02-12-2023, 01:58 AM
OK they're just not getting an air cooled 4 cylinder through euro 5 and even if they did it'd be so lean as to be unridable.
I didn't know, but according to Kevin Cameron even when utilizing liquid cooling, engines using more cylinders are at a disadvantage trying to meet the reduced limit of unburned hydrocarbons. For a given displacement more cylinders mean more total piston ring circumference for unburned hydrocarbons to leak past. So a twin has a lower seal length per liter than a 4 cylinder which contributes to less unburned hydrocarbons escaping past the rings.
I always wondered why the Japanese manufacturers didn't utilize fewer engines across their lineup? There was a time when about every Honda motorcycle had its own specific engine. Harley OTOH made two engines (Sportster 883/1200) and big twins, and these were used in countless different models. About 15 years ago Honda (and the other Japanese) really started doing this as well. The 300 single is one example, another is the 1,000/1,100 parallel twin that is used in the Africa Twin, Rebel, maybe soon to be GB750, and even in the Pioneer 1000 SXS.
Designing engines to meet the ever tightening emission levels has to be very expensive. As a result they are designing fewer of them and the ones they do have fewer cylinders which gives them a head start meeting those emissions.
I didn't know, but according to Kevin Cameron even when utilizing liquid cooling, engines using more cylinders are at a disadvantage trying to meet the reduced limit of unburned hydrocarbons. For a given displacement more cylinders mean more total piston ring circumference for unburned hydrocarbons to leak past. So a twin has a lower seal length per liter than a 4 cylinder which contributes to less unburned hydrocarbons escaping past the rings.
I always wondered why the Japanese manufacturers didn't utilize fewer engines across their lineup? There was a time when about every Honda motorcycle had its own specific engine. Harley OTOH made two engines (Sportster 883/1200) and big twins, and these were used in countless different models. About 15 years ago Honda (and the other Japanese) really started doing this as well. The 300 single is one example, another is the 1,000/1,100 parallel twin that is used in the Africa Twin, Rebel, maybe soon to be GB750, and even in the Pioneer 1000 SXS.
Designing engines to meet the ever tightening emission levels has to be very expensive. As a result they are designing fewer of them and the ones they do have fewer cylinders which gives them a head start meeting those emissions.
