It is an exact science. Torque is a measure of twisting FORCE, while horsepower is a measure of POWER (work done in a certain time frame).

They are proportional... but hp is also proportional to rpm. That's why low torque F1 engines (little 3 Liters) can produce 700 hp... high rpms (in the neighborhood of 12000 or so).

The nature of the combustion engine, and mechanical limits being what they are engineers have to try and maximize torque TO MAKE HP, since rpms are limited to sane numbers (like 7000 and below).

 

For an exact science, there seems to be quite a few opinions on how torque and hp are related...sounds more like a debate on religion or politics than an exact science....
Can you expand the discussion on how the hp/torque/rpm curve are related, especially after 5252 rpms...

 

Simple question... if we adapt a 3.2L 320HP NSX engine to a camaro... DO you think it will run faster than an ls1 Camaro? they both have 320HP.

The other option is... my old 86 nissan maxima had a 3L engine that made 150HP. My pops GSXR made 160 to the wheels.. what you think will happen if I adapted that high revving motor to the 3100 nissan maxima?

It will break eventually... That is why not everything has the same engine...

If I put a 500HP honda engine that has a lousy 250lbs of torque it wont move the camaro nearly as much as 400HP LT1 and even though you have the revs and the rear gears to do so you simply need the torque to get moving.

You want HP so you can get more torque to the patch with every gear possible...

What people tend to think is:

The more rpms the more air/fuel go through the engine per second as there are more cycles in one revolution for torque to be produced, and that is the idea behind many.

Its always a combo between the 2... put an F1 engine in a Nascar and lets see how it performs.. both have around 800HP.

You still need the torque and the combination of torque/hp for your gears to produce max multiplied torque at all times.

Lets say I have 2 engines... one has 1,000,000HP and the other one has 600HP. Both curves flat. and everything else in the car is equal

Both have 300lbs of torque at all times...

Both launch at the track.... the 1M HP car will start pulling only when the 600HP car shifts to second, because it will be at the first gear all the time with max multiplication of torque all the time. The engine has revs that can keep that torque for longer periods of time.

 

Try this thread from a few months ago.

http://web.camaross.com/forums/showt...01&perpage=15&


Torque and horsepower are related exactly the same way at any rpm. It's just that using the common units, the hp or torque number is the same at 5252. Below that rpm the hp number is lower than the torque number, above it, hp number is higher. If you had a torque curve that stayed absolutely flat after it reached peak, the hp curve would be a straight line continually rising and never peaking, because HP=Torque x rpm/5252, a linear relationship.

400 lb-ft @ 5252 = 400 hp
400 lb-ft @ 7878 = 600 hp
400 lb-ft @ 10504=800 hp, etc.

Perhaps what may get confusing is looking at the torque curve graph of an engine that peaks torque around 5200, which is somewhat typical for an NA engine peaking power in the mid 6000 range. The torque curve then falls off slowly or quickly depending on how the engine breathes. Intuitively, when you see the hp and torque curves cross at what appears to be torque peak, you may think that the torque/hp relationship changes there. Nope.


Yeah, The Highlander said it: It's torque at the wheels that accelerates a vehicle. It goes back to F=ma, or more correctly a=F/M. Acceleration = force divided by mass. Force at the tire contact patch and it's reaction force at the vehicle chassis is what accelerates. The physics and math aren't too complicated, but the concept of torque being applied at a rate (rpm) isn't always easy to visualize. That, by definition is POWER. Easy thing to get confused on, huh?

Visualize a 2500 lb. gross weight ricer racing a 5000 lb. gross weight SUV and running exactly neck and neck down the drag strip (or your local parkway?). The SUV is putting twice the force to the ground at the drive wheels at any instant as the ricer because it has twice the mass. This torque (force x tire radius) is being applied at the same rate (same acceleration), so SUV is putting out twice the POWER also. Driveline efficiencies would alter the fwhp a little, but surprisingly not a lot. Peak hp and maybe peak torque for the two engines would also be about a 2:1 ratio. More than likely the SUV would have a flatter torque curve and the ricer a peakier one, but the area under the usable torque curves might be very close to a 2:1 ratio.

