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help end a 12 year old argument

S

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i know im right but id like some back up in writting to shove in the face of my friends

ok heres the story, i dont remember how the conversation got started but about 12 years ago me and 2 buddies were at a bar drinking abd b.s.ing about cars trucks ect.and one of the guys said that i need to change my gears to get more power and i told him that changing gears doesnt make more power, well this statement turned into a 3 hour drunken argument that ended in a fistfight with no agreement on any thing.

my basic argument was that changing the gears did not make more power because power was made in the engine, and putting in low gears only allowed you to move faster through the power ban that your engine already produced, i tried to compare it to a stall converter or changing tire size but they just werent getting it, i even went alog with them as far as saying that maybe going to a ring gear with more teeth would have slighty less rotational mass an give you maybe 1 more pony

their only statement was that it would put more power to the ground but when i asked them why or how the only answer i could get was because you are putting in lower gears

now keep in mind that both of these guys are auto mechanics and im not and at the time one of them was in school to be a mechanic and was a helper at a dealership

the only reason i bring this up is because i was at one of their houses today and he asked me if was willing to admit i was wrong yet, personally i think hes still pissed that i kick his butt

so whos right?
 
mostwanted said:
you are both right. The motor makes the power, and the gears alow you to put it all to the ground.
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ok but lets say with 3.73 gears your getting 285hp to the ground is putting in a set of 4.11s gonna make you now have 300hp to the dirt, pavment or asphalt? im not being sarcastic if it does then well open mouth insert foot

but if your motor is making 350hp at 4000rpm weither you have 3.73 or 4.11s you still only have 350hp which still has to go through the same transmission and the same axle with different gears and you still have the same amount of moving parts. i still dont see how this gets you more power to the ground
 
with a higher numerical gear ratio there is less force needed to get the same force as previously required to the wheels... i.e before it may have taken 80ft/lbs to turn the axle shafts with 3.08's and now with 4.10's it takes about 60ft/lbs so since there is less torque required it means that the horsepower(hp is the rate at which tq is made) will be able to rise.

edit: if this doesn't make sense drink a 6-pack and get back to me
 
They are right.

Input 300 lbs of torque into a diff packed with 3.08 gears and you'll get 924 lbs of torque to the ground. Now swap in some 5.13's and change nothing else...1539 lbs of torque to the ground.

Ever wonder why tow rigs are geared deep? It allows them to put more power to the ground.

Rene
 
well in the original argument i brought basically the same statement up but that wasnt what they were arguing, to this day im still not sure where the TONS of extra power they were speaking of came from and im not sure they do either

i coulndt put down three hours of argument, but i origonaly said that you would gain a few hp power because it would take less force to turn the wheels, but i didnt belive it to be a whole hell of alot

the car in which we were originaly arguing about was a 81 trans am with a chevy 355 making about 350 hp with a th350, 12blt with 3.55s in them and they wanted me to go 4.10s
 
depends where you count the power, tahts all, at the engine? no it wont change a thing... at the tires, yes it makes the tq greater
 
Deeper gears reduce top end speed. Its a trade off. Mechanical Advantage. Basic physics.
 
well i under stand the whole thing about mechanicle advantage, i just didnt think it would be that significant, i guess i was wrong i was thinging more along the lines of 5hp gain and they were thinking more of 50hp gain

i was looking more along the lines of the fact that i already had trouble keeping the tires from melting and my top speed already sucked
 
No need for a dyno, all it takes is a very simple experiment you can do yourself. Grab a 1/2" drive breaker bar and tighen up a bolt with it as tight as you can make it. Now slip a 24" length of pipe over the same bar and see if you can tighten the bolt more.

Pretty ovbious result, and you're doing the same thing with gearing. You're giving the car a longer lever.

Another example. A 4 speed car cruising at part throttle, let's say a constant 2000 rpm. First gear...floor it and it'll take off nicely. Same rpm in 4th gear you floor it and it'll take off pretty sluggishly. Gears multiply torque.

