Torque. Is many times misunderstood as "power" at low rpm. Or, that torque is what pushes you back in your seat. Wrong! Acceleration does. Almost any number of torque can be created to the rear wheels by the gearbox. But the gearbox can NOT create a larger number of horsepower. The term that tells us how much acceleration force the engine is capable to give the car is horsepower. To make a 3000-pound car to do the quarter in 10 sec, will take 600 hp. The engine may produce 1000fp of torque, but if it does not rev beyond 3000 rpm to produce 600 hp, the car will not run a 10 sec ET. The "seat push" is nothing but G-force. What create acceleration is torque AND rpm. One without the other is of no use, and together they are named horsepower . a lot people claim that torque is what produce acceleration. If this is true, I look forward to see the equation that show how fast a 2000fp engine in a 2000 pound car will be in the quarter. So, to specify a quantity of work, I use the term horsepower. Even at low rpm. A drawback with a big incher is that the engine gets physically big and heavy.

 

I got an idea! Throw a Detroit Diesel out of an 18 wheeler into a gutted out Chevette and see what that will run in the 1/4!!!
:lol: :lol: :lol:

 

Usually when we say "torque" we mean low end HP; it's sort of a popular meaning though not scientifically correct.

A heavy car can gain starting power with better gears, but the engine will run out of the power band earlier and lose torque quicker after each shift.

Think about what happens on the strip after each gear change. The engine still builds the same HP at any RPM but the acceleration drops off with each gear change. So I guess torque at the rear wheels is very important.

Drag2000 drag strip simulation software shows the acceleration curve for my Vette down the 1/4 mile. You can see the acceleration curve slope drop at each gear change. This results from the drop in torque to the rear wheels.

What makes our L98s "feel" strong in a traffic light race is its terrific low end torque (HP) combined with the deep 1st gear (torque) in the 700R/4. At the drag strip we give up some low end engine torque to gain top end so we can stay in each gear longer; and then we use a high stall TC to launch higher up in the power curve to "recover" that torque (HP) we gave up.

Of course torque is what pushes us back into the seat but that torque must be applied continuously over time (i.e. HP) to keep us pinned back. Note how that "push" drops off as we pass through the torque peak...or is it through the HP peak.

 

Its not about having one or the other. Its about having a combination of the two in a good balance.

I did not gain any weight to pick up torque. My motor is no larger than any 350 (physically/weight wise). But at 437 rwhp/536rwft-lbs), you can bet it feels and outdoes many BBs. Hell its quicker than my dads 509 CI merlin motor. At least for now, till I beat him the other day and now he's looking at Supercharging it. :eek: Can you say low low 10s or evens 9's when that is done.

I would recommend to anyone building an engine, shoot for a nice even balance, all at a low RPM number. It will keep the car VERY streetable and awesome on the strip. :cheers:

 

I have to laugh everytime this subject comes up.

Horse power is simply a calculation based on the amount of torque produced at a certain RPM.

For example, a stock LT1, LT4 and L98 produce pretty close to the same peak torque (about 330 ft/lbs). Yet, the LT4 produces about 100 hp more than L98 and 50 hp more than the LT1.

Which one wins the drag race? Is the one with the most peak HP or most peak torque? Neither. It is the one with the highest AVERAGE torque over the acceleration RPM range. That is the LT4. The LT4 torque is virtually flat from 3000 rpm to 5500 rpm at around 330ft/lbs where the other engines torque peaks at a lower RPM then falls off compared to the LT4.

This is supported in Chapter 1 of the John Lingenfelter book. He says it much better than I can, so I suggest if you want to learn more about the Torque vs. Horsepower thing, check it out.

 

:iagree:

Amen, Brother! Lots of theories, assumtions, bad information and "heresy" about torque out there. In this case the bible is Lingenfleters book. If you can out perform John's work then you can be the authority and correct him. It would be useful if all folks would support the basis of their knowledge with a chapter and verse from their source like Mez did. :yesnod:

 

Not another one. :rolleyes:

