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Discussion Starter #1
OK, no snarky comments; I know this is a dumb question! There has been previous posts regarding peformance chips, new models being underpowered etc. To better follow these discussions, can someone please explain difference between HP and Torque to a non physicist? Is it correct to think of Torque as measure of car's ability to accelerate, while HP relates to a car's top speed?

Is it correct that diesel gives a flatter torque curve than gas, and if so, why. Why do you have to go high into the rev range of a Maserati to get Max torque and HP?

Also, what is difference in HP, BHP, RWHP, HP at the flywheel etc?

(Lest you think I am totally stupid and unworthy of my car, I do know what top speed, 0-60, 1/4 mile times mean! :) At least I think I do!)

Feel free to just refer me to a BASIC auto book (any suggestions?) if these are questions not easily answered or appropriate for this forum!

Actually, Most people have no idea what the difference between HP and Torque is... I can try to explain it, but I think someone like Jeff or one of the racing guys can explain it better...

Torque is how much "force" or work the engine can do (ie, how "hard" it can turn your rear wheels)

HP is how FAST it can do that work (ie, how FAST it can turn your wheels)

So, in order to have a fast 0-60, you will need torque (to get the car moving faster) and HP (to get the to get the car moving faster...faster)

HP and Torque in an engine are equal at 5252 RPM. Torque is always more than HP under 5252, and HP is always more than torque above 5252.

So, how high a car can rev will also determine how much HP and torque the car has... Lets say that for our purposes, engines can either only rev under 5252, or above 5252.

A heavy engine (like a diesel) can rev "under 5252", thus it will NEVER have more hp than torque... This means the engine can get itself moving no matter how much extra load it has, but it can never go "fast" (That's why I hate driving behind damn trucks on one lane streets... especially canyon roads!)

A light engine, like a sports car engine, can rev "above 5252", and thus can turn the wheels "faster". This is why the cars can go faster. The wheels can TURN faster because the engine can turn faster.

Another way to think of torque and hp in an engine is like this: Torque is how "hard" the explosion pushes the piston DOWN, and this turn the crankshaft. HP is how FAST it can push the piston down hard.

IE, Torque is how hard you hammer a nail in a piece of wood, and HP is how FAST you can hammer at it.

The following are just different ways of measuring HP.

HP- The engine's "theoretical" HP.
BHP- The HP at the flywheel.
RWHP- The HP at the wheels of the car (After losses by heat, and friction... ie, drivetrain loss).

Same for torque.. Torque, Brake Torque, and Rear Wheel Torque.
 

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OK, no snarky comments; I know this is a dumb question! There has been previous posts regarding peformance chips, new models being underpowered etc. To better follow these discussions, can someone please explain difference between HP and Torque to a non physicist? Is it correct to think of Torque as measure of car's ability to accelerate, while HP relates to a car's top speed?

Is it correct that diesel gives a flatter torque curve than gas, and if so, why. Why do you have to go high into the rev range of a Maserati to get Max torque and HP?

Also, what is difference in HP, BHP, RWHP, HP at the flywheel etc?

(Lest you think I am totally stupid and unworthy of my car, I do know what top speed, 0-60, 1/4 mile times mean! :) At least I think I do!)

Feel free to just refer me to a BASIC auto book (any suggestions?) if these are questions not easily answered or appropriate for this forum!
 

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BHP and 0 -60

So, in order to have a fast 0-60, you will need torque (to get the car moving faster) and HP (to get the to get the car moving faster...faster)
Thanks for the clear explanation. I think you are saying that acceleration i.e. 0 - 60 mph is related primarily to torque. I was interested in another post of yours ( see: "So I met my match tonight....") where you indicate:

"The general consensus is that a "basic" equation for approximate 0-60 is: kg / .9(bhp)"

Would it not therefore be more accurate to derive an equation utilizing torque rather than BHP for 0 - 60? :confused: If so, would you know what it is?
 

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Here's a useful URL: http://www.pumaracing.co.uk/POWER1.htm

There are a couple of other articles on there too.. http://www.pumaracing.co.uk/ & scroll down.

Horsepower = Torque x rpm / 5252.

This is the universal equation that links torque and horsepower. It doesn't matter whether we are talking about petrol engines, diesel engines or steam engines. If we know the rpm and the torque we can calculate horsepower. If we know horsepower and rpm we can calculate torque by rearranging the equation above:

Torque = Horsepower x 5252 / rpm
 

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Discussion Starter #7
Well, torque and HP are both related to each other in some equation... So HP does tell you your torque, etc.

It is just a rough estimate :) but it is damn accurate
 

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No problemo.. for the technically minded there's all sorts of info on AtlasF1.com too.. just generally all sorts of car (& F1) related engineering type stuff on there.

enjoy :)

oh & LOVING my 06 gransport ;)
 
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