So Where To From Here?

May 10, 2010
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by: Tim Hickox

Watch out! The marketing monster is loose. TM has also said that they will have "fuel injected" two-strokes. But notice that the OSSA has lubrication by premix. That means the fuel has to go into the crankcase. That means that their "fuel injection" is best thought of as an electronic carburetor.

Suzuki did this for many years on their outboards. The only advantage over a carburetor is that the mixture can be regulated in precise response to the engine's demands. A carburetor can only produce a mixture curve (as on a graph) and this may not match the engine, which often has a lot of bumps and dips. But that advantage, in my opinion, doesn't justify the cost and complication.

DFI, injecting the fuel DIRECTLY into the cylinder, is completely different. And if you are going to go to "fuel injection" in any way, why not go all the way and do it right?

I will mention that there is an in-between option: semi-direct injection. Skidoo/Rotax used this before going to E-TEC. They use a four-stroke type injector in a transfer port. The result, in emissions and fuel consumption, is about half way between that "electronic carburetor" scheme, and real DFI.

The TM, on the basis of what I have read, will be like the OSSA. The first true DFI system in a modern, production motorcycle should come from KTM - and I'm still waiting!

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May 10, 2010
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Submitted by: Tim Hickox

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Watch out! The marketing monster is loose. TM has also said that they will have "fuel injected" two-strokes. But notice that the OSSA has lubrication by premix. That means the fuel has to go into the crankcase. That means that their "fuel injection" is best thought of as an electronic carburetor. Suzuki did this for many years on their outboards. The only advantage over a carburetor is that the mixture can be regulated in precise response to the engine's demands. A carburetor can only produce a mixture curve (as on a graph) and this may not match the engine, which often has a lot of bumps and dips. But that advantage, in my opinion, doesn't justify the cost and complication. DFI, injecting the fuel DIRECTLY into the cylinder, is completely different. And if you are going to go to "fuel injection" in any way, why not go all the way and do it right? I will mention that there is an in-between option: semi-direct injection. Skidoo/Rotax used this before going to E-TEC. They use a four-stroke type injector in a transfer port. The result, in emissions and fuel consumption, is about half way between that "electronic carburetor" scheme, and real DFI. The TM, on the basis of what I have read, will be like the OSSA. The first true DFI system in a modern, production motorcycle should come from KTM - and I'm still waiting!

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So Where To From Here?

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