Van

You guys read the link Kurt posted in #37? That made it crystal clear to me.

wanna911

You are right, I skipped over that but that does explain a lot. And explains the benefits of high revs vs the "pull" of torque. High Revs FTW........

Veloce Raptor

High revs and torque are not mutually exclusive, Des. Torque gets you out of corners and braking zones faster. HP gives you higher speeds on the straightaways, but high RPM does not always mean high HP.

mark kibort

absolutely postively wrong.

did you not read the cliff notes and the detailed posts I made for you ?

QUIT confusing engine torque with the accelerative forces at the rear wheels.
HP determines rear wheel torques after the engine torques (high or low) are multiplied through the gear boxes.

Any race car that has 300rwhp at the exit of the turn, with 400ft-lbs of torque or 250ft-lbs of torque, will accelerate exactly the same out of the turn.

Its the shape of the HP curve that matters when comparing the different engine torque values.

So, I would pick the car that had the most average HP over any operational RPM/speed range. (or more accurately said, the one that produces more HP-seconds over a lap! )

mk

wanna911

VR,

How so, I've never seen a high torque and high revving motor, seems like it's always one or the other.

Maybe that's why the corvette's do so well, they are tweeners. The Z06 still makes only 94% of hp in torque. But the ones that are 99-120% are the ones that are questionable to me.

And more importantly is when the torque is made, I noticed many of the current races cars are making peak torque well into the power band. Not at 3800 rpm as in the example. That seems like difficult to drive range IMO.

mark kibort

It compares perfectly. What it is doing is actually getting the same result, but the long way. It gets you actual rear thrust values as well. I use both depending on what I am trying to find out. The entire reason for most of the confusion on the topic, is that most dont realize that the thrust force is directly determied by either looking HP at any speed, or engine torque, muliplied by the gear ratio at that vehicle speed. Both result in the same answer. When you look at an engine's HP curve, you just need to make notes of your gear spacing and then you can determine where your shift points are and what the average HP used over any speed range.

mark kibort

You are propagating the problem here. Dont you see it? re-read post 18/19 and 20.

absolutely wrong. (and it is not "as simple as that") two cars (like the viper vs the porsche gt3) can have 2x factor of torque differences, but if both have the same HP exiting the turn, both with have the exact same torque to the rear wheels!

Man you are stubborn!

want proof..........? all you need to do is show me two actual cars (maybe like the viper vs porsche dyno runs) that come off any turn and give me a speed. Do some simple math and determine who has more or less rear wheel torque which i assume you would agree that it determines the rate of accleration, at that speed. Until you you do that, you sound like the " hp sells cars, torque wins races" guy!

Mk

mark kibort

efficiency is not king. we are not even talking about efficiency here. that is assumed to be equal.

HP is king. Its the rate of doing work. the faster you do work, the quicker you will accelerate by definition. engine torque without a rpm attached to it is meaningless. rpm without a torque attached to it is meaningless. HP tells all at any vehicle speed. HP-seconds applied over any speed range tells ALL.

after all:

acceleration = Power/(mass x velocity)

this means HP dicates acceleration at any speed. For you torquees out there, torque at the REAR WHEELS , after being mulitplied through the gear box, will tell you the same thing.

Mk

mark kibort

Greg, Torque found at the rear wheels determines the acceleration of the car, not engine torque alone.

Hp determines torque at the rear wheels at any vehicle speed. HP doesnt need to be calculated from torque. rate of change of kinetic energy can tell us this without even knowing torque.

on a dyno, if you dont know engine rpm, how does it give HP as an output vs speed? dynos dont put out engine torque values as they only know the rear wheel torque that is on the drum based on its weight,diamater and speed change. (and this is never an outupt. the numbers would be 2000ft-lbs on most dyno runs )

This is a good point . If we dynoed the GT3RS and the Viper where i showed the HP vs torque comparisons and you didnt have a spark signal to show rpm, what would the output look like? could you tell the Viper from the GT3RS? Certainly not if the hp curves were ONLY the same shape. The hp would be the same and at ANY MPH, the accelerative forces would be the same. thats off the curves, down the straights, etc etc VR! Before anyone argues this point, find me a point on the track where this would not be true! (give me any speed anywhere on the track!)


mk

mark kibort

Bruce Augustines little web site was BLASTED by me 10 years ago. (Post 37 link)
It has more errors that you can count. It was confusing and misleading.
I have a point by point report I sent to him and never heard back.
Anyway, it propagated many errors, some even discussed here. Ill forward you the corrections if you are interested.

Mk

Greg Smith

You're not understanding this then. If both cars have the same transmissions and differentials then you're not taking advantage of the higher torque multiplication allowed by the higher rpm. What's the point in having a car that has a theoretical top speed of over 300mph?

PS-You mean same shift MPH

wanna911

No I meant same shift rpms. A car that revs to 9k rpms will not be shifting at the same rpms as a car whose rev limiter is set at 6100. At least that's what I interpreted.

I said to assume the gear ratios and final drive were that of the car from which it came. So for a Z06 we know that the gear are long ratio gears to distribute the torque/hp (hell I don't know) evenly where as the GT3 will be more aggressive with the gearbox because of lack of torque. I know the 6th gear can be a pain, but on most tracks you wont see the end of 5th anyways so it's still relative. So really the torque can be dissipated or magnified by the gearset no?

mark kibort

Torque is created when a mass is acclerated. (F=ma)

Gas burned and expanding in our combustion chambers creates a force on the piston

the amount of gas burned for any duration would determine the power.
as power is the rate of doing work. work being a force x a distance.

A gallon of gas burned in 1 min would be a unit measure of work, like a kilowatt hour or HP-second as i have used in prior descriptions. This is the foundation for where all the torque or accelerative forces comes from
How this is used is up to the car power conversion design. (ie high reving, low torque, or low torque, high reving and transmission to utilize it)

Since acceleration = power/(mass x velocity) this means that at for any given vehicle speed, power will determine acceleration. This acceleration is caused by the force at the rear wheels generated by the torque through the gear box coming from the engine.

This is "how" torque at the rear wheels is generated and is the total reason why your car will accelerate. It is determined by HP at any vehicle speed and a low or high torque engine can have the exact same accelerative forces at any of the speeds on a road course as long as the HP curves are the same shape.

mk

mark kibort

More confustion. Think in terms of what Greg just said. Shifting at a given MPH. Gear spacing. most all cars are around 73% rpm drop between gears. close ratio gear boxes like found on the GT3 are tighter to the tune of 82%. that just allows the shifts to drop the rpm to stay within the max hp range.

Please, go to the graph below and study two dramtically different engines. Ive equated the graphs so you can see where the trade offs would be. If the viper curve was shifted down to equal the porsche curve, you can see that even with half the torque and not even a close ratio gear box, it would have the exact same torque to the rear wheels at ANY vehicle speed.

Mk

Greg Smith

Oops, I said this earlier:
"The fair way to compare them is with gearing that sets them to have the same shift rpm's and top speed, which is what I did."
What I meant to say/type was this:
"The fair way to compare them is with gearing that sets them to have the same shift MPH and top speed, which is what I did."