• Welcome to RCTalk! 🚀

    Join the #1 RC community where hobbyists connect, share, and get expert advice on RC cars, trucks, boats, drones, and more!

    • ✓ Friendly & passionate RC enthusiasts
    • ✓ RC tips & troubleshooting
    • ✓ Buy, sell & trade RC gear
    • ✓ Share builds & upgrades

Fuel Injection

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, and others.
pyro29123 said:
is this gonna be a mechanical injector? how are you gonna time the fuel spray into the throttle body?
Click to expand...

Yeah that things gonna have to be one hell of an injector to fire at 35,000 rpm. And it would need a sensor on the flywheel or something. I'm starting to think it's impossible on a two stroke nitro, but maybe a four stroke. Kawasaki can inject a ninja 600 at 16,500 rpm.
 
its most likely going to be an electronic injector. my friend is building the computer and programming it
 
how many of you kids have seen much less worked on a real carb? that thing on our nitro engines by the strictest def is not a carb. to be a carb it must suck fuel into the air stream. that mesns suck ONLY, not pushed by the ext pressure. that is hard to do on our nitro engines. the pressure pules are to sharp.
 
if the carbs job was to suck fuel there wouldnt be a reason to have a line coming from your exuast. am i right? the carb just controls the fuel and air mixture.
 
moe7404 said:
how many of you kids have seen much less worked on a real carb? that thing on our nitro engines by the strictest def is not a carb. to be a carb it must suck fuel into the air stream. that mesns suck ONLY, not pushed by the ext pressure. that is hard to do on our nitro engines. the pressure pules are to sharp.
Click to expand...

You're right, it's a mixing valve, or, like on an lpg powered forklift, simply just a mixer.

Well svt I had a brain fart today and here's what I would be looking to try. I don't believe that any injector could pulse fast enough to feed an engine at 35-40,000 rpm. Therefore I would use something along the lines of an electronic metering valve. Put on a small fuel pump good for maybe 5-10 psi, feeding this valve. The valve would be run by a small ecm. The ecm gets it's input from a throttle position sensor. The unfortunate thing here is it's basically just over-engineering the system we already have in place! Would it be more precise, sure. Would it start up nicely, not without a crank sensor to keep it from flooding. It would also be nice to add yet another sensor for temperature. One that could richen/lean the engine ever so slightly if need be. It's something that I've been thinking about all day so please understand, I want to help you. I just don't think you can pulse an injector that fast .....electronically.
 
that sound pretty good 2revo1maxx

moe7404 said:
how many of you kids have seen much less worked on a real carb? that thing on our nitro engines by the strictest def is not a carb. to be a carb it must suck fuel into the air stream. that mesns suck ONLY, not pushed by the ext pressure. that is hard to do on our nitro engines. the pressure pules are to sharp.
Click to expand...

on these motors they may suck fuel but on a car or a lawn mower the dont. the carbs have bowls and floats they are usually fed by a fuel pump and some small engines are gravity fed. but i still disagree about the carb suckin becuz its actually crank turnin and creating a vaccum
 
Carbs work on vacuum created by the ventury which will draw fuel into the air as it passes over the spray bar. The nitro carb is very crude using one needle to meter most of the off idle tune, it is the most simple and cheap way to get the job done.
 
well pyro. my idea ( not that i am an expert on nitro carbs) is the the reason for the pressure line from the ext is that there is a lot of negative pressure, reverson. it in the intake tract. dont forget that when reversion goes through a carb it draws fuel out even if if its going backwards. reversion also effects fuel injection. i helped a guy with a big block, fuel injected, the reversion caused a layer of fuel to stand at half the length of the con rods above the top of the injector stack. it can't be avoided, all engines have reversion. the dif is how you deal with it. iam NOT trying to say any of you guys are wrong, my trouble is that the more i study something the more i realize i DONT know any thing.

ok pyro. thats what iam trying to say, the so called carbs on our nitro trucks are NOT carbs. i started working on street carbs in 1965, and you are right the carb doesn't suc the valves and pistons suc. and my idea is the that the nature of 2 strokes and 4 strokes are different. if iam right the fuel systems has to be somewhat different, but also somewhat alike.
 
On a nitro it is real simple. First off, the pressure line is only there to ensure that the engine has enough fuel on hand at any given time. Now, when the piston is coming up it is sucking the atomized fuel into the crankcase through the carb and that slot in the crank. When it comes back down the slot is closing creating positive pressure in the case (from the piston coming down). The pressure forces the mix up the sides of the sleeve and through the ports to the cylinder. All the while your tuned pipe is creating backpressure to help make sure the mix stays in the cylinder to be burned. That's the basic concept of it, I don't know all the details of it, but there is a real science to it all.;)
 
Well thankyou everyone for there input and help. I will take all of your tips and knowledge to heart and use it. But I found someone that is willing to take a risk and make the injector and see what we can do. Everyone tells me it isnt practical to do this but why not I say.
 
Svtcobra0388 said:
Well thankyou everyone for there input and help. I will take all of your tips and knowledge to heart and use it. But I found someone that is willing to take a risk and make the injector and see what we can do. Everyone tells me it isnt practical to do this but why not I say.
Click to expand...

Nobody ever got rich, famous or a patent without doing something that everyone said wouldn't work, or couldn't be done. I hope you read my post on page 2 so when you get rich I can have a cut!!........LOL just kidding, good luck!;)
 
moe7404 said:
ok pyro. thats what iam trying to say, the so called carbs on our nitro trucks are NOT carbs. i started working on street carbs in 1965, and you are right the carb doesn't suc the valves and pistons suc. and my idea is the that the nature of 2 strokes and 4 strokes are different. if iam right the fuel systems has to be somewhat different, but also somewhat alike.
Click to expand...

i wasn't tryin to say you were wrong moe i was just tryin to figure out how the carb was sucking the fuel. i have grown up with high performance motors and i raced lawn mowers soi have a basic understandin of a motor. wasn't tryin to start anything. i just misunderstood.
 
Hey no need to compete about who noes wut were all tryin to just giv good advice and I appreciate every1s input
 
are you gonna put a sensor on the crank? if so would it be magnetic? on a tmaxx they are pretty tight on room so where would you mount it? not tryin to discourage just curious.
 
yes there will be one along with a tps sensor and a temp sensor

The location right now is up in the air my buddy is workin on it tommorow
 
i have to say, because i saw amillion people posting about the pressure line from the exaust. my nitro truck that i have i never ran a pressure line and it ran perfectly fine. wich proves that the carb dous pull fuel.
 
to: pyro i didnt think you were puting me down or say i was wrong. ill be the first to say i dont have a lot of time messing with nitro carbs. i know that everyone is just putting out there ideas. i am not trying to flame any one, its just that when youv been around as long as i have there are a few things you learn. ok heres an idea, could you start with a nitro carb, remove th e fuel line going into it, mount an injector nozzle below the slide. the injector fuel pressure is going to have to be higher than the highest natural positive pressure in the crankcase. the thing is there are so many ways to make an injector system. the parts are going to have to be small. realy when you look at a nitro carb it is a good system. the bigest adventage of going to an injector is having fuel flow control on the fly. years ago holly carburetors had an adjust on the fly street carb. the main thing they did was use a solenoid to control the the fuel. useing a pwm circuit. just look up 555 timer on google. didnt mean to be so long winded.
 

RC Builds

Back
Top