MOPED ARMY

Nice, I've been thinking that a Nutella jar might make a good airbox but my girlfriend's vitamin bottle looks pretty similar to yours so I'll have to give that a shot too

Few things.

You need a dome at the terminal end. That really reflects the wave back into the intake.

Then the tubes you’re using are no good.

Use irrigation tubing. It’s very thin and pliable. You can flare the end for a Venturi effect. Really helps pull air in.

The trick to a good air box is to calm down the air before entering the motor making the air more dense and less turbulent!

Plumbing bits are great because they already figured out fluid dynamics

This would really lend it's self well to 3d printing.

I would normally comment on how it could double as a one-sided legshield, but I am more interested in the banjo string fuel line and completely unhinged cabling.

JBOt is of course correct, you preferably want a conical/rounded end to bounce the wave back. This is a first iteration, but if it were me I would remote mount to get that vibrating weight off the end of that intake and stop it from sticking 12" off the bike.

I’ve used air boxes on piston port and it worked ok, not as good as it works on reed but it does capture blowback.... One can have issues if there’s too much and pooling occurs

Whether is reeds shutting or a piston, when the intake port shuts there’s still inertia to the column of air proceeding.

When that flow hits the reed/piston it creates a reflected wave. Another opportunity for 2 stroke optimization. Give that something to reflect off of in the airbox, and it is similar to an exhaust chamber.

I think a lot of people leave this power laying on the table because it has to be matched with other rpm related tuning and can make carbs harder to tune.

Shifty bikes don’t need as broad of a power band. I assume reeds and variators are more compatible. PP?

I would like to try it for shits and giggles

The resonant wave is sound, just like an expansion chamber. Whether it's reeds or PP, matching that to your tune helps push blowback back into the cylinder just like a return wave on the exhaust pushes back unspent charge into the combustion chamber.

There’s a reason not many people do it.

This isn’t 1:1 comparison to exhaust chambers. The gasses in the exhaust are high pressure. Good density means efficient and fast wave travel.

The intake is being evacuated constantly. Very low pressure. And the wave isn’t the exploding mixture of fuel, just that very low pressure column of air bumping into a closed reed or piston skirt.

I think the greatest good of a tuned intake length is to, at a min, not let that weak ass return get OUT of the intake before the next signal pulse pulls the air and fuel back in. And, If I understand it correctly, that’s mostly at low rpm where most of use tune our clutches to stay clear of.

Top it off with the majority of people on mopeds tuning with butt dynos, and it’s hard to get an accurate picture.

I will throw something together this weekend and share too. Can’t go wrong if it’s all for fun.

I’ve played with many different lengths of an airbox hose length and shorter is usually better

What seems to be most important is bottle ID.

Too small a diameter and it just doesn’t work right. I’ve found that these fat shampoo bottles are basically the perfect size.

Maitland, please ride this next time you ride in Sacramento. I wanna see it in action!

im sure i read a long time ago (jennings?) that much of the benefits of intake tuning is lost on reed valve motors.

but i remember seeing formula to work out the desired tuned length.

much like with exhaust pipes. get it right and its free power. im gonna read up on jennings and bell. (cant understand blair)

Found a sweet ABS drain pipe that fucking JAMS