QUOTE(khelben @ Nov 6 2013, 08:28 PM)
wat is kapcai cc n power ar?
KTM RC125, RC200, RC390
KTM RC125, RC200, RC390
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Nov 6 2013, 11:35 PM
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#1
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Nov 7 2013, 12:22 AM
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Sep 17 2014, 10:17 PM
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QUOTE(terradrive @ Sep 17 2014, 06:16 PM) Banyaknya yang mempersoal tapau-menapau sesama motor. Jadi aku akan explain dari segi engineering (ambik elektif dulu automotif engineering): acterly this is already wrong concept.1) Torque determines the acceleration. 2) Horsepower determines the top speed. power is produced by torque on a rotatating shaft. so power = torque (x a constant) when the shaft is rotating there is no such thing as max torque = max acceleration, which occurs on a fix ratio gearbox. more so when you throw in a CVT into the concept then max acceleration occurs at max power, not at max torque. |
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Sep 17 2014, 10:30 PM
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Sep 17 2014, 10:36 PM
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QUOTE(terradrive @ Sep 17 2014, 10:30 PM) Torque is the rotating force along a shaft, it is translated back into translational force by the wheels. ah but what if you change the final drive ratio to the rear axle.. now that changes your acceleration doest it..? why cos input RPM to the rear gearbox axle is higher, output is lower.. hence producing more torque.. hence producing more power, so accelerate faster.This is why a Silvia S15 has faster 0-100km/h time than a Honda S2000, both have about the same weight and horsepower. But the force exerted by the wheels of the Silvia is larger than the S2000 (because of higher torque), thus it accelerates faster. Remember F=m.a, so a = F/m remember, dyno shows results in power, but all it does is measuring force acting on a drum at known RPM.. at the end you can say torque and power have linear relation ship.. This post has been edited by ar188: Sep 17 2014, 10:37 PM |
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Sep 17 2014, 10:40 PM
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one more thing, the assumption is F=m X a only linear when in one gear.. but what if 0-100 you need 3 gear ratios.. (2gear changes)
or if you have 4 gear ratio, with 3 gear changes. at the end the 0-100 times are all different when you take into account what happens in the gearbox. ![]() sorry no linear relationships to be found.. only exponential.. and affected by multiple ratios in a gearbox.. as chart above. This post has been edited by ar188: Sep 17 2014, 10:43 PM |
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Sep 18 2014, 10:23 AM
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QUOTE(terradrive @ Sep 18 2014, 09:52 AM) If you change the final drive ratio, you changed the rpm & torque produced. But power only affects the acceleration at higher vehicle speeds because at high vehicle speeds the aerodynamic drag is pushing the vehicle back. ah but you are giving the example of 2 same vehicle with double the torque and same horsepower and example 2, double horsepower, same torque.. Dyno shows results in power & torque, check back the charts. Refer to the equation I posted before, torque and power isn't the only parameter, you have to factor in rpm. If you want to see the effects of torque and power, you have to set the other parameters to be the same: Checking the effects of different torque values: 1) Both vehicle A & B have same weight, same horsepower, same aerodynamic drag (same shape). Vehicle A has double the torque than Vehicle B. Results: Vehicle A will accelerate faster to top speed than Vehicle B but both will have the same top speed. Checking the effects of different horsepower values: 2) Both vehicle A & B have same weight, same torque, same aerodynamic drag (same shape). Vehicle A has double the horsepower than vehicle B. Results: Vehicle A will have higher top speed than Vehicle B, in addition, vehicle A will accelerate faster than vehicle B because vehicle A have higher rpm (check back the power to torque equations, with the same torque value, higher power means rpm must be higher). This is simply because when the vehicle A have higher rpm, it can hold on to the gear longer than vehicle B. When vehicle A is still on gear number 2, vehicle B already shifted to third gear and have to accelerate with lower torque even at the same speed as vehicle A. might as well compare, proton with porsche..can conclude with certainty which one will sure win the acceleration test. why dont you say 10% difference in torque and horse power, but different gearing/gearbox which will affect the outcome differently. as i said, in a conventional ICE, max power comes at 6-7k rpm , at 3-4k rpm max torque level, you dont get full power., hence you wont get full acceleration. if you got a gearbox that lets you rev to max power sooner, and stay there.. then if both cars with same horsepower+torque, the one with the gearing advantage to let you do so will accelerate faster. This post has been edited by ar188: Sep 18 2014, 10:24 AM |
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Sep 18 2014, 01:23 PM
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QUOTE(terradrive @ Sep 18 2014, 01:17 PM) Gearing/gearbox doesn't affect the outcome at all. Gearing ratios are calculated from the given engine's power and torque chart. The one that would affect the outcome is the difference in torque and power chart between so engine alone doesnt tell the whole picture.. you need to take into account gearbox, drive ratios, component losses.. wheel size etc.. 3 same cars same engine /weight, with 3 different gearbox (say 4speed auto vs 5speed manual vs CVT) gonna give 3 different real world results. |
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Sep 18 2014, 01:26 PM
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QUOTE(terradrive @ Sep 18 2014, 01:17 PM) ![]() You said that max power rpm must be higher than max torque rpm, but why the chart above indicates the max torque rpm is the same with max power rpm, is this blasphemy? No, sorry just great engineering. but why dont you dare say max torque is higher than max power in this case.. |
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