Unfair RWHP Advantage for LS3
03-21-2008, 10:54 PM
#1
Burning Brakes
Thread Starter
Unfair RWHP Advantage for LS3
I thought "Unfair" might get your attention on this overworked topic. For some time now I have noticed that two important considerations have been left out of discussions involving LS3 chassis dyno numbers so I have made an attempt to present them here. The first three paragraphs are for the uninitiated, but hope everyone will find them interesting.
____________________
Chevrolet gives Corvette LS2 engines a 400 horsepower rating at 6,000 rpm and LS3 engines a 430 horsepower rating at 5,900 rpm. When equipped with the optional NPP exhaust system, LS3 is rated 436 horsepower at 5,900 rpm. LS3 was rated using the updated SAE J1349 procedure and then certified under SAE J2723. LS2 was only rated under the previous SAE J1349 standard, however, GM engines that were rated under both SAE procedures gained from 1 to 5 horsepower under the newer certified method except for the Cadillac STS-V. Its Northstar V8 gained 29 horsepower when re-rated under the new method.
According to Chevrolet testing, a LS2 equipped C6 Corvette with Z51 performance option and manual shift is able to go from 0 to 60 mph in 4.1 seconds and the quarter-mile in 12.5 seconds at 115 mph. Chevrolet states that the LS3 Corvette with Z51 option and manual shift is able to run from 0 to 60 mph in 4.1 seconds and the quarter-mile in 12.4 seconds at 117 mph. Corvette forum member Jim Schindler presently has the best quarter-mile elapsed time for a stock LS3 Corvette on “The List”. He owned both LS2 and LS3 equipped cars and ran the quarter-mile in 12.49 seconds at 114.9 mph in his 2005, manual shift, Z51 coupe and 12.409 seconds at 114.7 mph with his 436 horsepower manual shift, Z51, 2008 coupe. However, Jim had a top speed of 117.03 mph on one of his seven runs at Houston Raceway Park. Overall, it looks like he matched the Chevy performance spec with both cars, but he believes with a little more seat time he would be able to improve his time in the LS3. Chevrolet performance numbers are derived from an average of numerous runs adjusted for standard day temperature and barometric pressure. Also, corporate professional drivers drive the cars. All of this results in a consistency difficult to duplicate outside of corporate testing.
Schindler had his LS3 Corvette tested on a chassis dynamometer by MTI in Houston, Texas. The best dyno run resulted in SAE corrected numbers of 390.5 horsepower and 380.5-lb.ft. of torque. Jim asked what a stock LS2 rates on MTIs chassis dyno. MTI pulled a typical stock LS2 dyno sheet showing 353.7 horsepower and 354.3-lb.ft. torque. The difference between Schindler’s LS3 and the LS2 was 36.8 horsepower and 26.2-lb.ft. torque. That is a nearly perfect match for Chevy’s rating for both engines. Chevrolet numbers show the LS3 with NPP exhaust has a 36 horsepower and 28-lb.ft. torque advantage over the 400 horsepower and 400-lb.ft. torque rated LS2.
Using a percentage such as 15% to calculate loss of power between the flywheel and rear wheels is somewhat common even though it is incorrect. Drivetrain loss between cars with different horsepower ratings is much closer to a fixed number assuming peak power occurs at equal rpm and both cars use the same transmission, differential, wheels, tires, tire pressure, etc. The Corvette LS2 seems to lose, on average, 50 horsepower (400 – 50 = 350 rwhp and *363 + 338 = 701/2 = 350.5 rwhp) between the flywheel and rear wheels. Drivetrain loss for the LS3 is likely to be less than for the LS2 mainly because it reaches peak horsepower at 5,900 rpm rather than 6,000 rpm. Higher rpm results in more frictional loss, especially when the drivetrain is involved. Calculating frictional loss in strict linear relationship, results in close to a 7 horsepower advantage at the rear wheels for the LS3 Corvette. (6,000 – 5,900 = 100/6,000 = 1.67%--400 x 1.67% = 6.68 horsepower) If we use LS3 as the base, the advantage is even greater (100/5,900 = 1.695%--436 x 1.695% = 7.39 horsepower). A mechanical engineer would probably say that using a linear calculation is not accurate for determining drivetrain frictional loss. However, I use this only as an example to show that the LS3 Corvette has a definite advantage on a chassis dyno. Another factor may be weight of the rear wheels. Forged wheels on 2008 cars are lighter than the cast wheels that were on the 2005 to 2007 cars. Rear wheels with less weight but same diameter result in less rotational mass and therefore an advantage on the chassis dyno. The combination of less frictional loss from peak power occurring at a lower rpm and lighter forged wheels give LS3 cars, especially those with forged wheels, a distinct power advantage on a chassis dyno as compared to LS2 cars.
