Nobody cares about torque anymore!
 

There's no doubt these rotary motors are capable of producing wads of horspower coupled with the light weight equaling a fast car. However, everyone talks about horsepower so much that it overshadows torque. For the dragstrip, ok, put slicks on, dump the car over 4500 and keep it over 4500 to make the car pull down the track, great!
Practically, on the street it is ridiculous. My motor was built by KD Rotary and makes 340hp at the wheels. When 4500 hits, those n/seq-twins kick in like gangbusters and blow the car sideways on street tires. Not very practical for short little blasts in everyday driving.
I had a 1965 Mustang that I raced on the street all the time, torque was always a factor, not so much hp. And a car that runs 13.10 on street tires will smoke a 12 sec slicks car anytime on the street.
So why are most of you buying these big turbos making 450 hp only to run radial tires? Silly. Spend the money in traction and suspension, and the car would be much faster, and that's truely something to brag about. Because, let's get real, all rx7's feel like about a 6 cylinder car under 4000 rpm's...at best. I've been in hot rods with torque and our cars don't have them. Torque is a forgotten word around this site, and until we work on helping the low end, MOST of us our defeating our purpose.
Get some gearing and traction...who gives a shit about a 180mph top end, it's not practical, and if you're caught you won't be driving your car anytime soon anyway.
Ditch the big spooling turbos and make the car torquey to have fun. NO DRAG RADIAL will help hook these cars with a 4500 launch. Not if you are making any decent power.

are you kidding? Its no different with torquey cars. instead of breaking traction at 4500 rpms, you break it at 2k rpms. Whats the difference?

taken from yaw...

Have any of you ever watched Bill O’Rielly on the Fox news channel? You know, the guy with the huge ego, stating his opinion as fact to "save the country" from its own evils. Bill has a section of his daily show devoted ridiculous happenings in the world of politics.

If I were to do my own "Most Ridiculous" item in the world of racing it would be based on the following statement. "Horsepower sells motor cars, but torque wins motor races." This couldn’t be further from the truth.

Like it or not, everything that goes on around us is governed by the laws of physics, and these laws are non-negotiable. The good news is that we don’t have to be Einstein to apply the basic laws of physics to racing. The fact that too few do is the reason that such ridiculous statements are common in racing.

Let’s start with a few definitions. Webster’s dictionary describes torque as "A turning or twisting force." Note that the definition does not imply motion. As applied to an engine, it is simply a measure of the twisting force at the crank/eccentric shaft. Torque is normally rated in Lbs.-Ft. Since pounds feet doesn’t exactly roll off the tongue, most of us refer to it as foot pounds.

Notice that there are two terms. Force (In lbs.) and distance (In ft.). At first it may seem strange to describe a "Turning or twisting force." in terms of distance, but a more detailed description makes it clear. If I were to put a shaft in a bench vice, attach a 1-ft. long lever to the end, perpendicular to the shaft, and then hang a one pound weight off the end of the lever, I would be applying one ft.-lb. to that shaft. Notice that the shaft is not rotating even though a torque is applied to the shaft.

If I were to replace the one-foot lever with a 100-foot lever, I would now be applying 100 ft.-lbs. to the shaft with the same one lb. weight. As you can see, the amount of twisting force on the shaft will vary depending on the length of the arm, and that requires that we specify a measure of distance to properly describe the force seen at the center of the shaft.

Let’s say for instance that I pull the shaft from the vice, and ask you to hold it in your hand. If I do this with a one pound weight hanging from the end of the one foot lever, I will be applying a force of one ft.-lb. to your hand, and you will have no problem holding on to it. If I replace the lever with one that is 10 ft. long, with the same 1lb. weight on the end, (For all these scenarios, we assume that the lever itself is weightless.) You will now have a force of 10 ft.-lbs. applied to your hand, and it will be much harder to keep the shaft from rotating, even though you are still only resisting the one pound weight.

This would have exactly the same effect as setting a torque wrench to 10 ft.-lbs., attaching it to the end of the shaft, and applying force until the wrench clicks. Ten ft.-lbs. is ten ft.-lbs. whether it is applied with a one-foot lever and a ten-pound weight, or a ten-foot lever and a one-pound weight. Torque is equal to the weight, or force, times the length of the lever. It’s that simple.

If a particular engine has a peak torque rating of 200 ft.-lbs., that force is equivalent to attaching a one foot lever to the shaft, and hanging a 200 lb. Weight from the end of it. Or…any other combination of weight and lever length which has the product 200.

Notice that I can take you from easily holding on to the one pound weight, to not even having a chance of holding it just by changing the length of the lever. (Like a one-lb. weight, and a 100-ft. lever.) Of course you say, that’s just leverage! Well…you’re right! Keep that in mind, because it is that leverage that makes all the difference, and a gear is in fact just a clever way to apply leverage between two or more rotating devices.

Let’s say that the shaft used in our example is the input shaft of the transmission from a 1993 RX-7 with the following ratios.

