Dragaholic

iTrader: (180)

I've run into this phrase before and was wanting to know what it meant. Usually when this is mentioned, I read that its not about how much peak power your car makes, its all about power under the curve. What exactly does that mean? Because Ive seen cars with substantially less amount of peak power than other cars run faster at the track, I assume because he has better power under the curve. Obviously car owners that are solely concerned on track times dont care about dyno numbers, but what they put down on a slip. Power under the curve is what race car driver's are looking for and all others are just dyno queens. So can someone explain to me what this means? Thanks.

matts22

iTrader: (2)

You have 2,700 posts and you don't know what this means? No offense man, but it's pretty much common sense. If you look at a dyno graph, it is just implying that the area under the curve is greater, even though it might make less peak power. In other words, the flatter the torque curve is, the more area there is under the curve, and the more "overall" power the car will have. If the power is lower at lower rpms, the torque curve would increase at a much higher rate (higher slope of the line), making less "power under the curve". I guess for racing, you would want the peak power, but for a street/strip car, "under the curve" is where it's at.

Dragaholic

iTrader: (180)

Just because I have 2,700 posts doesnt mean that I know everything or just about everything. I asked a lot of questions and reply to them as well, that is why my post count is so high. Ive always read this phrase before and just ignored it, but I wanted to understand it if I ever came across it again. Are there any other ways to putting it because I still really dont understand.

cyphur

iTrader: (10)

BB, go find a dyno graph. Then read matts22's explanation with it in front of you. If you can't understand it after that, you're gonna need someone to draw you a picture(no offense intended). Power under the curve relates to how flat the torque band is, starting at what rpm's, in relation to where your hp really starts picking up. Power "under the curve" is concerned with how much power the car is making all along its power band, its a better measurement of how strong a setup is. Try and think about how much time your car spends @ 6000+ rpms....in relation to the band between 3000-6000 during racing. Thats why "under the curve" power is so important.

dug

iTrader: (10)

Its really quite simple. The curve is defined what rpm you shift at and the rpm after the shift. This is the powerband youre most worried about during racing excluding the one during launch.

For example, say you shift at 6500rpms and the rpms drop down to 5000rpms after the shift. You want to maximize the average hp through this range. Lets say one cam makes more peak hp during this range but makes less average hp than another cam that makes less peak hp. The cam that makes better average hp will be quicker in the quarter mile even though it makes less peak hp than the other cam.

The power under the curve term gets thrown around a lot. I dont think people realize how narrow the curve is during racing. Typically, rpms rarely drop below 5k rpms during drag racing. A cam thats strong at 3k rpms makes the car fun to drive but doesnt make it any faster.

XTrooper

Look here.

http://www.sportcompactcarweb.com/ed..._technobabble/

There's a fairly good explanation of "power under the curve" there. It's literally the area under the curve. The greater the area under the curve, the more useable power your engine is making.

Avengeance

iTrader: (4)

Ok.. I just fabbed these up using my own dyno sheet and a paint prog. This should make it simple to understand. Dont be offended by having to see it "drawn out" for you, its just REALLY easy to see what it means on paper.

The "area, or power, under the curve" is everything in red UNDER the dyno graph hp line.

Heres car "Y". Notice the hp line and all the red under it.. that is this cars "power under the curve"... it represents all the power the car is making.



Here is car "X". Notice the dyno graph hp line reaches max hp EARLIER then car "Y".... both cars peak the same hp buuuuuttt.. since car "X" reaches that max a lot earlier that means it will also have more "power under the curve". Meaning that all things equal car "X" will be significantly faster.



Easy to understand now huh?

matts22

iTrader: (2)

Thanks for posting the pics, hopefully that will help explain it to him. But shouldn't it be for torque instead of horsepower? Because horsepower is just a calculation based on torque. Plus, the way you have the green line drawn has the torque and horsepower lines crossing way before they're supposed to (5250 I think or around that). The best way I could explain it is to look at the horsepower line and think of it as the torque line for another car. Compare that to the other torque line. Obviously, there is more area under the curve for the one that is higher throughout the rpm range (especially early on). This equals more power throughout the powerband, as there is more "area under the curve". Am I right on this?

Avengeance

iTrader: (4)

Well.. the graph is nothing but a very simple tutorial... nothing more then to explain the "power under the curve." I couldve easily made the same example and kept them crossing at the same point. Didnt think about it though.

XTrooper

This is still a question of great contention even among the "experts."

Is it horsepower or torque that's most important? Who knows?!

Sport Side

iTrader: (6)

When I think of power under the curve, I think of 2000rpm - peak tq. This is where a over-cammed car will suffer. Usually, at around 5200 rpm the hp and tq curves cross and a larger cam will shine past this point.

In my opinion, its alot easier to focus on under the curve power by watching tq. HP is at such a rise, its hard to make comparisons. Look for the table flat, torque curve in the mid range.

Thats the way I understand it at least.

NLang

iTrader: (12)

HP and Torque will always cross @ 5250...It's just how hp is calculated.

TAQuickness

iTrader: (28)

I ran across this article a few years ago. After reading it then, and re-reading it a few minutes ago, it seems to me that what really matters is horsepower. And as the late Smokey Yunick put it, "...it's not how much horsepower you have at the start of the race, it's how much horsepower you have at the finish line"

PREDATOR-Z

Sure but in drag,
"It's how much trq you have at 60' and how much HP at the end."
Torq is an acceleration figure while HP is a trap speed figure. A high trapping car doesn't mean it's the quickest.

DaleMX

iTrader: (4)

Yea, but a car with the most torque under the curve wins.

PREDATOR-Z

That's what I said.

2MuchRiceMakesMeSick

You need both to go fast.

DaleMX

iTrader: (4)

It's under the curve, right like your saying. (edit)

I shift @ 6500. That puts my rpm @ 4350 on 1 to 2, 4750 on 2 to 3, and 5000 on 3 to 4.

My torque is about 370 @ 4300, peak is 390 @ 4700 and is down to 320 @ 6500.

So that is about 360 average between 4300 and 6500.

TAQuickness

iTrader: (28)

agreed. In simple terms, horsepower is a measurement of torque over time.

Torque is a measurement of force, not work. Horspower is what gets you to the 60' mark. The more torque you have under the curve, the more effeciently (or easily) your car will make the horsepower to get you to the 60' mark.

agreed. Trap speeds are more of an indication of how hard your car had to work to cross the traps.

My favorite example for this is when I compare time slips from my stock ws6 agianst my step-dads SC'd mustang GT. My best time, with my #2 piston rings shot, was 13.1 @ 105mph where as his is 13.8 @ 108.