Chassis dyno numbers for factory stock, manual shift, NPP exhaust, LS3 Corvettes have ranged from 374 to 399 horsepower. *Numbers for factory stock manual shift LS2 Corvettes range from 338 to 363 horsepower and twice I have seen claims of 365 hp posted for an LS2. Comparing the ranges, excluding the 365 numbers, we come up with a difference of 36 horsepower at both ends of the scale. It sure looks like Chevy was right on target with their ratings.
Considering that SAE Certified procedures verify the accuracy of a 436 horsepower rating for a NPP equipped LS3, I wonder what LS2 would have rated using the same procedure, especially since it loses more power in the drivetrain.
____________________
Chevrolet gives Corvette LS2 engines a 400 horsepower rating at 6,000 rpm and LS3 engines a 430 horsepower rating at 5,900 rpm. When equipped with the optional NPP exhaust system, LS3 is rated 436 horsepower at 5,900 rpm. LS3 was rated using the updated SAE J1349 procedure and then certified under SAE J2723. LS2 was only rated under the previous SAE J1349 standard, however, GM engines that were rated under both SAE procedures gained from 1 to 5 horsepower under the newer certified method except for the Cadillac STS-V. Its Northstar V8 gained 29 horsepower when re-rated under the new method.
According to Chevrolet testing, a LS2 equipped C6 Corvette with Z51 performance option and manual shift is able to go from 0 to 60 mph in 4.1 seconds and the quarter-mile in 12.5 seconds at 115 mph. Chevrolet states that the LS3 Corvette with Z51 option and manual shift is able to run from 0 to 60 mph in 4.1 seconds and the quarter-mile in 12.4 seconds at 117 mph. Corvette forum member Jim Schindler presently has the best quarter-mile elapsed time for a stock LS3 Corvette on “The List”. He owned both LS2 and LS3 equipped cars and ran the quarter-mile in 12.49 seconds at 114.9 mph in his 2005, manual shift, Z51 coupe and 12.409 seconds at 114.7 mph with his 436 horsepower manual shift, Z51, 2008 coupe. However, Jim had a top speed of 117.03 mph on one of his seven runs at Houston Raceway Park. Overall, it looks like he matched the Chevy performance spec with both cars, but he believes with a little more seat time he would be able to improve his time in the LS3. Chevrolet performance numbers are derived from an average of numerous runs adjusted for standard day temperature and barometric pressure. Also, corporate professional drivers drive the cars. All of this results in a consistency difficult to duplicate outside of corporate testing.
Schindler had his LS3 Corvette tested on a chassis dynamometer by MTI in Houston, Texas. The best dyno run resulted in SAE corrected numbers of 390.5 horsepower and 380.5-lb.ft. of torque. Jim asked what a stock LS2 rates on MTIs chassis dyno. MTI pulled a typical stock LS2 dyno sheet showing 353.7 horsepower and 354.3-lb.ft. torque. The difference between Schindler’s LS3 and the LS2 was 36.8 horsepower and 26.2-lb.ft. torque. That is a nearly perfect match for Chevy’s rating for both engines. Chevrolet numbers show the LS3 with NPP exhaust has a 36 horsepower and 28-lb.ft. torque advantage over the 400 horsepower and 400-lb.ft. torque rated LS2.