1st 3.483 to 1

2nd 2.015 to 1

3rd 1.391 to 1

4th 1.0 to 1

5th .719 to 1

If the transmission is in 4th gear, one complete revolution of the input shaft will result in one complete revolution of the output shaft, just as if there were a solid shaft running all the way through. If we attach a 1-ft. lever to the input shaft with a 10-lb. weight on the end, the torque at the input shaft will equal 10 ft.-lbs. as we have already determined. Since we have a 1 to 1 ratio from input to output, we will also have 10 ft.-lbs. at the output shaft.

If we were to keep the same weight and lever on the input shaft, but switch the transmission to third gear, we would still have 10 ft.-lbs. at the input shaft, but we would now have 13.91 ft.-lbs. at the output shaft. This value is the product of the input torque and the gear ratio. (10-ft.-lbs. times 1.391 gear ratio equals 13.91 ft.-lbs.) If we were to switch the transmission into 1st gear, the result would be 34.83 ft.-lbs. at the output shaft.

As you can see, a gearbox gives us a simple way to vary the torque through leverage, and it is equivalent to changing the length of the lever. Thanks to gears, we can have any amount of torque that we want! In fact, a bone stock 12A making only 100 ft.-lbs. of torque could be geared to pull an 18-wheeler up a steep hill, as long as we are not in any big hurry to get the job done.

Let’s say that it takes 10,000 lbs of force to pull a heavy weight up a hill. No problem! We could even do it with our stock 1980-GS in 4th gear if we are willing to build a custom ring and pinion gear with a ratio of 100 to 1. (100-ft.-lbs. times transmission gear ratio of 1:1 times ring and pinion gear ratio of 100:1 equals 10,000 ft.-lbs.)

If we are using a tire with a diameter of 24", the distance from the axle center to the ground is exactly one foot, and so the force is equal to 10,000 lbs. Remember, the torque is equal to the lever length times the force. If we re-write that formula to solve for force, force is equal to torque divided by the lever length, and so that 10,000 ft.-lbs. at the rear axle results in 10,000 lbs. of force at the tire contact patch.

With this same information, we can also calculate the acceleration rate of the vehicle, but first we need to consider Newton’s second law of motion, which states that "Acceleration is proportional to force." and "Acceleration is inversely proportional to Mass." This law is normally stated more simply as "Force equals mass times acceleration." or F=MA. If we rewrite this to solve for acceleration, we get A=F/M. To find the rate of acceleration for a vehicle, we simply divide the force (In lbs. at the tire contact patch.) by the mass (Total weight of the vehicle in lbs.)

Let’s calculate the acceleration rate of a 1st. gen. RX-7. The engine has a torque peak of 100-ft.-lbs. In fourth gear, the ratio is 1 to 1, and so the torque at the output shaft is also 100-ft.-lbs. The ring and pinion ratio is 3.909 to 1, and so the torque at the rear axle will be (100 times 3.909) 390.9-ft.-lbs. The tire diameter is 24 inches, and so the lever length (Distance from the center of the axle to the ground.) is 12 inches, or one foot. The resulting force at the tire contact patch will be (390.9-ft.-lbs. of torque divided by lever length of one foot.) 390.9-lbs. of force. The total vehicle weight with a driver is 2600 lbs., and so the acceleration rate in G’s (The force of gravity.) will be force (390.9) divided by mass (2600) which equals .15 G’s.

If we do the same calculations for first gear acceleration, we find that the force at the contact patch is 1,436 lbs., and the acceleration rate is .55 G’s. It’s clear that we have used the gears for leverage, with the result being a greater rate of acceleration in 1st gear. Of course you knew that already, but now you know why.

By now it should be clear that the acceleration rate of a vehicle is determined by the weight, and the force at the contact patch, which is the result of the torque output of the engine, and all the levers/gears between it and the ground.

You’re probably thinking that we have just determined the acceleration rate of the vehicle, and even changed it with gearing, with no mention of horsepower. So torque really is the determining factor right? Wrong! We haven’t considered speed.

We can gain acceleration by changing the gear ratios, but we can’t go very fast in first gear, so what’s the point? We have effectively changed the amount of torque available to accelerate the vehicle, but our top speed is limited to about 25 mph.

Confused yet?

Read on.

OK, so we all know what torque is, now let’s get to horsepower.

Referring once again to Webster’s dictionary, horsepower is defined as "A foot/pound/second unit of power, equivalent to 550 foot/pounds per second."

Put more simply, horsepower is a measure of work done over time, or the rate at which work is done.

So now we have another term to confuse things. As if force and distance weren’t enough, we now have time involved, and the shaft must actually be spinning. Why… Well, if you are just standing there holding on to a shaft with a lever and a weight, you are doing no work. If you stand there long enough, you will feel like you are working, but in fact you are doing no such thing. Don’t believe me? Clamp the shaft back in the vice, and you can leave it there indefinitely without having to feed it, add gas, and any other means of supplying it with energy.

Torque, all by itself does nothing useful. In fact, the definition of torque does not even require that the shaft be moving. I am sure that all of you want your car to do something useful, like take you to the movies, or get you around the track before the other guy. In other words, you need your car to do some work, and you want it to do that work in the least amount of time possible.

