custom airbox, controlling air intake

matt boda1nz /

anyone ever rig up a custom airbox? whereas the air inlet is fully adjustable? thus eliminating changing jets? i have a qt50 and have been thinking about modding a stock airbox. thoughst? am i crazy?

Re: custom airbox, controlling air intake

Fluter valve.

Re: custom airbox, controlling air intake

It's called a constant velocity carb...LOL

Re: custom airbox, controlling air intake

I do this on every moped and scooter.

It rules for fine tuning air intake.

It's designed off the k&n karting airbox, but is smaller.

The input tubes are irrigation tubing, the length and amount of them can really fine tune the airflow. Most I make out of a shampoo bottles, but made one recently out of a hand lotion bottle with a similar dome shape but smaller.

It also quiets the intake a ton.

Re: custom airbox, controlling air intake

But you still need to change jets.

You have to be close in jetting to have an adjustable airbox to work.

However, you'd be surprised how after you think you're jetted right, you play with the amount and length of the tubes, you can often squeeze out a few more mph....

Re: custom airbox, controlling air intake

Get a vm18 & K&N filter. Will change your game

Re: custom airbox, controlling air intake

The point is that you can adjust the air coming in, thus fine tune while the bike is running, in seconds.

Can't do that with an open filter

If you find that you're running lean for whatever reason at a rally, you either have to upjet or seize.

I can plug one intake tube, or add a longer one in it's place,

And I'm rolling again with a good mix.

Re: custom airbox, controlling air intake

matt boda1nz /

nice! great post jbot. thats exactkly along the lines if what im talking about. i figure i would start with a larger jet than needed and open up or close as needed, adjusting until it bogs and open up until the bogs just go away.. i kinda picure an aperture in a camera lens...

thats awesome that you use that...

Re: custom airbox, controlling air intake

matt boda1nz /

yeah.. instant tune.

Re: custom airbox, controlling air intake

If my airbox would fall off I'd be fuckrd.

I'm probably restricting the airflow by about 10-20%.

That way I can go leaner or more rich easily by air flow control.

If you go too rich with the jetting, it won't even run with the box.

Every carb is different, I usually run 2 tubes with the top hole closed as well.

On my reeded hero kit, that equates to a 95 jet on my mikuni 16.

Probably would take 105+ or higher if no filter....

Also, if you oil the inside of the box,

It catches dust really well with minimal filtering. (edited)

Re: custom airbox, controlling air intake

Swoopid Woody /

"On my reeded hero kit, that equates to a 95 jet on my mikuni 16.

Probably would take 105+ or higher if no filter...."

uhh..seems like restricting the air flow that much would just hurt performance? ive always gone for more flow with best mixture. having a 95 jet with super restricted air doesn't mean you are running "leaner" than 105 jet w/ more flow. seems like that's just making ur 16mm carb and shit pointless. am i missing something? or are u going for more mpg and having the luxury of not using jets to tune over having a fast ped?

Re: custom airbox, controlling air intake

It's not super restricted....it's got really good power.

I'm not on the track where i need every bit of power it can give. It already feels like a variated bike and gets to 50. How much more do I need? I could drop a 24 on it and a bigger reed setup...but why when I have less than a gallon tank?

Slight restriction doesn't hurt performance much. Some setups seem to prefer some restriction on the airflow, 2t variated scooter motors perform best with slightly modified airboxes. Hell, cv carbs require back pressure to run goodly

.

Id gladly take a lil hit on my mph to give me the flexibility of fine tuning the intake flow without rejetting often. It also makes for a much less noisy intake. I contend that by being able to fine tune the air coming in, I can actually get the mix perfect easier than y'all with open filters or no filters. (edited)

Re: custom airbox, controlling air intake

Swoopid Woody /

all am say;n, and it seems like u agree in ur last paragaph is your killing your top end just so u can tune with your filter instead of jets/needles/screws. u got a nice carb there, tuning the correct way should be a breeze. i just dont see the point, ur hurting ur performance and if that filter falls off or gets a leak u can seize so easy. what i was saying about your carb size is your defeating the purpose of the larger carb/intake. u might as well go back to an up-jetted stock carb with high flow, probably give you almost the same gas/air. different stokes i guess, but there's a reason we use jets n shit to tune. i get slight restriction, but 10+ jet sizes lower than where you should be?

Re: custom airbox, controlling air intake

Swoopid Woody /

and who does't like the roar of a happily flowing intake1?1

Re: custom airbox, controlling air intake

You don't get it, probably never will.

Tuning the "correct way"? Lol.

Of course I use jets to tune, I get the jetting close then use the airbox to fine tune.

A 16mm carb is tiny, it's the smallest I'd go on a kitted motor.

Nevertheless, after I reeded the top end, I had to go up from a 78 up to a 95 because of the 360 deg intake and porting. Then adjusted my airbox to give optimal air for that 95.

Killing my topend? 50 is bad? Lol. Not blasty enough for you?

I rarely need to get over 45 with all the hills and stop signs... and this thing pulls like a tractor which I need because of the massive hills out here.

Basically, Ive never seized a motor when running a box like this.

I've seen many many riders at rallies seize their shit because they start to run hot n lean, or get an air leak then can't compensate for so they stick. I adjust the airbox a tad and off I go.

Sorry you don't get it. I build reliable shit that goes pretty quick usually.

Wanna race me for pinks?

Edit: when riding locally, Fuck a roaring intake. I hate that shit.

