DirtyJohn

iTrader: (8)

What exactly is the curve?
Is this the curve on the dyno sheet where the TQ and the HP meet @ ~5200?
So does that mean power under ~5200 RPM?

And this also may be a poorly informed question, but what is a good curve supposed to look like, a straight sharp climb or kind of convex or concave?
Is it depending on your application and personal prefrence or is there one "best" to shoot for?

I guess I'd just like to have this squared away, so when I look at examples of dyno's that people post, I can tell where the gains were and how they effect results in the RPM ranges where there were gains.

I hope this message made sense, I've been wading through alot of this stuff for a while and just want to have it conceptually correct before I move on to more complicated mods.

Also, moderators, if you think this belongs in a different forum, could you shoot me an email where you move it. I wasn't sure where to go with this one.

thanks
DirtyJohn

Lt1FBoDy209

"the curve" is the graph of horsepower and torque across the powerband. rice rocket curves spike at 8000rpm or whenever up to 150hp which makes them think they are fast.

its all about power under the curve i.e power across the whole rpm band

sorry for being kind of vague. hope that helps.

Louie83

iTrader: (3)

You have the right idea Dirty. It's the power that your car makes under the rpm band.

That is why ricers are so idiotic when they talk about HP/Liter.
1. They don't know what torque means.
2. They don't realize that there car does not make peak horsepower the entire time they are flooring it.

DirtyJohn

iTrader: (8)

I think i need to read the HP vs. TQ thread again.
Is there power ABOVE the curve. Maybe i get the idea, but the terminology is throwing me off.

thx folks
DJ

LSWannabe

Yeah, there's power above the curve. It's called nitrous.

Power under the curve refers to how much power the car is making at lower RPMs and has nothing to do with peak numbers. Say you've got your LS1 making 400rwhp at 6000 rpms. Then you've got your supra making 500rwhp at 7000 rpms. If you look at the HP and TQ curves the LS1 is going to be making alot more power in the lower rpms and will probably put down a better 1/4 mile time.

See here the big displacement NA LS1 makes big torque at low rpms and the hp level climbs steadily to its peak.

The turbo car shows much lower torque in the lower rpms and you can literally see when the turbo spools and boost kicks in.

This supra is making a little more power than I had mentioned. But if you look at when it was running the stock twin turbos it peaks about 40hp/60tq higher but is barely making 100 hp/tq at 3000 rpms. The LS1 is making over 3 times that amount of torque(the **** ricers forgot is important) at the same rpms.

There is no replacement for displacement.

(Hopefully that helps clear up the meaning of "power under the curve")

v8hunter

iTrader: (2)

Hey enough of the supra bashing...in a drag race where the (likely bolt on only) tt supra shifted near redline (see 418 hp dyno) against the (likely full bolt on / cam) ls-1 (see 375 hp dyno) with a similar 1.9 60 foot shifting near redline. I would project the supra pulling about a 11.8-12.0 at approx 119 with the ls-1 pulling a 12.2 to 12.4 at approx 115.

I remember beating a head/cam/full bolt on ram air 01 t/a at the dragstrip with my bolt on only supra with less than $1500 in mods (no nitrous). He had a better 60 foot time so was also likely a better driver.

I really enjoyed my former tt supra and would have bought one again instead of an ls1 t/a if they weren't so damn expensive. The lack of torque below 4k sucked but the top end and handling kicked ***...and you didn't have to worry so much about breaking drivetrain parts (i.e. 10 bolt rear ends & trannys).

Makes me wonder if my 3k+ 380 rwhp ls1 buildup is gonna cost me more like 6-7k by having to add a ford 9" and a built up tranny.

stock for stock the tt supra and ls1 fbody would be a very good race though

Looks like I got a little off topic here but the power under the curve (average power rather than peak power) would give the ls1 an advantage from a roll over the tt supra.

jaberwaki

Sorry but this is a TERRABLE example and there is NOTHING about the car this depics that is "rice" 600+ hp not rice.
in a race the supra that this dyno shows will never be out of its power band... how is that rice?
off a redline clutch dump this supra will remain in the 5k-7k rpm range for the whole trip down the 1/4 mile. look at the graph, what kind of power is he making in this range...
did someone change the definition of rice on me ???
last i checked rice was a 105 hp civic that looks like it was super magnitized then driven thru a pepboys. not a 600+ rwhp supra

davered00ss

iTrader: (4)

Difference between the before and after Dyno graph lined in all rpm ranges. You may see a peak gain of 10rwhp, but 25rwhp gain at say 200-3500 rpm.

davered00ss

iTrader: (4)

Difference between the before and after Dyno graph lined in all rpm ranges. You may see a peak gain of 10rwhp, but 25rwhp gain at say 2000-3500 rpm.

jrp

iTrader: (16)

those graphs that LSWannabe arent the best examples. here is what i use as illustration and why you have to look beyond peak power; hence area under the curve.



if you look, Ryan035 actually has more peak HP. however its clear which car would be faster in any situation.

jrp

iTrader: (16)

here's another example from Tony Mamo's build up. the only mechanical change is the addition of a 4" stroke, the 383 actually has .3 less compression as well.