If I give you a wagon full of cement blocks, and ask you to pull it one mile up a hill, you would agree that I am asking you to do work. If I ask you and your buddy to each pull a wagon full of cement blocks up the hill, you will both be doing the same amount of work. But…If it takes you an hour, and your buddy does it in 30 minutes we have a very different situation. You have both done the same amount of work, but your buddy, by completing the task in half the time, has proven that he can develop twice the horsepower that you can. You both traveled the same distance, and exerted the same amount of force, but the third term in the definition of horsepower, time, was different.

For those of you who are sticklers for details, the force required to pull the wagon up the hill at a steady speed is equal to the weight of the wagon, times the sine of the angle of the hill. If the wagon weighed 100-lbs., and the hill was at a 45-degree angle, the required force would be (Sine 45 Times 100 lbs.) equals 70.7 lbs.

If we were interested in moving the wagon by driving the wheels rather than pulling it by the handle, we could convert the force to torque by dividing the required force by the radius of the driven wheels. Let’s say that we have 6" diameter wheels. That would give a lever length (Distance from the center of the axle to the ground.) of 3 inches, or .25 feet. The required torque would then be (70.7 lbs. times .25 ft.) which equals 17.675 ft.-lbs.

James Watt, who spent the majority of his life perfecting the steam engine, created the term horsepower. He was looking for a way to measure the rate of work done by a horse so that he could make valid comparisons between horses which did most of the work in those days, and his steam engines which he hoped would do most of the work in the future.

Watt found that on average, a horse could lift 330-lbs of coal 100-ft in one minute. He then stated that the power available from one horse was equal to (330-lbs. times 100-ft.) or 33,000-lbs./ft./min. If you divide that by 60 to convert to lbs./ft./sec. you get 550-lbs./ft./sec. Watt called this one horsepower, which leaves most of us wondering why he didn’t call it one watt. I don’t have the answer to that, but I do know that 746.6 watts equals one horsepower. If you ever see an engine rated in watts, (This is still popular in some countries.) you can divide by 746.6 to determine the horsepower. Or, you can tell you pals that your bone stock 3rd. gen. RX-7 puts out One hundred ninety thousand, three hundred and eighty three watts.
http://www.yawpower.com/Image7.gif



So if one horsepower is equal to 33,000 lbs.-ft. per minute, we can rearrange that to say that horsepower equals torque times rpm, divided by 5252. How do we get there?

In the above formula, force and distance are stated in ft.-lbs., and time is stated in RPM, so we need to convert our terms. First we need to express that 33,000 lbs. of force as 33,000 ft-lbs. As you now know, that is equivalent to a 33,000-lb. weight hanging from a 1-ft. lever. Then we need to express the one-foot per minute as RPM.

The circumference of a circle is defined as the diameter of the circle times Pi, which is 3.14159. We have a one-foot lever, so if we were to spin the shaft, the outer edge of the lever would scribe a 2-foot diameter circle. The circumference of a 2 foot circle is (3.14159 times 2) 6.282 feet. If we divide 1 foot by the distance traveled in a complete revolution (1 divided by 6.282) we get .159 revolutions per minute, which is equal to one foot per minute.

So now we have: One horsepower equals 33,000 lbs.-ft. of torque per .159 RPM.

That’s still kind of ugly dealing with just a fraction of an rpm, so we divide both terms by .159 and we get: one horsepower equals 5252 lbs.-ft. of torque per 1 rpm.

This can be rewritten a few different ways that are valuable to us.

Horsepower equals torque times rpm divided by 5252. Horsepower = (Torque X RPM) / 5252

Torque equals horsepower times 5252 divided by rpm. Torque = (Horsepower X 5252) / RPM

RPM equals horsepower times 5252 divided by torque. RPM = (Horsepower X 5252) / Torque

If you know any two of the terms, you can calculate the third. You might also notice that torque and horsepower will always be equal at 5,252 rpm, horsepower will be greater than torque above 5252 RPM, and torque will be greater than horsepower below 5252 RPM. ALWAYS…NO EXCEPTION! Just look at any dyno sheet, and you will see what I mean. If you see a dyno sheet where this is not true, you can be sure that someone fudged the numbers to help sell a product.

Back to the issue at hand, I’m sure that the coal tugging horse and a wagon full of cement blocks probably doesn’t seem all that relevant to your racecar. So let’s look at things another way.

The definition of horsepower includes three terms. Force, distance, AND time, where torque is simply a force applied over a distance. In the case of Watt’s experiment, the force was exerted by the weight of the coal, which was being lifted from the mine. In a car, we are interested in acceleration, not the ability to lift an object. In our case, the force is exerted by the inertia of the vehicle, which resists acceleration.

So now I need to bore you with another definition. Back to Webster’s dictionary, inertia is defined as "A property of matter that causes it to resist changes in velocity." In more simple terms, your car would rather not be accelerated from 30 to 70 mph, and so an external force is required to make this happen. This force comes from your engine.

To accurately describe the acceleration capability of your vehicle, we must consider time. If we just considered force, and distance, we wouldn’t really be saying much about the car. If I tell you that my car can pull a 3,000-lb. weight 100-ft. up a hill, would you be impressed? Certainly not, because I haven’t really told you much. If I told you that I could do it in 10 seconds, while your car needed 15 seconds to do the same job, you might be impressed.

After all, what we are really interested in is the ability to cover distance in a period of time. The distance from the exit of one corner to the entry of the next, or the quarter mile, or maybe even the distance from one stoplight to the next.

