why the lost hp

[rayhawk]

Originally Posted by tav8ws6

Sounds like it has something to do with where they took the number readings.

Corvette site:

6.2 Liter LS3 V8 − standard in coupe and convertible − produces an SAE-certified 430 horsepower at 5900 rpm and 424 lb.-ft. of torque at 4600 rpm.

Camaro site:

Horsepower (hp @ rpm):
(projected)
422 @ 5000 (LS3)
Torque (lb.-ft. @ rpm):
(projected)
408 @ 4500 (LS3)

Actually, those numbers posted by GM make no sense. For the car to produce 422 hp at 5000 rpm it would be over 440 ft-lbs of torque (at 5k). It is either a misprint or they are playing games with the numbers. I think the actual difference between the Corvette LS3 and the Camaro LS3 will be very small.

And by the way, not everybody really understands cars or mechanical things well, but that does'nt mean they should be attacked for trying to chime in on something they thought they understood. You end up discouraging the guy and he never really learns anything-he'll probably go buy a Honda now...

[jordan 572]

why would the vette run 900 more rpm

[baileyrx]

Originally Posted by jordan 572

why would the vette run 900 more rpm

thats where the tune comes into effect,

if you shave some timing off the higher rpm's or dump some fuel in the upper rpms on the camaro the hp flattens out...

also the l99 doesnt rev as high as the ls3 due to the cam & the cylinder deactivation...

[headpunter]

Originally Posted by rayhawk

Actually, those numbers posted by GM make no sense. For the car to produce 422 hp at 5000 rpm it would be over 440 ft-lbs of torque (at 5k). It is either a misprint or they are playing games with the numbers. I think the actual difference between the Corvette LS3 and the Camaro LS3 will be very small.

And by the way, not everybody really understands cars or mechanical things well, but that does'nt mean they should be attacked for trying to chime in on something they thought they understood. You end up discouraging the guy and he never really learns anything-he'll probably go buy a Honda now...

yeah i started to look at that and it doesnt make much sense.

[rayhawk]

Originally Posted by jordan 572

why would the vette run 900 more rpm

It is not that the vette runs 900 more rpm, both cars run to 6500/6600 rpm. If I recall correctly, for some reason the Camaro has it's redline 100rpm higher than the vette-don't know why. The quoted numbers are just the peak horsepower and the rpm it occurs at. To achieve that hp at only 5000 rpm, the torque peak would be much higher than they are stating. My guess is the hp/torque peak numbers are correct, but the peak hp should be around 5800-6000 rpm.

The 422 hp (vs 430) could be due to more conservative tune but my guess is slightly more restrictive exhaust, or maybe there really is'nt any difference and just like in the past they just want the vette to have a bit higher number for advertising. Either way, it is a pretty small difference.

[headpunter]

Originally Posted by rayhawk

It is not that the vette runs 900 more rpm, both cars run to 6500/6600 rpm. If I recall correctly, for some reason the Camaro has it's redline 100rpm higher than the vette-don't know why. The quoted numbers are just the peak horsepower and the rpm it occurs at. To achieve that hp at only 5000 rpm, the torque peak would be much higher than they are stating. My guess is the hp/torque peak numbers are correct, but the peak hp should be around 5800-6000 rpm.

The 422 hp (vs 430) could be due to more conservative tune but my guess is slightly more restrictive exhaust, or maybe there really is'nt any difference and just like in the past they just want the vette to have a bit higher number for advertising. Either way, it is a pretty small difference.

these are fly wheel tests that arent in the car so i dont know if there is even an exhaust on them

[tav8ws6]

As for the HP and TQ #s, a i figured different tune is most likely the reason, but what i was thinking earlier about my post is that GM didnt necessarily take the peak ratings. They just took some numbers a little before peak came up becuase of the Vette being top-dog. Ive read the 4th Gen made 345 hp just like the Vette, tho at its highest it was rated 325 hp.

We'll just have to throw some camaros on the dyno to be sure!

[TheClassicCarKid]

this thread got weird hahaha

[CamaroSpike23]

Originally Posted by rayhawk

Actually, those numbers posted by GM make no sense. For the car to produce 422 hp at 5000 rpm it would be over 440 ft-lbs of torque (at 5k). It is either a misprint or they are playing games with the numbers. I think the actual difference between the Corvette LS3 and the Camaro LS3 will be very small.

And by the way, not everybody really understands cars or mechanical things well, but that does'nt mean they should be attacked for trying to chime in on something they thought they understood. You end up discouraging the guy and he never really learns anything-he'll probably go buy a Honda now...

not attacking you, but its completely possible to have 422hp at a certain rpm and not have that amount of tq.
serious riceburners do it all day long. 600hp motors with 300ft lbs of torque.

you are right tho, the difference will be small. i imagine that the timing is pulled back slightly along with the manifolds being just a tad more restrictive. also depending on the accessories mounted to the motor during testing could make up for 1-15 hp on any given day.