Using a percentage such as 15% to calculate loss of power between the flywheel and rear wheels is somewhat common even though it is incorrect. Drivetrain loss between cars with different horsepower ratings is much closer to a fixed number assuming peak power occurs at equal rpm and both cars use the same transmission, differential, wheels, tires, tire pressure, etc. The Corvette LS2 seems to lose, on average, 50 horsepower (400 – 50 = 350 rwhp and *363 + 338 = 701/2 = 350.5 rwhp) between the flywheel and rear wheels. Drivetrain loss for the LS3 is likely to be less than for the LS2 mainly because it reaches peak horsepower at 5,900 rpm rather than 6,000 rpm. Higher rpm results in more frictional loss, especially when the drivetrain is involved. Calculating frictional loss in strict linear relationship, results in close to a 7 horsepower advantage at the rear wheels for the LS3 Corvette. (6,000 – 5,900 = 100/6,000 = 1.67%--400 x 1.67% = 6.68 horsepower) If we use LS3 as the base, the advantage is even greater (100/5,900 = 1.695%--436 x 1.695% = 7.39 horsepower). A mechanical engineer would probably say that using a linear calculation is not accurate for determining drivetrain frictional loss. However, I use this only as an example to show that the LS3 Corvette has a definite advantage on a chassis dyno. Another factor may be weight of the rear wheels. Forged wheels on 2008 cars are lighter than the cast wheels that were on the 2005 to 2007 cars. Rear wheels with less weight but same diameter result in less rotational mass and therefore an advantage on the chassis dyno. The combination of less frictional loss from peak power occurring at a lower rpm and lighter forged wheels give LS3 cars, especially those with forged wheels, a distinct power advantage on a chassis dyno as compared to LS2 cars.
Chassis dyno numbers for factory stock, manual shift, NPP exhaust, LS3 Corvettes have ranged from 374 to 399 horsepower. *Numbers for factory stock manual shift LS2 Corvettes range from 338 to 363 horsepower and twice I have seen claims of 365 hp posted for an LS2. Comparing the ranges, excluding the 365 numbers, we come up with a difference of 36 horsepower at both ends of the scale. It sure looks like Chevy was right on target with their ratings.
Considering that SAE Certified procedures verify the accuracy of a 436 horsepower rating for a NPP equipped LS3, I wonder what LS2 would have rated using the same procedure, especially since it loses more power in the drivetrain.
Last edited by Marina Blue; 03-22-2008 at 02:32 AM. Reason: Added to introduction
03-22-2008, 12:33 AM
#7
Melting Slicks
I thought "Unfair" might get your attention on this overworked topic. For some time now I have noticed that two important considerations have been left out of discussions involving LS3 chassis dyno numbers so I have made an attempt to present them here. The first three paragraphs are for the uninitiated, but read them anyway. Read carefully so as not to miss an important piece of information.
____________________
Chevrolet gives Corvette LS2 engines a 400 horsepower rating at 6,000 rpm and LS3 engines a 430 horsepower rating at 5,900 rpm. When equipped with the optional NPP exhaust system, LS3 is rated 436 horsepower at 5,900 rpm. LS3 was rated using the updated SAE J1349 procedure and then certified under SAE J2723. LS2 was only rated under the previous SAE J1349 standard, however, GM engines that were rated under both SAE procedures gained from 1 to 5 horsepower under the newer certified method except for the Cadillac STS-V. Its Northstar V8 gained 29 horsepower when re-rated under the new method.
