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Old 02-06-2014, 03:25 PM   #41 (permalink)
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Originally Posted by American Viking View Post
The later efi equipped vtr250 is a great choice. I just don't know where you could find one here in North America.

Another bike that would fit very well would be the VFR400. 400cc v4, but its not a US market bike, so finding one would be tough and the few that were imported have a cult following, so your not going to find a running one cheap.
There are several great bikes that would fit into trike really well.
Honda CB-1, Honda hawk gt, Yamaha fzr400, ..
But they all have a cult level following, so finding a healthy example to hack into a trike is not going to be easy.
I like all the bikes that you mentioned, but for a vehicle with economy in mind they couldn't compare to the CBR250, especially considering he feels it (CBR) may have too much power. Single cylinder and F.I. (like the CBR) will be significantly more efficient.

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Old 02-06-2014, 07:05 PM   #42 (permalink)
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Quote:
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I like all the bikes that you mentioned, but for a vehicle with economy in mind they couldn't compare to the CBR250, especially considering he feels it (CBR) may have too much power. Single cylinder and F.I. (like the CBR) will be significantly more efficient.
I recently was on a ride with a guy with a cbr250. Now the owner was a sparse individual (150 lbs) and he was getting like 55+mpg when the rest of us were on larger bikes getting 40+ mpg's. Then he let a mutual friend that weights 265 ride it for a tank. Shazam, the bike is netting 45 mpg. Some of that was the unfamiliar rider, but some of that shift was the heavier rider.

So how efficient is that cbr250 going to be when the weight it has to move goes up by a factor of 4 or 5.
Adding front suspension, front subframe, safety cage, seats and body is going to more than triple the Gross weight.
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Old 02-06-2014, 07:18 PM   #43 (permalink)
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The gross weight is NOT going to triple! It will go up some - 2 front wheels (each lighter than the original), some extra frame weight (probably 25 lbs), front suspension will probably be about equal; steering probably not much, if any, more than the original handlebars. The single seat will also be light weight, probably no greater than the seat that comes on the bike. A small roll bar will be included, but there won't be a "safety cage" intended to withstand being run over by an SUV. The body will add a little weight, but probably no more than 25 to 50 lbs over the plastic that will be removed.

If you don't think this is realistic, look at the California Commuter - 230 lbs COMPLETE! Weight is a BIG issue! It's one of the reasons I'm inclined to start with a 125cc Grom at 225 lbs curb weight rather than the CBR250R at 360 lbs.
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Old 02-06-2014, 07:30 PM   #44 (permalink)
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Details: Honda CBR250R FI Single - 2011 Honda CBR250R Fuel Economy - EcoModder.com

95 MPG on a CBR250R. Member here.

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Old 02-06-2014, 08:15 PM   #45 (permalink)
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Quote:
Originally Posted by American Viking View Post
I recently was on a ride with a guy with a cbr250. Now the owner was a sparse individual (150 lbs) and he was getting like 55+mpg when the rest of us were on larger bikes getting 40+ mpg's. Then he let a mutual friend that weights 265 ride it for a tank. Shazam, the bike is netting 45 mpg. Some of that was the unfamiliar rider, but some of that shift was the heavier rider.

So how efficient is that cbr250 going to be when the weight it has to move goes up by a factor of 4 or 5.
Adding front suspension, front subframe, safety cage, seats and body is going to more than triple the Gross weight.
That's very strange. My 650 twin does that - in town.

Typically the CBR will out-perform most highway-capable cycles in the mpg department. Just under 70 mpg is average, with some in the 90s.

Weight will increase certainly, but that will mostly effect acceleration. Reducing drag should decrease the load and throttle opening at highway speeds and give you better cruising mileage.
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Old 02-06-2014, 09:49 PM   #46 (permalink)
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American Viking is new, need to adjust the nut behind the wheel...
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Old 02-07-2014, 02:26 AM   #47 (permalink)
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There is a guy with a Honda horizontal on here and he streamlined it.
The engine failed because of overrevving becoming possible and the norm because he didn't re-gear it.

What I am trying to discuss is that since best efficiency out of an engine is happening at lower rpm, that the vehicle is probably be heavier and with a tad more rolling resistance than a bike, maybe a bigger capacity engine is gonna help on take off while not being too detrimental on cruise through agressive re-gearing.

After all, it is a required hp per mile/hour (efficiency of the vehicle) equation but the hp of the engine could well be a fraction of its peak and gain back in efficiency what it lacks in capacity.

Truck engines are spinning real low.
What is their FE / load (weight hauled) compared to other vehicles ?
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Old 02-07-2014, 08:06 AM   #48 (permalink)
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semi trucks have tons of gears, and live with low acceleration. If you want best hiway mpg, you size your engine for hpNeededForCruise=peakBSFCHP and gear accordingly, and live with whatever acceleration you get. There will be reserve power beyond bsfc. If the engine is "right sized" for most efficient cruise, then yah more gears would be better.

A larger engine will fall away from bsfc peak on rpm and/or load, you could probably make an educated guess how much even without an actual bsfc map, i.e. if a 250cc is just right for bsfc cruise and getting 225gm/kwh, a 500cc at that hp and rpm is getting very roughly 300gm/kwh (load cut in half), or at that hp and load is getting 250gm/kwh (rpm cut in half).

So very roughly a 10-25% loss doubling the engine size away from "right sized" for cruise. Depending if you cut the rpm in half or the load at cruise in the larger engine.

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Old 02-07-2014, 11:11 AM   #49 (permalink)
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By the same token, if you right size your engine/gearing for bsfc@cruise, you can roughly double the rpm from peak bsfc for about twice the horsepower when accelerating/hill climbing and only lose ~%10 on bsfc.
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Old 02-07-2014, 03:21 PM   #50 (permalink)
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Am I right believing BSFC is roughly 75% throttle at a given RPM ?

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