Well, the link is down sometimes, but keep trying it.

I know you want HP vs. tq but really you cannot have 1 w/o the other. Its always TQ that moves you, the question is what is better, a big peak TQ number at some low RPM or higher average tq across the usable power band. The answer is the latter. Higher HP is produced by moving the tq curve up in the RPM band, the net result is more net power to the wheels.

The article I linked to gives a great explanation of this, and why really it is "power" that you are looking for.

 

...So why don't you call your shop "Power Engineering" rather than Horsepower Engineering if "fast" is really "power?"...

 

just a guess... but "Horsepower" sells better than "power" does.


Seriously, this question is fairly easy to answer:

Horsepower is a result of torque AND rpm. Horsepower it the ability to do work, while torque is just the abilty to apply a force (regardless of the speed or result of that force).

Find the most HP you can over a power BAND, and shift gears to stay there. Hardcore racers choose trannies (or at least tranny ratios) based on power bands... likewise rear gears are adjusted for the same reason.

To quantify the quickness of your vehicle, you need to understand that HP is a rating of work being done, and THAT is what you need to pay attention to.

Torque is great data for engine design/tuning, as it is closely related to volumentric effiency... but once the engine is putting down hp numbers on a power band fat enough to cover the rpm differential from changing gears, that's what counts.

 

Cajun-Z,

Who knows what our name will be now! It may be Cuddly Cupcake Motorsports next week.

 

http://www.horsepowerengineering.com...s/P0002481.jpg

your bores after you hone them should reflect white bright light back to you , and not dark shinny light back to you

White light= you are CUTTING the cylinder bores with stones, not folding over peaks but cutting peaks for plateau finish

Dark Light= you are cutting the cylinders bores but also FOLDING peaks over valleys trapping debris in valleys , so you get a darker looking shinny bore when you shine a light in it

Erik..good "White Light" example of good hone

 

I can find some bores that are all dark like people that don't realize how hard a 460 is and use regular 525s.

 

The longer you can carry out your torque, the faster you will go. That's why L98s are slower than LT1s...for example...They have just as much peak torque, but it's at a lower rpm, and the tq starts dropping off way before the LT1s torque begins dropping off. So when that L98 is right by your side for a few seconds, it's because he makes as much torque as you, but as his tq starts falling off, you keep your torque going...and you keep accelerating, while his acceleration capabilities are going down hill fast, cause he just shifted into the next gear (gears are tq multipliers, and the higher gear you are in, the less multiplication there is) and you're still in the same gear. In SOTP terms, the L98 will feel just as fast as the LT1, even though it is not. Weird huh? Well think of it this way, TQ is what moves your car. Hp is really only a calculated value of tq and rpm. The Tq values being the same will feel the same (as long as the weight and gearing of the vehicle are the same, but you know what i mean). Anyway, the answer to the question is you want to hold your tq out as long as you can (which increases hp due to the formula)...but it has to be also low enough in the rpm band so you don't bog your engine out of the hole. That's what cams do, they allow you to hold your tq out for a longer period of time, basically.

 

When hp increases (mods to increase hp...i.e. cams, exhaust, etc.), does torque proportinately increase analogrhymically?...
Why I ask is that I never heard anyone build engines for increases in torque, only hp...

 

Remember hp is just torque related to rpm. HP = torque x rpm divided by 5252. If you increase torque at ANY rpm, you increase the hp at that rpm. The higher the rpm you add an increment of torque, the more hp you add.

Example:

10 lb-ft at 2626 rpm = 5 hp.

10 lb-ft at 5252 rpm = 10 hp

10 lb-ft at 7878 rpm = 15 hp

Effectively you are trying to build the most TORQUE at the rpm you are concerned with. That gives you the hp.

Perhaps you mean PEAK hp or PEAK torque. Those are nice numbers to brag about, but the hp or torque 'under the curve' or average hp and torque numbers in the range you run your engine are what makes it fast.

 

when a new guy's 1st time on Dyno, they always look at the "Peak HP Numbers" ...then i explain its the "Average HP/TQ" in the required/desired RPM range you need to look at

then i run a Quarter Mile Simulation that shows to them ;
what the RPMs will have to be each Foot distance down the DragStrip...show them a Histogram of HP/TQ numbers under curve
where Engine RPM will be staying at the longest , and where you don't want to sacrifice anything
--------------

Another different example of Peak Torque numbers =

a NHRA C/ED Dragster we set the NHRA record years ago
it made Peak Torque at 7800 RPM
and Peak Hp at 9000 RPM

had a 8300 Stall Converter...Engine never saw the Peak Torque point down the DragStrip

putting a 7800 Stall Converter would have hurt ET/MPH

Shift point was 9300-9500 and crossed 10300 RPMs

----------------------

Another example =
NHRA SuperStock s like SS/IA Class 350 ( 4.065 x 3.493=362)

the 1st Time i had a SS/IA engine on dyno it made=
523.0 Peak HP and 465.0 Peak Torque

thru the years of Track testing and trying many different combos on the same engine
we got 585.0 Peak HP and "still" 465.0 Peak Torque

Very same Peak Torque numbers thru the years , but
each and every time without failing, the car ran down the DragStrip faster in ET/MPH each and everytime we found any HP increases
...while still Peak Torque remained at 465.0

------------------------------
i could give you a tremendous numbers of actual dyno data with backup DragStrip times that follow the above examples , but there is not enough time

of course its always nice to make peak torque gains likewise

just wanted to point out that many record setting Pro cars never see Peak Torque point down Dragstrip

and Peak Torque is only "One Point"
and Peak Hp is only "One Point"

the engine down the Dragstrip doesn't stay very long at "either point"

 

Torque is just a snapshot of the engine, a single dimensional view of how hard the engine is pushing at a certain speed.

