I posted previously about a race-built variable tranny that would "stall" at peak torque and would hold a constant RPM corresponding to that torque. Take the "shift tranny" and a few other variables out of the equation and I think torque is what gets the job done...

 

You're correct, torque IS what gets the job done. There is no such force as
horsepower.

Horsepower is a measurement of how much torque is being applied per minute
which indicates the strength of the motor.

What myself and many others are trying to convey is that allowing the engine
to spin faster, creates more power because you are hitting the rear wheels
with more torque per minute (hence more Horsepower).

In addition, the crankshaft rotations are higher which gives you more axle RPM.

 

OMG this thread can't POSSIBLY still be going.

Here it is as simple as I can make it:

1) The ENGINE'S Horsepower determines the total work that can be done in a given amount of time... by it's very defiinition.

2) The CAR is accerated by the FORCE the rear wheels generate (i.e. Rear wheel torque).

3) REAR WHEEL TORQUE IS A PRODUCT OF THE ENGINE'S HORSEPOWER minus drivetrain losses, divided by RPM, multiplied by 5252 (to convert units), and MULTIPLIED BY THE GEAR RATIO.

THEREFORE... for ANY given gear ratio (i.e. tranny x rear) the MOST rearwheel torque you can produce occurs at PEAK ENGINE HORSEPOWER.

Engine torque curves are pointless to look at from a driver's perspective unless you are swapping parts and trying to get a bead on why their doing to you hp curve.

Please end this thread.




</vent>

 

Actually in any gear you accelerate hardest at the peak torque in that gear. but at any wheel speed you accelerate hardest at peak power because when you are at peak TQ in one gear you could probably drop down a gear and be at that same mph in the next lower gear with way more tq multiplication. I am on your side though since it's power that gets a car down the track fast. Knowing tq numbers tells you really nothing.

 

After going through this novel, I find two posters (OS & MRS) (along with a small but accurate supporting cast) that consistantly speak without twisted tongues.
Steve, it make it, as you put it, as simple as possible, I suggest not ignoring important facts.

HP is a product (IOW, a calculation) of torque and rpm. It is not the other way around. The horse and wagon are traveling down the road. The wagon is not pushing the horse. (see #3 above)

Torque is what turns the tires, and thus propels the vehicle forward. (see #2 above)

Torque is what is measured on the dyno, not hp. From that MEASURED reading, hp is determined/calculated. (see #1 above)

Additionally, 'racer' is posting the answer, but is insistant on stating the color is green, rather than stating green is a product of blue and yellow. Torque propels the vehicle down the track, HOWEVER without rpm, the track is too long. A 'quicker' race car is the product of increases/improvements in efficiency (VE) that translates to more actual torque generated, along with hardware improvements to allow higher rpm operation. This equates (calculation) to more HP, which again....is the result/effect, not the underlying cause.

OS notes reference to the air grinder. My grinders spin to 14-15 thou. Without enuf air pressure to provide the force (torque) the spinning cutter will stop faster than you can say 'who the hell stepped on the hose'.
Engine reving to 10,000 rpm without any torque/force will fall on it's face at the line. RPM capability allows the option to multiply the torque with gearing.

HP is a calculation that can be manipulated by rpm. A somewhat artificial figure. Allow higher engine rpm operation, while maintaining, or even a slight decline (don't need to increase it) torque level, will calculate into higher HP. No big secret. This is the approach ricer deriatives use.

As for where the shift point should be, again common sense here. Shift point is high enuf to allow the engine to 'drop' into the most effective rpm to allow most effective acceleration, in the next gear. How many decades have we been using ths technique? To state it is not done at the torque peak, is misleading and not proving anything relevant.

BTW, I believe OS was very effective in his approach to explain the relevant info he presented. He was probably an instructor of higher learning, in one of his previous lifetimes. But like alot of subjects in general, you can lead a horse to water.....

 

Gee thanks!

Had to LOL though. My classroom teaching involved teaching radar and computer controlled navigation and bombing to fighter pilots so they could check out in a new fighter. I also got to instruct them in the air, which was sufficient reward for the classroom work. Best part was it was a single seat airplane so I got to instruct from another airplane flying "chase".

And the beat goes on...

 

Not to rain on anyones parade but Arnie still hasn't learned that TQ is not something that will tell you much about a powerplant. HP will. TQ is only part of it but so is everything else. TQ is nothing but a static measurement that means nothing in the absense of time. HP has all the info needed to analyze whether the car can haul *** where as TQ is just one part and HP is the whole so it is what is looked at.

 

Arnie,

You still don't understand and after reading this "novel" you should be ashamed.

I have two cars and one makes 400 ft pounds of TQ and one makes 500 ft pounds. They both weigh 3000 pounds and have the same weight distribution and drag coefficient. (You DO NOT know the HP since it is not a factor in accelerating the car according to you!)

