Horse Power is King

[bit]

I have not posted around here in a while but I just finished up my engine design class and I thought I would stir things up a little bit. I hear people say HP sells car and torques wins races and you can tell them otherwise. Well here is proof.

Horse Power is King!

About the cars:
Speed= 60MPH
Mass car 1 = Mass car 2
Rtire=1.2ft
Ctire=7.53ft
Froad= torque*(Gratio/Rtire)


Car 1
Torque at Max Power-300 ft*lb @ 16000RPM
Max Power-914 HP@ 16000RPM
Total Gear ratio-22.8:1
Force to the ground-5700lb
Froad1=300*(22.8/1.2)=5700lb

Car 2
Torque at Max Power-630 ft*lb @ 7000RPM
Max Power-840 HP@ 7000RPM
Total Gear ratio-10:1
Force to the ground-5250lb
Froad2=630*(10/1.2)=5250lb

Difference in force:
1-(5250/5700)*100=8%
Car 1 puts down 8% more force to the ground. Why?
Difference in HP:
1-(840/914)*100=8%

The difference in their HPs makes car 1 out run car 2. Not torque!
Horse Power is King!

-Brent

 

[90mustangGT]

Power is a measure of torque in relation to speed. So you have two motors, one that revves twice as high as the other but only makes half as much torque, but has the same torque curve, the high revving motor could be geared twice as low and would have the same shift points and would make equal power. However, it is much easier and more economical to build a lower revving high torque motor. Usually motors which revv really high are less dependable and have shorter powerbands.

Indy F1 cars only run 3 liter V12's but they revv to about 18000+ rpm, making over a thousand HP all motor, (Imagine putting a turbo on one) however, do you have any idea how much their motors costs. I think I saw it on speed channel and they said over $100,000. I think the cost of the whole car is something like 1.2 MILLION. If I had that kind of money, i would probally buy one to be honest. The upkeep would be insane though.

 

[bit]

I agree with everything you said 90mustangGT. I am just making the point that it is not as black and white as everyone makes it out to be. And the statements like "HP sells car and torque wins races" are just not true. Just a little food for thought.

-Brent

 

[90mustangGT]

I agree with everything you said 90mustangGT. I am just making the point that it is not as black and white as everyone makes it out to be. And the statements like "HP sells car and torque wins races" are just not true. Just a little food for thought.

-Brent

Your right Brent, for us that know, it's just not that simple. HP does sell cars though. Most people you will take to will know how much HP thier cars are rated but if you ask them how much TQ, unless they are disel freaks they probally don't know. Peak number are BS. I belive that you want the most average tq in the powerband you are racing.

Application also has a lot to do with it also. The same reason they put Disel's in big trucks and 4 bangers in small cars.

 

[87'GTstang]

Without torque, you don't have horsepower - not the other way around!
People do like horsepower numbers though.

 

[deftsound]

yea but 9 times out of 10 your not going to be racing fast enough to ever see that 900hp meaning that the torque in the short run is going to be more decisive

atleast thats how it seems to me...

 

[ms93gt]

I'm definately jumping in on this subject. Horsepower is not king, it's power to weight ratio. For Example, the new Honda S2000 has 240 horspower and 140 ft lbs of torque, well that stupid pos only runs mid 14's with a good driverand it weighs only like 27000 lbs. Now thats not bad but the reason it runs that with a good driver is because of the high powerband, you literally have to dump the clutch at like 6000rpms. Now just imagine if that car had equal torque with horsepower, it would be really fast. Another example, look at Mac trucks (18 wheelers), they have like 1000 horsepower and those things are the slowest turtles on the planet! Now our mustangs only have 225 horsepower and almost 300ft lbs of torque and with practice we can run low to mid 14's. Ive seen 14.1 stock before, now 225 horsepower is **** compared to what most cars are pumping but because of our light ass body and high torque capacity it makes it a quick car especially for the street. And therefore thats y is what rated king of the street.

 

[Michael Yount]

Brent - it all depends on application and even the particular driver's preferences. Many, many races have been won when the driver/crew/tuner figured out how to get more torque out of the engine at 2/3rds of engine peak rpm because that allowed them to accelerate off a certain turn better than another racer - even though that change cost them a few peak HP. It's NEVER as simple as one is better than another - both are important; and in different circumstances with different vehicles/drivers/types of racing - increases in either HP or torque have made the difference between winning and losing. School is great for theory - the track will allow you to see the practical applications of all those equations and that theory. It's never as cut and dried in the real world as it is in class.

But here's the real kicker when it comes to stirring the pot a bit - when it comes to road racing, more passes are made due to improvements in stopping - brakes/tires/suspension/technique - than are made due to HP improvements. Being able to more successfully convert all that hardwon HP-induced speed into heat and reduced kinetic energy may just be more critical than finding the few extra HP or lb-ft.

 

[Michael Yount]

Besides that - your comparison doesn't really illustrate what happens when cars really put power to the ground. As a practical matter, it's hardly ever a steady state situation as your example is. On the track, cars are constantly accelerating or decelerating through a range of rpm. So you need to look at the area under the torque and HP curves over the range of rpm being used during the acceleration, and calculate forces put to the road over that range of revs. You might get a different answer - especially when you consider there are many parts of some tracks where peak revs can't be used....

 

[hllon4whls]

unless they are disel freaks they probally don't know.

I resemble that remark.
525 ft-lbs at 1600 rpms. Makes passing cars in od unbelievable. Even pulling a trailer.

Back to the program already in progress.

 

[grrrrrrr]

I believe you meant that you resent that remark... if you resembled it, you'd look kinda funny... sorry, had to bust your balls a bit...

 

[90mustangGT]

Bit is completly wrong, HP may be one knight at the round table, but all of us who are really about anything know:

ET is King

What is the point of power if you can't put it on the ground. Peak numbers are for bench racers, and dyno queens love HP numbers. Both are a waste of space in my opinion.

 

[Michael Yount]

"525 ft-lbs at 1600 rpms" -- we don't need no stinkin' diesel; Mercedes 331 cubic inch twin turbo V12 gasoline engine (powers the Maybach) makes 595 lb-ft at 1800 rpm.

 

[deftsound]

yea i definately think torque is equally important. I mean my dad has a ford turbo diesel 3500, that thing weighs a ton but ive raced and beat honda civics in that thing (not that its saying much) solely because the thing has a massive amount of torque so it can get off the line respectively quick.