gregsfc
New Member
Schultz Engineering - Custom Motorcycle Parts and Renewable Energy Products
I have a theory and have been trying to prove it spite of Fuelly data, with all else being equal (all else being equal is the hard part of proving theories) that the 670 parallel twin can be a more economical power train, at least with respect to the CTX700 manual (manual version no longer available in U.S. or Canada) and probably the NC versions as well, than is the 471 twin that's in the new Honda CB500s; nearly as economical (all else being equal) as the CBR and CFL 250/300s; and pretty much as good or better than any power train out there for a fully highway capable bike. The reason this is so important to prove is that in eco motorcycle circles, it has been assumed and even proclaimed by well-respected designers and engineers that the smaller the displacement and the less rated horsepower, the better achievable mpg, because horsepower is the enemy of fuel economy, and I agree with that second part, but one has to consider also how much horsepower is being generated going down the road; not just the peak rated horsepower of the engine itself. Maybe an engine the revs lower with a little more displacement and peak rated horsepower could travel down the road generating the same or less horsepower as a screamer. That's what I think; but can't prove.
So for a highway capable motorcycle, these guys are assuming and have even said that we need something on the order of a little bigger than 200 cc's and, for a scooter, maybe just a little more due to the slightly less efficient drive train. The requirement for power at the event is to have a vehicle that can achieve 70 mph sustained in a 30 mph headwind as a highway capable bike. I think that requirement is about right. But the horsepower proclamation that has been made is that the best design would be 17-28 rated peak. Now the contest has already shown this belief and proclamation to be flawed. A diesel motorcycle rider; with a fairly big guy riding, hooked up to a 667 single cylinder diesel naturally-aspired, mechically injected, light weight, Hayes diesel engine on a modified KTR650, that can generate 31 hp rated and 35 peak ft lb torque has won this event and other times has been right there with two, perfectly streamlined, cut-down low Ninja 250 streamliners. Fred Hayes rides the diesel, and I think his best score has been at or about 175 mpg; and Vic does the best usually of the two Ninja guys (he's smaller built than the other Ninja fellow and much smaller than Fred). Vic has accomplished 187, but the best he's done when Fred was also present the same day was around 181; barely beating out Fred the last time they both ran, but Fred hasn't ridden in the last few years. His streamlining is not as perfect for mpg purposes; he used the same near bike configuration to break a land speed record for a diesel motorcycle, and his bike is much heavier. So my theory is that this engine strategy can also be used with a gas powered engine and compete very well against a screamer. If someone would just build a more car-like powered bike with larger displacement, more horsepower, but with a design for great mpg, and flat torque built in. It'd be right there with the Ninjas and Honda 250s. Anyway, that's my theory.
And somebody did. Honda did...Enter the near-perfect candidate; the 670 parallel twin. Maybe just a little less displacement and lighter bike would have been even more perfect, but close enough to prove a point...Right? Peak torque coming at 4700 RPM or so, but still really good torque down at 3,000 and even lower due to its flat curve. Peak rated horsepower maybe up to 47; the CTX at the wheel probably more like 43 and peak torque close to 42. Much higher numbers than the believed perfect engine for a high mpg bike. I'm a 5'8 145 lb guy with a short torso on a low riding cruiser style bike. I should be able to do well against these smaller stock bikes with easy throttle inputs and keeping RPM not much over 3000. That was my plan...
I've been to this controlled fuel economy contest twice with my CTX700 to see some amazing streamlined bikes and also to try and prove my point. The problem though, even though I've gone on forums and tried to encourage other owners of economical bikes to come and ride is that I can't get other stock bike riders out there to the event and compare them against each other. I'd like to have some BMW 650 singles and 799 inline twins to ride with; and a bunch of 250s of different brands; Honda 471 twin; maybe a Burgman 400; one of those Burgman's finished at 80 in one event not too many years ago. In 2014 I went and rode my CTX700 and accomplished 96.9 mpg. I beat all other stock bikes by 20 mpg or more; it's still published at Craig Vetter's website, but there were very few competitors of the stock variety and no modern bikes like I wanted to run against. I came within 2 mpg of beating Craig Vetter himself who was on a perfectly streamlined Honda Helix but that was an aging machine that was losing efficiency. The only pure stock bikes/scooters in the challenge that could be of some competition that year was a DR200 and a Vespa 200. They actually did not get disqualified on speed; they were able to maintain 72 mph and not get passed for several miles on the interstate stretch, but I beat them to death on mpg even though they met the performance standard that year and were much, much lighter and smaller. Small riders to boot.
I just came back from the 2017 event. I did not do nearly as well @ 86 mpg; speeds got up to 75 this year and sustained for several miles, and then went down to around 72, for an 18 mile total interstate stretch with a total 95.3 mile run that included some back roads and a couple small towns. I still beat all other stock bikes by 8 mpg or more. There were only three of us and one was a liter plus that got 46. This year there was a Honda CBR250R rider in the ride. He got 78. I beat one fully streamlined Honda Helix Clone, and I beat a partially streamlined Kawasaki Ninja 250 by 3 mpg, but that bike still needs some work as its in the middle of streamlining rebuild with a legend rider.
So will they get the theory now. There is more than one way to do this...I'm not sure. The stock CBR250R rider is a bigger framed guy than me and I noticed he wasn't riding as steady as I do when I followed him. That was until I passed him and got up toward the front with more steady speed riders. Another Honda 250 rider scored 126, but he designed and built and installed a tail that gets him way up there, however, even before the tail, he had a history of good scores over 100. So this thing is a hard thing to prove. Too many variables. I think I'm below the Honda 250/300 all else being equal, but above everything else being built today, comparing stock to stock.