If we consider the rate of acceleration, AND miles per hour, we have all three terms included in the definition of horsepower. Time, distance, and force. Force is the rate of acceleration, or the force of inertia. Time is in hours, and distance is in miles.

So now instead of just considering the rate of acceleration arbitrarily, let’s include miles per hour.

And while we’re at it, let’s consider the acceleration rate of two very different motors to illustrate the importance of horsepower, and the absolute irrelevance of torque.

At one extreme we have a Honda F1 motor which revs to 18,000 rpm, makes nearly 800 horsepower, but a measly 281 ft.-lbs. of torque. At the other end of the spectrum we have the Cummins turbo diesel available in the 2003 Dodge Ram which makes a whopping 555 ft.-lbs. of torque, but only 305 horsepower. So which one do you think will accelerate faster?

Everyone that you ask will answer that the Honda F1 engine will accelerate faster. Even your neighbor with the big block who claims that torque is the key to going fast. If torque were the determining factor, the Cummins diesel would win hands down. So what gives?

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Let’s calculate the acceleration rate for both engines in a hypothetical 2500 lb. car using the transmission from the 1995 RX-7 with a two-foot diameter tire. Since we know that an F1 car will go 200 MPH, we will gear the car for that speed with both motors.

Starting with the F1 engine which redlines at 18,000 rpm, we need to calculate the required ring and pinion ratio to achieve 200 mph at redline in 5th gear.

First we convert miles per hour to miles per minute by dividing by 60.

200/60=3.333 miles per minute

The tire diameter is rated in feet, so we must convert this 3.333 miles per minute into feet per minute. There are 5280 feet in a mile, so:

3.333 X 5280 = 17,600 feet per minute

If our tire is 2 feet in diameter, the circumference is 2 feet times Pi

2 X 3.14159 = 6.28318 feet per revolution.

Now we divide the feet per minute, by the feet per revolution and we get:

17,600 / 6.28318 = 2801.13 tire revolutions per minute to achieve 200 MPH.

The engine redlines at 18,000 RPM, and in 5th gear the transmission ratio is .719 to 1. To determine the RPM of the output shaft at redline, we take the engine RPM divided by the gear ratio to get:

18,000 / .719 = 25,034 RPM

The output shaft is spinning 25,034 RPM, and we need the wheel to spin 2801.13 RPM to go 200 MPH. To find the correct ring and pinion ratio, we divide the output shaft RPM by the required tire RPM and we get:

25,034 / 2801.13 = 8.937 to 1

Going through all the same boring math for the Cummins diesel which is only spinning 3000 RPM at redline, we get a required ring and pinion gear of 1.489 to 1 to go 200 MPH at redline in 5th gear.

(Note that the F1 engine is spinning 6 times faster than the Cummins, and so the required ring and pinion ratio is exactly 6 times higher.)

With the transmission in first gear, both vehicles will be traveling at 13.76 miles per hour at the bottom of their powerband. (1,000 RPM for the Cummins, and 6,000 rpm for the Honda.) The following chart shows the acceleration rate of both engines in our hypothetical vehicle from that point to 200 MPH.

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Note that at any point on the chart, the percent difference in the rate of acceleration is EXACTLY the difference in horsepower. For instance, at 200 mph, the Honda F1 engine is accelerating at a rate of .572 G’s, while the Cummins diesel is accelerating at a rate of .228 G’s. If we divide .228 into .572 we get 2.5, and so the acceleration rate of the Honda is 2.5 times greater than that of the Cummins.

The Cummins, at 3,000 rpm is making 305 horsepower, while the Honda is making 763 horsepower. The Honda is making 2.5 times the power of the Cummins, which is exactly the difference in the rate of acceleration. You can work this out at any point on the chart, and you will find that this direct relationship between horsepower and rate of acceleration always holds true.

I’m sure there is someone out there that still thinks I’m off my rocker, but as I stated earlier, the laws of physics are non-negotiable. After showing this article to a few people for proofreading, one person stated that the results aren’t valid because torque motors are for low rpm grunt, and aren’t meant to run at 200 MPH. Ignoring the fact that this is a ridiculous statement, let’s consider what would happen if we geared both combinations for a top speed of 100 MPH. It should occur to you that this would be a simple matter of doubling the ring and pinion ratio, and that would be correct.

The end result is that the acceleration figures would simply double across the board for both combinations. The difference in acceleration would still match the difference in horsepower, and ultimately the difference in performance would be the same.

So there it is. Horsepower is the determining factor in the rate of acceleration of any vehicle. The next article will go into more detail, and show you how these simple calculations can be used to choose appropriate gearing for any track.

Below are some useful definitions and formulas.

TORQUE IN LBS./FT. = (WEIGHT IN LBS. X LEVER ARM LENGTH IN FEET.)

1 HP = 550 LBS./FT./SEC.

1 HP = 33,000 LBS./FT./MIN.

HP = (TORQUE X RPM) / 5252

TORQUE = (HP X 5252) / RPM

TORQUE AT THE REAR WHEELS = (ENGINE TORQUE X TRANSMISSION GEAR RATIO X RING AND PINION RATIO)

ACCELERATIVE THRUST = (TORQUE AT THE REAR WHEELS / TIRE RADIUS IN FT.)