According to Chevrolet testing, a LS2 equipped C6 Corvette with Z51 performance option and manual shift is able to go from 0 to 60 mph in 4.1 seconds and the quarter-mile in 12.5 seconds at 115 mph. Chevrolet states that the LS3 Corvette with Z51 option and manual shift is able to run from 0 to 60 mph in 4.1 seconds and the quarter-mile in 12.4 seconds at 117 mph. Corvette forum member Jim Schindler presently has the best quarter-mile elapsed time for a stock LS3 Corvette on “The List”. He owned both LS2 and LS3 equipped cars and ran the quarter-mile in 12.49 seconds at 114.9 mph in his 2005, manual shift, Z51 coupe and 12.409 seconds at 114.7 mph with his 436 horsepower manual shift, Z51, 2008 coupe. However, Jim had a top speed of 117.03 mph on one of his seven runs at Houston Raceway Park. Overall, it looks like he matched the Chevy performance spec with both cars, but he believes with a little more seat time he would be able to improve his time in the LS3. Chevrolet performance numbers are derived from an average of numerous runs adjusted for standard day temperature and barometric pressure. Also, corporate professional drivers drive the cars. All of this results in a consistency difficult to duplicate outside of corporate testing.
Schindler had his LS3 Corvette tested on a chassis dynamometer by MTI in Houston, Texas. The best dyno run resulted in SAE corrected numbers of 390.5 horsepower and 380.5-lb.ft. of torque. Jim asked what a stock LS2 rates on MTIs chassis dyno. MTI pulled a typical stock LS2 dyno sheet showing 353.7 horsepower and 354.3-lb.ft. torque. The difference between Schindler’s LS3 and the LS2 was 36.8 horsepower and 26.2-lb.ft. torque. That is a nearly perfect match for Chevy’s rating for both engines. Chevrolet numbers show the LS3 with NPP exhaust has a 36 horsepower and 28-lb.ft. torque advantage over the 400 horsepower and 400-lb.ft. torque rated LS2.
Using a percentage such as 15% to calculate loss of power between the flywheel and rear wheels is somewhat common even though it is incorrect. Drivetrain loss between cars with different horsepower ratings is much closer to a fixed number assuming peak power occurs at equal rpm and both cars use the same transmission, differential, wheels, tires, tire pressure, etc. The Corvette LS2 seems to lose, on average, 50 horsepower (400 – 50 = 350 rwhp and *363 + 338 = 701/2 = 350.5 rwhp) between the flywheel and rear wheels. Drivetrain loss for the LS3 is likely to be less than for the LS2 mainly because it reaches peak horsepower at 5,900 rpm rather than 6,000 rpm. Higher rpm results in more frictional loss, especially when the drivetrain is involved. Calculating frictional loss in strict linear relationship, results in close to a 7 horsepower advantage at the rear wheels for the LS3 Corvette. (6,000 – 5,900 = 100/6,000 = 1.67%--400 x 1.67% = 6.68 horsepower) If we use LS3 as the base, the advantage is even greater (100/5,900 = 1.695%--436 x 1.695% = 7.39 horsepower). A mechanical engineer would probably say that using a linear calculation is not accurate for determining drivetrain frictional loss. However, I use this only as an example to show that the LS3 Corvette has a definite advantage on a chassis dyno. Another factor may be weight of the rear wheels. Forged wheels on 2008 cars are lighter than the cast wheels that were on the 2005 to 2007 cars. Rear wheels with less weight but same diameter result in less rotational mass and therefore an advantage on the chassis dyno. The combination of less frictional loss from peak power occurring at a lower rpm and lighter forged wheels give LS3 cars, especially those with forged wheels, a distinct power advantage on a chassis dyno as compared to LS2 cars.
Chassis dyno numbers for factory stock, manual shift, NPP exhaust, LS3 Corvettes have ranged from 374 to 399 horsepower. *Numbers for factory stock manual shift LS2 Corvettes range from 338 to 363 horsepower and twice I have seen claims of 365 hp posted for an LS2. Comparing the ranges, excluding the 365 numbers, we come up with a difference of 36 horsepower at both ends of the scale. It sure looks like Chevy was right on target with their ratings.
Considering that SAE Certified procedures verify the accuracy of a 436 horsepower rating for a NPP equipped LS3, I wonder what LS2 would have rated using the same procedure, especially since it loses more power in the drivetrain.
