Is Direct Injection the future?
It seems the DI Rotax sled engines now run injectors at the inlet port that fire once the pipe is 'on'. makes a bit of a mockery of DI. DI also has to start injecting before the exhaust port is closed as the revs increase, once again making a mockery of DI.
This TPI isn't as bad as everyone would have it (know it alls on the internet) with the gas dynamics in a twostroke its the lower end power (rpm) where the short circuiting takes place (hence DI systems not being pure DI up in the revs only low down), its the position and late firing of the B port injectors that save the day for TPI. This is where most fuel is lost to the exhaust on a carburetor engine and lets face it, where we ride our bikes most, off the pipe or at least in transition.
The real answer is to keep the transfer gas speed up at lower RPMs and lower the port timings (including exhaust port) in conjunction with a modified TPI system. Sliding cylinder anyone?Cylinder could do the throttling (power controlling) while the inlet would have no throttle body, just straight in through the reeds, so the crank case would always be under pressure. Always a good, high inertia, gas flow into the cylinder under an amount of control. This system would require my new TPI system to operate. Results would show a very wide torque curve and excellent fuel economy.