Clearly a simplistic explanation. Torque and HP are part of the same equation but there are different reasons for favoring one over the other. The advantage of torque in acceleration is that it is there when you need it. If torque is a constant then you can put your foot down and have it on demand (flat curve is best). RPM is not constant and not instantaneous. If your little engine has the necessary RPM at the time you want the torque then you can achieve the same acceleration as a bigger engine with more torque at lower RPM.

Mustang GT vs. S2000: The mustang's V8 has the same torque at 2000 RPM as the S2000 at 6500 RPM. These are the RPMs required to achieve the same acceleration. The Mustang GT is a tad slower than the S2000 in acceleration due to the additional weight it must haul. An S2000 with Mustang V8 power and torque will beat an F20C powered S2000 hands down. People say that this torque differential makes the biggest difference from a standing stop but they are wrong. Since from a standing start you can generate enough instantaneous RPM to match the raw torque of the V8. The biggest difference, and the primary weakness of the high RPM low torque approach is corner exit speed.

When exiting a corner you have little control over RPM (it's a product of vehicle speed and the gear you have selected) thus the acceleration you can achieve is limited. With a high torque engine, RPMs are not as important. A high torque engine will power out of corners and onto straights more reliably and near maximum acceleration where as we get what we get. Anyone who's lagged up the hill between turns 3 and 4 of the Willow Springs fast track knows what I'm talking about.

Torque is torque. HP is a function of torque and RPM. RPM is a multiplier of torque and unless you have enough of it to balance the equation, you'll lose. If we could run our engines at 8500 RPM all the time....

 

The other thing wrong with the Mustang V8 in particular (unless you are towing a boat) is its 5500 RPM redline. RPM is a multiplier and if you could (and many do) boost the redline to 7000 RPM or higher it would smoke most everything.

The article fails to account for the Mustang's dynamic power-to-weight ratio: as parts fall off the Mustang it gets quicker.

 

I had an actual LOL experience!

 

To put it into one sentence, torque figures at the engine are not as important as drive force at the wheels. We take the torque # at the engine and we gear it up, since the s2k can rev higher, it can be geared shorter and thus multiply available engine torque higher. Why doesn't the mustang also gear higher if it is a a good thing? Because your engines RPM is directly tied to the speed in mph of your wheels, if you use gears that are too short on a car that can not rev high, you end up with some really wacky and low speeds in each gear. Since the s2k can rev to 9000 while the mustang to 5500, this means the s2k can be geared 63 % shorter. To put this into an understandable situation, it is like taking the s2ks peak torque of 153 and multiplying it by 163%, it gives 250 pounds of torque at peak. These are only numbers at peak, a better indication is torque throughout the RPMs.... Yes if the mustang engine was in the s2k, it would be quicker straight line because it makes more HP. HP gives us a better picture of powerband and engine flexibility as it takes into account torque and RPMs...

There is your one sentence explanation.

If anyone wants to read more than a sentence, read the link posted...

 

It's funny, every board/distr list I've been on goes through this same discussion with the same questions...

IN any case, weight does affect the top speed a little - indirectly because of suspension compression (which then affects aerodynamics under the car) and also rolling resistence of the tires.

 

Why has no one mentioned engineering? Simply put, if the HP and Torque figures were the same via the same engine the S2000 would still beat a Mustang, and the more weight you take off of the cars the more the S2000 would gain an advantage because it's engineered to put the power down better. I have several friends with Mustang GT's, and the car has an adhesion problem for sure, it has it's sweet spot and you better stick to it. I've seen mildly modified Mustangs destroy built 351 mustangs at the street races because of the ability to put the power to the pavement instead of turning it into smoke. For more on this principal see: Keith Black. Of course, put slicks on the two cars and take them to a track and the outcome would be very different, but what matters to me is what I can do on the street, and it takes a talented driver in a mildly tuned Mustang to beat me.

Andrew

 

cthree has touched on a key point that should be considered.

What really matters is your power to weight ratio over your normal operating rpm range. If we assume weight is constant (say, comparing one S2K to another) then what really matters is average power over your normal operating rpm range. With an S2K on a racetrack, this typically involves 5000 rpm to 9000 rpm. Where the F20C, in stock form, loses out in this comparison is in the 5000 to 6000 rpm range. You can help this with power mods, or you could regear 1st, 2nd and 3rd gear to help avoid this situation (Honda was focused on making sure we could hit 60 mph in 2nd gear, even though that isn't optimal gearing for our cars to get off the line well).

Where high absolute torque cars have an advantage, as cthree pointed out, is in coming out of corners where our S2K might be below 6000 rpm. Their average power/weight ratio coming out of the corner is higher than ours, hence they pull some distance. Strong acceleration at the slowest point on the racetrack is where you can make your biggest gains vs. an opponent. Hence the attempts by companies like Spoon to improve midrange for their S2K race car.

UL

 

[QUOTE]Originally posted by ultimate lurker

Where high absolute torque cars have an advantage, as cthree pointed out, is in coming out of corners where our S2K might be below 6000 rpm.

 

Maybe you should go do a track first But seriously, like cthree said:

You choose your entry speed and that typically determines the gear and RPM range. It's a compromise. For instance, you can probably choose to take a 50mph turn in 2nd gear, but as you are powering out, you will have to immediately shift to 3rd gear. So it's probably better to stay in 3rd which would mean you will be at or slightly below VTEC.

 

On a race track exit speed on corners is king, particularly corners followed by a straight. Any loss you take there you have to carry all the way to the next corner. Corners with an exit speed of 50 MPH are killer because you are in 3rd on entry and either need to downshift to 2nd mid corner (You can't downshift on entry as the revs will be too high) or stay in 3rd through the corner and exit with less than opitmal RPMs. The S2000 will do best on tracks without these kind of corners (WIR is not one of them). You can adjust the gearing but really you are just moving the problem somewhere else. If you were racing it this would not be a problem because you would change your gearing to match the course so you don't get those dead-zones on a given track. Since we don't race them competively it's not practical to do this and in the end the dead-zone is of no consequence (it's just a bit frustrating).