Air pickup

[Jackal]

I've got a very simple question:

Where should i put the air pickup to the fuel tank in my tuned pipe? ???

At this moment if i just crank my engine the fuel just wont go to the carb, well ectually it will but that is only because of the suction from the carb itself, but in my opinion that is not enough, 'cause after about 10 meters my engine dies on me.

And yes i've triple checked all the fuel and air lines.

p.s it's a 0.82 k&b installed in a 1/8 scale hydro, dunno the make of the tuned pipe though

 

[TimD]

Most people mount it at the widest point of the pipe.

 

[Jackal]

That is just the problem, the pickup IS at the widest part.

If i blow air in the tank the fuel does come out, but with pressure from the pipe it won't.

The only thing i haven't tried is an other pipe.

So can anybody tell me what the best pipe is for a 0.82 k&b

inboard?

 

[Grimracer]

Jackel

Check to see if the low seting is lean. If it is the motor will not start well. Also if the boat dies after launch and you think you have the right prop. It is most likely lean. Richen the low end up and then test again. If you have some luck richen the high end also.

Grim

Remember they only stop running if their lean. That is unless you crash or sompthing like that.

 

[Jackal]

Thanx, i'll try to adjust it again (if the weather improves overhere)

But that still doesn't explain why i can't pressurize my fuel tank with my exhaust.

in my opinion i have to do that cause my tank is located behind my engine, and there is no way i can place it fwd (unless i can find a flexible badder tank witch can withstand nitro)

 

[Jackal]

Jee, gues what.

It didn't work.

I'm really thinking about buying a new pipe.

At this moment i've got a steve muck pipe, but does any body know what kind of pipe i could try

 

[Propjockey]

Don't know if this will help or not...I've seen K&Bs that had the crankcase tapped for pressure, drilled horizontally thru the mounting lug.

 

[Marc]

Jackal,

just a question : how do you check that pipe pressure does not pressurize your tank? May be it does and changing the pipe will not help... I would try a relatively small prop and play with the main needle adjustment.

Marc

 

[Jackal]

Answers to marc: In my opinion if i crank my engine with the fuel line disconnected from the carb, i should be able to build up enough pressure in my fuel tank to push the fuel out of the tank, but this does not happen. :'( :'( I know it should cause i've seen it with a buddy of mine, he only uses a 15cc picco with some kind of russian tuned pipe ( i'm not able to try his pipe cause my cowl won't fit then) the other reason why i know this should work is because my 3.5cc nova rossi with a robbe tuned pipe builds up enough pressure aswell.

I am already using a smaller prop than the one i got with the kit. ;D

I don't know about drilling holes in the crankcase, never seen it around here and it would be a shame if i destroy my engine that way :-

 

[Jackal]

Jee might have found an other solution for my boat dying on me:

I've been talking to some guy's they said i should use fuel with a bit more nitro ;D ;D.

I'm currently using 15% nitro, they said i had to go up to at least 30 to 35% . What do you thik about that?

 

[GRand]

you might try to reduce the diameter of the stinger of the tuned pipe. look at the pics of Genes tunnel in one of the other posts, you can see how he reduced his. it will create more pressure for fuel, but also build up more heat. i run 50% fuel and know a few guys using 70%........if you go up in nitro content i would richen the mixture a little. do you have NEW fuel line?

 

[Jackal]

The fuel lines are brand new, including filter.

 

[Grimracer]

Jackel

Says::In my opinion if i crank my engine with the fuel line disconnected from the carb, i should be able to build up enough pressure in my fuel tank to push the fuel out of the tank, but this does not happen.

This is incorrect. It does not work this way. As the air passes past the fuel inlet in the carb the low pressure that is created pulls the fuel. If you have a good fitting pistion the better the pull.

The pipe sees little to no pressure durring start. As a matter of fact your boat can run quite well with no pressure hook up at all...

Make sure that you have a high idle seting on the carb as you try to start it, otherwise no air can pass through and creat the low pressure you need. Small bore carbs have more pull then a big bore..faster air past the fuel inlet. Heck my airbrush works this same way..

Rock on

Grimracer

 

[Jackal]

Hey guess what, i tried fuel with a bit more nitro and it worked, for about 1 minute and them my piston rod snapped right at the big end, major bummer.

now thats not the real problem, the problem is spare parts here in the netherlands.

Well thanks anyway for the replies

and grim you'r right, it was a bit stupid thinking from my side.

now to quote swarzenegger: I'LL BE BACK