EugThinks

Everyone in this thread's already posted the right information, but I thought I could maybe help clear up the terminology a little bit...

The "curve" is basically the line on the dyno graph. Peak power is the number taken from the highest point on that curve, and is usually what people give as dyno results, and what manufacturers give to sell cars. "Power under the curve" refers to having high numbers all along that line, or along as much of it as possible. Think of it has having as much space under that line as possible... for those results, you'd want to have the line as high as possible all along the graph, not just at one point.

Power under the curve is good because the car will not always be operating at the exact RPM that gives it peak hp/torque. A car with a significantly better curve can go faster than a car that has high peak, but a bad curve. This could just be my opinion, but a desirable power curve would be as flat as possible, what's sometimes called a table. That would mean the car is making close to peak power at any RPM.

Example 1: A car that has 350 peak hp and 350 peak lb-ft of torque (I'm making these numbers up, they aren't connected to reality), at around 5500rpm. The lines on the dyno graph stay around 300-350 the entire time. This car has significant power under the curve.

Example 2: A car that has 400 peak hp and 400 peak lb-ft of torque, at around 5500rpm. However, the rest of the line on the dyno graph hovers between 250-280 hp and less torque, before jumping up to the peak numbers at high rpm. This car does not have as much power under the curve, although it has better peak power.

Because power under the curve is important, for a well-functioning and well-performing car, you want to be wary of peak power numbers. Just because a certain mod makes your peak numbers jump up, doesn't mean it's necessarily good... gaining 30 peak hp or torque isn't worth it if you're losing 30 along the rest of the curve.

I only have a vague understanding of these things, but I thought this might help the original poster. If anyone else can say it better than me, or correct any mistakes I might've made, please do.

jrp

iTrader: (16)

um, no. first of all to bring up the 2jz is pointless as thats an apples to oranges comparo. secondly, that supra would walk an ls1 in the 1/4 if it was setup properly and could hook. low end tq (1500 - 3000) means dick in in drag racing as shifting at 6500 you'll never dip that low.

power under the curve is relative to application. the ls1 sucks dick in area under the curve compared to say a c5r. does that mean the ls1 is a , of course it doesnt.

DanO

A better way of putting it is "average power/torque" If you have a higher average in the useful rpm range, your vehicle will perform better given everything else equal.

LSWannabe

The car is not rice unless the owner makes it look so. Ricers are people not cars and by no means big power supras in my book. I made the ricer comment as a bash on ricers in general and their 105hp civics that have 0 torque.

Also, not everyone does redline clutch dumps at the track.
When I read this I figured you thought I had the right train of thought but the wrong track. Good intentions though.
Then you turned on me and put me in my place. I apologize for the err in my ways. When I made those references I said 1/4 mile but in my mind I was thinking feathering it out on the street. I'm pretty much 99% street so I'll take the blame on not being specific. I didnt come across the first graph you posted in my search otherwise I could have saved myself some flaming. That's a dynomite example of power under the curve.

I wasn't sure if any of the Tech big dogs would show up in the post so I was trying to do some good, although it wasn't the best help. No hard feelin's

RAIDER

iTrader: (4)

also what does it mean when it says SAE corrected, and what does STD #'s mean? thanks

GMC_DUDE

"Power under the curve" really shows its merits more in regular street driving than in drag racing. During a drag race, the engine rpms are generally kept within a fairly narrow band, and the accelerator at or near WOT. So in that case, the Toyota example given would not be at a disadvantage. But, consider which car would be more enjoyable driving around town? or in heavy stop-n-go traffic? or going up a long steep mountain grade? or pulling a horse trailer (with horse)? The broader torque curve makes for better overall driving, which is why manufacturers of positive displacement blowers, which produce broad torque curves, generally advertise their "more power under the curve" for street applications.

DirtyJohn

iTrader: (8)

Thanks folks, for the replies.
Time will tell if I have this figured out with my mods and my results, and I appreciate the comments / discussion.
Your comments did help clear it up a bit.

Thanks,
DirtyJohn

RAIDER

iTrader: (4)

Sorry i had to ask again, i see it a lot but don't know the meaning, SAE corrected, and STD#'s what exactly do they mean?

jaberwaki

this might help ya...

http://www.i-speed.us/technical/sae_...n_method.shtml