topher

Can someone explain how horsepower and torque translate to real-world performance? Specifically, what is the difference between a car that has 270 HP, 236 ft-lbs torque versus a car that has 260HP, 265 ft-lbs torque?

Also, when these numbers are printed in brochures and press releases, where is torque measured? At the crank? Wheels? How does the difference matter?

TIA-

topher

04acura tl

tq will get you off the line hp will keep you going!
it is usally measured at the crank.
unless stated at the wheels.
I would take the 260hp with the 265 tq over the 270hp and 236tq if the choices were givin in the same car...

cM3go

I think the TL's power (HP) is more than sufficient. What it needs is a little low end torque. Anyone with a TL looking for engine performance mods to make their car faster should look at mods that increase torque, and even more so at the low end.

btw, the TL has 238 lbs-ft of torque, not 236

topher

But that would create significant torque-steer since it is all going to the front wheels. I am sure this is why Acura put it out the way it is.

And two pounds really doesn't matter - unless it is on your wife

hrana98

You can judge on the numbers alone. You also have to look at the transmission gear ratios along with the final drive ratio. All of these things together will determine how well the car will move.

lindros2

That's not entirely accurate.

The behavior of VTEC (and iVTEC, VANOS/Double VANOS/etc.) engines is similar to a turbo - a lot of power at high RPM's. Although the S2000 is rear wheel drive (and a 4-cylinder), it has 240HP but very low torque numbers (162 lb-ft).

It doesn't have to do with that the car is FWD.

Just as another point of reference, the BMW M3's S54 engine (with the Double VANOS system) produces 333HP (343 in Europe) with only 262 lb-ft of torque. The new M5's V10 does 500HP and 383 lb-ft.

-josh

SouthernBoy

Horsepower is defined as work over time. One horsepower = 550 pounds lifted 1 foot off the ground in 1 second or 33,000 pounds lifted 1 foot off the ground in 1 minute. Torque is a constant, twisting force.

One of the simplest ways to understand the two is this. Suppose you are traveling down a two-lane road when you come upon a slower moving car and you want to pass him. You pick your time and spot and make your move. But them about two-hundred yards ahead, a car pulls out of a side road, heading in your direction, so you downshift to a lower gear and nail the throttle. The engine hits 4000 RPM from the downshift and starts to climb quickly from the full throttle. This is horsepower at work for you.

Now you are driving on that same two-lane road, running the A/C and using the cruise control. As you start to ascend an upgrade, you notice that the RPMs don't fall off and, of course, neither does your speed. And you recall in your previous 4-cylinder sedan, this was common place. That's torque at work for you.

For some reason over the years, the car manufactures have managed to sell the public on horsepower and that's what they advertise for the most part. But in reality, what most people are really talking about when they talk about power, is torque. Torque is what you feel ALL the time when driving. Horsepower is only felt under more throttle coupled with more RPMs.

Years ago, it was common for engines to output quite a bit more torque than horsepower and that was because engines were larger (more cubic inches). Here's a good example. In 1965, Chevrolet offered the Corvette with a 327 fuel injected engine rated at 375 HP and as I recall, 365 lb/ft of torque. In 1966, Chevy offered the L78 396 in the Chevelle: an engine rated at 375 HP and 415 lb/ft of torque. Now which one do you think would win in a drag race? First you have to see where these numbers (RPMs) take place. I just so happens, they're pretty close for their peaks. As to who would win? The 396/375 Chevelle would eat the Corvette for breakfast.. no contest.

Another thing that was fairly common in the 60's, at least at General Motors. The maximum torque ratings were generally pretty much true. So an engine rated at 460 lb/ft of of torque at 4400 RPM was really doing that. But Chevy took their horsepower ratings at a lower RPM to satisfy the insurance companies and get their cars at the top of drag racing classes (when the classes were based upon weight / advertised HP). So the engine I just mentioned would be rated at 425 HP at around 6200 but the power was still climbing there and didn't reach its peak until around 6700 where it was in the area of 450 HP. Chevy did this a lot.

As for having an engine of 260 Hp and 265 lb/ft of torque over one rated at 270 HP and 236 lb/ft of torque (ours is 238 lb/ft incidently), it depends upon where those numbers occur. If they're in the same range, the 260/265 engine is definitely the one to go with.

topher

Thanks for the clarification!

wackjum

Torque is a force. Specifically, it is a twisting force. If you had a one pound weight attached to a level weightless one foot long bar that was attached to a motor, the motor would have to generate 1 lb/ft of torque to keep the bar stationary.

