I've specifically stated that gearing is a factor and that redline plays a part, the point is simply making more horsepower without adding mechanical advantage WILL NOT make you reach 30 MPH faster in my previous example, however raising the redline and adding torque via gearing WILL make you, as long as you dont gear it so short that you have to shift out of first but thats another matter.

I have NEVER said that torque is WORK, or if i did pardon me as i probably got sidetracked by all the other arguments going on here, my entire problem is witht he thread title that HP is acceleration and not torque when BOTH are involved. Torque (at the wheels, engine torque multiplied by gearing) and RPMs as well as the speed at which the wheels rev up is what determines accleration (as well as the rest of the car, weight etc.) and not HP, or if you want to nitpick not JUST HP. If HP were what determined acceleration then why do we have gears? all they do is add torque, not like that stuff does ANYTHING the torque is the force behind each revolution, it's VERY involved with how fast you accelerate.

You're right, HP tries to unify everything, the fact is it CANT be unified, you can never just look at torque and know how fast your car will accelerate, nor can you do the sme with HP, the fact is though HP alone does not equal acceleration.

er, lets see here, engine HP hasnt changed, engine torque hasnt changed, however the gears which multiply the torque fed to them by the engine have changed, how do you gain HP to the ground when HP can't be multiplied, it is just a calculation of torque and RPM you know. You drop down a gear because you want to increase wheel torque, it's what slows you down as you upshift due to the wider ratios not multiplying as much torque, which is exactly why torque is involved with acceleration.

sorry if i wasn't clear, i was half asleep writing that, i meant raise the cars HP by increasing redline and not changing the torque output, yes its unlikely but it still serves a purpose in the argument, torque matters to acceleration, and not just because it's part of the HP calculation.

the torque is the force, the force in motion is work, you'll only actually accelerate faster (dont confuse that with simply holding each gear longer) when you increase torque. Say you put in a rearend diff twice as short a ratio as your stock one, get in first gear assuming you have perfect traction, you'll accelerate twice as hard but for half as long (not literally theres obviously imperfections in there but just stay in the dream world) but HP won't have changed, torque wouuld've though.

This whole deal about engine torque not making any difference is not th epoint, the original poster claimed HP was acceleraation and not torque, and engine torque DOES matter, it's just not a constant nor is it the only factor, the point is still that TORQUE (wheel torque) is what accelerates your car, i've been saying this all along. Besides, engine torque has to exist anyway, without it theres no wheel torque, and the more you have to multiply the more you produce exponentially, the S2K requires its redline due to the short ratios it uses, if it were just to add 50 ft lb of engine torque it could widen the gearing by a large bit and still be just as fast, faster likely, and more reliable due to less engine RPM needed.

 

 

No it's not. FORCE accelerates the car. PERIOD!!!!!!!!!!!!!!

I understand what you mean, but it's your use of the words torque = force in the same sentence to try to prove your point. It's just plain WRONG.

The resistance of the tire to the pavement (FORCE ***here is that word again***) is (technically) what is causing the car to accelerate. I don't care how much torque (both engine or wheel) you produce, if it does not have a force applied to it, no work can be done. Example: tires spinning without touching something will product NO ACCELERATION. PERIOD!!!!!!!!!!!!! Why is this the case, because again no force is applied to the tires. Tires spinning have a net force of ZERO until a force is applied.

Which is most important. ALL OF THEM COMBINED.

If I had my wish, I would have a car that:
1. Weighted the 2000 lbs.
2. Had 1000hp
3. 19000 rpm redline
4. 300 lbs of flat torque that was full at 2000 rpm
5. Almost no drag
6. Big sticky slicks

OH wait that a Formula One car

 

[QUOTE]Originally posted by FYRHWK1
[B]

 

[QUOTE]Originally posted by wc_one
[B]

Engine torque is measured in foot pounds.

 

I don't think the comprehension is the problem. It's admitting that they could be wrong that's the problem.


I may not pull as hard as your car, but I pull longer.

 

Zoran, you're almost there but you're not quite correct. Consider the acceleration of an S2000 at 6000 rpm in first gear, and compare that to the acceleration of an S2000 at 6000 rpm in 5th gear. Same HP, but vastly different accelerations.

You can precisely calculate a car's acceleration in Gs if you know three things - how much torque is being applied to the car's drive wheels, the diameter of those wheels, and how much the car weighs.

That, at least, everybody should be able to agree on - it's simple highschool physics. Right?

The part where it gets tricky and people start disagreeing on is how do you quantify this at-the-wheel torque bit? Is crank torque and good indicator of it, maybe it's hp, or is it something else entirely? Basically it boils down to hp being the best metric, and here's why.

There are certain things we can take for granted in the real world. One, all car's tires are about the same diameter, and two, all cars redline at about the same speed. Now before anybody gets their knickers in a knot, obviously that doesn't always hold true. Tire diameters can vary by quite a bit, and transmissions can have very different setups. Hell, some ultra-high hp cars (like the McLaren F1 and Saleen S7) can go over 60mph in first gear. You'll just have to accept that nothing is precise in this discussion.

So now we need to get back to calculating the amount of torque at the wheels. To figure this out, we need to know two things - first the engine's crank torque, and second the total gear reduction (includes transmission, rear end and any other secondary reductions in the line.) But given the generalization that most cars redline first gear somewhere around the same speed, we don't have to know those exact numbers - we can use another figure that's a good indicator.

Namely, horsepower. This is because of the relationship of horsepower to torque. At a given engine speed, hp = (rpm * torque) / 5252. Obviously, if the torque stays the same but it's available at twice the rpm, you get twice the hp. If that's all we did, the acceleration of the car in Gs wouldn't change. However, you must keep in mind that at the same time we double the rpms available, we must also double the gear reduction in order to maintain the same mph at the new redline. Which in turn doubles the amount of torque produced a the wheels. That's how you can increase a car's acceleration without increasing it's engine torque.

Therefore there are two methods for determining a car's ability to accelerate. 1) Look at a car's engine crank torque, total gearing, and mass. 2) Look at a car's horsepower and mass.

Obviously the approximation of method 2 has some complications in the form of torque curve shape and more accurate gear ratio measurements. But in the absence of the desire to do gear ratio calculations to determine drive wheel torque, it's really the best way to estimate a car's acceleration.

Zoran's example of the two cars with the same torque and weight with vastly different accerations is spot-on.

 

[QUOTE]Originally posted by Destiny2002
[B]Evidently I've completely wasted my time typing because those that read without trying to comprehend will continue to misquote me, repeat musunderstandings that I've cleared up, and contradict me without supporting evidence.