Test question: what happens if the equally matched SUV & ricer each add a 200 lb passenger and then race?

If you carefully measure the acceleration (g) of a vehicle in a given gear and plot the gs vs. vehicle speed, you'll get almost an exact torque curve plot. Friction and aero drag modify it some if high speeds are used. That's how drag race or other performance simulators accurately predict acceleration performance.

And the beat goes on...

 

Simple

The SUV will win....

Why? because if you do the a=F/m equation you will get it, but a simpler and easier way to see it will be...

200# on 4000# of weight is just a 5%
200# on 2000# of weight is 10%

The effect is less in the SUV than the Ricer...

And another thing.. you still need the torque to move the weight, regardless of HP. which is why I keep saying, put the WONDERFUL NSX engine in a camaro and lets see how it runs... I dont doubt it'll do 14s.. but it wont do 13s as the ls1 does. And the NSX engine will probably break.

 

Torque matters not.

I think there are too many misconceptions about torque and hp. People seem to think that torque is what they feel on the bottom end, and hp on the top. While that may do great explaining how a vehicle feels when they drive it, it doesn't stand up very well in a scientific explanation and showing the relationship between hp and tq and it's effects on a vehicle.

Comparing an LS1 and the nsx engine won't help much either, because other than the obvious underrating to the ls1, the ls1 most likely has a much stronger powerband than the nsx engine. Now if you raced from a roll, and the nsx and ls1 had the exact same hp under the curve between the shift points, the race would be dead even- actually the nsx engine would edge the ls1 out due to weight but that's another argument for another time. Of course, if you raced from a stop, the LS1 would win, but that has to do more with low end hp than torque. It's true, the LS1 makes more torque at lower rpms than the nsx, but if you take into consideration the direct relationship between hp and tq, more hp is being deliverd at those rpms also.

Torque is just how much the engine is pushing, or a force, as stated earlier. A force applied at the flywheel and a force applied at the rear wheels are completely different things. Why does an LT1 with a 3500 or so stall make it off the line quicker than one with the stock stall, even though the engine is not at the rpms it needs to make peak torque? Because hp is what determines what kind of force is being applied to the rear wheels, not torque. Horsepower is a force being applied, torque is just, well, a force.

Another example is that if you took an two identical engines and placed them into identical vehicles, ran one at peak torque and one at peak horsepower (assuming a continuously variable transmission of course), the one running at peak hp will always win, no matter what.

Why will a wrx launching at 6k rpms do a lot better than one launching at 2? Because it's keeping the engine in it's powerband, the area where the engine makes the most hp, which applies the most power to the wheels and accelerating the vehicle the fastest. Why does launching a near stock Camaro at 2k yield better results than one launching at 5k? That has more to do with traction issues and people not wanting to destroy their 10 bolts than anything else. I'm sure people that have 9 inched it and have slicks on the back will tell you its better to launch up higher.

Why does a dyno-queen supra have such a crappy e.t.? Because it's hp under the curve, not peak numbers. If you can't keep the engine in it's powerband from launch to finish, you're not going to yield respectable numbers with a vehicle that isn't near stock.

Since torque and horsepower are so directly related yet different at the same time, it's no wonder that it gets so confusing, especially with automakers only showing peak hp and peak tq numbers, saying "most torque in it's class", etc. Would a truck producing 100 ft lbs of torque at 2k and 400 at 6k make it get off the line quick? No. But put a 5000 stall on that sucker and it will move like nothing else, and keep moving. Not to mention, it obviously produces a very pathetic amount of hp at low rpms, with a very respectable number up top.

With hp and tq being different, torque can obviously be an important number when determining what power your engine makes and where. But the key word there is power, its the amount of power your engine produces at a certain rpms that determines the level of acceleration your vehicle will see at that point. In the end, all that matters is a dyno sheet. Torque isn't gonna help.