Horsepower is work over time.

If you were pushing a lawn mower across the grass at 5 mph, you're exerting energy and doing work. If that lawn mower suddenly hit super thick Texas style grass, you'd come to a stop. You'd still be pushing hard but the lawn mower won't go anywhere. Your work over time has dropped to zero.

A guy named Watt decided that a single horse connected to a rope that went over a pulley and down a well or mineshaft could pull (thereby lift) a 550 lb weight one feet per second. Conversely, a horse would be able to lift 1 lb of weight 550 feet in one second. Either way, the amount of work over time is the same. Remember the torque one foot bar one lb weight thing? Well lifting a 1 lb weight 550 feet means the horse is generating 550 lb/ft of torque. If you multiply it out, 550 lb/ft x 60 sec = 33,000 lb/ft per minute. This is exactly one horsepower.

topher

Very thorough explanation - thanks.

So when you hear about "low-end torque" - that's power at low RPMs which gives that take-off feel, right? That is the twisting force that ultimately turns the wheels is high so they turn with more force, yes?

I am still confused about how horsepower translates to actual performance (other than usually more = faster) especially since torque seems to relate to accelleration if I am understanding you correctly.

Let me put this in comparison form - The TL is 270/238 and the G35 is 260/260, both at about 6100RPM/4900RPM respectively. The TL is @200 lbs heavier. Yet both the TL and the G35 sedans are roughly 6.6 second 0-60 times and a 15.1 1/4 mi. in a 5A config.

How can performance be so close when these numbers are so different?

jdone

Answer: different gear ratios

Road Rage

It is a matter of useable power. If you had one gear, having a lot of torque would be preferable to a lot of HP at high RPM.

A truck with 150 HP and 700 pounds of torque will be able to move itself off the line, and pull a heavy load as well. It generally will have a low top speed, partially because of its aero drag, but also because all that torque runs out of gearing at some point, and the high torque is usually diesel-sourced, so it has has a relatively narrow power bandwidth.

An F1 car may have 1000 HP, and 300#'s of torque - it needs gearing to allow it to accelerate like blazes, and in top gear, to reach dizzying speeds, since its bandwidth is large, but oriented toewards the higher RPM range.You need all the gears to keep it doing its "work" in that sweet spot of RPM.

For street driving, with 5 or 6 speeds, it is great to have a power curve shaped like a plateau. It rises fast, and stays flat up to and just past red line. The SVT Cobra 4.6L DOHC has it - the power adder (the supercharger) provides gobs of torque just off idle, and maintains it up to redline. So the car is quick (accelerates) AND fast (has high top speed). With a few tweaks (I invested about $1k) like a better exhaust, a slightly smaller blower drive pulley, and a dyno-tuned fuel/timing map chip, I improved RWHP and torque by over 100 each.

I have cars that exemplify the best of both approaches. The light, 6-speed S2000 is nimble andf capable of high speeds because it has a close-ratio transmission to overcome its relatively puny torque stats, and revs to over 8k RPM, making a lot of power in the last few thousand RPM, where the VTEC turns it into a screaming banshee. The high RPM with HP allows it to exceed 160 mph!

The SVT Cobra has gobs of torque, and a flat HP curve, with good vreathing well past 6K RPM. So its top gear can be a true overdrive, and in 5th or 6th, it can get to outrageous top speeds quickly. In 6th, I have seen a calibrated top in excess of 175 mph, with the speed limiter programmed out of my special chip. The upshift light is also gone. With a bit more spark advance down low, the car just pulls and pulls, I can smoke an S2000 starting in 2nd gear.

Rule of thumb?
A high torque car is a street monster, and almost always very quick.

Fast means the power (torque @ a given RPM) isa maintained into the higher RPM.

Look at the formula for HP and you will see it is a time constant derivative - it measures work performed, whiule HP measures work capability. Both can "work" well, as long as the low torque car is light, or has enough gears to make use of its RPM capability.
T = (HP x 5252)/rpm

HP = rpm x T(torque)
5252(constant)

A good reference tool:
http://www.elec-toolbox.com/Formulas/Motor/mtrform.htm

I have an amplifier for my hi-fi rig that can produce 1/2 HP per channel! That is a lot of work.

cvajs

alot of tech info posted.

in simple terms, torq will put you back in your seat. you need HP to win the 1/4 mile.

bruce.augenstein@comcast.

