It does make you wonder (And kind of getting back to the point in the OP) just what 2-strokes would be capable of consumption/emissions-wise if the manufacturers had been able to persist with them and thrown R+D time and money at them over the past 20+ years.
Direct injection (Such as Piaggio's idea) would be great to see - I'd be fascinated to see just what the art of the possible is with such a set up.
As for the F800 series Beemers - Great bikes that happened to be crackingly good on fuel too. From what I can see the only big (Over 500cc) mainstream bikes that focus on this aspect now are the NC 750 Hondas though I'm not sure what the latest F850 series Beemers are like.
Tell me about it!
I suspect road going 2t's were canned, not due to emissions, but the realisation that advancing the technology would cut into profits. The CRM Active Radical, fuel injection, computer engine management, CAT's, performance and a dearth of moving parts would be less profitable than 4t's which require a higher capacity for the same bang and higher maintenance costs.
I don't really smell a conspiracy but I do wonder what might have been. Quite often.
Manopausal.
Don't write that off too quickly . On another thread apparently the Obama administration were responsible for marxists popes, so maybe they, or the shape shifting lizard people killed off the blue smokers.
It's all making sense now
Best I get up and go earn some more taxes.
Don't you look at my accountant.
He's the only one I've got.
David Icke blamed the shape shifting lizard people for the demise of the 2t and chocolate bars getting smaller in one of his podcasts. He's an authority on these matters so you must be correct.
It would be interesting to compare the emissions of carbie v FI 2t's. The KTM Enduro models come road legal in some countries and US states. Apparently.
Manopausal.
Well I've just had a piss off the balcony and it was quite glorious. Got some fair distance which isn't always apparent standing at the bowl.
Maybe this is more of an Instagram thing. Not sure how that works. Can I post a video?
Don't you look at my accountant.
He's the only one I've got.
Well... it's not straightforward and it certainly isn't as simple as emissions are in proportion to engine size. There's emissions from unburnt fuel (vapour out of the tank or intakes), emissions from high combustion temperatures like nitrogen oxides, sulphur emissions from nasty fuel, and things like soot and particulates which is not good to breath in. Then there's the noise emissions, Harley rally anyone?
The bit that's a surprise is that you can get small engines that are dirty and large engines which are relatively clean. Small displacement two-strokes are among the worst because there's a lot of mixing of exhaust and inlet charges. High performance 4 strokes which use valve overlap and exhaust resonance will have a similar issue, it won't be as bad per cc but since there are so many more of them... But yeah, nothing's more obvious than a worn out diesel.
Just reading the posts above...
Fuel consumption is helped by ratio of cylinder volume to surface area. A high volume to low area means low radiation heat loss to head and piston. There's also inertial loss, pistons and conrods being thrown back and forth does require energy. So does bearing and ring friction. The most fuel efficient engine is large displacement, limited number of cylinders, low revving, square or undersquare bores. This is exactly not what racing competition, where it's all about HP / cc, has given us... thirsty engines that rev like hell and are all about throwing air and fuel through as fast as possible.
Two strokes: a really interesting type was opposed piston, uniflow, positively scavenged by blower. By the time you've done all that though you might as well make a 4 T. Would be really interesting to see what a modern, direct injection version of that could do.
In a way that explains why my H-D 48 does quite well on fuel, as does my wife's Sportster 883. The bore and stroke of the motor as well as it being low revving are all in its favour with regards to this particular argument. I guess that's partly the reason why the Honda 750NC motor does so well too.
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