Fuel Injection System

[david_or_johnny]

My newest project is very, very ambitious:

I'm planning to make a miniature fuel injection system for my carbureted RC model car motors. I'll program it a lookup table taken from approximate factory settings on the carburetor, and write a genetic algorithm for it to learn how to produce peak power without harming the motor itself by being too lean. I will use atmega168 for controller.

I hope to solve a major problem in nitro RC: engine tuning. It's incredibly annoying.

The plan is to find a very small pump that can run off 6 volt power (maybe 7.4, 2S LiPo receiver pack) and a small high switching rate solenoid valve that controls fuel flow. Do you guys know where I can find a micro pump and solenoid valve?

[Rebelgium]

The smallest pump I can think of this fast is a pump for watercooling a PC. Or maybe a very small fontain you can place on the table.

[ed1380]

the fuel pump on a car always runs providing 40-60psi

the fuel injectos themselves open and close very fast controlling how much fuel gets in the cylinder

all nitro rc cars run on nitro and dont have sparkplugs

maybe ask this guy
http://www.youtube.com/watch?v=mLvBWuE5RFA&feature=related

[david_or_johnny]

Yup, they run on nitro.  So not having to worry about spark plug timing is a plus, since the heat of the glow plug (the equivalent to a spark plug on nitro motors) controls ignition timing. Essentially this "fuel injection" now that I have thought about it more is much less complex than I anticipated because most of the timing is already hard-machined into the engine. Its only role is adjusting air-fuel mixture.

Thank you very much for that link! That youtube vid is much like what I would like to do, but my motor is much smaller and all the stuff needed for the fuel injection must fit on a 1.5 ft x 2 ft monster truck or buggy.

[ed1380]

that should work

the sparkplug on a car is what ignites the fuel at the special time (AKA the timing)

where are you planning to put the injector? drill a hole in the head? or put it instead of the carb?

i did some searching and it turns out all small motors are carbed (I might have missed somehting)

I bet you'd like one of these 
http://www.youtube.com/watch?v=1PK2BzUE8aw

[david_or_johnny]

No way! 

The link is eluding me at the moment, but someone made a V8 with the Lego Technic pneumatic kit .

Yeah, they're all carbed. So what I'm going to do to make things easy the first time is to just tear out all the needles on the carb (there's 3!), plug up all the holes but the low speed needle hole, and put the injector tubing and spraybar / atomizer there. Before that, there will be a micro solenoid valve and a micro water pump to deliver the pressure (hopefully the pump will only be used by starting since the exhaust manifold provides more fuel tank pressure), all controlled by an Atmel 168.

[ed1380]

sounds good. good luck and report back to us

one Q though. 3 needles? idle, high, low right?

[david_or_johnny]

Yup. I may keep idle as is.

[ed1380]

wont do anything. the injector will control fuel input

[dunk]

going back to your question about a small pump,
what about a servo pushing a syringe closed?

dunk.

[david_or_johnny]

Yeah, but I want a nice hardware stop for the air mixture control (aka the throttle servo) so the idle would be nice.

Hm, servo pushing syringe... that's a good idea. I'll look for a very large syringe, but it's not optimal unless I'm not thinking of something.

If I can find that pump OS puts on its helicopter engines, that might work.