wayleft

Please don't think I am too thick to live.
I just don't know much about cars.

How will HP change my speed? What I mean is my speed at 4000 rpm is exactly twice what it is at 2000 rpm in gears 1-4 in fifth the proportion is the same but I don't think I can reach 4000 rpm that would be 160+ mph. But I think that relationship is based on my gear ratio (3.27) So if I build up more horsepower that relationship wont change, right? Then how is it that I would go faster with more horsepower. Is it that my rpm will increse faster and I'll speed through gears faster.

Please someone help me.

Chopper

An increase in HP that will allow the engine to pull to a higher RPM level and that will make the car faster.An increase in torque will make the car take less time to get to the higher speed.(quicker)This is kind of misleading as HP and torque are tied directly to each other.When one increases the other does also.If someone says that"torque drops off at 4500 RPM",what happens is HP isn't building as fast as it was in the first part of the power curve,HP is still climbing but just not as fast.

bahbahblacksheep

Are you talking about how HP will affect your acceleration?

if you are, then you have left out one very important part of the equation...Torque.

Your car, in every gear will only accelerate at a rate that exactly matches its torque curve. Put it another way, your car will accelerate most at the peak of your torque curve. You need torque to access your hp. If there is little torque, then the engine will need to be setup with higher RPMs and you'll get power when reaching redline. So more HP will allow you to pull "longer", but at the same rpm, two cars with equal torque will accelerate at the same speed until the car with more hp reaches higher rpms.

4600cc

Speed is constant, you can reach 120 mph in 2 minutes or you can reach it in 10 seconds, 120 mph is the speed. The term you are wanting to use is acceleration. A car that reaches 120 mph in 10 seconds is faster than the car that reaches 120 mph in 16 seconds.

Torque is rotational force, the more torque you have the higher the force of a shaft you want to rotate. Take a wrench for example, if you spin it on a nut using one finger you have less torque than if you pull the wrench around the nut using two hands.

Horsepower is the measurement of the ability to deliver torque. Take a wrench for example, if you spin it on a nut using one finger, around and around, horsepower is how fast you can spin it.

A 100 ft/lbs of torque could be delivered while spinning the wrench on a nut at 1 revolution per minute, or it could be delivered while spinning it at 80 revolutions per minute. Such a relationship is equivalent to 100 ft/lbs of torque and 80 horsepower. (no relationship to engine rpm)

Horsepower makes you go faster, while torque make you move. Imagine yourself pushing a 200 lb dolly, your a ability to push it is torque, your ability to push it and increase the speed you are pushing it with is horsepower.

Gear ratios are a relationship between how fast your wheels spin and how fast your engine spins. That is a relationship between MPH and RPM. A single gear will propel you from mph0 to mph1, the shorter the gear the lesser this gap in MPH is, the taller the gear the greater this gap is. 3:27 gears have greater gap in mph0 and mph1 than 4:10 gears.

Engine's horsepower and torque is delivered into gap mph0 - mph1. As you shorten gear ratio from 3:27 to 4:10, this gap decreases while horsepower and torque remains the same, thus acceleration is greater. This is similar to acceleration in 1st gear and in 2nd gear, mph0 - mph1 gap is greater in 2nd than it is in 1st, thus acceleration is greater in 1st gear.

Theoretically top speed will be reached in 5th gear, then you will hit rev limiter and no more acceleration will be possible, speed will remain constant and it will be top speed. In real life there is drag. Drag is your vehicle's weight, it is the trailer you are pulling, it is the resistance of the air as you go thought it, and it is the resistance of your tires to the road. Drag is that 200 lb dolly you are pulling. Torque is required to pull the dolly. In real life your top speed is the speed at which there is no more torque available to push the dolly.

Chances are that you have 3:27 gears and your top speed is when there is no more torque available to push the dolly. It could also be that you have 4:10 gears and your top speed is reached when you hit the rev limiter. In this latter case it means that there is not enough drag to counteract the torque. This is due to mph0 and mp1 gap you have in 5th and 3:10 gears, you are not reaching high enough speeds to encounter drag necessary to counter act the torque.



AL

wayleft

okay I should have included torque i my original post. I uderstand that torque is a unit to measure work. specifically the work needed to move one pound one foot. And it seems your saying HP is the unit of power (duh?) work(ft.lbs.)/time. So increasing HP/torque while keeping the weight the same means you will travel faster (the same distance in less time or further in the same time)

but since the rpm of the engine and its relationship to to the rpm at the wheels is a constant based on the gearing, and the wheel rpm is directly related mph. The factors that limit speed for instance weight and wind resistance also limit engine RPM more torque will allow the rpm to go higher and more HP will allow rpm to accelerate faster?

4600cc

Um. More HP allows faster acceleration, your wheels accelerate faster and thus engine accelerates faster, RPM go up faster. More torque means you can tow more, your vehicle, two fast chicks in the rear seat, and incredible wind resistance at 140 mph. Torque and HP go hand in hand. Racers prefer more HP than torque, because you can always make more torque using a lower gear. It's best to have HP and torque close together for a good street machine. Trucks like to have more torque to tow things.

They are stuffing a 6.8L V10 into ford panther bodies. Those things are only 350 HP at the crank. With 350 HP at the crank, 320 at the wheels, on your 4.6L, you will not move 180 MPH. Those things go 180, and they weight around 4500 lbs and have air dynamics of a brick, they can because of torque. However, those vehicles are only 13.8 in the 1/4, that's because they only have 320 HP at the wheels.



AL

Deannostang

Old rule of thumb.....HP = Top End......Torque = Acceleration or "pulling" power. Moral of the story: you are always better off with a "high torque" engine.

Maybe someone out there looking at this thread can answer my question for me. I have read, and have been told face to face by engine/car builders, that when you increase your rearend's gear ratio, you are also effectively increasing the torque rating on your engine due to the vastly increased "pulling" power of your new set-up. It is not necessarily that your engine changes its HP/torque rating, but rather the sum of your modifications to the drive train system will equal an overall increase in preceived torque. Sounds logical to me but would like some back-up on this one.

99saleen351r

Thats not true....Either of them, torque will not change by your gears and Hp doent mean your car is fast without torque you car wont be fast.

What is a ford panther??

I have never heard anyone ask that question before but they say the only stupid question is the one you dont ask

4600cc

Prove it.

bahbahblacksheep

a car with 1000hp but low torque will be dirt slow.