Horsepower and Torque - a Primer

There's been a certain amount of discussion, in this and other files, about the concepts of horsepower and torque, how they relate to each other, and how they apply in terms of automobile performance. I have observed that, although nearly everyone participating has a passion for automobiles, there is a huge variance in knowledge. It's clear that a bunch of folks have strong opinions (about this topic, and other things), but that has generally led to more heat than light, if you get my drift. This is meant to be a primer on the subject.

OK. Here's the deal, in moderately plain English.

Force, Work and Time

If you have a one pound weight bolted to the floor, and try to lift it with one pound of force (or 10, or 50 pounds), you will have applied force and exerted energy, but no work will have been done. Work requires movement. If you unbolt the weight, and apply a force sufficient to lift the weight one foot, then one foot-pound of work will have been done. If that event takes a minute to accomplish, then you will be doing work at the rate of one foot-pound per minute. If it takes one second to accomplish the task, then work will be done at the rate of 60 pound feet per minute, and so on.

In order to apply these measurements to automobiles and their performance (whether you're speaking of torque, horsepower, Newton meters, watts, or any other terms), you need to address the three variables of force, work and time.

A while back, a gentleman by the name of Watt (the same gent who did all that neat stuff with steam engines) made some observations, and concluded that the average horse of the time could work at a rate that would lift a 550 pound weight one foot in one second, thereby performing work at the rate of 550 pound feet per second, or 33,000 pound feet per minute. He then published those observations, and stated that 33,000 pound feet per minute of work was
equivalent to the power of one horse, or, one horsepower.

Everybody else said okay.

For purposes of this discussion, we need to measure units of force from rotating objects such as crankshafts, so we'll use terms that define a twisting force, such as torque. A foot pound of torque is the twisting force necessary to support a one pound weight on a weightless horizontal bar, one foot from the fulcrum.

In fact, what standard engine dynamometers actually measure is torque (not horsepower) by using a resistance to hold the engine at a constant speed while at full throttle, and then measuring the resistance required to keep the engine from accelerating. Then we can calculate actual horsepower by converting the twisting force of torque into the work units of horsepower.

Here’s how:

Visualize that one pound weight we mentioned, one foot from the fulcrum on its weightless bar. If we rotate that weight for one full revolution against a one pound resistance, we have moved it a total of 6.2832 feet (Pi * a two foot circle), and, incidentally, we have done 6.2832 pound feet of work.

Okay. Remember Watt? He said that 33,000 pound feet of work per minute was equivalent to one horsepower. If we divide the 6.2832 pound feet of work we've done per revolution of that weight into 33,000 pound feet, we come up with the fact that one foot pound of torque at 5252 rpm is equal to 33,000 pound feet per minute of work, and is the equivalent of one horsepower. If we only move that weight at the rate of 2626 rpm, it's the equivalent of 1/2 horsepower (16,500 pound feet per minute), and so on. Therefore, the following formula applies for calculating horsepower from a torque measurement:

Torque * RPM
---------------- = Horsepower
5252

This is not a debatable item. It's the way it's done. Period.

The Case for Torque

Now, what does all this mean in car land?

First of all, from a driver's perspective, torque rules, to use the vernacular. Any given car, in any given gear, will accelerate at a rate that exactly matches its torque curve (allowing for increased air and rolling resistance as speeds climb). Another way of saying this is that a car will accelerate hardest at its torque peak in any given gear, and will not accelerate as hard below that peak, or above it. Torque is the only thing that a driver feels, and horsepower is just sort of an esoteric measurement in that context. 300 pound feet of torque will accelerate you just as hard at 2000 rpm as it would if you were making that torque at 4000 rpm in the same gear, yet, per the formula, the horsepower would be *double* at 4000 rpm. Therefore, horsepower tends to not be particularly meaningful from a driver's “belt in the back” perspective, and the two numbers only get friendly at 5252 rpm, where horsepower and torque always come out the same.

In contrast to a torque curve (and the matching push back into your seat), horsepower rises rapidly with rpm, especially when torque values are also climbing. Horsepower will continue to climb, however, until well past the torque peak, and will continue to rise as engine speed climbs, until the torque curve really begins to plummet, faster than engine rpm is rising. However, as I said, horsepower doesn't have much to do with what a driver feels.

