Do you see a real jump in performance? is it worth the money. I have a Hpi 15fe engine but im about $50 away from a new fantom.

save your money and buy the fantom!!!

save and get a fantom, they are good for the price.

Is that what the tube from the bottom of the carb going back into the engine is? Me and my Dad were stumped last night when we were looking at my RC Car Action.

What your probably thinking of is a boost bottle and its supposed to smooth out the powerband but I have heard it doesn't work to well.

I second that, I would bet money thats for a boost bottle. Boost bottles are fairly popular with 2-stroke motorcyle/atv engines, but have to be pretty carefully matched to the engine to work correctly. They are designed to prevent excessively uneven idle and low-throttle running as a result of a fuel/air "backwash" from the downward stroke of the piston. Basically, they store mixed fuel/air between the carb and the intake channel of the crankshaft and smooth out idle and low-mid throttle response. The idea is to get performance up before the engine comes "on the pipe" and the pipe starts to handle the fuel/air on the exhaust side. Like I said, it works well when set up right on bigger engines, but I doubt it will have much effect on an R/C motor.

As a disclaimer, I do not have an engine that uses a boost bottle, and nobody I race with uses one, so I can't say that i have any first-hand experience with them in an R/C application.

I too would save up the dough to buy the screamer engine and not waste cash on a cold-air intake that may or may not make much difference. Get a solid powerplant, get it tuned, and focus on driving skill, its free and it will make you a hell of a lot faster than a cold air intake will.

I don't think its even possible to put more air into the engine than it takes normally as it can just go right out the other side. Even if it did work it would just raise the compression, nothing you can't do by just removing a shim.

Thats not really what they are designed to do. They are there to catch the fuel/air backwash when the piston goes down and to give an immediate supply before the carb can provide the fuel/air. They hook-up between the crank and carb, so they are independant of the carb's throttle position. In any case, I would imagine that they would be standard on all of the high-end engines if they made much difference, but I generally only see them on the thunder tiger low-end models.

speaking of boost though, I've designed a few turbo systems for full-size cars, and I can't help but wonder about forced induction on an r/c engine. A turbo would probably not be useful with a carb and FAR too intensive to manufacture, but a positive displacement "screw-type" blower might be possible. Anyone ever tried this?

Yeah turbo's don't work on 2 strokes, I know people have used NOS though.

I have seen a turbo setup for a 2 srtroke model engine.
Ill try to dig up the picture...

so what is the tube for on the engines? it was a ad in a magazine so I dont think it was a stock boost bottle.....