Motor geek - on the ecu's you were involved with, what manufactures were they?
Where they mapped on throttle position vs rpm or boost/vacuum vs rpm?
Chuck D - I agree with your comments but if you made and changes to a carb'd bike engine it would still need rejetting
The engine already has a crank sensor fitted to work the electronic ignition, all I can see that would be needed to work the ecu would be throttle position sensor, air temp, water temp and possibly map sensor and a battery with charging system.
Injection Research Specialist, Echlin Engine Systems, Pacer Industries, EFI Technologies, and Electomotive Industries, were some of the companies that I was involved with.
IRS, Echlin and Pacer were primarily aiming to supply the two-stroke snowmobile and jet ski industry. EFI Technologies was one of the pioneers in EFI for Cosworth and Ilmore Chevrolet Indy Car engines as well as Buick GTP engines. EFI Technologies wanted to get into the two-stroke engines market. EFI technologies teamed up with Wescoast Performance. Products. Westcoast worked on the project for about a year and then came to me for help. Electomotive was a company that supplied controllers for the automotive hot rod industry and also wanted to get into the two-stroke market.
We tried the Alpha N (throttle position vs RPM) and the Speed Density (Manifold pressure vs RPM) as well as a combination of both systems. Alpha N systems were the best systems on most two strokes with one throttle body per cylinder. Speed Density did not work very well on the one throttle body per cylinder because of the weak vacuum signal. On multi-cylinder engines that had all of their intakes connected to one common plenum with one throttle body, Speed Density systems showed a flicker of hope.
The airflow into the engine follows the tuned length of the pipe on a two-stroke. The tuned length of a two-stroke pipe is not fixed. The tuned length depends primarily on exhaust temp and the density of the exhaust. The density of the exhaust depends upon the ACTUAL air/fuel ratio of the by products of combustion and not what an O2 sensor “sees” and the trapping efficiency. An O2 sensor only "sees" oxygen and does not see raw fuel or any other gas that may be present. A O2 sensor will see a rich miss-fire as the most lean condition possible!!!!!!!!!
Many versions of mass flow sensors running in closed loop with different plenums sizes between the engine and the mass flow sensor were also developed. It required huge volume plenums to damp the extreme amplitudes and the reverse flow from the two-stroke intake process. The optimum plenum sizes were not practical for the vehicles the engines were to be used on.
The alpha N system requires the engine to always consume the same amount of air at a given RPM and throttle position and corrected by barometric pressure, intake temp. and engine temp. A four-stroke’s engine volumetric efficiency repeats the above process very well. A highly tuned two-stroke engine will not consume the same amount of air at a particular RPM and throttle position each time it returns to that same throttle position and RPM. because of the inconsistency of a tuned pipe. I learned how to test two strokes long before the inertia dynos became popular and anyone with $15,000 to $20, 000 in their pocket can become an instant expert on dyno testing and tuning This is one of the reasons that I use heavy rollers on my chassis dyno and I my experience will not allow me to become one of the sheeple that follow the recommendations of the dyno manufactures on what type of dyno should be used to test two stroke engines with highly tuned pipes.
Most of the EFI development that I was involved with was about 20 years ago. We now have faster processors and the diesel industry has technology like the ultra high-pressure electronic injectors and pumps that might have some application for two-stroke EFI. We still have to solve the age-old problem of predicting the airflow into the engine and knowing the exact amount of air that got trapped into the combustion chamber so that we can fuel it properly.
The direct injected two-strokes are not simple two strokes. The direct injected two-strokes are very expensive to build and repair. We still need to figure out how to fuel inject two-stokes to reduce emissions and keep them simple or face extinction.