equal amount of both, but i believe in having more hp than torque.

:lolg: :lolg: :lolg: :lolg:

 

HP is great if your building a relatively high revving motor and want to race it around. RPMs is one of the mathematical multipliers for HP.

But I dont drive thru town at 6000rpms. I prefer a car that performs between idle and 5500 because that is how I drive 99% of the time. Torque wins on the street.

WA 2 FST -- I dont think you can tell from "peak" numbers alone which car will win. Have to see the whole curve to get a better idea.

 

The definition of hp is, the amount of energy necessary to raise or lift 550 lbs one ft in one second. Note the definition refers to raising or lifting not rotating.

Rotating force is torque, and guess what.....engines rotate, driveshafts rotate, drive axles rotate, tires rotate....Vehicles have all these rotating parts so it would seem that a measurement of rotational force would be a better gauge of performance.

Torque will give you a much better indication of a vehicles ability to accelerate than does hp. High torque #'s suggest stronger acceleration potential.

I don't know about you but I do most of my driving on the street not the track and high torque at low rpm gives the low end grunt that makes cars fun to drive in the real world. :chevy

 

A rotating assembly can still do work, i.e. The crank used to rotate spindle to raise the bucket of water in the well. horsepower and torque are rigidly tied to one another. If I know the value of either one at a particular rpm, I can easily calculate the value of the other at that same rpm. Torque breaks it loose, horsepower gets it there.

My exammple above is extreme, but I don't think the 1650 pound of torque with the Cat engine will beat the 500 hp 302 small block in cars of equal weight. Since the horspower is the same for both the Cat and the Z engines, the Cat engine could be geared to to go over 125mph in the 1/4 too, but since the power is at 1/3 or the rpm of the Z, it will have to be geared with a final drive ratio of about 1.5:1 instead of the Z's 4.56:1. The cat would probably only use 1 gear since it's torque is virtually flat from idle on up. Therefore, the Z with only 350 pound of torque would actually make 3,500 pounds of torque in 1st gear (4.56 x 2.2 x 350# = 3500#) The Z makes more average torque over the race track.

Wes had it right, it is the average power available withing the rpm range used during the race that counts.

Chuck

 

I think I did open a can of worms here.

 

Ummmm...torque wins WHAT? :confused: :confused: :confused:
And be careful what you confess on here ;)

Dep

 

Spoken like a true "low horsepower" smallblock owner!!! :lolg: :lolg: :lolg:
Thanks for proving my point! :D

Dep

 

The way it was explained to me back in the day is that horsepower it torque over time (Not necessarily in the mathematical sense.) Street engine? Build torque and let let horsepower take care of itself. Want more horsepower? Chances are you're going to have to trade off some low-end torque to get it.

 

Horsepower is torque...multiplied with the rpm at that point on the torque curve. You can picture it as the "staying power" of torque. Brute torque will launch you very well, but if the engine falls flat on its face, you'll be very limited in how well you can do in the quarter mile. On the flip side, if you're all horsepower and low torque (like the Honda S2000), you'd have to rev the snot out of it to perform on the street, and it'll be a challenge to launch well.

I think you want a balance. A little less top end, and a stouter torque band with more area under the curve, will probably combine to make your car quicker AND faster. If the car is heavy, lean more towards torque, and maybe suplement the top end horsepower with a shot of nitrous. If the car is light, then build a little more horsepower, because the torque would otherwise just light up the tires forever.

 

Lots of good points here, so someone answer me this question of torque vs HP;

In the same car which GM engine would be faster in 60ft and 1/4 mile
ZZ4; HP 355 @ 5250
TQ 405 @3500

GM383; HP 340 @ 4500
TQ 435 @ 4000

 

If the car is very light, the higher horsepower ZZ4, if the car is perhaps 500 to 1000 pounds heavier, the the 383

Chuck

 

Both, they are interalated.

This is what I would suggest, if you have a specfic car in mind, that will be used mostly for drag racing, then take several practice runs with what you have now. Have a buddy go with you or maybe use on of those portable data collection devices.

Have your buddy time how long you stay at each RPM. This is difficult, you can also have you buddy take notes on your engine RPM at shift points, but more importantly, what RPM your engine drops to when you shift.

The goal is to find out what RRM you spend most of your time and build an enigne with the most amount of TORQUE in that RPM band.