You don't believe all this?

Fine. Take your non-turbo car (turbo lag muddles the results) to its torque peak in first gear, and punch it. Notice how the seat belted you in the back? Now take it to the power peak, and punch it. Notice that the belt in the back is a bit weaker? Okay. Now that we're all on the same wavelength (and I hope you didn't get a ticket or anything), we can go on.

Torque is What You Feel, but Horsepower Rules

So if torque is so all-fired important (and feels so good), why do we care about horsepower? Because (to quote a friend), "It's better to make torque at high rpm than at low rpm, because you can take advantage of gearing."

For an extreme example of this, I'll leave car land for a moment, and describe a waterwheel I got to watch a while ago. This was a pretty massive wheel (built a couple of hundred years ago), rotating lazily on a shaft that was connected to the works inside a flour mill. Working some things out from what the people in the mill said, I was able to determine that the wheel typically generated about 2600(!) pound feet of torque. I had clocked its speed, and determined that it was rotating at about 12 rpm. If we hooked that wheel to, say, the drive wheels of a car, that car would go from zero to twelve rpm of its drive wheels in a flash, and the waterwheel would hardly notice.

On the other hand, twelve rpm of the drive wheels is around one mile per hour for the average car, and, in order to go faster, we'd need to gear it up. If you remember your junior high school science classes and the topic of simple machines, you'll remember that to gear something up or down gives you linear increases in speed with linear decreases in force, or vice versa. To get to 60 miles per hour would require gearing the output from the wheel up by 60 times, enough so that it would be effectively making a little over 43 pound feet of torque at the output (one sixtieth of the wheel's direct torque). This is not only a relatively small amount; it's less than what the average car needs in order to actually get to 60. Applying the conversion formula gives us the facts on this. Twelve times twenty six hundred, over five thousand two hundred fifty two gives us:

6 horsepower.

OOPS. Now we see the rest of the story. While it's clearly true that the water wheel can exert a bunch of force, its power (ability to do work over time) is severely limited.

At the Drag Strip

Now back to car land, and some examples of how horsepower makes a major difference in how fast a car can accelerate, in spite of what torque on your backside tells you.

A very good example would be to compare the LT-1 Corvette (built from 1992 through 1996) with the last of the L98 Vettes, built in 1991. Figures as follows:

Engine--------------Peak HP @ RPM-------------Peak Torque @ RPM
L98---------------------250 @ 4000----------------------340 @ 3200
LT-1--------------------300 @ 5000----------------------340 @ 3600

The cars are essentially identical (drive trains, tires, etc.) except for the engine change, so it's an excellent comparison.

From a driver's perspective, each car will push you back in the seat (the fun factor) with the same authority - at least at or near peak torque in each gear. One will tend to feel about as fast as the other to the driver, but the LT-1 will actually be significantly faster than the L98, even though it won't pull any harder. If we mess about with the formula, we can begin to discover exactly why the LT-1 is faster. Here's another slice at that torque and horsepower calculation:

Horsepower * 5252
-------------------------- = Torque
RPM

Plugging some numbers in, we can see that the L98 is making 328 pound feet of torque at its power peak (250 hp @ 4000). We can also infer that it cannot be making any more than 263 pound feet of torque at 5000 rpm, or it would be making more than 250 hp at that engine speed, and would be so rated. In actuality, the L98 is probably making no more than around 210 pound feet or so at 5000 rpm, and anybody who owns one would shift it at around 46-4700 rpm, because more torque is available at the drive wheels in the next gear at that point. On the other hand, the LT-1 is fairly happy making 315 pound feet at 5000 rpm (300 hp times 5252, over 5000), and is happy right up to its mid 5s red line.

So, in a drag race, the cars would launch more or less together. The L98 might have a slight advantage due to its peak torque occurring a little earlier in the rev range, but that is debatable, since the LT-1 has a wider, flatter curve (again pretty much by definition, looking at the figures). From somewhere in the mid-range and up, however, the LT-1 would begin to pull away. Where the L98 has to shift to second (and give up some torque multiplication for speed, a la the waterwheel), the LT-1 still has around another 1000 rpm to go in first, and thus begins to widen its lead, more and more as the speeds climb. As long as the revs are high, the LT-1, by definition, has an advantage. As a practical matter, a typical L98 6-speed car might cover a quarter mile with an ET of around 14 seconds at around 99 or 100 mph, while the equivalent LT-1 will generally be at least a half second faster, at 104 – 105 mph. Mind you, as I’ve mentioned, the LT1 doesn’t pull any harder – just longer.

