Quote:
Originally Posted by jkv357
I do think a bigger engine running at a lower RPM can do pretty well, but there are a few mechanical factors that will hold it back. The numbers are good, but the potential is much more limited. I have a SV 650, and I've seen over 60 mpg in normal back-road riding - which is pretty good IMO.
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For the competition, a streamlined 125-250cc single would most likely be the most efficient, but your CTX can do pretty well and still be a very useful all-around street bike.
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I'm glad you brought up the SV650, and I agree that the potential is limited for larger displacement engines, including Honda's 670 cc for these competitions versus an engine that can just barely make the speed requirement before streamlining, because the smaller the engine, the less fuel it will consume generally speaking, but it is in the real world where a mid-size bike like mine has some advantages in safety and refinement w/o the fuel economy drop off that one would expect. I would expect that a streamlined CTX700 or NM4 would not reap the same level benefit than a minimum-displacement bike in the 125-300 setup exactly the same, because the 670 cc twin is already only mildly stressed with the weight and drag on the highway versus the smaller bikes, but my point is that if this 670 cc is already efficient enough to achieve 80mpg or so in this competition w/o tucking, that in streamline form, we'd see a bike with double the capable horsepower, and even more than double torque, at least 100 more pounds, and at least 125 mpg, versus--say--160 using the proclaimed minimalist approach.
The SV650 is a perfect example to illustrate my point. When one compares a typical, but well-engineered mc engine that was designed with fuel economy as at least one major factor in it's design, to Honda's bold, new choice that offers a similarly-sized engine extracted from the automobile industry; a few interesting things happen. There is a curb weight discrepancy of 30-40 pounds, but tires/wheels are exactly the same. The point you made about top-end performance is well taken, and this has been the problem for Honda with this entry. They have been raked over the coals for this power train by enthusiasts and mc media outlets due to the fact it hits the rev limit at 6500 RPM, it's not-so-impressive performance north of 70 mph, and the fact that for the first time in this size and style of bike, one has to short shift for best and most refined performance. The typical, high-revving mc, comparing near-equal displacement, in near-equal components to an automotive-style power train, will always produce more peak power, and therefore, will provide better performance at the top end and overall performance. And this is why most reviews regarding Honda's 670 versus other 650-700 bikes, gets a bad score.
But this limited high-end performance aspect from this unprecedented entry from Honda, is why it is so efficient. You're experience in the SV650 can return at or about 62 mpg along backroads. My experience, with my CTX700 with the manual shift can return, in normal riding (not lugging or tucking, but revving to 3500 or so between gears, which is pretty quick on this bike due to its torque curve), in warm weather, is at or about 78.
Most motorcycle enthusiasts in this range have an expectation of performance, but the Honda 670 provides a performance style more akin to a mid-size or compact sedan, a large scooter, or a big, torquey cruiser; and so it has been mostly scooter enthusiasts, downsizers from big bikes, and beginners who have sought out this bike, and most of them choose the DCT automatic, which gives up at least 3 mpg and a touch of performance to the straight shift. And this is a shame that this concept has been rejected by and large by the media and the consumer base, because this efficiency advantage of a lower-revving engine can be applied up and down the displacement range until we reach a point at which the auto-style engine cannot provide an acceptable peak horsepower for highway transportation, which is likely at or about the 400 cc range, compared to a similar set up with a 250 cc.