Lab Notebook‎ > ‎Shelved till later‎ > ‎

Fuel Injection

If I get back to this - this link will be handy on EFI'ing a two-stroke


Fuel Injection is back on the agenda with the availablity of a new kit which is ideal for a supercharger combination (as jetting such a beast would be very hard).

Small Engine EFI Conversion Kit:

I have some concerns though over the fuel flow required for a 2-stroke. I am worried that a 200cc 2-stroke needs twice the fuel flow as provided by a 4-stroke EFI unit. See my forum post (and hopefully the answer)


Some old notes transferred here...

Here are some notes on setting up fuel injection...

MicroSquirt is a fully-assembled surface mount technology (SMT) version of the MegaSquirt fuel injection controller and is most like the MegaSquirt-II and V3 main board assemblies. MicroSquirt is suggested by RZ350 EFI Conversion

Orbital Direct Inject systems are not feasible as they require complex set-up and cost will be way out of the range of back yard Vespa researchers. Orbital suggested port inject as an alternative.

Notes from talking to someone that built their own Fuel Injection for a Karman Ghia (4 stroke car)...

  • expect only about a 5% improvement in power
  • fuel injection is more forgiving with engine timing (i.e. the engine will run where a carb'd engine would not)
  • you use a throttle body with a fuel injection fitting (either make one or buy one)
  • no venturi effect needed, aim for a bit more in a throttle body size than in a carb (i.e. if you were to go 30mm carb go 34mm throttle body)
  • may need to consider ram effect, throttle body allows more sonic wave action (need to read up on this)
  • high pressure (40 psi) fuel pump is required. The normal way of retrofitting this is to have a second smaller fuel tank with the fuel pump inside (quite tricky to do)

Summary: It is possible but not an easy task. His recommendation is if you have a 30mm carb, plug that on first and have some fun. The fuel injection will take some time so work on that in the background. Based on this advice I (--internetscooter 00:30, 22 December 2006 (EST)) may still get a MicroSquirt but use it just for timing to start with, later revisit fuel injection as more of a fun project rather than fun to increase power.