There are numerous examples of this phenomenon. The Acura RSX Type S, for instance, is faster than the garden variety RSX, not because it pulls particularly harder (it doesn't), but because it too pulls longer in each gear. It doesn't feel particularly faster, but it is.

A final example of this requires your imagination. Figure that we can tweak an LT-1 engine so that it still makes peak torque of 340 pound feet at 3600 rpm, but, instead of the curve dropping off to 315 pound feet at 5000, we extend the torque curve so much that it doesn't fall off to 315 pound feet until 15000 rpm. Okay, so we'd need to have virtually all the moving parts made out of unobtanium, and some sort of turbo charging on demand that would make enough high-rpm boost to keep the curve from falling, but hey, bear with me.

If you raced a stock LT-1 with this car, they would launch together, but, somewhere around the 60-foot point, the stocker would begin to fade, and would have to grab second gear shortly thereafter. Not long after that, you'd see in your mirror that the stocker has grabbed third, and not too long after that, it would get fourth, but you wouldn't be able to see that due to the distance between you as you crossed the line, still in first gear, and pulling like crazy.

I've got a computer simulation that models an LT-1 Vette in a quarter mile pass, and it predicts a 13.38 second ET, at 104.5 mph. That's pretty close (actually a bit conservative) to what a stock LT-1 can do at 100% air density at a high traction drag strip, being power shifted. However, our modified car, while belting the driver in the back no harder than the stocker (at peak torque) does an 11.96, at 135.1 mph - all in first gear, naturally. It doesn't pull any harder, but it sure as heck pulls longer. It's also making 900 hp, at 15,000 rpm.

Of course, looking at top speeds, it's a simpler story...

At the Bonneville Salt Flats

Looking at top speed, horsepower wins again, in the sense that making more torque at high rpm means you can use a stiffer gear for any given car speed, and have more effective torque (and thus more thrust) at the drive wheels.

In fact, operating at the power peak means you are accelerating the absolute best you can at any given car speed, measuring torque at the drive wheels. I know I said that acceleration follows the torque curve in any given gear, but at any given car speed, horsepower is the absolute governor of how fast you can accelerate. In fact, horsepower is a kind of shorthand in this context. No matter what gear you’re in or what the final drive ratio is, more power at that speed means more acceleration because you’ll have more torque at the drive wheels. I'll use a BMW example to illustrate this:

At the 4250 rpm torque peak, a 3-liter E36 M3 is doing about 57 mph in third gear, and, as mentioned previously, it will pull the hardest in that gear at that speed when you floor it, discounting wind and rolling resistance. In point of fact (and ignoring both drive train power losses and rotational inertia), the rear wheels are getting 1177 pound feet of torque thrown at them at 57 mph (225 pound feet, times the third gear ratio of 1.66:1, times the final drive ratio of 3.15:1), so the car will bang you back very nicely at that point, thank you very much.

However, if you were to re-gear the car so that it is at its power peak at 57 mph, you’d have substantially more torque at the drive wheels. You'd have to change the final drive ratio to approximately 4.45:1 in order to do this, but with that final drive ratio installed, you'd be at 6000 rpm in third gear at 57 mph, where the engine is making 240 hp. Going back to our trusty formula, you can ascertain that the engine is down to 210 pound feet of torque at that point (240 times 5252, divided by 6000). However, doing the arithmetic (210 pound feet, times 1.66, times 4.45), you can see that you are now getting 1551 pound feet of torque at the rear wheels, making for a nearly 32% more satisfying belt in the back.

Any other rpm (other than the power peak) at a given car speed will net you a lower torque value at the drive wheels. This would be true of any car on the planet, so, you get the best possible acceleration at any given vehicle speed when the engine is at its power peak, and, theoretical "best" top speed will always occur when a given vehicle is operating at its power peak.

Force, Work and Time

At this point, if you're getting the idea that work over time is synonymous with speed, and as speed increases, so does the need for power, you've got it.

