Maybe the question is… which classes/engines would benefit from it the most?
I love tech… but I’m not into using it unless the benefits are clear…
In general, EFI just doesn’t seems to bring good value when you compare it to the cost of (most) kart engine packages and the fact that most of those packages are spec anyway…
If we say the 206 is the most commonly raced engine right now, the cost of bolting on EFI would be at least $250 + time. Benefits would be pretty marginal I think. You have to carry all the extra “schtuff” to run the EFI as well as protect it from weather and hope that any one of those parts doesn’t fail on your unsuspended, pavement pounding vehicle.
On the other end of the scale, implementing EFI with two stroke engines that rev in the 16,000K RPM range is challenging. I know Riley Will of BRC engineering has worked on a system for it comprising of two injectors, but I think he said it would be minimum $800 DIY. That kind of an application is trying to meter/time fuel impulses in the same window as a four stroke at 32,000RPM because there’s an induction cycle for every crank turn.
Having said that, I’d love to play with an EFI kit sometime… and maybe a little bit of boost. I have about 20x 460cc engines here sheltering from COVID ha
I agree LO206 is not the place. It would need to be in the shifter or high end two stroke. Shifter would be cool because it would make no lift shift a no brainer. As for 32,000 rpm comparison, I do not think it is a big deal. It is also the same as a 4000 rpm V8. If it is not direct injection then the fuel delivery does not care how often the engine fires. That could still be induction pickup with a simple device to advance or retard actively
I actually considered this until I realized they are not run it this country. Would be easy to spec with a sealed Electronics package like what Rotax and IAME use for their Rev Limiters/Ignition. No crazy last minute jetting changes before next heat. No futzing with the carb on course. You could just focus on Driving! Just let the CPU adjust Fuel & Ignition while you work on your Craft.
Downside: Might put a few Voodoo Track-Side Turners out of work, but the builders will still find a way to squeeze every ounce out of it (within legal limits…hard cough(blueprint)…snickers).
I thought that too until I talked with riley and others that were working on developing EFI for performance two strokes in single gear kart applications… It turns not it’s not that simple…
The two stroke still requires very different injection timing (Both pulse width and crank angle/pulse timing) compared to a four stroke. It’s much more sensitive than a four stroke where you can just (kinda) dump the right amount fuel in there and send it. The intake impulses, especially blowback play a bigger role.
I am an electrical engineer for a living. I often say when you think something is simple it usually means you do not know enough yet to understand the details. I guess this is another of those situations. Now I am curious
I’ve tried to entice Riley to join the forums but no luck so far
One thing to note about the KTM is that the injectors are in the cylinder, injecting in the transfer ports vs the other side of the reeds.
I posted in a two stroke facebook group to see what feedback I get on EFI and two strokes…
In the KTM system, two-stroke oil is pumped into the throttle body, to lubricate the crankshaft, barrel, and eventually the cylinder bore and rings. Fuel is squirted into the cylinder via two injectors in the transfer ports, rather than into the inlet port or head.
The window of time for the injector to be open and getting the large amount of fuel a two-stroke needs is the challenge, especially in even smaller displacements we are told. Plus when a two-stroke has a “flame-out” inside the combustion chamber, it can take up to 50 strokes for the engine to recover. This was a big issue in high RPM, low throttle times. For instance when you are going down a hill with the engine revving and then you give it a little gas. Making the throttle response as good as that antiquated carburetor was very difficult. There is not a lot of time for the computer to decide how much fuel and when to shoot it from one stroke to the next since the conditions inside the two-stroke engine can change drastically and very suddenly.
This won’t happen, karting will jump straight to electric. The only manufacturer I thought might do it would be Rotax, as they have the direct injection tech already with Evinrude. But they are going down the electric route.
If you were selling 10,000 of units or could make use of an injector from a mass produced bike/snowmobile/jetski, I would estimate (just from my experience working in the manufacturer of diesel engines) that you could get the injector down to sub $50. But I can guarantee karting manufacturers would sell them $200 because a carb costs a similar amount (or more).
TM went fuel injected with the dirtbike range this year, but the reality is that in terms of a karting application it is incredibly unlikely to come in. We’re with carbs until the end of 2-stroke karting. I doubt the FIA will mandate it, and there’s little appetite in the market placed for a shift over in the recreational classes.
I looked at this last year in some detail. Besides KTM, which wouldn’t sell me an engine directly, there were no other 2-stroke FI suitable engines for kart road racing. Really, FI makes the most sense with 4-stroke engines, something I can see karting and other 2 cycle sports being pushed towards as states also start cracking down more on all 2-stroke engines.
To get good low end torque out of slow corners AND high end performance with a 4-stroke, FI really helps. And it’s much simpler to meter since standard wideband O2 sensors and controllers can be used due to the lack of oil in the exhaust. Yes you need a small high pressure fuel pump, an injector, O2 sensor, computer, and a small battery to run it. Most of the weight added is in the engine with the valvetrain. So heavier and a little more expensive for the same power than a 2-stroke, but with a start and just run it experience like a 208, even on the coldest days.
And yes, I’d love to go there. A 449cc Kawasaki engine on a kart is something I may just build this year even though I’m not allowed to even provisionally kart “race” it due to nothing bigger than a 250cc engine insurance regulations allowed. 52.63 hp at 9,480 rpm and 32.80 pound-feet of torque at 6,730 rpm on pump gas should provide a lot of grins for the money, even if it has to be at the drag strip.