____________________
Chevrolet gives Corvette LS2 engines a 400 horsepower rating at 6,000 rpm and LS3 engines a 430 horsepower rating at 5,900 rpm. When equipped with the optional NPP exhaust system, LS3 is rated 436 horsepower at 5,900 rpm. LS3 was rated using the updated SAE J1349 procedure and then certified under SAE J2723. LS2 was only rated under the previous SAE J1349 standard, however, GM engines that were rated under both SAE procedures gained from 1 to 5 horsepower under the newer certified method except for the Cadillac STS-V. Its Northstar V8 gained 29 horsepower when re-rated under the new method.
According to Chevrolet testing, a LS2 equipped C6 Corvette with Z51 performance option and manual shift is able to go from 0 to 60 mph in 4.1 seconds and the quarter-mile in 12.5 seconds at 115 mph. Chevrolet states that the LS3 Corvette with Z51 option and manual shift is able to run from 0 to 60 mph in 4.1 seconds and the quarter-mile in 12.4 seconds at 117 mph. Corvette forum member Jim Schindler presently has the best quarter-mile elapsed time for a stock LS3 Corvette on “The List”. He owned both LS2 and LS3 equipped cars and ran the quarter-mile in 12.49 seconds at 114.9 mph in his 2005, manual shift, Z51 coupe and 12.409 seconds at 114.7 mph with his 436 horsepower manual shift, Z51, 2008 coupe. However, Jim had a top speed of 117.03 mph on one of his seven runs at Houston Raceway Park. Overall, it looks like he matched the Chevy performance spec with both cars, but he believes with a little more seat time he would be able to improve his time in the LS3. Chevrolet performance numbers are derived from an average of numerous runs adjusted for standard day temperature and barometric pressure. Also, corporate professional drivers drive the cars. All of this results in a consistency difficult to duplicate outside of corporate testing.
Schindler had his LS3 Corvette tested on a chassis dynamometer by MTI in Houston, Texas. The best dyno run resulted in SAE corrected numbers of 390.5 horsepower and 380.5-lb.ft. of torque. Jim asked what a stock LS2 rates on MTIs chassis dyno. MTI pulled a typical stock LS2 dyno sheet showing 353.7 horsepower and 354.3-lb.ft. torque. The difference between Schindler’s LS3 and the LS2 was 36.8 horsepower and 26.2-lb.ft. torque. That is a nearly perfect match for Chevy’s rating for both engines. Chevrolet numbers show the LS3 with NPP exhaust has a 36 horsepower and 28-lb.ft. torque advantage over the 400 horsepower and 400-lb.ft. torque rated LS2.
Using a percentage such as 15% to calculate loss of power between the flywheel and rear wheels is somewhat common even though it is incorrect. Drivetrain loss between cars with different horsepower ratings is much closer to a fixed number assuming peak power occurs at equal rpm and both cars use the same transmission, differential, wheels, tires, tire pressure, etc. The Corvette LS2 seems to lose, on average, 50 horsepower (400 – 50 = 350 rwhp and *363 + 338 = 701/2 = 350.5 rwhp) between the flywheel and rear wheels. Drivetrain loss for the LS3 is likely to be less than for the LS2 mainly because it reaches peak horsepower at 5,900 rpm rather than 6,000 rpm. Higher rpm results in more frictional loss, especially when the drivetrain is involved. Calculating frictional loss in strict linear relationship, results in close to a 7 horsepower advantage at the rear wheels for the LS3 Corvette. (6,000 – 5,900 = 100/6,000 = 1.67%--400 x 1.67% = 6.68 horsepower) If we use LS3 as the base, the advantage is even greater (100/5,900 = 1.695%--436 x 1.695% = 7.39 horsepower). A mechanical engineer would probably say that using a linear calculation is not accurate for determining drivetrain frictional loss. However, I use this only as an example to show that the LS3 Corvette has a definite advantage on a chassis dyno. Another factor may be weight of the rear wheels. Forged wheels on 2008 cars are lighter than the cast wheels that were on the 2005 to 2007 cars. Rear wheels with less weight but same diameter result in less rotational mass and therefore an advantage on the chassis dyno. The combination of less frictional loss from peak power occurring at a lower rpm and lighter forged wheels give LS3 cars, especially those with forged wheels, a distinct power advantage on a chassis dyno as compared to LS2 cars.
