Saw that starpuss is planning on attempting efi on his Zilla build. Looked at some efi 2 stroke conversion kits on the web starting at $599 for 42mm throttle body for 400-800cc 2 stroke single cylinder engines. Is this really something that is doable? I mean the benefits f efi are far greater performance and reliability wise to that of carborated engines. Is this something I should consider with my Zilla build? If its as simple as it seems why hasn't more people been doing it? Excuse me if I'm way wrong I'm not the most knowledgeable regarding engine building and such and I'm the first to admit that. Just thought this topic should maybe be breached in depth so I can learn all the options I have for my build. Thanks

If you have a ton of expensive testing equipment as well as unlimited access to a dyno it would be an experience that would be very educational.  The theory of how to apply conventional EFI to a two-stroke sounds very simple until you have been down this road.  I do not think that any of the members on the forums have the financial resources to perfect EFI for two-strokes.   


It was common knowledge in our engineering circles that GM, Chrysler, Toyota, and Mercedes had two stroke R&D projects with conventional EFI going on in the late 1980s.  I am sure all of the other auto companies around the world also had two stroke EFI projects, but I did not know any engineers at those companies.  The insiders in the automotive industry said that the various companies would have high-powered two strokes in some of their sport cars by the mid to late 1990s.  Engineers from GM, Chrysler and Mercedes told me that the engines and fuel management systems would work well in the test cells and under the watchful eye of an army of engineers but did not have the longevity to pass the certification tests.  The bean counters stopped funding the research and most of the big companies pulled the plug on their projects by about 1995. 

Direct injection is found some of the snowmobiles and outboard boat engines.  Direct injection is not a EFI type system that you can add on to an existing engine. 

I have been working with conventional EFI on two strokes since the early 1990s.  I did some consulting work for two of the EFI controllers manufactures.  High performances two-strokes have some problems that do not exist in the four-stroke world.  If someone could figure out a way to accurately monitor the instantaneous airflow rate into the engine and simultaneously monitor the trapping efficiency, it might allow us to go forward with two-stroke EFI.  O2 sensors, mass flow sensors, speed density systems, alpha N systems have not proven too be the proper approach to sensing and controlling the fuel management systems for a two stroke.  We can make one type of EFI system work on a particular model of engine for a specialized application but not for another application of the same model.  The various sensors that work flawlessly in the four-stroke world are not durable or sensitive enough to serve the two-stroke needs.

I wish EFI was as easy and as inexpensive as all of the advertisements and internet forums makes it out to be.  If it was that easy, two strokes would have been using EFI as long as four-strokes!!!!!!!!!!