I think my physics teacher would be proud.

 

Exactly.

 

No. You gear the engine to get as much HORSEPOWER as possible. keeping a car in a high-torque rpm range is useless if added rpms will cause a increase in hp (and a LOSS in torque).

Quote:

What people tend to think is: The more rpms the more air/fuel go through the engine per second as there are more cycles in one revolution for torque to be produced, and that is the idea behind many.

yep, now your gettin' it... that's EXACTLY what the goal is... more HP. sacrificing 40% of your torque for a 50% gain in rpm will give you more hp, AND make you faster.

Quote:

Its always a combo between the 2... put an F1 engine in a Nascar and lets see how it performs.. both have around 800HP.

You still need the torque and the combination of torque/hp for your gears to produce max multiplied torque at all times.

no, torque to the wheels is not the point. For a given gear ratio the multiplication is the same for the whole rmp range... fast racers go for highest average HP, not average TQ when choosing shift points. Torque numbers tell you how much force is being put on the piston, HP numbers tell you how fast your engine can accelerate the vehicle...

Quote:

Lets say I have 2 engines... one has 1,000,000HP and the other one has 600HP. Both curves flat. and everything else in the car is equal

Both have 300lbs of torque at all times...

Impossible in exicution of course but ok this may help show the difference. Assuming a flat torque curve the ONLY way this is possible is if the engines have different redlines (TQ=5252*HP/RPM). Solving for each engine:

Engine A | 600 hp @ 10504 rpms ; 300 ftlbs @ all rpms.
Engine B | 1,000,000 hp @ 17,506,666 rpms ; 300 ftlbs @ all rpms.

As you guessed by now, this is gonna be a total blow-out. The hp curves will be identical until engine A hits red-line at 10504 rpms... then shifts gears to a LOWER hp (with the same 300 ft lbs of torque). Engine B will continue to sky-rocket hp while keeping with 300 ftlbs torque.

Quote:

Both launch at the track.... the 1M HP car will start pulling only when the 600HP car shifts to second, because it will be at the first gear all the time with max multiplication of torque all the time. The engine has revs that can keep that torque for longer periods of time.

Nope, the "pull away" will have nothing to do with gear ratio and the amount of torque getting to the wheels... it has EVERYTHING to do with hp. As I said before, the torque can be adjusted for any situation you want... but the total hp available is what you have to work with. Will you spend it on larger forces (torque)? or on more RPM? that's just how it works.




Look, this discussion is pointless. It's like asking which stereo will be louder:
a) one with more average Amps (and lower watts...say due to resistance/impedance differences)?
or b) one with more Watts (and lower amps)?

(Watts, a measure of power is = Amps * Volts)

If you picked B: Watts, you win... that's hp.

This isn't a "theory"... it isn't a "conditional" situation... this is the FACT of the matter. More average hp will get you there faster. Torque is a good way to MAKE that hp (as is RPM), but trying to gauge the acceleration of an object based on the force applied to it without considering time is just an exercise in futility.

 

You left out at least a couple of variables in the equation. The effeciency of the speakers may have something to do with "loud" and the overall design (or engineering) for "loudness" may also play a roll. Now comparing that to torque vs. hp to amps and watts...that's why there are speed competitions and stereo competitions...people using their combos to win...and sometimes the combos don't work out just the way they were intended, mostly because of "trade-offs" that come into play. More engineering, lighter design, more hp or torque at different rpm, different gear ratios both through the shift process and the final drive, etc., etc., etc. .... Loudness and speed may be an "exact" science in your eyes, but it sure hasn't been "proven" in this discussion, at least for me!....

 

HP is what gets cars down the 1/4 mile fast not torque. Torque is mainly a function of how big your engine is for the most part.

 

The ability for the engine to accelerate will be dictated by the available torque at all times to the rear wheels...

I will put it to you this way


Get a small chissel and a light hammer and start breaking through a concrete wall....

