Hi res photos are courtesy of Rob van der Heijden, he took them while working on his ST20/25

Current Systems in use

Currently know model engine fuel supply systems are: 

- Bladder type fuel injection for speed flight

- Exhaust muffler pressure to the tank which in fact is a make-shift fuel injection

- Using the two-stroke positive crankcase pressure to pressurise the tank

- Using special tubing routing inside the tank to create constant fuel pressure

- Providing a hopper tank close to the engine, combined with the chicken feed principle.

- Using fuel pumps which are driven by vibration or crankcase pressure variations.

-    Cline Associates provides a fuel pressure regulator that can be fitted close to the engine in order to minimise fuel level variations, and uses a pressurised tank and spring-controlled fuel pressure regulating. Drawback here is, that if pressure is set above atmospheric, fuel starts to flow without the engine demanding any, thus flooding the engine. So pressure has to be set at just equal to atmospheric or slightly below. This system comes close to what is needed, but does not account for the increased fuel demand as the engine loads change in the air. It also puts a rather high pressure in the fuel tank due to the crankcase pressure being applied through a check valve.  

While all of these systems work to some degree, each has significant drawbacks that we all have learned to live with. There has to be a better solution if our glow engines are to perform as stable as for example a car engine. 

In general, good systems are available for petrol (US gasoline) engines such as.

-         Carburettors with a fuel pump or gravity feed, and constant fuel level regulated by a float system which feeds the fuel jets.

-         Floatless carburettors as found on chain saws, which have an integrated pump and fuel pressure regulator according to the fuel demand principle. (Drawn away fuel is supplemented until the pressure is right again)

-         Fuel injection, using electronic control and engine parameters to determine the amount of fuel injected. This amount is regulated by a function of pressure, time and jet size.

For one reason or another, none of these systems are perfectly suited for model use when used on methanol burning model engines, but a clever combination of available systems can do the trick.