salishmoto
Active Member
Hi Folks,
We've had the 21 NC for almost a year now and continue to delight in the little thing. A technical question I wonder about is in the design of the new 21 engine that according to MCN: "With a rumbling 270˚ crank and different valve timing for each cylinder the Honda has plenty of feel. The first three gear ratios are lowered for sharper acceleration helping it to be the peppiest NC750X so far, feeling brisker than its modest numbers and limited rev range suggest." I understand ICE engines better than most, but am not an engineer. I don't understand how you can vary valve timing for each cylinder without negatively impacting the combustion process.
Presuming there is an optimum timing to maximize combustion, any retarding or accelerating of the timing would be less optimal, no? The engine has a throaty growl over 4K RPM and the 270 crank explains much or most of that. So what is the story of this valve timing change? How does that make sense from a mechanical perspective? VVT systems make sense because at different RPM's you can vary the timing to maximize combustion. But doing each cylinder of a two cylinder bike differently, when they are at the same RPM, defies my understanding. Any insights?
We've had the 21 NC for almost a year now and continue to delight in the little thing. A technical question I wonder about is in the design of the new 21 engine that according to MCN: "With a rumbling 270˚ crank and different valve timing for each cylinder the Honda has plenty of feel. The first three gear ratios are lowered for sharper acceleration helping it to be the peppiest NC750X so far, feeling brisker than its modest numbers and limited rev range suggest." I understand ICE engines better than most, but am not an engineer. I don't understand how you can vary valve timing for each cylinder without negatively impacting the combustion process.
Presuming there is an optimum timing to maximize combustion, any retarding or accelerating of the timing would be less optimal, no? The engine has a throaty growl over 4K RPM and the 270 crank explains much or most of that. So what is the story of this valve timing change? How does that make sense from a mechanical perspective? VVT systems make sense because at different RPM's you can vary the timing to maximize combustion. But doing each cylinder of a two cylinder bike differently, when they are at the same RPM, defies my understanding. Any insights?