RATE OF ACCELERATION = (ACCELERATIVE THRUST / TOTAL VEHICLE WEIGHT.)

You don't have to launch the snot out of a torquey car to go fast! And what wins street races..torque!

My point is this: Given 2 cars that both run 11.40 in the 1/4 one being a small block that revs to 5000, and another small block reving to 6500...the one that revs to 5000 will LAST longer, be more streetable and practical, and overall fun. Engines that you rev the piss out of to make power don't last long, hence the problem with the RX8 issue. No freakin torque, and every show that does a review on them says the same thing. So yes your figures look good on paper, but happens on a cold road at midnite is a different story. As a street racer myself, I know there are many factors involved and anyone can lose at any given time.

This thread pretty nicely sums up the problem with internet message boards. Someone writes (or copies) a factual, educational post explaining something and backs it up with facts and figures. Does everyone go "hey thanks for tha, looks like I've got some learning to do"...? Nope. You get shit like this:
"And what wins street races..torque!"
I feel sorry for guys like rxrotary2_7, he doesnt realise that for some people everything, no matter how complex, can be explained in less than 5 single sylable words.

-pete

You know hardbodeez, that's why I bought kwik's car with its killer sequential setup. Yea, it's complicated, but not as complicated as some people's day jobs. Nice torque and nice horsepower. Not as much as torque as my Viper and not as much horsepower as some RX-7s, but it's a fine ride. And as for getting across the line the quickest, one's driving skill is always the biggest limiting factor.

Lou

Its illegal to race on the street.

One more thing:

"And what wins street races..torque!"

Actually, it's area under the curve, but Pete's point/retort is still valid.

Lou

And incredibly irresponsible, but hey, I'm an old guy, what do I know?

Lou

And if you do anything besides drag racing this would not even be an issue.

Re: Nobody cares about torque anymore!
 

Yo u just gatta admit it man....you were owned:p: Also what you are saying is not true. I also have a Honda CRX with a 1.6L B16a that only makes 118 ft/lbs. and 177hp but i still do beat corvettes and mustangs on the street. How do u figure. lol

Wow, thats an awesome response rxrotary 27, been lookin for an explanation like that. And in responce to hardbodeez, you say that torque wins on the street-but from my experiance with street racing the opposite is true. Everyone running high torque numbers on the street (ie v8's) cant get traction from a stop, while cars like mine dont have traction problems. Instead of dropping the clutch at high rpm I slip it and buy the time the turbo lag is gone and I have boost I am travelling fast enough to catch traction easily ( granted I am rolling on 285's). I might get beat slightly off the line as a result of it, but the look on the v8 drivers face is priceless when flying by them. And you say that the rx7 feels like a v6, is that supposed to be an insult? Ever heard of a 2jz-gte or better yet an rb26dett?

Wrong, You obviously didn't read the article.

no he did not read it. ;)
even if he did, i am guessing he wont believe it anyways. :dunce:
part of the reason i dont post much technical stuff. nor do many other people.... :D waste of time. i will continue to read to myself now. :)

Yep...
Oh, Next time I pull up to the light next to the semi with 800 ft lbs of torque I'll remember not to race because it's torque that wins races...(just like the trucks dominating the NHRA)...:rlaugh:

wow, i have just learned a ton, thanks rxrotary. I can believe after all that explaining, hardbodeez had only one sentence to say. dude torque does not win street races. Dude to much torque on a non treated surface like street pavement, results in nothing but wheel spin. this is why my little 244 rwhp rx7 consistently is beating up on these big ass 400 cubic inch engine muscle cars in the the quarter mile on the street. I really dont spin, i just go. Once your moving torque is pretty much pointless since you are at the top of your rpm band after your first gear pull. On the track is a different story cause you have the traction from the treated pavement and all the sticky rubber.

good Adam. i am glad a few people learned something. :)
btw, i have no heard back from you about that problem you had. keep me posted :(

Re: Nobody cares about torque anymore!
 

I just figured I point out the stupidity of the comment. Lets take for example.. honda motors.. rev to 9grand, and last well over 100k miles. If you think your small block v8s are just so great, well then go grow your mullet and buy a mustang cause noone around here really could care less. We build are cars the way WE like them. Not how YOU think they should be. If I want to wait til 3500-4000rpm to make my power thats fine... to each his own. You should remember that.

i knew this guy was a troll from the second i read the title to the thread. :) see sig. LOL

btw, rxrotary2 your post above was total kickass.. I learned alot from that. Thanks.

Off Topic
The 1st Gen Mustangs handled poorly. Shelby made his GT350 drivers turn with the throttle. (powerslide) This is with all the suspension mods avalible back then.

That is the truth. Usually a street race starts with both drivers "rolling" on the throttle to stay out front. With a big boost car they will get their ass beat if they aren't expecting to race.

What wins races is a wide, useable powerband. Don't make full boost until 5000 rpm, can't use that very well most of the time.

I don't

True.

What some people aren't considering is that a big cube engine only makes massive amounts of torque at WOT. There's an amazing invention called the human foot which can modulate the amount of throttle the engine is given which can control that prodigious torque quite effectively.

