and disadvantages, you have to decide which filter fits your situation best.
« Last Edit: February 27, 2017, 09:25:00 AM by Jerry Hall »

Offline DeathPunch88_250R

Anybody ever made a homemade air intake?
« Reply #18 on: February 27, 2017, 08:35:53 AM »
Good Info Everybody! Thanks

Offline Jerry Hall

Anybody ever made a homemade air intake?
« Reply #19 on: February 27, 2017, 09:28:20 AM »
Quote from: Big_Mike;71989
In my honest opinion an air intake with a "bell type" velocity stack would be the best design to go with as opposed to a straight pipe leading into the carb..  Such as this, I know BDT and LED have a velocity stack design in their intakes..


You are correct as long as the straight portion of the velocity stack has the correct tuned length.

Offline Goose

Anybody ever made a homemade air intake?
« Reply #20 on: February 27, 2017, 01:52:23 PM »


I made this one then powdered it black. Nothing fancy or much thought into it. Just bored and figured it could suck more being an open filter instead of in the box. My 250r will spend 99% of it's running life in the sand so mud/water shouldn't be much if an issue.
I made it for stock intake tube and filter. Have a uni on it and welded a nut to hold the brake RESI. Essentially just made the front of the stock airbox out of steel

Offline DeathPunch88_250R

Anybody ever made a homemade air intake?
« Reply #21 on: February 27, 2017, 04:09:35 PM »
:redbull:That's a nice job on the fabrication Goose!

Offline Goose

Anybody ever made a homemade air intake?
« Reply #22 on: February 27, 2017, 11:44:44 PM »
It was a pain in the ass, atleast the circle was. The rest wasn't too bad.
Made it all by hand out of a 2x2 sheet I had laying around, was bored one day and decided to do it. I'm happy with how it turned out.

Offline DeathPunch88_250R

Anybody ever made a homemade air intake?
« Reply #23 on: February 28, 2017, 01:42:52 PM »
Looks good that's for sure

Offline The norm

Anybody ever made a homemade air intake?
« Reply #24 on: February 28, 2017, 08:15:23 PM »





I made mine from a aluminum conduit bushing and an ESR center mount hanger.
« Last Edit: March 01, 2017, 07:58:53 PM by The norm »
I had a BDT motor once.....It SUCKED!
Currently: Hybrid Engineering 310 stroker built by Pete

Offline DeathPunch88_250R

Anybody ever made a homemade air intake?
« Reply #25 on: February 28, 2017, 10:44:43 PM »
Looks good! Wish I had welding machines.Lol