If you find that you spend most of the time between 4,500 and 6,500 RPM, when comparing cylinder heads or cams in DD2000, which ever combo has the most torque between 4,500-6,500 would be a good starting point.

 

Isn't this fun?

You have to quit thinking of the two as being separate entities. We all talk about HP, but it's all just math. On an engine dyno we measure TQ and then do the math to come up with a HP number. You can do just as much analysis looking simply at the TQ numbers.

The key things you're looking at is the curve as everyone mentioned and where you want it to be. If you have "high" gearing and the engine is likely to spend a lot of time in each gear accelerating, then moving the curve lower will help. The parts you choose to do that will increase the actual TQ production in the lower ranges,(which also increase HPin that range) but it will "run out of breath" early. That's fine as long as your gearing enables the engine to work within its range. Might even be desirable.

But as Chuck mentioned, if you already have more than you can use, the choice is to add more traction or go ahead and move power band upwards and take advantage of the possibilities at a higher rpm. Of course you may need to change gearing to compliment it.

For example, the first version of my 540 with unported aluminum heads, 10.5 compression, relatively small intake and 262/273@.050 cam..made unreal TQ in the 4200-4600 range. When it came on, it was a literal handful and pretty hard to control.

The newest version with the same heads ported, much larger intake, 272/278@.050 cam and 11.0 compression, makes almost identical TQ numbers at the peak, but they are at a higher 5200-5300 or so. Of course that puts the HP numbers at that speed much higher too. The real trick is that whereas the old version was pretty much done by 6200-6300 rpm at 732 HP and was down to 591 hp at 7000 rpm, the new version peaks in the 7200-7400 range and is up over 230HP at the peak. At 7000 it's up a little over 200 hp already.

It's down on power under 5000 as compared to the old version, but not that much. So far this has proven to make the car much more controllable.

So best thing is to determine more than anything what RPM range you want it to work in. If you don't have O/D and want to cruise highway a bunch, then you are a little limited unless you like spinning it alot. Figure something running 4.10 gears needs to be able to pull strong to 6500 rpm or so. 3.73's need to be able to hit 6000+rpm pulling hard and so on. Any attempt to build an engine that makes power at 6500 rpm and then stick 3.08's in it will most likely make a stone unless you have a 5 or 6 speed to allow it.

Warren Johnson's favorite line is "Whoever makes the most explosions on the way to the line will win" is still true. In his case he gears car to operate in a narrow range and then build engine for that range. He knows how much power it takes to go a certain speed at a certain weight. of course his RPM range is very high, but it still works for us too.

If two cars have the same HP, but one car has ungodly mid range TQ, it is going to have a tough time beating a car with less mid range TQ *if* they are both geared appropriately for each engine. There are ways around this, namely BOOST..which changes the whole picture. They can make SO MUCH TQ after a shift that if you can make it hook up it will fly!

So build your engine to perform in the RPM range you want, but don't choke it. Don't be afraid of using larger heads. cams and intakes. If chosen correctly they will extend your rpm range and make the car a LOT more fun to drive.


JIM

 

Blondes ... Brunettes???

One+ more of either suits me just fine!

Can of worms... No no no... this is the topic that spurred men onto the field of battle. ITS A WAR OUT THERE!!! WHICH SIDE ARE YOU ON?

 

Count me firmly on the side of high horsepower-torque is for trucks and SUVs :D

Dep

 

You must love those 800 hp rice/rockets....all hp no torque. :lol:

 

Nooooo...but I do love the 427+ cubic inch big block Chevys that never concern themselves with torque :D

Dep

 

Interesting comment.

What's not to love about a 427, however each model produced more torque than hp.

L36> 390hp/460ft/lb......L68> 400hp/460ft/lb....L71> 435hp/460ft/lb...

So you may not be concerned with torque, but it's obvious GM engineers were. :D

 

I won't even bother with the truck engines you list (hydralic lifter versions are NOT really performance engines). Take a look at the REAL performance engines...the L-88 and ZL-1. THEN THROW AWAY THOSE FACTORY numbers.
They are :bs Chevy purposely UNDER-rated the L-88 and ZL-1 for insurance and corporate reasons. Yeah...they had lots of torque too...but who CARES? Those engines were putting out around 550-600 HORSEPOWER!!!!
Who needs torque with THOSE numbers???

Dep

 

See I told you it was war... or maybe its just Dep... hehe :D