I try to be as quiet as I can while getting the performance I need to get. (edited)

Re: custom airbox, controlling air intake

Swoopid Woody /

i think running 10+ jets too small just so u don't have to use the fun tuning options ur carb gives u is..... but whatever man, i'm not being mean, just sharing my opinion on your method.

Re: custom airbox, controlling air intake

Swoopid Woody /

and i do "get it" u made ur own restricted air filter with tuning tubes https://www.treatland.tv/vespa-polini-PHBG-air-filter-p/vespa-polini-phbg-evo-filter.htm like what used to come one stock *restricted* peds. just slapping that bad boy on a kitted ped with pipe and bigger carb/intake seems silly, she wants to breath :)

Re: custom airbox, controlling air intake

I think you're assuming alot of wrong stuff about my method.

I tune everything... needle, jets, slide, float, etc..... The airbox is just another tuning tool.

To each their own when it comes to tuning. Everyone has their own technique and tune to suit their needs .

I've tuned without the airbox before, just an open carb.

There were minimal gains, really loud, and frankly it was a huge pain to replace the main jet up/down many times in incremental amounts to find the perfect combo. Then with altitude changes or weather changes, things can get weird and your bike can run like shit.

I'd rather jet close, then restrict/derestrict the airflow to be perfect.

Just my style...

Re: custom airbox, controlling air intake

Swoopid Woody /

jetting close to what? u said u were running 10+ sizes smaller than with hi flow right,,, i would think all that gas and air ur not using could make a huge difference. maybe im wrong. yes, to each his own.

Re: custom airbox, controlling air intake

Downhill Harvey (OFMC) /

Harlan said, ive always gone for more flow with best mixture. .

The problem is that you're sacrificing velocity for flow. I came from the VW world and there's a reason why you don't throw on two Webber 48IDA's onto a 40hp 1200cc. Increased velocity will give more power. There's a tradeoff with big carbs. He is doing 50 right? I bet his fuel mileage is better, and that's because increased velocity equals more efficient running. Yes, I understand your all out approach, but I too, would settle for 5mph less to have a more efficient, more rideable bike. Big carbs don't work well at all throttle position, and with hi-flows, they're too fucking loud. I bet his bike is more fun to ride than yours.

Re: custom airbox, controlling air intake

Re: custom airbox, controlling air intake

† CH∆D † /

JBOT can you describe how the cone & bolt are rigged up too?

Re: custom airbox, controlling air intake

I designed mine to be like the k&n box, they aren't dummies over there...

They know a thing or 2... My version is just cheap as dirt.

I use a hole saw into the bottom of the bottle (drill bit hole cutter) with a diameter that's the approx size of the ID of the radiator hose I'm using. That makes for a very tight interference fit when I get the hose jammed thru it (thus no air leaks)

Then I use a 1 inch slice of some thin metal pipe (motorcycle exhaust pipe) that goes inside the bottle to hold the hoses round shape and act like a coupler, either to wrap a pantyhose filter around, or to attach a standard gauze or foam filter to.

I prefer the pantyhose because it's much less restriction.

Re: custom airbox, controlling air intake

Oh, one more interesting thing.

Let's say I'm riding and notice my temps are about 30deg too hot.

I can put in slightly longer tubes and actually drop temp by incremental amounts. In my opinion, that's super cool to be able to do in a few seconds without disassembling the carb.

But really, there's 3 camps here.

No filter at all: loud, most flow possible, can have bad blowback, can get crap into the engine, max power if tuned perfect, if not tuned perfect then can perform fair

Pod filter: loud, ever so slightly restricted flow, clean, blowback can still be an issue, similar power to no filter dependent on tuning

airbox: pretty quiet, slightly restricted, adjustable flow for fine tuning, blowback is captured, filtering can be up to the settings and filter element. Power may be slightly reduced, but not much.

I might do a side by side experiment with gps to compare max speeds with all 3 types of air intake setups

Re: custom airbox, controlling air intake

Swoopid Woody /

^ yes. all i'am saying is there's some trade-off going on. your settling for less power/speed for the ability to tune with your air-box. and that's assuming u know how to tune a carb right with hi flow. i was just putting it out there because no one was saying: hey its not simply "make this filter and it will be easier to tune", there will be side effects. there's a reason you don't see those on the race-track, and for me the fun in mopeds is seeing the few extra mph you can squeeze out of these tiny engines. an experiment w/ gps would be cool, but don't tune the carb like shit to prove your point :)

Re: custom airbox, controlling air intake

Puch Twingle aribox is adjustable.

Re: custom airbox, controlling air intake

matt boda1nz /

there are people that just want to have a nice daily driver to get to work, like myself. i am not obseesed with speed, i am however obsessed with reliability and ease of tuning. i'm not looking to suck every last drop of power out of the engine. i want good gas mileage and a way to quickly open up more air easily, or to shut it off.. i like the weber grill style posted.. i want to do something custom along that line.

Re: custom airbox, controlling air intake

Swoopid Woody /

^ i get that for sure. nothing wrong with talking about the downside along with the benefits is there?

Re: custom airbox, controlling air intake

matt boda1nz /

definitely not.

Re: custom airbox, controlling air intake

matt boda1nz /

ok, so here is what i finally figured out for the qt50.. its a 1" pvc ball valve from ace hardware. i shaved a little off the stock carb to airbox grommet with an exacto knife and the ball valve slips on nice and snug. the k&n filter pushes in and holds firm. crazy how this worked out. it works exactly as i hoped..

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