Think about this. Early on, we made the point that 300 pound feet of torque at 2000 rpm will belt the driver in the back just as hard as 300 pound feet at 4000 rpm in the same gear - yet horsepower will be double at 4000. Now we need to look at it the other way: We NEED double the horsepower if we want to be belted in the back just as hard at twice the speed. As soon as we factor speed into the equation, horsepower is the thing we need to use as a measurement. It's a direct measure of the work being done, as opposed to a direct measure of force. Although torque and horsepower are obviously related (and each in a sense a function of the other), a good way to think about this is that torque determines the belt in the back capability, and horsepower determines the speed at which you can enjoy that capability. Do you want to be belted in the back when you step on the loud pedal from a dead stop? That's torque. The water wheel will deliver that, in spades. Do you want to be belted in the back in fourth gear at 100 down the pit straight at Watkins Glen? You need horsepower. In fact, ignoring wind and rolling resistance, you'll need exactly 100 times the horsepower if you want to be belted in the back just as hard at 100 miles per hour as that water wheel belted you up to one mile per hour.

Of course, speed isn't everything. Horsepower can be fun at antique velocities, as well...

"Modernizing" The 18th Century

Okay. For the final-final point (Really. I Promise.), what if we ditched that water wheel, and bolted a 3 liter E36 M3 engine in its place? Now, no 3-liter BMW is going to be making over 2600 pound feet of torque (except possibly for a single, glorious instant, running on nitromethane). However, assuming we needed 12 rpm for an input to the mill, we could run the BMW engine at 6000 rpm (where it's making 210 pound feet of torque), and gear it down to a 12 rpm output, using a 500:1 gear set. Result? We'd have *105,000* pound feet of torque to play with. We could probably twist the entire flour mill around the input shaft, if we needed to.

The Only Thing You Really Need to Know

For any given level of torque, making it at a higher rpm means we increase horsepower - and now we all know just exactly what that can do for us, don't we? Repeat after me: "It's better to make torque at high rpm than at low rpm, because you can take advantage of gearing."

Thanks for your time.

Bruce Augenstein

ChuckDu

Wow! Only 2 1/2 years to write that up. Nice explanation, Bruce.

Atrain

I've seen my dyno graph compared to a similar cars the difference between the two were the type of supercharger.

I used an Eaton M90S and intercooler with a 2000 Mustang GT 4.6L SOHC V-8. The engine had a static compression ratio of 9.0:1 and I was making 10-psi of boost and most of it right idle. My car made 325 RWHP and 380 RWTQ (SAE) on a dynojet.

The other car was very similar except it used a Vortech supercharger @ 8-psi without an intercooler. His static compression ratio was higher at 10.5:1 due to the use of late model Mustang PI heads on a stock 1996 4.6L engine block. Same cars, same weight, same automatic transmissions, same IRS suspensions. We are talking about 4,000 lb. T-Birds here.

His dyno chart showed a peak maximum RWHP of 368 while his torque was around 353 at the wheels.

Just by looking at the numbers you would say his car beat mine in a race right?

I mean I'm down by 43 RWHP compared to his numbers. Well look at the chart for yourself and you be the judge. My car is on the right side of the graph and his car is on the left side.

