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Can anyone explain engine "tuning" to me (re: CCs to HP) Login/Join 
Savor the limelight
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quote:
Originally posted by dwd1985:
quote:
Originally posted by trapper189:
With the three motorcycles you mentioned, it’s not a difference in tuning. The answer to your question is torque and engine rpm. That’s it. More displacement (cc in motorocycle engines) equals more torque. For a given amount of torque, the faster you can rev the engine, the more horsepower it will make.

The 675cc Speed Triple makes 106hp at 11,850rpm, but max torque is 50ftlbs at 9,750rpm.

Next up, the slightly larger 689cc MT-07 makes 74hp at 9,000rpm. Amazingly enough, max torque is the same 50ftlbs as the Speed Triple only at a lower rpm of 6,500.

Lastly, the 798cc BMW makes 90hp at 8,000rpm. Being roughly 20% larger than the other two also produces roughly 20% more torque as well. In this case, 63ftlbs at 5,800rpm.



This almost seemed contradictory to me, but then I think it clicked: making torque at higher RPMs produces more HP than making torque at lower RPMs, correct? This is why the Street Triple making the same torque as the MT-07 but at 1.5x the RPMs is producing 20% more HP? And why the BMW producing 20% more torque but at almost half of the RPMs produces 15% less horsepower?

Yes. Another example that might help:

The motors in my F350 and my wife’s Explorer are rated at 400hp. One of them make 860ft-lbs of torque at around 2,000 rpm the other makes 415ft-lbs of torque at around 5,500rpm. Which is which and which? Which will get a get a load moving easier?
 
Posts: 8701 | Location: SWFL | Registered: October 10, 2007Reply With QuoteReport This Post
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Picture of Prefontaine
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Internals matter a lot. High strength while light weight matters a lot, friction, so many things. A MotoGP bike is pushing 280-300 HP per liter, and that’s wheel HP.



What am I doing? I'm talking to an empty telephone
 
Posts: 11681 | Location: Down South | Registered: January 16, 2010Reply With QuoteReport This Post
half-genius,
half-wit
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Talking about revs-v-output, my old pal Alan Hilton is the head honcho of the vintage Matchless team that go to the IoM every year racing their [very] old bikes in the vintage races. We were actually discussing this very subject last Wednesday, and he, being a crumbly old fart, was reminiscing on the 'old days' when the East Germans raced their lunatic two-strokes in the 125 and 250 classes. revving up to an insane 18,000 rpm, the engines did not last long - one race, in fact. The Eastie-beasties would literally re-engine the bike for the next race, saving only the crankcase.
 
Posts: 11043 | Location: UK, OR, ONT | Registered: July 10, 2003Reply With QuoteReport This Post
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