Which is quicker?



NOW one has 400 HP and one has 500 HP.

Which is quicker?

 

Sorry, but this is getting closer to splitting hairs than a logical determination of what measurement to use for vehicle performance.

The mathmatical relationship between TQ and HP is simply a construct used to quantify a system. I'm not talking with a "twisted tounge", I'm trying to explain that an engine will do a set amount of work in a set amout of time. Gearing is simply used to adjust the time vs. work relationship, but the total power we have available doesn't change.... which is why we (and every successful race team on tha planet) looks at engine horsepower curves when determining gear ratios and shift points.

ENGINE torque (only one component of power output) is inconsequential as a result. Yes, rear wheel torque is the goal, at the wheel rpms (proportional to vehicle spees) but that is not a product of engine torque alone and focusing on a torque curve is pointless in this regard unless you're doing the hp conversion in your head by referencing rpm.

no, torque and RPM'S are meansured on a dyno... in an effort to quantify horsepower (power output). Having a graph of torque vs. time or even sample frame is pointless... a single variable is no way to describe a system of this nature.

again, you're trying to pick one or the other. What I'm telling you is that it's clear that output POWER is vastly more important than just FORCE alone. 500 lbs-ft of torque is amazing for a 3000 pound car... unless you redline at 1000rpms. Even with insane gear ratios, you're only dealing with a best case of 95 hp and redardless of what torque multiplication you have, an engine with less torque but more hp (as a result of more rpms) WILL be faster. How can you tell how much rpm is enough to offset lower torque values? easy.... look at the HP curve.

yes... that's my point. Torque and RPM are both required... which is why we reference a system with a HP curve.

This isn't a question of HP vs. Torque with "the best measure" being the one that retains a high enough torque level... it's one of TQ vs. RPM and the winner is decided by the product: horsepower.

Chosing shift points to maximize torque is not the way to maximize rearwheel torque. it never has been and will not make a car faster. If you want to look at "how many decades" we've been using this concept, just look at road racers that choose gearing based on horsepower curves, not just the torque.

Just a reminder, it's the Area under the torque curve that matters... not the torque reading itself. That area (the RPM integral of Torque) is horsepower.... not torque.

 

Eric, surely you know, I'd have to know the torque CURVE, and the usable rpm range of either engine, to make an educated determination.

As I noted above, because HP, especially peak HP #s, can be manipulated, they are at times, somewhat superfiscial. I can take an engine, establish a safe max rpm, and obtain peak HP #s. With no change to the engine whatsoever, I can change (increase) HP #s solely, by twisting the engine a little tighter. Great for substantiating some valueless add on. This would apply more so, to a street engine, with the race variety normally operated much closer to the max attainable rpm.

Given a choice of either one (torque or HP), I'd much rather view the actual measured torque/rpm graph. From there, I can calculate HP #s, at any rpm, if I so desire. BTW, I've felt ashamed B4, at some point in my life.


As for attempting to respond to Steve's post.......geez. I'll state this much, the 'flair' you use with words, is consistant with previous posts, in this thread. By NO means am I implying any disrespect, Steve. To save frustration, I see no point in encouraging further word 'sparing'. The final word, was yours. I'll leave it at that.

 

If you need to know the torque curve vs rpm you are needing HORSEPOWER. You said that did not matter.

Also you can infinitely manipulate TQ but power can not be manipulated. I CAN MAKE ONE MILLION FT LBS OF TORQUE! but I can't accelerate a big 3000 pound car at all since I have almost no real horsepower to speak of but give me a lever and I can move the world (very very slowly)!

Give me more HORSEPOWER and I can move the world a lot faster.

 

Horsepower lets you know how fast you can apply the force to the ground. That's why HUGE trucks that haul a ****load have monster torque numbers, but low horsepower ones.

 

so why not measure tq per minute for every rpm?

 

Horsepower = Torque * RPM/5252

 

<smirk> That's what hp is (although your using rpm instead of rotations... factoring the time twice).

hp = torque * rotations / minutes (then / 5252 due to units conversion)

You'll also notice that:

hp = [Work Done] / minutes (then / 5252 due to units conversion)

and that work / minute (i.e. power) is what you WANT to calculate for determining acceleration... the wheel speed (i.e. rwRPM) determines how much rwTQ you can generate from the rwHP that's present. rwTQ is the acceleration force.

For any given (non-slipping) wheel speed, the greatest force you can apply comes from the lowest gear the engine can handle (I.e. engien rpm under red-line), and the greatest rwhp you can generate. rwhp horsepower is proportional to engine hp... not engine torque. That's why engine torque doesn't tell the whole story, although it does FEEL that way at low rpms since torque is the dominate factor in hp production at low rpms. Either way works, but hp is your goal... not tq itself.