I have a theory and have been trying to prove it spite of Fuelly data, with all else being equal (all else being equal is the hard part of proving theories) that the 670 parallel twin can be a more economical power train, at least with respect to the CTX700 manual (manual version no longer available in U.S. or Canada) and probably the NC versions as well, than is the 471 twin that's in the new Honda CB500s; nearly as economical (all else being equal) as the CBR and CFL 250/300s; and pretty much as good or better than any power train out there for a fully highway capable bike. The reason this is so important to prove is that in eco motorcycle circles, it has been assumed and even proclaimed by well-respected designers and engineers that the smaller the displacement and the less rated horsepower, the better achievable mpg, because horsepower is the enemy of fuel economy, and I agree with that second part, but one has to consider also how much horsepower is being generated going down the road; not just the peak rated horsepower of the engine itself. Maybe an engine the revs lower with a little more displacement and peak rated horsepower could travel down the road generating the same or less horsepower as a screamer. That's what I think; but can't prove.
So for a highway capable motorcycle, these guys are assuming and have even said that we need something on the order of a little bigger than 200 cc's and, for a scooter, maybe just a little more due to the slightly less efficient drive train. The requirement for power at the event is to have a vehicle that can achieve 70 mph sustained in a 30 mph headwind as a highway capable bike. I think that requirement is about right. But the horsepower proclamation that has been made is that the best design would be 17-28 rated peak. Now the contest has already shown this belief and proclamation to be flawed. A diesel motorcycle rider; with a fairly big guy riding, hooked up to a 667 single cylinder diesel naturally-aspired, mechically injected, light weight, Hayes diesel engine on a modified KTR650, that can generate 31 hp rated and 35 peak ft lb torque has won this event and other times has been right there with two, perfectly streamlined, cut-down low Ninja 250 streamliners. Fred Hayes rides the diesel, and I think his best score has been at or about 175 mpg; and Vic does the best usually of the two Ninja guys (he's smaller built than the other Ninja fellow and much smaller than Fred). Vic has accomplished 187, but the best he's done when Fred was also present the same day was around 181; barely beating out Fred the last time they both ran, but Fred hasn't ridden in the last few years. His streamlining is not as perfect for mpg purposes; he used the same near bike configuration to break a land speed record for a diesel motorcycle, and his bike is much heavier. So my theory is that this engine strategy can also be used with a gas powered engine and compete very well against a screamer. If someone would just build a more car-like powered bike with larger displacement, more horsepower, but with a design for great mpg, and flat torque built in. It'd be right there with the Ninjas and Honda 250s. Anyway, that's my theory.
And somebody did. Honda did...Enter the near-perfect candidate; the 670 parallel twin. Maybe just a little less displacement and lighter bike would have been even more perfect, but close enough to prove a point...Right? Peak torque coming at 4700 RPM or so, but still really good torque down at 3,000 and even lower due to its flat curve. Peak rated horsepower maybe up to 47; the CTX at the wheel probably more like 43 and peak torque close to 42. Much higher numbers than the believed perfect engine for a high mpg bike. I'm a 5'8 145 lb guy with a short torso on a low riding cruiser style bike. I should be able to do well against these smaller stock bikes with easy throttle inputs and keeping RPM not much over 3000. That was my plan...
I've been to this controlled fuel economy contest twice with my CTX700 to see some amazing streamlined bikes and also to try and prove my point. The problem though, even though I've gone on forums and tried to encourage other owners of economical bikes to come and ride is that I can't get other stock bike riders out there to the event and compare them against each other. I'd like to have some BMW 650 singles and 799 inline twins to ride with; and a bunch of 250s of different brands; Honda 471 twin; maybe a Burgman 400; one of those Burgman's finished at 80 in one event not too many years ago. In 2014 I went and rode my CTX700 and accomplished 96.9 mpg. I beat all other stock bikes by 20 mpg or more; it's still published at Craig Vetter's website, but there were very few competitors of the stock variety and no modern bikes like I wanted to run against. I came within 2 mpg of beating Craig Vetter himself who was on a perfectly streamlined Honda Helix but that was an aging machine that was losing efficiency. The only pure stock bikes/scooters in the challenge that could be of some competition that year was a DR200 and a Vespa 200. They actually did not get disqualified on speed; they were able to maintain 72 mph and not get passed for several miles on the interstate stretch, but I beat them to death on mpg even though they met the performance standard that year and were much, much lighter and smaller. Small riders to boot.
I just came back from the 2017 event. I did not do nearly as well @ 86 mpg; speeds got up to 75 this year and sustained for several miles, and then went down to around 72, for an 18 mile total interstate stretch with a total 95.3 mile run that included some back roads and a couple small towns. I still beat all other stock bikes by 8 mpg or more. There were only three of us and one was a liter plus that got 46. This year there was a Honda CBR250R rider in the ride. He got 78. I beat one fully streamlined Honda Helix Clone, and I beat a partially streamlined Kawasaki Ninja 250 by 3 mpg, but that bike still needs some work as its in the middle of streamlining rebuild with a legend rider.
So will they get the theory now. There is more than one way to do this...I'm not sure. The stock CBR250R rider is a bigger framed guy than me and I noticed he wasn't riding as steady as I do when I followed him. That was until I passed him and got up toward the front with more steady speed riders. Another Honda 250 rider scored 126, but he designed and built and installed a tail that gets him way up there, however, even before the tail, he had a history of good scores over 100. So this thing is a hard thing to prove. Too many variables. I think I'm below the Honda 250/300 all else being equal, but above everything else being built today, comparing stock to stock.