 

first thing to keep in mind is that theres no such "thing" as horsepower, horsepower is a mathmatical formula for the RATE at which TORQUE can be applied the formula for hp is (tq x rpm/5252=hp
example
450 ft lbs of torque at 3000rpm=257hp
450 ft lbs of torque at 6000rpm=514hp
because the torque at the higher rpm useing gearing can be applied faster
here read this
http://www.69mustang.com/hp_torque.htm

http://www.ubermensch.org/Cars/Technical/hp-tq/

http://vette.ohioracing.com/hp.html

[b] where most guys go wrong is in not correctly matching the cars stall speed and gearing to the cars tq curve, if you mod the engine for increased high rpm performance but fail to also match the stall speed and gearing to that higher rpm tq curve much of the potential improvement is wasted.
example

in the close to stock engine above, the engine should be geared to stay in the 3500rpm-5000rpm range for max acceleration (lower in the rpm range if mileage is a big factor)

in the moded engine above the rpm range moved to 4000rpm-6500rpm requireing differant rear gears and slightly higher stall speeds to gain max acceleration in the same car,
you should readily see that a trans that shifts at 5000rpm will work in the first example but would waste most of the power curve in the second example,
a 3.08 rear gear and 700r4 trans matches the first example well but it would take a swap to a 3.73-4.11 gear to allow the engine in the second example to keep its most effective power band matching that second power curve well.

links youll need to figure out correct rear gear ratios

http://www.miata.net/garage/tirecalc.html

http://www.wallaceracing.com/reargear.htm

http://users.erols.com/srweiss/calcmph.htm

http://users.erols.com/srweiss/calcrpm.htm

http://users.erols.com/srweiss/calcrgr.htm

http://www.prestage.com/Car+Math/Ge...io/default.aspx

http://www.geocities.com/z28esser/speed.html

http://server3003.freeyellow.com/gparts/speedo.htm

http://www.pontiacracing.net/trannyratios.htm

http://www.tciauto.com/tech_info/gear_ratios.htm





[Modified by grumpyvette, 5:58 PM 7/3/2003]

 

I've seen this arguement before, the conclusion I've come to is Torque and Horsepower are related. Torque is good, horsepower is good, for any given car the more you add the happier you will be. :yesnod:

 

grumps you are very intelligent and you hit the subject right on the money and i could not have agreed more .
but are you a book worm? :cheers:

 

well if being a retired engineer (mech. eng ) (hired by AT&T )and life long hot rodder , having almost always owned corvettes, owning 3 now (1992,1985,1996)have experiance with well over 150 engines built durring the last 34 years and supporting my family at times by building engines, having raced a vette (BBC)496cid 13.7cpr crower injected corvette that ran low- mid 10s is a book worm than GUILTY AS CHARGED
btw the only reason I have time to do this is I crushed my ankle about 15 months ago, and the damn things taking forever to heal up!
and if you think 150 plus engines is alot keep in mind thats only about 4.5 engines average per year and for over 18 months I was building 1-2 a week as a side business and still do it as a side buisness







[Modified by grumpyvette, 11:42 PM 7/3/2003]

 

What's the full name of the Lingenfilter book?

 

http://www.amazon.com/exec/obidos/AS...008370-2782238

BTW ITS VERY WELL WRITTEN, AND VERY WELL RESEARCHED


[Modified by grumpyvette, 3:27 AM 7/4/2003]

 

"Horsepower sells cars, torque wins races." -Carol Shelby

 

On the street where races are short, impromptu and the first guy ahead and shuts off wins, TORQUE is King!

On the track, HP is King!

FWIW,
BIG JIM

 

torque is horsepower for one rpm of the engine.

 

There is no such thing as horsepower?
Let me quote my physics book: Fundamentals of Physics; Halliday/Resnick 1974
"One horsepower was chosen to equal 550 ft-lb/sec. One horsepower is equal to about 746 watts or about three fourths of a kilowatt. A horse would not last long at that rate."
That is if we raise 550 pounds one foort in one second, our work is equal to one horsepower. Power=force* linear velocity
In engines we are dealing with rotational dynamics : Power =torque*angular velocity
We relate torque to horsepower by the formula hp=(torque*RPM)/5252.
You can push on a block all day long and if it does not move, no work is done.
You can put a wrench on a bolt and apply torque all day long and if nothing moves, no work is done.
In a nut shell, Horsepower is a measure of work done.

 

Not the best pic but here is a direct comparison of a slightly modded 1990 L98 6 speed vs a stock 1996 LT4 6 speed on the same dyno with all numbers corrected. The L98 has the LT4 beat hands down on low end torque but above 4k rpm the LT4 is starting to eat. Both cars were/are mine. The 1990's best run at Beech bend was a 13.52 at 105.xxmph with a 2.02 60 foot time. It had 3.33 rear gears.
The 1996 so far has went 13.32 at 105.xxmph with a 2.12 60 foot time and it has 3.45 gears [4.09s are sitting on the kitchen table as I type this ;) ]. The 1990 crossed the traps in 4th gear. The 1996 crosses the traps in 3rd gear still. I looked at some old timeslips and the 1/8th mile times are close but the 1996 traps about 1-2mph better in the 1/8th than the 1990. Anyways, some more food for thought.



