rfdjr58

I've done some research here, and elsewhere on the Internet on the subject of horsepower and torque. Most of the reading is rather technical. Since I'm not an engineer, I wanted to ask this question from a layman's perspective. I'm curious what impact additional horsepower provides if there is not more torque.

The 997S compared to the GT3 seems like a good comparison for this purpose. The GT3 has significantly more horsepower but only slightly more torqure.

I notice that the 0-60 time is improved by about half a second, but I'm more interested in the driving experience -- i.e. what effect does the additonal horsepower provide.

I've owned a C5 Corvette Z06 which has more torque and horsepower than my 997S. It had about the same horsepower as the GT3, but also 400 lbs of torque. Maybe another question would be how the driving experience of the GT3 would compare to the Z06 which had more torque.

Sorry to ramble, but I would appreciate any (non-technical) observations.

nhs156

I was once told by someone speaking in VAST generalities:

HP = top speed
Torque = acceleration

I'm sure it's not that simple - in fact I know it's not (other factors obviously come into it, like weight etc. - lb/HP is a measure that many race car fans/drivers put a lot of stock into).

PAULSPEED

Hi,
Torque is really good for the drag strip.
Paul

krC2S

nhs is right

alot of torque means alot of initial acceleration(immediate) and possibly wheels spinning smoke etc
like vettes etc

since power=torque X rpm

to have good power with less torque you hae to have higher revs like
gt3 8400 rpm vs 7200 997s

i suspect the GT3 will not seem that much of a monster on inital acceleration compared to 997s
but as it revs up it will reach higher speeds quickly

kauai_diver

a perspective i use:

If you have a perfectly flat torque curve (same torque @given rpm) you will accelerate at the same rate from 1rpm to 8000rpm for example. No engine has a perfectly flat torque curve but the vettes come pretty close for production cars. That is why even at low rpms corvettes have very good acceleration.

If you have a high horsepower car with low torque or torque that peaks, ie a v8 Ferrari with small displacement, you will get maximum acceleration at high rpms.

Chris from Cali

When comparing acceleration times of the 997S and GT3, keep in mind that the GT3 is significantly lighter.

golfman

The old expression HP sells cars but torque wins races seems to fit. The car will move quicker off the line with more torque but hp helps to keep a car in it's gear longer. If you reach 5250 rpm torque and hp meet. Torque will start to drop but if there is still hp to be made you can stay in that gear longer before shifting. So I would say that hp helps not only in the speed of the car but when driving on say a drag strip it will help as well. That is why you see the gt3 quicker in the 1/4 mile. You can rev higher and stay in the gears longer taking away the time it takes to shift to another gear in that same 1/4 mile stretch. Shift time is dead time in racing.

This is just my opinion. I may be full of crap. lol

Inrev

Maybe I'm full of crap because I'm a track noob, but my guess is less torque vs higher hp at higher rpm would mean a lower possibility of spinning tires and losing traction while for example coming out or a turn. So it would make a better, safer track car perhaps?

cleanme

Not exactly! Hahaha the more hp&torque the better...in fact coming out of a hard corner you'd want lots of torque in case you short shifted for some reason to set for another turn/straight.

As an Engineer, I congratulate you all on being right! Everyone has basically got it.

clubrcr

I have raced for several years and have driven a lot of different race cars.

You really can't compare hp and torque of the GT3 to the 997S, although bhp and torque does make a hugh difference, so do other little items like the DME, gearing, suspension and weight. In racing, you would always want more torque. Since many tracks have low speed turns, coming off the turn quicker, with the right amount of traction is the most important. To overcome the difference at the end of the straight for a low torque car, you need a lot of straightway to gain an advantage.

It is also hard to compare the low end torque of a big block V-8. Yes, the tire might spin coming off a turn, but that is why you set the car up differently. I have had Porsches that would spin the back tires coming off of corners.

MichaelL

By definition, Horsepower=Torque x RPM / 5252 . Torque can be measured by a dynamometer, but horsepower is a derived quantity that expresses the work done in an interval of time. At 5252 RPM, horsepower and torque are always equal.

Mike Murphy

Jim Newman is right-on, and I will supplement his comments with some of my own: It is gearing that makes all the difference in the world when it comes to comparing horsepower versus torque. A 16-liter, 400HP Tractor-trailer CAT diesel makes the same power as a 400HP Vette engine, but the diesel has 3 times the torque output at a much lower RPM. If everything is equal (which is impossible, I know), the cars with each respective engine will be the same speed around the track. The key is gearing. In other words, the Diesel I was describing can pull a house off it's foundation if the gearing is correct. And so could the Vette engine just as easily, but only with the right gearbox.

If you want to pull a house off a foundation, you need a HUGE amount of torque. If you want to pull the house off faster than the next guy, you need more horsepower. Make sense?

MM3.9GT3

This is a great question. Look at the area under the torque curve of the 997S and the 997 GT3. While the torque numbers are almost identical, the GT3, because it revs to 8500 RPM, has a much bigger area under the torque curve. Therefore, since it can rev higher in each gear, it will accelerate faster. If the torque numbers are equal, the car with the peak torque at a higher RPM will accelerate faster, assuming the gearing is set up to take advantage of this fact.

However, cars that produce a lot of torque at a low RPM "feel" faster, since they do pull harder for a brief amount of time. The cars with torque higher up the RPM ladder can pull consistently for a longer period. Therefore, the "butt meter" may feel the other car is faster, but, a car like the GT3 will be faster when measured with a stop watch.

Here's a great article.

MM3.9GT3

Article:

It won't let me post a link. Google torque versus hp, and the first article should be from vettenet, called torquehp.

911Dave

Torque is the force that turns the crank. More torque gets the crank turning faster and translates into better acceleration. So more torque means faster 0-60 times, all other things being equal.

Horsepower is a measure of the amount of work being done to move the car. It takes more horsepower to move the car at a constant 80 mph than it does to cruise along at 60. Since BHP = torque*RPM/5252, if torque increases past 5252 RPM then horsepower will also. Usually, high horsepower translates into greater top speed, because moving a car faster requires more work.

The two most important factors in how a car feels to drive it are 1) the shape of the torque curve, meaning how flat it is and where the hump is, and 2) the transmission gearing.