Horsepower is torque over time, basically telling how much power the engine is putting out at a certain speed.

For an example of which is more important, let's say an engine puts out the exact same amount of torque at 2000 and 4000 rpms. At which point will the engine be making the most power? At 4000, of course.

Basically, when you're talking about a dragstip vehicle, torque figures are worthless. What you need to be looking at is an average hp figure for the area at which the engine will be running at during it's trip down the strip- that's what will tell you what kind of times you will be looking at.

Of course, for a production vehicle, torque figures are very important, because the manufacturers aren't going to be handing out dyno sheets with their advertisements, are they? So torque can now be your best friend, because it will tell you exactly what kind of powerband the vehicle has.

For a good comparison, take an LT1 and and LS1. One makes peak torque in the 2000 area, the other in 4000. So which has more power at 2000? LT1. LS1 has more at 4000. - hp is directly related to torque. This goes to show that although the LT1 has an awesome powerband, it's really a little too broad for the dragstrip. It's so spread out that a lot of the good stuff gets wasted on the bottom when you're running full throttle down the dragstrip- but nice for a street vehicle. Since the LS1 has more power, even though the powerband isn't as wide, it doesn't really matter at wot, no one is going to see 2000ish rpms with the pedal mashed. Keep in mind that the LT1 produces more power at 5000 than 2000, so trying to "torque" your way down the strip will yield some very crappy times. It's all about average hp in the rpm range you will be running at, that's all you need to see if you're paying attention to full throttle blasts.

Well, I had more but I'm starting to confuse myself.
So thanks to all that bothered to input on this, good reading.

 

After reading the three previous posts, I seem to get the jest of the torque vs. hp thread...but I do see different opinions that make me wonder if this is science (for the most part) or is this still "gray area" theory? It seems that torque is a factor "built-in" to hp, but doesn't depend on absolute power to propell a vehicle down the strip (i.e. torque breaks-off and hp continues "the climb") past the max. (peak) torque range. So it's actually not proportional...correct?...

 

What you guys are forgetting is that what really pulls yuo is the torque to the rear wheels...

if you get peak torque on an engine but have very few rpms you need to put your gears down way low to achieve that mph target... otoh if its done to an engine with higher rpm band and have the same torque you can multiply it more than the previous combo achieving the mph goal you want.

I believe that is all there is to it...


there is a combination from weight and engine torque that will tell you when torque or HP is needed.. I cant put my engine (700HP flywheel s/c) and put it on a MACK that has 500HP... it will simply not move it... Doesn't have enough torque... and vice versa...

its like the combination of rpms and cam... why more duration makes more torque higher in power band. past 180 the piston is pushing up and the valves should be closed for compression, but when the speeds are high enough air can come in faster than the difference in volume the upward motion of the piston is creating and you get more mass of air and fuel in it.

More or less like that.. its always the combination....

If I have a 8000rpm range in my engine I will probably use 5.00 rear differential which will multiply quite more than my 4.11s and the car will run a lot lot faster having the same engine torque...

 

no, what you are describing is the very reason why hp is used.

Torque is a FORCE.
Horsepower is an ENERGY. (aka WORK)

gear multiplication or torque (through tranny gears, rear gear, or torque converter) is a great way to get more force on the contat patch... but the ENERGY transmitted is what matters.

I can gear any engine alive with a 6:1 final drive and a 5:1 first gear ratio to get some insane torque to the wheels... but it won't be accelerating worth crap if there's no hp behind it (i.e. you need some SERIOUS rpm's with gear reduction like that to get the wheels moving at all). This is the concept of a gear-reduction starter. Most electric motors don't do wheel turning a lousey 500 rpms and are definitely torque-limited for high-compression engines. Throwing a gear in there though lets the motor run high rpms and it's lack of torque becomes a moot point... why? because torque is a force and you can adjust it almost infinitly... but you won't get any more or less work done with a different force.

What matters is how much power you have... not torque.

From an engine building perspective you are obviously limited to a certain amount of gear reduction (based on trannys, rear ratios, and wheel sizes that fit your application), so keeping the power band within a certain range is nessesary.... as is keeping it under or above certain mechanical limits.

Horsepower is the work available on a car, and gearing can ajust from there... but it's pointless to run less power (by shifting early say) because you're focusing on torque numbers that are deceptive without factoring in rpms.

There's really no discussion here once you understand what the terms actaully represent. Not the mathematical relationship between them (and rpms), but the concept of what they were designed to represent.

I could apply 1000 ft lbs of toque to an axle shaft all I want, but if it's indestructable and welded to a moutain it won't turn... ZERO hp. You could say that you "tried" to work, or "tried" to generate power... but the force is pointless if it doesn't move anything. Likewise, an engine which averages 300 ftlbs up to it's redline may SEEM like it would be faster than one that has 200 ft lbs to it's redline... but if the lower-torque one can operate at higher rpms, that disadvantage goes away. The torque is pointless... it's the hp produced that tells you how fast it can move your car.

 

I don't see why not. If you need more torque, use a larger rear gear. gear reduction gets any torque you want... it may not be feasible to run a 20:1 ratio or something equally obscene, but this is no different in concept than a gear-reduction starter.