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Discussion Starter #1
Could you explain HP in terms of torq? Does HP has to do with how quick to get to max torqe?
 

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Supercharged Mod
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Horsepower, torque, and RPM are mathematically related.

In the old English units, HP = Torque x RPM / 5252

One caution that people new to this often fail to understand: maximum torque and maximum horsepower generally do not occur at the same RPM.
 

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Discussion Starter #7
i read somewhere that the more HP the more quicker to get to max torqe? if i understand the explaination from the link above correctly, this isn'tthe case?

with allthe vtwin/I4 thread im just thinking how they compare. i know people say this is apple and orange. is it really all there is to it? vtwin just makes torq at lower rpm and i4 just rev's higher? end of discussion?
 

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Hp is an equation of torque. Torque is what actually moves the bike and gets you going.
 

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nobody said:
i read somewhere that the more HP the more quicker to get to max torqe? if i understand the explaination from the link above correctly, this isn'tthe case?

with allthe vtwin/I4 thread im just thinking how they compare. i know people say this is apple and orange. is it really all there is to it? vtwin just makes torq at lower rpm and i4 just rev's higher? end of discussion?
If my vtx1800 could rev to 13,500rpm it would make more power than my zx10r but with a short stroke v-twin the mean piston speed at 6000rpm is higher than the mean piston speed of the zx10r at 13,500rpm. My vtx feels very fast becasue of the torque and all the power comes on fast, the zx10r comes on strong over a wide rpm range.
 

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Torque is force. Horsepower is force vs time or rpm, as stated earlier. Say you have two identical ZX10r motors. Both produce 70 lb. ft. of torque at 12,750 rpm, both will produce (by the equation) 169.9 hp at that rpm. Now add a 100 lb. flywheel to one. Both still produce the exact same horsepower and torque, but accelerate completely different. The work available is the same, but part of the engine's energy is dissapated accelerating it's own mass. This is why inertia dyno's (Dynojet) often show an increase in horsepower with lighter wheels, and brake dyno's don't.
 

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Supercharged Mod
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nobody said:
i read somewhere that the more HP the more quicker to get to max torqe? if i understand the explaination from the link above correctly, this isn'tthe case?

with allthe vtwin/I4 thread im just thinking how they compare. i know people say this is apple and orange. is it really all there is to it? vtwin just makes torq at lower rpm and i4 just rev's higher? end of discussion?
More or less, that's all there is to it. By the way, the "V" versus "inline" means nothing for this, all that matters is the number of cylinders and their size, not how they are arranged.

An engine with larger cylinders (and in this case a smaller number of cylinders) has inherently heavier moving parts so it cannot rev as high, and it ends up being tuned to make its torque in an RPM range that the engine itself can mechanically deal with. Given an equal "level of technology", a two-cylinder engine and a four-cylinder engine of the same total displacement will make (as a first approximation) the same amount of torque, because both engines are capable of breathing in the same amount of air/fuel in one revolution (they're the same displacement). But the four-cylinder engine will be capable of running at higher revs, and thus making this peak torque at higher revs, and will therefore make more power.

You CAN make an engine rev higher by using a wider bore and shorter stroke. (Current Formula 1 car engines are an extreme example of this.) But it creates other problems ... notably, the flame speed means that combustion takes longer, this limits power and efficiency of the engine (and it seems to be why my buddy's RC51 uses more fuel than my ZX10R on the same trip ...)
 

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Discussion Starter #13
thanks. let me soak in the info first. by tuning the engine for RPM range you mean with gearing ratio?
 

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No, I mean with cam timing, valve sizes, intake runner length, exhaust primary header pipe length, ignition timing, etc.
 
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