Falcons Cuz

Hello Guys
i have been playing with Baja 5b from last three or four months but now i am going towards nitro powered rc trucks and after reading a few articles on nitro engines i am very excited about thee but i am confused that how the carburetors on nito engines works? because there is no walbro pumping carb on the and i have seen that a pressure pipe is going into the fuel tank coming from the tune pipe and i am thinking that the exhaust gases are entering into the fuel tank to pump the fuel into the carb so guys tell me that is it right or not
also tell me that how they work and if there is a vedio on youtube about how do they work then give me a link to it


waiting for your answers
Falcons Cuz

Anthoop

Yes the fuel tank is pressurised by the pipe from the exhaust. However the pressure is not enough to force fuel into the carburettor alone which is why you have to prime the carburettor before starting, so really the combination of the exhaust pressure and the vacuum in the venturi supplys fuel.
The carburettor can be primed in a couple of ways- hold a finger over the end of the exhaust and turn the engine over or remove pressure pipe from exhaust and blow down it. Either way only prime until the fuel has just reached the carburettor.

Falcons Cuz

thanks Anthoop
can you also tell me that do the exhaust gases go into the fuel tank or not?

D.DJ

The exhaust gasses do go into the fuel tank, but that pressure is to keep the fuel flowing into the fuel line up to the crab, otherwise g-forces will send it backwards and all sorts of places OTHER than the carb inlet. As Anthoop said, the tank is pressurised by the pipe but that force alone doesnt push fuel into the carb. Its just a means of keeping the fuel flowing through.

Falcons Cuz

thanks again
do you guys alos tell me that how two speed transmission shift the gears automatically in nitro cars how do it happens

D.DJ

depending on which car, they work slightly differently, but they all use centrifugal force to make something expand and engage the second gear.
here are 2 I know of:

1: there is a metal "thing" that has a spring loaded claw that will extend itself out once it spins at a rate fast enough to overcome the load of the spring holding it in. Once it is protruding out enough, inside the second gear housing is a pin adjacent to the 2-speed unit and claw, and at the right instance, the claw will hit and pretty much grab onto the 2nd gear.

2: Basically the same as the first one, but the design is like a clutch you have in the RTR cars. 2 shoes are on the main drive shaft and the 2nd gear has a ring around the 2-speed unit. Like a clutch, depending on how tight the springs are set, once it spins fast enough, the 2 shoes expand and grab onto the 2nd gear.

The spring tension in both styles determines when it will go from 1st to 2nd. make it too loose/not enough tension and it will quickly go into 2nd - may not even be noticable. Too tight and it will either rev its heart out and finally hit 2nd, or just stay in 1st gear.

I find the 2-shoe style clutch much better in terms of reliability and the way it works - no metal to metal contact and it isnt really instantaneous as the 1st type I mentioned. Either one of them work, but I like the design of the 2nd type.

Argess

Here's a good page on engine and carb stuff...plus more:

http://www.nitrorc.com/

A nitro engine will provide sufficient suction to draw fuel from an unpressurized fuel tank, but will really succumb to fuel mixture changes as the fuel level drops. Pressurizing the tank helps make the pressure change due to fuel level (gravity) less significant.

I like the shoe design for shifting gears better as well. Much easier on things. However for off-road, the pawl type is fine. The shoe type really excells on pavement. Also, once 2nd gear engages, 1st gear just spins freely as it is driven by a one-way bearing.