With the lighter stuff you will be able to pound it (with less torque and more rpms thus more HP)

Then do it with a bigger chissel and a heavier hammer, you will probably get tired faster but you will get through it faster too.

You need torque to move the weight no matter what. You will always have more torque applied to the ground in first gear than in second gear...

if all we want is HP we would all be DESTROKING the engines to 302 and reving it up sky high... We need a combination of both to move the weight and finally accelerate it how we want it to... The reving will allow you for more gearing, and it applies going uphill or against the wind...

Torque gets you off the line too...

 

I'm not so sure he/she would be too proud of you. Ask him/her about "work" and "power" and the relationship. Ask about Newton's laws of motion. Ask about gears multiplying torque and dividing rpm, but not changing hp (except for friction, etc losses).
Ask about what an engine dyno actually measures other than rpm.

quote: "torque can obviously be an important number when determining what power your engine makes and where."

Of course. Is that not the definition of power? torque and rpm?

 

I have read the post that Old Stroker refered me to and there seems to be just as much controversy there as here. Although interesting reading, my logic is saying "not science" but conjecture...
Science seems to work when things are (for the most part) "repeatable" and the results can be duplicated by anyone within controlled variables. Even different manufacturers of dynos have a bit of variance built in to their results (i.e. I know of people who want to go on a dynojet rather than a superflow or some other brand to get the higher numbers. I feel standards, if indeed it is a science, should be in place to assure common results. Duplication is essential in any scientific endevor...I know it comes down to the math, but since few can agree on the validity of "units" and "standards" and such, I just don't know....

 

Good points. I would suggest not getting lost in the measuring accuarcy thing. Just because a given engine tests differently on different dyno installations, which it certainly may, doesn't mean the engine changes. It's the measuring device that changes.

Give three trained people the same bore gage and setting device and ask them to measure a finished bore of an engine block, and you will get different answers, at least in the fourth decimal place (.000x), even if the bore gage reads to the 5th place (.0000x). That's due to measuring technique and manual skills. Sure a computerized CMM might be closer, but when the block is still in the hone (and maybe even hot), the CMM isn't practical.

Now send that block to a different shop and have three other folks measure it. You'll probably get different absolute answers in the 4th decimal place. What should stay consistant is the relative size among the bores and the measured shape of the bore. Remember the block never changed, just the measurement.

I have an acquaintance who is creating pressures in a lab in the megabar (millions of atmospheres) range. I asked how they measured it accurately. He laughed. (He didn't want to have to shoot me after he told me. ) I'm sure a different lab might measure his pressures at a different value. So what's a megabar or two among friends? When they achieve their goal (win the race?) they'll know about where the pressures are.

Comparing chassis dyno readings between different installations and even the same installation can be difficult because of all the other variables, especially in the vehicle.

IMO, the "conjecture" you mention comes more from lack of understanding than lack of accurate measurement. What is, is. The explanation is often the difficult part.

My $.02

 

Okay, I've read these arguments and still do not agree wholeheartedly.

I have a 440RWHP 383, that puts out 445 RWTQ. Prior to my buildup (stock LT1), I could punch the throttle at anytime and the car would simply accelerate, with nary a chirp.

Now when I punch it, I melt the tires in 1st, 2nd or 3rd. If my RPM is only at 1500 when I punch it, then I am only using about 90HP, but my Tq is at about 300. When I was stock, my Tq was about 200 at 1500, therefore my HP was only 57.

If you think the 88 HP is melting my tires at 1500 RPM, but 57HP was insufficient, then please explain why my tires don't explode when the HP exceeds 400?

It is the torque that is melting my tires, not the HP. The Torque is spinning my tires and breaking contact with the pavement.

Why do you think they call it a "torque-converter" instead of a Horsepower-Converter?

I would rather have 450 RWTQ at 3000 RPM, than 450 RWHP at 7000 RPM.

Respectfully Submitted,

UD