Originally Posted by headpunter

these are fly wheel tests that arent in the car so i dont know if there is even an exhaust on them

there will be manifolds at the very least

Originally Posted by tav8ws6

As for the HP and TQ #s, a i figured different tune is most likely the reason, but what i was thinking earlier about my post is that GM didnt necessarily take the peak ratings. They just took some numbers a little before peak came up becuase of the Vette being top-dog. Ive read the 4th Gen made 345 hp just like the Vette, tho at its highest it was rated 325 hp.

We'll just have to throw some camaros on the dyno to be sure!

some of the SS LS1s made about that, but it was a rare occurance, and usually it was attributed to the LS6 heads/intake that was put onto some of the late model cars.

but we do need to get some rear wheel numbers, flywheel hp dont mean squat. its all about what you can put to the ground.

[theholycow]

Originally Posted by CamaroSpike23

not attacking you, but its completely possible to have 422hp at a certain rpm and not have that amount of tq.
serious riceburners do it all day long. 600hp motors with 300ft lbs of torque.

I'm pretty sure that at a given RPM, if you know HP then you can calculate torque, or if you know torque then you can calculate HP.

See http://en.wikipedia.org/wiki/Horsepo...ip_with_torque

According to http://www.dragtimes.com/horsepower-...conversion.php 422 hp at 5000RPM is exactly 443.27 lb-ft of torque. http://www.corvetteactioncenter.com/...ls/torque.html agrees too.

http://www.car-videos.net/articles/h...wer_torque.asp has this formula posted:
Horsepower = torque * RPM / 5252

So, no matter how you slice it, if you have a given horsepower at a given RPM, you can't have different torque measurements.

The ricers you speak of could have 600hp at 10,500 RPM and have only 300 lb-ft of torque.

[CamaroSpike23]

Originally Posted by theholycow

I'm pretty sure that at a given RPM, if you know HP then you can calculate torque, or if you know torque then you can calculate HP.

See http://en.wikipedia.org/wiki/Horsepo...ip_with_torque

According to http://www.dragtimes.com/horsepower-...conversion.php 422 hp at 5000RPM is exactly 443.27 lb-ft of torque. http://www.corvetteactioncenter.com/...ls/torque.html agrees too.

http://www.car-videos.net/articles/h...wer_torque.asp has this formula posted:
Horsepower = torque * RPM / 5252

So, no matter how you slice it, if you have a given horsepower at a given RPM, you can't have different torque measurements.

The ricers you speak of could have 600hp at 10,500 RPM and have only 300 lb-ft of torque.

the one thing to remember is that horsepower is found using torque, and while you can go backwards from hp to find torque, its not as accurate as finding hp via torque measurements



love the little disclaimers on these calculators:

The accuracy of this calculator and its applicability to your circumstances is not guaranteed. You should obtain personal advice from qualified professionals

those calculators are nice, but dont account for the variables included with measuring an individual engines power.


for instance, the calculators say that my friends 383 stroker motor that makes 432hp at 6400rpm only makes 354.51 lb-ft of torque. gauging from his dyno sheet, thats off by just a tad.... like 117lb-ft.



and the 600hp was at 9300rpm...lol

[theholycow]

Originally Posted by CamaroSpike23

the one thing to remember is that horsepower is found using torque, and while you can go backwards from hp to find torque, its not as accurate as finding hp via torque measurements

Are you saying that the formula is wrong? Mathematical formulas work just as accurately no matter which variable you're solving for. I am not an engineer and don't know much about this, so I can accept that the formula may be wrong, but I know enough about math to know that a formula is just as accurate no matter which way you figure it.

Another possibility is inaccurate dyno readings, which I'd guess probably explain the discrepancies you've noticed. How accurate can a random ricer on a random chassis dyno be?

[knowitman]

Originally Posted by CamaroSpike23

the one thing to remember is that horsepower is found using torque, and while you can go backwards from hp to find torque, its not as accurate as finding hp via torque measurements

I believe that you don't know what you are talking about. The relationship between power and torque is just a unit conversion taking the engine speed into account.

http://www.howstuffworks.com/question622.htm

[rayhawk]

Camarospike, it's ok, I don't take it as an attack. Hp and torque are not independent of each other. Basically, as has been said, they are dependent on each other. At 5250 rpm, torque=hp. As a matter of fact, a dyno really measures the torque output and horsepower is calculated from it. The number you start with makes no difference to the outcome.

HP=Torque (ftlbs)*rpm/5250

So if you were to take 422 hp at 5000 rpm, you would get 443.1 ft lbs of torque, which is higher than the peak even for the Corvette LS3. Torque is a unit of work, hp is a unit of power, or work per given time period, which is basically figured out by the rpm which the torque was generated at. And I think they test the engine with all accessories and full exhaust as it will be installed in the car, but I could be wrong.

Try the formula and you will see the 432 hp at 6400 rpm does come out to 354 ft lbs. The peak torque, however is typically at a lower rpm, which is why most times you see the two listed at two separate rpms's.