Their are many factors that grow with this question. Standard Transmission (clutch, pressure plate), Automatic (Clutches, stall coverter, and Trany fluid), Dia of tire, gear ratial, and change of each as you determan these factors... Motor rated Horsepower is based on the displacement of the engine cylenders... there is also the final output power that is the horse power that is at the ground... torq is also rated at both place too... you can gain or loose power at the ground depending on your transmission, transfer case, ring & pinion, even your tire size.. So both are correct... it all depends on what your looking at.... Engine Horsepower or at the ground horsepower...
CK5
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help end a 12 year old argument
- Thread starter schmuck
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Cmoe said:
Actually, based on his original question most of these are not a factor.
His question seemed to be about a gear change in a "known" vehicle and it's effects....which would imply that everything in the driveline (engine, trans, transfercase, etc) would not change.
82smokindiesel
Newbie
its just a math problem
Ok, heres some math that i learned in college in my basic engineering tech class last fall. HP= torque x speed/5252, which also translates into Torque= HP x 5252/speed. just to clarify, torque is in lb-ft and speed is in rpm's. So, lets say that your engine puts out 300 horse at 4000 rpm, its 300x5252/4000 which comes out to 393.9 lb-ft of torque at that rpm. Now we'll take the transmission ratio which we'll say is 1:1 and then we'll take the axle ratio which i'll say is 4.10:1, you multiply those which makes 4.10:1 final drive. so that 393.9 lb-ft x 4.10 is 1614.99 lb ft of torque in the center of the axle shaft turning at 975.61 rpm. do that math and its 1614.99 x 975.61/5252 and you have 300 hp. now i'll take 3.73:1 axle ratio, that same axle shaft at 4000 rpm is turning 1072.38 rpm with 1469.25 lb-ft of torque. do the math again and its 1469.25 x 1072.38/5252 which is 300 hp if its rounded up. all of these figured depend on where and when you round. It is also the torque at the axleshaft, which that would be distributed equally between both the left and right sides and the torque at the ground also changes because of the size of the tires. These also do not include efficencies in each gear set and in an automatic the hp and torque it takes to pump the oil also. So sorry to make this so long but I feel that i just proved it mathmaticly that horsepower will not change, but the torque will with a gear change. i should add that these are figured with 100% efficencies
Ok, heres some math that i learned in college in my basic engineering tech class last fall. HP= torque x speed/5252, which also translates into Torque= HP x 5252/speed. just to clarify, torque is in lb-ft and speed is in rpm's. So, lets say that your engine puts out 300 horse at 4000 rpm, its 300x5252/4000 which comes out to 393.9 lb-ft of torque at that rpm. Now we'll take the transmission ratio which we'll say is 1:1 and then we'll take the axle ratio which i'll say is 4.10:1, you multiply those which makes 4.10:1 final drive. so that 393.9 lb-ft x 4.10 is 1614.99 lb ft of torque in the center of the axle shaft turning at 975.61 rpm. do that math and its 1614.99 x 975.61/5252 and you have 300 hp. now i'll take 3.73:1 axle ratio, that same axle shaft at 4000 rpm is turning 1072.38 rpm with 1469.25 lb-ft of torque. do the math again and its 1469.25 x 1072.38/5252 which is 300 hp if its rounded up. all of these figured depend on where and when you round. It is also the torque at the axleshaft, which that would be distributed equally between both the left and right sides and the torque at the ground also changes because of the size of the tires. These also do not include efficencies in each gear set and in an automatic the hp and torque it takes to pump the oil also. So sorry to make this so long but I feel that i just proved it mathmaticly that horsepower will not change, but the torque will with a gear change. i should add that these are figured with 100% efficencies
RGV72BLAZER
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holy crap...engineeringk5.com...good explanations...i just know that gears will not produce more power than the engine can put out...lol...
jeeptuff
1/2 ton status
Basicly if you have 300HP to the ground and hell say 300 Lb Ft of torque at say 2500 RPM with 3.55 ratio. Then you jump to a 4.10 ratio, you are still going to have 300 HP but not at 2500 RPM, as for torque your Lb Ft of torque is going to go up, your HP rating will stay the same, just not going to be at 25oo RPM..
Damn I can't even type what I am thinking in my head, one to many ICE COLD CORONA'S tonight..
Damn I can't even type what I am thinking in my head, one to many ICE COLD CORONA'S tonight..
82smokindiesel
Newbie
engine horsepower stays the same
The engine horsepower will stay the same at the same rpm, the engine torque will also stay the same, actually horsepower is the same all the way through the drivetrain, gears are a torque multiplier(or reducer). thats the only change made with gears is torque
The engine horsepower will stay the same at the same rpm, the engine torque will also stay the same, actually horsepower is the same all the way through the drivetrain, gears are a torque multiplier(or reducer). thats the only change made with gears is torque
82smokindiesel said:
I am with this the engine is the power producer (whether you are talking torque or horsepower of kilowatts or whatever) Everything downstream is a mechanical advantage or disadvantage. If you are taking horspower or torque at the rear wheels and saying that a gear change will increase the amount of horsepower or torque than in 1st gear you would also make more "power" lose a little in second gear and lose more in third and fourth. Its a perceived thing. You are losing mechanical advantage. The engine at the same RPM will make very similar if not the same power at a given RPM. But at higher gears it loses the long lever effect hence less perceived power.
