2 stroke EFI?

Anyone think (or know) if there might be a chance that 2T EFI could be in the pipeline for karting in the near future, or is it too expensive for our market?

Only asking because I’m building another shifter & getting the motor next yr, & EFI would be an interesting twist on the project.

I like your thinking. A chance - sure, I think it will happen. When it would be broadly accepted is the question.

It just makes good sense, as that is where 2 cycle engines have to go to stay available on the market. Of course there is the question then if karting will continue to use non kart specific engines. Also class wise in between then and now, I’m not sure where they will fit. Tuned for like fuel they will most likely have more bottom end torque based on what KTM’s done and carb people will probably not like that.

For a road race single 250, that would be my choice right now. For 125’s, I’m sure the tech will be applied down-line soon enough. Others will need to follow suit ASAP if they want to keep selling 2 cycle dirt bikes.

Only thing I’ve seen at all for two strokes in production, outside of outboard boats is KTM’s system.

There’s a kit you can order if you wanted to try it yourself from ecotrons, but you probably already k is about it…


The ecotrons kit, while neat, is restricted to 400cc-800cc engines. At any rate, this would have to be a production engine in order to be sanctioned.

I’ve heard rumor that TM has (or had) an EFI test mule in R&D, but nothing confirmed. Of course, there was also the Modena EFI trade show prototype revealed back in '14 that never got out. That had me hoping it might be around the corner, but no joy so far.

That kit also says for 4-stroke. 4-stoke is a cake walk compared to 2-stroke and oil injection.

They have a two stroke kit too, I might have linked the wrong one in a hurry. Either one is not anything I’d be personally trying on anything but the most consevative two stoke.

Haven’t heard about TM. Honestly I think EFI on a two stroke kart might cause as many issues as it might solve.

I belive Riley Will was testing something and it worked quite well. As you would imagine though, not practical en-masse

Is it an issue of cost scaling, or something else? I think KTM & Husqvarna show the way, but the details of implementing it can push development costs & the price point becomes prohibitive for a smaller market. I want to believe that the Euro karting sector is big enough to spread costs out to bring pricing into realistic levels, but the fact that there hasn’t been even an incremental marketing effort for an EFI karting engine would seem to indicate that it isn’t seen as a viable strategy. Here’s hoping I’m wrong, though.

There’s no drive to do it in karting. From a CIK-FIA classes (OK, KZ etc) the engine manufacturers follow the regulations and the regulations don’t allow EFI. I don’t see the regulation heading that way, they gone more simple recently but Felipe could change that I guess.

It might be a feasible in one of the commercial classes (Rotax, X30, Vortex) but out of those only Rotax has the industrial might to make it affordable out of the box, and they have a division that does it for outboard boats and skidoos. They’ve still chosen not to do it, yet. I think its more likely karting will skip EFI (or other such enhancements) and go straight to electric, which is what rotax have/are doing.

The interesting thing (for me) about the skidoo engine is the top end bares a remarkable resemblance to the rotax max, I wonder if it you could just machine a head to fit the injector.

It would be all calibrated wrong but interesting.

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Electric - love the idea, hate the cost, weight, and overheating issues.

So I’ve been giving this some more thought…

The KTM type setup as-is (pump gas) could be great as a step-up from the LO206. Low maintenance, cheap gas, not as peaky power as C12 powered shifters to manage, etc. But, it is a bit expensive and they really don’t seem at all interested.

Of course that new KTM style EFI is very old-school, essentially TBI for 80s carb engines. There is really so much more you could do to create a modern 2-stroke engine. Enough so I think this will be my winter frankenstein project.

For a POC test mule, start with a decent 2-stroke engine. Block off the carb to under-piston air passages that normally pressurize the air charge. Use splash lube for the crank and bottom of the piston (like a 4-stroke). Attach a very small supercharger (turbo compression wheel) to the crankshaft and plumb the output to the revised intake port. Mill out the top to add a direct inject fuel injector. Add a small crank-driven high pressure fuel pump, or possibly a very high pressure low volume electric fuel pump. Add O2 sensors to the exhaust so it can calculate the correct mixture. Setup some crank angle sensors to track piston movement. Attach a computer to take all the inputs to calculate optimal fuel and spark. Wha-la, a modern direct injected 2-stroke engine with no need for oil injection or mixing. It will need to run unleaded race gas, but that’s actually more available and cheaper than C12 anyhow.

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There are relatively tamer shifter engines like KZ-TaG that can handle 98 pump in stock trim. I just haven’t seen any significant evolution in engine development. Prices have gone up, though, so there’s that.

I found this informative article on how KTM arrived at TPI instead of DI. It seems cost and complexity were the main reasons they didn’t go that route. One other thing I’ve now read is that the reason DI doesn’t have the gains with a 2-stoke compared to a 4-stroke is due mainly to the lack of time (at speed) available for the gas to mix well with the air. Not only is the piston moving faster, there is less sealed cylinder travel time (after the ports close) in which to do it. An OHV design would remove that issue, but of course add weight and more complexity. Crud.