With big cubes and a large stroke, there's a lot of power on tap *everywhere* in the usable rpm range. What some people apparently don't understand is that you don't have to use all of it all the time... but it's *always* there when you need it, not after your turbo spools up or after your engine climbs another 3,000 rpm.

With larger naturally aspirated engines, the power band is very linear and very predictable without the spike of power that a small engine with a power adder is stuck with. The smaller the engine and the bigger the turbo, the worse the spike, the narrower the powerband, and the less control you have over that power.

good posts Jim and Jeff. :)

That kind of power is expensive and doesn't make cool wooshing noises!
:rolleyes:

In all seriousness I think too many people get caught up in trying to cram the biggest turbo into their engine bay and don't find the right balanced turbo for their application. It won't matter if a t78 makes 500 rwhp at redline if a quicker spooling turbo makes it exponetially faster in the low end.

Jim makes a great point, linear powerband. Go back to rxrotary's chart of the F1. F-L-A-T.

course if you dont have your foot on the floor, your not making all your tq, and your not going very fast.

I like a nice linear hp band. I run my peak hp for around 1500rpms which is how far the rpms fall when I change gears. I'm always at peak hp, the only time I'm not is when I'm just cruising around but thanks to gears its just a gear change away.

Just cause you can make the same tq at 2000rpms as 5000rpms with a V8 doesnt mean your car is as fast at 2000rpms as it would be at 5000rpms. You would still need to gear down to get in your powerband (if you want to be fast anyway) so whats the difference.

BTW - I absolutly LOVE Paul Yaw's site, I've spent many hours there reading.

STEPHEN

Please don't. I really enjoyed the article

This is the difference. :)

A vehicle accelerates at its greatest rate of speed (g-force) at its torque peak in 1st gear. Unfortunately, you can't stay at the torque peak indefinitely, and you can't stay in first gear indefinitely, so eventually you'll have to shift. Why wouldn't you shift to the next gear after reaching your torque peak? Because even after the torque peak, torque at the axles is still higher in the current gear than the maximum possible torque (again, peak) at the axles in the next gear up. Maximizing acceleration is all about maximizing torque at the axles, in any gear, at any rpm in the usable band.

Example: A stock FD peaks at about 235 lb-ft. of torque at 5,000 rpm. In first gear, maximum torque at the axles is ~2,850 lb-ft. (235 x 3.483 x 4.1 x 0.85). The engine is down to 137 lb-ft. of torque at 8,000 rpm, but torque at the axles is still ~1,660 lb-ft. (137 x 3.483 x 4.1 x 0.85), higher than it would be at maximum in second gear (235 x 2.015 x 4.1 x 0.85 = 1,650). Not by much, but you're still faster holding 1st gear to redline, assuming traction, than you are shifting.

When torque at the axles in the current gear falls below maximum torque at the axles in the next gear, you shift. Ideally, the drop between gears would also result in the engine rpm falling only as far as its torque peak. This would result in maximum acceleration through all gears.

The difference of having an engine which makes a lot of torque (let's say 400 lb-ft.) at 2,000 rpm (and even more at higher rpm) compared to one that doesn't make the same 400 lb-ft. of torque until 5,500 rpm, is that you can accelerate in your current gear at a high rate of speed immediately, even at lower rpm, as opposed to the engine with less low-end torque which must be downshifted first to get up into its powerband. Shifting takes time.

In addition, wheel speed is a factor. If you can accelerate as hard in 3rd gear as another car can in 2nd gear, you're going to gain a lead on them, assuming adequate traction. Simple math dictates that if torque at the axles is the same for each, the car in the higher gear will cover more ground at any given rpm because it will have a higher wheel speed. Turn your tires faster (without losing traction) and your vehicle covers more ground in the same period of time. It's as simple as that.

Read to yourself, but don't talk to the voices in your head :p:

Where was all the "reason" in this thread?: Drifting

It's like having an argument with someone who refuses to listen and then says "Oh yeah? Well you suck!" :p:

LOL! but they talk to me and get mad if i ignore them! LOL!!

Sounds like hardbodeez needs to go sequential to find low end torque. seq'l can be controlled nicely at his 340 whp.

Nice analysis from yaw. Main point is that for 2 engines with very different redlines, hp is the main thing. But his graph does seem to have a wierd nonlinear mph axis, and curves suggest redlines are being exceeded. mabe just a plot axis error.

from jim:

"In addition, wheel speed is a factor. If you can accelerate as hard in 3rd gear as another car can in 2nd gear, you're going to gain a lead on them, assuming adequate traction. Simple math dictates that if torque at the axles is the same for each, the car in the higher gear will cover more ground at any given rpm because it will have a higher wheel speed. Turn your tires faster (without losing traction) and your vehicle covers more ground in the same period of time. It's as simple as that."

agree will all but this last paragraph. if in both cases the torque at the axles is the same, and same weight, tire radius, and traction, both cars will accelerate at the same rate, same change in mph per sec. doesn't matter that one is in 2nd, other is in 3rd. If you imply the 3rd gear car is at a higher speed for this example, then he will not pull away from the 2nd gear car.