[Modified by Dr. Evil, 11:32 PM 7/4/2003]

 

IF EVERYONG IS GOING TO MIS-QUOTE THEN OF COURSE,YOU CAN GET DIFFERANT IDEAS
"theres no such "thing" as horsepower, horsepower is a mathmatical formula for the RATE at which TORQUE can be applied, the formula for hp is (tq x rpm/5252=hp )
if you increase the RATE at which TORQUE IS APPLIED you can of course increase the POTENTIAL WORK that can be DONE, but its force exerted over time that moves the car, and increaseing the rate that force is exerted effectively potentially increases the cars rate of accelleration
HORSEPOWER , is a MEASURE of the effective rate(RPM) at which force (TQ) is potentially applied.
force,time and the rate at which that force is exerted over time can be measured , and that man made scale of measurement refered to as hp is used to express that RATE/force/time relationship ,but hp it self is only the measurement

Definition
The term horsepower was invented by the engineer James Watt. Watt lived from 1736 to 1819 and is most famous for his work on improving the performance of steam engines. We are also reminded of him every day when we talk about 60-watt light bulbs.
The story goes that Watt was working with ponies lifting coal at a coal mine, and he wanted a way to talk about the power available from one of these animals. He found that, on average, a mine pony could do 22,000 foot-pounds of work in a minute. He then increased that number by 50 percent and pegged the measurement of horsepower at 33,000 foot-pounds of work in one minute. It is that arbitrary unit of measure that has made its way down through the centuries and now appears on your car, your lawn mower, your chain saw and even in some cases your vacuum cleaner

http://static.howstuffworks.com/gif/horsepower1.gif

What horsepower means is this: In Watt's judgement, one horse can do 33,000 foot-pounds of work every minute. So, imagine a horse raising coal out of a coal mine as shown above. A horse exerting 1 horsepower can raise 330 pounds of coal 100 feet in a minute, or 33 pounds of coal 1,000 feet in one minute, or 1,000 pounds 33 feet in one minute. You can make up whatever combination of feet and pounds you like. As long as the product is 33,000 foot-pounds in one minute, you have a horsepower.

You can probably imagine that you would not want to load 33,000 pounds of coal in the bucket and ask the horse to move it 1 foot in a minute because the horse couldn't budge that big a load. You can probably also imagine that you would not want to put 1 pound of coal in the bucket and ask the horse to run 33,000 feet in one minute, since that translates into 375 miles per hour and horses can't run that fast. However, if you have read How a Block and Tackle Works, you know that with a block and tackle you can easily trade perceived weight for distance using an arrangement of pulleys. So you could create a block and tackle system that puts a comfortable amount of weight on the horse at a comfortable speed no matter how much weight is actually in the bucket.

Horsepower can be converted into other units as well. For example:

1 horsepower is equivalent to 746 watts. So if you took a 1-horsepower horse and put it on a treadmill, it could operate a generator producing a continuous 746 watts.

1 horsepower (over the course of an hour) is equivalent to 2,545 BTU (British thermal units). If you took that 746 watts and ran it through an electric heater for an hour, it would produce 2,545 BTU (where a BTU is the amount of energy needed to raise the temperature of 1 pound of water 1 degree F).

One BTU is equal to 1,055 joules, or 252 gram-calories or 0.252 food Calories. Presumably, a horse producing 1 horsepower would burn 641 Calories in one hour if it were 100-percent efficient.
again, its a MEASURE of FORCE USED OVER TIME TO POTENTIALLY DO WORK,NOT AN ENTINTY IN AND OF ITSELF, BUT A MEASUREMENT OF FORCE AND TIME






[Modified by grumpyvette, 3:14 PM 7/5/2003]

 

Yeah, and the physics books say electrons flow from negative to positive too. But how reliable were positive-ground cars?

We're not talking about something powered by a horse. We're talking Horsepower. Horsepower doesn't mean anything unless you use that necessary adjective in front of the word. "SAE" (Standard of American Egotists) Horsepower = 745.7 watts, "Electric" Horsepower = 745.4 watts and "Metric" Horsepower = 735.5 watts. No, I'm not an electrical engineer but I answer questions all day long on my electric motor forum from them who actually believe all the crap they learned in college from the physics books. Sheepskins must be cheap these days.

Grumpy,

At least YOU got it right.

FWIW,
BIG JIM


[Modified by BIG JIM 54, 7:53 AM 7/5/2003]