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Author Topic: Transfer Port Injection  (Read 8434 times)

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Offline Flettner

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Re: Transfer Port Injection
« Reply #15 on: June 19, 2017, 04:37:10 PM »
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.



     
« Last Edit: June 22, 2017, 01:19:19 PM by Flettner »

Offline rsmith

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Re: Transfer Port Injection
« Reply #16 on: June 20, 2017, 07:41:00 PM »
Interesting, I always assumed the DI system to be more like a diesel system where the injection cycle happens very late in the power stroke hence the need for a burly injector to overcome the compression.

--Ron.

Offline Flettner

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Re: Transfer Port Injection
« Reply #17 on: June 21, 2017, 01:34:23 PM »
Yes a large (burly) injector is needed because at some stage injection is taking place under compression. At higher speeds there is just not the time to inject and mix all the fuel with all the air, thats where Diesel comes unstuck. Cant process the injection and burn at high engine speeds, thats why they react so well to over boosting with air (turbo)but there is a time limit and thats why you don't see diesels doing 13000 rpm. Apart from the general size Im just talking burn wise. This is where HCCI has a major benefit, all air and fuel is already mixed so its just a matter of compressing it at the right time for combustion (controlled detonation). Hence my HCCI test engine, sown here already? Another project in itself. Yes sorry, we have talked about this already.

« Last Edit: June 22, 2017, 01:18:50 PM by Flettner »