Nice link to show optimum shift points. It's clear that being beyond the torque peak after a shift doesn't really matter in most cases.

http://homepage.ntlworld.com/daniel....ally/tech1.htm

:eek: I just read through the drifting thread....the fact that earumazda is a senior in aeronautical engineering is just slightly terrifying....

I think that, more than ever, our society is developing people that can't think for themselves. I blame computers for a lot of that....in engineering circles anyway....(hey I'm guilty of this too, before anyone gets bent out of shape).

Re: Nobody cares about torque anymore!
 

Why are you running a non-sequential setup, if the ideal purpose of your car is to have responsive low end power?

On top of this, I find it funny that anyone would be complaining about the lack of torque in rotary vehicles, as if it comes as any surprise. Our strongest points, along with our method of forced induction, simply do not lie in the low end.

Your example doesnt seem to be taking time into consideration. The amount of tq produced in a given period of time is more important that just flat out tq. Why would you want to put out 300lbs of tq 2000 time a minute when you can put out 300lbs of tq 5000 times a minute??? Tq at a higher rpm will ALWAYA accelerate faster provided its at the same gearing. Your examples dont take into account for rpm. If you only apply that tq for 1 rpm your not going anywhere (maybe a couple feet). You have to have revolutions per minute to go somewhere. It seems to me your example would be best at showing which vehicle would pull the biggest trailer.

This is contradictory to what you were saying before. You last section was saying you always get the most acceleration with the lowest gear. Why would you stay at 2000 rpms when you can downshift and get the next gear which is a much lower gear. The amout of time someone is going to take to downshift should be more than made up for with the much lower gear ratios they are going to be in.....provided they are a decent driver and can shift fast.

If you can accelerate as hard in 3rd gear as another in 2nd then either, your car has MUCH more hp than thiers OR your 3rd gear is super low (or maybe their 2nd is super high). You are right that it will cover more ground at any given rpm HOWEVER, that doesnt mean its acceleration. There is a difference in covering a lot of ground and acceleration. The tq can keep you at a constant 100mph and you will cover a lot of ground but that doesnt mean you got to 100 FASTER than the other car.

You can turn your tires with 500lbs of tq 2000 times a minute or you can turn them with 300lbs of tq 7000 times a minute. The later will accelerate much faster because its getting a lot more tq to the ground per minute, this is basically the fundemental basis for HP. Its tq times rpm....or tq over time.

STEPHEN

Don't make this too confusing guys. Torque is a measurement of force, NOT power (because there is no work involved with torque). You can apply a hell of a lot of torque to a bolt for instance, but unless the bolt turns you did no work and therefore made no power.

Engine power is the entire area under the curve of the dyno graph, not merely the highest horsepower attained at a certain RPM. I would much rather have my power nearly consistent across a very wide RPM range as opposed to having higher, peaky power around a certain RPM.

Check out umrswimr's Vette for instance:


http://www.digitex.net/ecarter/david/DNDyno-9-9-03.jpg

Now that's FLAT!

Are you serious?? Dude if a semi only weighed 2700lbs and was geared for it it would kill you.

You guys are forgetting HP/weight ratio which plays a huge factor. The CRX that beats vettes has nothing to do with high torque, or HP or anything it has to do with a crx weighs 2000lbs and a vette weighs 3 couple.

Torque is king but Weight is the queen. for every 100lbs dropped you will gain .1 sec off your et at the track.

:rolleyes: :rolleyes: :rolleyes: :rolleyes: :rolleyes: :rolleyes: :rolleyes:

Crikey...all this mental masturbation. :jerkit:

It should have been asked in the very beginning-- as Shinobi X pointed out-- why hardbodeez was complaining about a lack of low-end torque when he was running a non-sequential setup. In addition to driving a small-displacement turbocharged vehicle. Yeah, some "street races" may be won by torque, but others (especially real races at a track event) are usually won by horsepower (of course, that doesn't mean you cram everything up at the top of the powerband).


If you want boat-loads of instant response torque, then get that Mustang or another V8-powered car, or shoe-horn that V8 or Rolls-Royce Merlin or whatever into your FD. But one of the appealing aspects of the FD is its ability to get such great overall performance from such a small engine.

... is there an echo in here...

(to no one in particular)

What are you refering to as flat? His tq line or his power line cause I dont see anything special about his power line, its only flat for 1000rpms. His Tq line is long and flat but like you pointed out tq numbers dont accelerate a car.



STEPHEN

Aside from the fact that both of those are I-6 engines which kind of proves the original intent of this thread since I-6 generally has higher torque than V-6 of the same displacement, I agree.

This has been an interesting read. I think the bottom line is that you need to chose a vehicle that is suited to the purpose that is intended for it. People don't buy RX-7s for raw low end power, people buy them because:
1) they look nice
2) handle better than anything in it's price range
3)they have unique, high-reving engines wich put out tons of power considering their volume.
4) the interior is one of the best ever designed.

If torque is what your really after, go invest in some aftermarket gearing and smaller wheels. If that still doesn't do it for you, sell the car and buy a Stang.

Rob

Having had a car with a dyno graph a hell of a lot like that I can safely say that I find cars like that boring. See how the whole thing just dies after 5k? (the torque curve). That means the car is going to lose accel and feel like it's dying as you rev it out. It doesnt matter if you still have 300lb.ft at redline, if you start at 400lb.ft as you grab each gear, it's still going to feel like it's falling. To me it's not a lot of fun because the car feels like it's choking the whole time.

