what sense does that make? - K-Bikes.com - Excellence in Motion
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post #1 of 20 (permalink) Old Jan 10th, 2006, 3:52 pm Thread Starter
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what sense does that make?

i noticed in the spec sheet the new GT has been de-tuned down to 153 HP from the 167 HP of the S. stupid move, in my opinion.
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post #2 of 20 (permalink) Old Jan 10th, 2006, 4:00 pm
 
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Originally Posted by jdsmith1953
i noticed in the spec sheet the new GT has been de-tuned down to 153 HP from the 167 HP of the S. stupid move, in my opinion.
normally this is associated with better power/torque in the mid-rev range. Nice move IMHO

/Michael
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post #3 of 20 (permalink) Old Jan 10th, 2006, 4:05 pm
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Originally Posted by jdsmith1953
i noticed in the spec sheet the new GT has been de-tuned down to 153 HP from the 167 HP of the S. stupid move, in my opinion.
It is anything but stupid. It makes extremely good sense.

The small drop in HP results from creating a much broader torque band, specifically better low-end torque. This is in keeping with the bike's stated character as a Tourer.

High peak horsepower always comes at the expense of low end torque. Touring bikes are not crotch rockets, or at least that is not their primary purpose. Improved "stump-pulling" low end torque is very much in keeping with the character of a tourer.

The amazing thing here, is that BMW was able to improve the low end so much, with only a ~8% (or so) loss in peak HP.

Bob.
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post #4 of 20 (permalink) Old Jan 10th, 2006, 10:46 pm
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Horsepower means nothing on a touring or sport-touring bike, unless your definition of sport-touring is crossing the country doing one quarter-mile run after another. Torque means everything to the sport-tourer, it is what pulls you effortlessly up a hill when packing double and gives you a usable launch exiting a corner. Trimming 14hp from the "S" motor will be a good thing if it results in more mid-range torque.

A better question is what BMW plans to do about the general buzzines and unrefined feel that the S, and presumably the new GT, exhibit in comparison to the old K1200GT and to a lesser extent the FJR1300. All I-4 engines have an inherent buzz from their lack of perfect primary balance,a lack that can be helped but not cured with balance shafts. On the old K1200RS/GT this was eliminated via rubber-mounting. So the real question is what's the engine mounting system on the new GT? Rubber? Or solid? If the latter, then can we expect the new GT to exhibit at highway speeds the same lack of refinement, that feeling of "busy-ness" that has the rider constantly searching for a 7th gear, that the S already exhibits??

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post #5 of 20 (permalink) Old Jan 11th, 2006, 6:19 am
 
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...A better question is what BMW plans to do about the general buzzines and unrefined feel that the S, and presumably the new GT, exhibit in comparison to the old K1200GT and to a lesser extent the FJR1300...
GTRider

In my opinion the S does not have "general buzziness" nor is it unrefined. It is not as smooth as the K12RS (with its rubber mounted engine), but is still quite smooth.

Ken
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post #6 of 20 (permalink) Old Jan 11th, 2006, 7:14 am
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This is a test, this is only a test ...

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Originally Posted by GTRider
......... All I-4 engines have an inherent buzz from their lack of perfect primary balance ...........
Yes, this is true, but it seems as if BMW is the only manufacturer to actually use this "excuse". Now for the test...

Does anyone rememer the Honda add where the guy balances a nickle on it's side on a running engine? I want to say it was a 550 Four, but that was in the 70's and, even though I was there, I seem to have forgotten a lot of details. :think:

Trivia, while you're all hopefully trying to find a 30+ year old Honda TV add .... Did anyone else ever see the TV add where a Porsche Carerra takes off on a road course while a guy on a Yamaha is still putting on his gloves? They talk about the Porsche, show it sliding some turns, and then, as the Yamaha passes it in an overhead shot the commentator says, "Porsche makes the fastest production car on the planet. Want to know how fast it is? Ask the guy on the Yamaha." That was sooooo cool.
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post #7 of 20 (permalink) Old Jan 11th, 2006, 8:03 am Thread Starter
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the peak torque did not change, it moved down 500 rpm from 8250 to 7750 big zip. no significant improvement.
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post #8 of 20 (permalink) Old Jan 11th, 2006, 10:49 am
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buzziness

Quote:
Originally Posted by kencorsun
In my opinion the S does not have "general buzziness" nor is it unrefined. It is not as smooth as the K12RS (with its rubber mounted engine), but is still quite smooth.

Ken

I agree with Ken. The only buzziness felt is around the 6 and 7 mark on the tach, if you transition through it, no problem. Even in low gear twistie stuff, the buzz isn't felt much because you are constantly in and out of that rev range. I took a 4000 mi. trip on my S last summer and never was bothered by engine buzziness.

Keep a high visual horizon,
Bob
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post #9 of 20 (permalink) Old Jan 11th, 2006, 11:15 am
 
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Does anyone rememer the Honda add where the guy balances a nickle on it's side on a running engine? I want to say it was a 550 Four, but that was in the 70's and, even though I was there, I seem to have forgotten a lot of details.

The engine in question was the Honda 350cc 4-cylinder. One of the guys I rode with back in the '70s had one and it was the second smoothest bike I had ever ridden at that time. The first one was the TX500A Yamaha, a 500cc twin with double balance shafts and a 14,500 rpm redline.
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post #10 of 20 (permalink) Old Jan 11th, 2006, 1:08 pm
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Quote:
Originally Posted by jdsmith1953
the peak torque did not change, it moved down 500 rpm from 8250 to 7750 big zip. no significant improvement.
That was not the point. What they were REALLY after was to BROADEN the torque curve. In other words, to improve the torque at much lower RPM than just at the peak.

Tuning for maximum HP results in a motor that generates a LOT of torque at a narrow band of RPM, and relatively poor torque at lower RPM. This requires shifting more often to keep the motor at an RPM where useful torque can be generated for passing, hill climbing and so on. That may be great fun for a performance bike, but it is a pain in the ass for a tourer.

For a touring bike, absolute maximum torque is sacrificed, to result in a broader torque curve, with much better low end torque. If you look at the torque of the K1200S at (say) 3000 RPM, as compared to the K1200GT, I think you will see that the GT has bags more torque at this lower RPM, resulting less shifting being needed.


Bob.
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