By going to 4.10's from 3.55's your old car likely would have launched harder with less wheelspin...and with 4.10's the engine could likely have hit a higher rpm at the top end.

Rene
 
tRustyK5 said:
No need for a dyno, all it takes is a very simple experiment you can do yourself. Grab a 1/2" drive breaker bar and tighen up a bolt with it as tight as you can make it. Now slip a 24" length of pipe over the same bar and see if you can tighten the bolt more.

Pretty ovbious result, and you're doing the same thing with gearing. You're giving the car a longer lever.

Another example. A 4 speed car cruising at part throttle, let's say a constant 2000 rpm. First gear...floor it and it'll take off nicely. Same rpm in 4th gear you floor it and it'll take off pretty sluggishly. Gears multiply torque.

By going to 4.10's from 3.55's your old car likely would have launched harder with less wheelspin...and with 4.10's the engine could likely have hit a higher rpm at the top end.

Rene
Click to expand...
right, i under stand the physics behind it i also uderstand that what happens in theory is usualy not how things are in real life, but part of my argument with them was just like you said, the reason why the car is faster with lower gears is because the gearing allows the car to move through the engines power band faster so if peak power is at 4500rpm then the car can make that move from 2000 rpm to 4500rpm faster in 1st gear than in fourth gear

the gears dont make the power they just let you use the power you already have to your advantage
 
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There is a huge difference between power and torque. Just going by the math of it when you change the gear ratio the torque output will change but the power will not. When you put lower gears in the rear end you will get more torque output. You will also get a slower output. The combined result is that the power won't change at all (it can't!).

If you want to get into the efficiencies of the gears (a very small difference) I think higher gears (lower numerically) would put out more power because there would be less sliding friction between the gears because of the larger pinion.
 
i dont know, i think we all argee, we just say it differently, i belive block and tackle or a chain fall would be a better example
 
i know a lot of people have responded but, my input is...say u have 300hp engine....u put down 275hp at the tires, because of loss of power through the drivetrain. if u put a higher gear ex: 3.73 and change them to 4.56 im guessing you would lose less power through the drivetrain because of the less torque it takes to turn the wheels, so instead of have 275hp put down with 3.73 gears,you will probably have 290hp put down with the 4.56s....anyone agree with me?
 
stockk5 said:
i know a lot of people have responded but, my input is...say u have 300hp engine....u put down 275hp at the tires, because of loss of power through the drivetrain. if u put a higher gear ex: 3.73 and change them to 4.56 im guessing you would lose less power through the drivetrain because of the less torque it takes to turn the wheels, so instead of have 275hp put down with 3.73 gears,you will probably have 290hp put down with the 4.56s....anyone agree with me?
Click to expand...


No.


As Dan (Triaged) already mentioned, gearing changes affect available TORQUE, and not HORSEPOWER.

Remember, Horsepower is a "calculated" number based on an engines ability to create torque over time. Deeper gears give you higher torque at the wheel, but at the expense of maximum wheelspeed. You are gaining in one area, but losing in the other....so the horsepower number won't improve with a gearing change.

Adding deeper gears will help acceleration, to the extent that you have the traction to hook up all that multiplied torque at your tires.
 
Greg72 said:
Adding deeper gears will help acceleration, to the extent that you have the traction to hook up all that multiplied torque at your tires.
Click to expand...

this is why its so easy to break the tires loose on something with really high gears in it. the wheelspeed overcomes the traction, very soon.
 
Think about a bicycle with multiple gears. The rider has a certain amount of power. If the bicycle is in 10th gear and maximum power of the rider is applied the bike will begin to move and ultimately will travel faster than the same bike with the same rider in first gear. However in first gear the bike will move sooner than in 10th gear and it will achieve its maximum speed sooner than in 10th gear and that speed will be slower than the maximum speed of the bike in 10th gear.

Bottom line depends on the performance you want. high speed low RPM's or low speed but high RPM's. either way the motor or in this case rider has the same amound of available power.
 
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