What you really need is good LINEAR torque in the area you need it Some people want a car to punt to the shops, so a torque curve like the one posted would feel ideal. People like me have a second car to get to the shops, so we want a car that has a nice flat pull near redline.

Everything is a compromise. There's arent many engines like the ones jim talks about that have solid torque from idle to redline and those that do invariably have a low redline so they suffer in the gearing stakes and end up with less impressive torque at the wheels.

-pete

My first post has been taken all wrong. First, it's funny to see how most of you "rotary enthusiats" which I am one myself, are quick to jump on me with subject of torque in an FD. I am a HUGE fan of this car's quickness, speed, handling, braking, looks etc. I LOVE this car and said nothing to cut up an rx7. I spent enough money buying it. As an unbiased opinion....since I have only had this car a few months...I say we need to build more bottom end. I agree it's nice to have a big single turbo with wads of power making these cars scream!
I would like to hear more about a flatter torque curve and quicker 0-60 times than read another magazine article about an rx with "500 rwhp" that some guy drives around on 18" radials, that doesn't own a pair of slicks. It's a waste, and MOST racers know that you'll never USE that power it's overkill.
The reason my car is n-seq is because I bought it that way,..it was what I could afford at that time. To me, in my opinion or IMO (For you computer geeks..who hang out here waiting to post nasty and arrogant rebuttals) this car feels like a an un-supercharged GTP under 4500rpm. The GTP at best would run high 14's stock. TO ME, that's not fast. To others it might be. The car hits 4500rpm while I am passing someone at mid throttle, the boost hits and blows the car sideways. I love the power, but it would be nice to have that power lower in rpm.
With the 340 rwhp I have and radial tires 225f/245r on stock rims with the boost controller on "high setting, 17pounds" this is what happens: From a dead stop, I lay into it it revs up near 4000 and blows the car sideways and qucikly bounces the 8500 rev limiter. I powershift second only to realize 1st gear was completely wasted. Even feathering the clutch numerous ways can't stop the insane wheelspin as soon as the turbos both hit. In fact I have more fun with the boost controller set on "low" around town because I can actually use the boost and not shredding the tires off on each throttle hit. This car only has 340 rwhp. I can just imagine some of you with the big 450-500 rwhp on the street. Those cars must be just nuts!! I don't believe anyone can hook those cars on street radials with that much power, I'm sure it's the same as what I am dealing with.
The rx7 is one of my most admired cars. I am not "insulting it" by saying it feels undesireable under 4000rpm, because it really doesn't make power down there, let's get serious! Yes a V-8 does, but I wasen't comparing it to a Viper or a Vette. This thread was about trying to get more torque out of these motors, and that would really help these cars since it is a weak spot.
No, I barely hear mentions to torque, and yes, I hear hp #'s all the time.
Motor trend television's drivers tested the rx8 and said it felt good when being revved and sluggish when way under the powerband. Why? Because it makes such shitty torque. AGAIN, the RX8 feels sluggish around town(by MANY who have driven it)because the torque isn't there. The rx7 makes up for it more with it's turbos and light weight. This is a production car, it's purpose was all different types of driving, and in most cases around town, and that's where torque is used most.
I drive my car around town and keep it revving under 4000rpm, TO ME it just feels like there's very little down there! There's really no in between with this car, it feels like a 2 stroke, on or off, and I would love to see that transition smoothed out keeping the same power.

YES- speed is dangerous, streetracing is dangerous and illegal. If you want to put-put around buy a stock cavalier..(suckers!)
P.S. This site is to post info on people's own thoughts, opinions, and help for others with problems. If some, are too intelligent to waste their own time here, don't be here or reply something ignorant! Too many times I see honest people posting comments that everyone knows, and the person gets hammered for asking such an "Easy" question. Well NO SHIT SHERLOCKS...if the person asking the question knew the answer to the problem wouldn't bother posting! Most of the people on here are kind and helpful, it's the odd few that can't wait to bitch at threads. Go in a chat room, then you can cut people up all you want!

That is why man invented the variable-ratio-drive-take-off. You may know it as the transmission ;)

OMG I'm dying! :rlaugh: :rlaugh: :rlaugh: :rlaugh: That's hysterical

DamonB:
so what are you going to do with that? Change up to the next gear? Unless you're running an 18 speed truck box, you're going to lose acceleration again, because you just dropped your torque multiplier.
What am I missing here?

Hardbodeez:
I think you've just got off on the wrong foot. What you sound like you really need is more low-end torque for city driving. Not more peak torque. It wont make your car go any faster (well not by much) but going back to sequential would be a bloody good start. Non-seq takes away a lot of the practical street enjoyment of these cars IMO :)

-pete

I completely understand where you are comming from. This torque issue is one of the reasons I will be putting in a 20b in the near future. With more low end torque, the car doesn't have to be driven as hard to be enjoyed. I too have driven the Rx8 and was a little dissapointed about the low end power. However thats me comparing it to my stock 3rd gen that is running seq. My car feels so much faster down low. Have you driven an Fd thats running seq? Big differance.