RPM..........RWHP......RWTQ.........RPM........... .....RWHP.......RWTQ 2000.........90...........242..........2000....... ...........140.8......355.5
2100........100..........252..........2100........ ..........142.5.......356.7
2200.........105..........252..........2200....... ...........149........355.7
2300.........110..........260..........2300....... ..........156.7.......357.8
2400.........117..........265..........2400....... ...........164.5........360
2500.........125..........265..........2500....... ...........171.5........360.4
2600.........135..........263...........2600...... ............181..........356.6
2700.........140...........275..........2700...... ...........189.1.........367.9
2800.........150............276..........2800..... ............197..........369.5
2900.........160............288...........2900.... ............204.6.........370.6
3000.........165............285...........3000.... ...........213.7.........374.1
3100.........170............290...........3100.... ...........223.2........378.1
3200.........170............285............3200... ...........230.8.......378.9
3300.........180............284............3300... ...........236.9.......377.1
3400..........190............290...........3400... ............244.3.......377.4
3500..........200............300............3500.. ............250.7.......376.2
3600............210...........312...........3600.. ............258.3.......376.8
3700............230............322..........3700.. ............265.7........377.1
3800.............240............333.........3800.. .............272.6........376.8
3900.............250...........340...........3900. .............278.6........375.1
4000.............260............338..........4000. .............283.4........372.1
4100.............265.............333..........4100 ............288.3.........369.4
4200..............275............340..........4200 .............293.8........367.4
4300..............285............350.........4300. ..............298.9..........365.1
4400...............290............350.........4400 ..............302.4...........361
4500..............300.............352.........4500 ..............304.5........355.4
4600...............310............353..........460 0..............308.1........351.8
4700...............320............350...........47 00.............311.6..........348.2
4800..............320.............348............4 800.............314.4...........344
4900..............322.............342............4 900.............314.9.........337.5
5000..............320.............341............. 5000............315.5.........331.4
5100..............322.............340............. 5100............321.5..........331.1
5200..............330.............338............. 5200.............321.1..........324.3
5300..............340..............330............ .5300.............320............317.1
5400..............345..............328............ ..5400............320.2.........311.4
5500..............348................325.......... ...5500............324.2.........309.6
5600..............350...............323........... ...5600...........322.8..........302.8
5700...............360...............320.......... ...5700...............n/a............n/a
5800...............365...............318.......... ...5800................n/a............n/a
5900...............360................320......... ....5900...............n/a............n/a
6000...............355................308......... ....6000.................n/a............n/a
MAX...............368.5..............353.7........ ....MAX.............325.1..........379.5



There is no way you can argue that I basically owned his set-up up to 4,500 rpm. Then I fall behind and by 5,000 rpm he has a slight edge. At 5,500 rpm he is making 24 more rearwheel horsepower and 15 more RWTQ.

Obviously my engine was running out of steam so we shut it down at 5,700 rpm. The Vortech blower was just starting to come alive so his engine was making more power closer to the physical redline.

He peaked 368 RWHP at some ultra high rpm that he most likely would never see on the street. I guess it also helps to point out that his set-up grenaded a few months after his dyno run sending the connecting rods out of the engine block.

My engine is still running strong 6 YEARS later!

NOW THE MILLION DOLLAR QUESTION...Which car ran a faster 1/4 mile time and why?

A-Train

mishar

Lots of talking about simple physics. And all what it is:

power / rpm = torque

So those curves are closely related. If you divide power at any given rpm with that rpm you will get torque at that rpm. I am not using any constants because they are there just to correct imperfections of measuring system.

Now transmission:

torque(cs) x i = torque(w)

So, if you multiply crankshaft torque with gear ratio, including final drive ratio, you will get torque at the wheels. In the real world you have to subtract losses because transmission is not perfect.

Next are the wheels:

torque(w) / r = F

So, you divide wheels torque with wheels radius and get force that push your car forward.

Then comes air resistance:

F – F(ar) = F(a)

From pushing force you have to subtract air resistance at given speed in order to get force available to create acceleration.

And finally:

F(a) / m = a

You divide that available force with mass that includes car, gas, you, your passengers, all junk in your trunk … and get acceleration at any given rpm in any given gear.

This can give the answers to the most questions. You just have to evaluate right equation.

darksom1

Hmmm...can I quote you guys on that? All of you?

camporealer

The above explanations are great....

I am a little simple today. I always think of it

Torque = Acceleration

HP = Top Speed

In everyday driving, when you rarely get anywhere near your car's max speed. Torque = Fun....

mishar

Well, that’s one of those short explanations that sounds, but actually make people confused. You are mixing big low rev engines with torque and small high rev engines with power. And that’s only when you are talking about fun part. When you are talking about acceleration you are completely wrong. More power makes better acceleration as well as higher speed.

bruce.augenstein@comcast.

My guess is that you ran the better ET, and he probably had a better trap speed.

You get the jump, and his high rpm power advantage isn't enough to make up the difference over a quarter mile.

Bruce

mishar

That depends on his gearbox and especially clutch. If he can get high-rev launch and keep rev high try the gears he would be faster. But since you are posting the question that probably was not the case. But if you meet him on a racing track he would be faster anyways.

geekybiker

See, this is where almost all torque vs HP arguements make the biggest mistake. When you're talking f=ma we dont care about the engine torque. That's really immaterial. What we care about is the wheel torque. And again the old addage That "hp is better than torque because it can take advantage of gearing" is what counts. The same hp= the same wheel torque after gearing (given good transmission design.)