Chassis dyno numbers for factory stock, manual shift, NPP exhaust, LS3 Corvettes have ranged from 374 to 399 horsepower. *Numbers for factory stock manual shift LS2 Corvettes range from 338 to 363 horsepower and twice I have seen claims of 365 hp posted for an LS2. Comparing the ranges, excluding the 365 numbers, we come up with a difference of 36 horsepower at both ends of the scale. It sure looks like Chevy was right on target with their ratings.
Considering that SAE Certified procedures verify the accuracy of a 436 horsepower rating for a NPP equipped LS3, I wonder what LS2 would have rated using the same procedure, especially since it loses more power in the drivetrain.
Thank you so much for this excellent post... it was long overdue
03-22-2008, 12:38 AM
#8
Melting Slicks
This post reminds me of some of the math tutoring I used to do where the students would look up the answers in the back of the book and then work backwards to the original problem.
Very creative thinking.
Very creative thinking.
03-22-2008, 12:43 AM
#9
I thought "Unfair" might get your attention on this overworked topic. For some time now I have noticed that two important considerations have been left out of discussions involving LS3 chassis dyno numbers so I have made an attempt to present them here. The first three paragraphs are for the uninitiated, but read them anyway. Read carefully so as not to miss an important piece of information.
____________________
Chevrolet gives Corvette LS2 engines a 400 horsepower rating at 6,000 rpm and LS3 engines a 430 horsepower rating at 5,900 rpm. When equipped with the optional NPP exhaust system, LS3 is rated 436 horsepower at 5,900 rpm. LS3 was rated using the updated SAE J1349 procedure and then certified under SAE J2723. LS2 was only rated under the previous SAE J1349 standard, however, GM engines that were rated under both SAE procedures gained from 1 to 5 horsepower under the newer certified method except for the Cadillac STS-V. Its Northstar V8 gained 29 horsepower when re-rated under the new method.
According to Chevrolet testing, a LS2 equipped C6 Corvette with Z51 performance option and manual shift is able to go from 0 to 60 mph in 4.1 seconds and the quarter-mile in 12.5 seconds at 115 mph. Chevrolet states that the LS3 Corvette with Z51 option and manual shift is able to run from 0 to 60 mph in 4.1 seconds and the quarter-mile in 12.4 seconds at 117 mph. Corvette forum member Jim Schindler presently has the best quarter-mile elapsed time for a stock LS3 Corvette on “The List”. He owned both LS2 and LS3 equipped cars and ran the quarter-mile in 12.49 seconds at 114.9 mph in his 2005, manual shift, Z51 coupe and 12.409 seconds at 114.7 mph with his 436 horsepower manual shift, Z51, 2008 coupe. However, Jim had a top speed of 117.03 mph on one of his seven runs at Houston Raceway Park. Overall, it looks like he matched the Chevy performance spec with both cars, but he believes with a little more seat time he would be able to improve his time in the LS3. Chevrolet performance numbers are derived from an average of numerous runs adjusted for standard day temperature and barometric pressure. Also, corporate professional drivers drive the cars. All of this results in a consistency difficult to duplicate outside of corporate testing.
Schindler had his LS3 Corvette tested on a chassis dynamometer by MTI in Houston, Texas. The best dyno run resulted in SAE corrected numbers of 390.5 horsepower and 380.5-lb.ft. of torque. Jim asked what a stock LS2 rates on MTIs chassis dyno. MTI pulled a typical stock LS2 dyno sheet showing 353.7 horsepower and 354.3-lb.ft. torque. The difference between Schindler’s LS3 and the LS2 was 36.8 horsepower and 26.2-lb.ft. torque. That is a nearly perfect match for Chevy’s rating for both engines. Chevrolet numbers show the LS3 with NPP exhaust has a 36 horsepower and 28-lb.ft. torque advantage over the 400 horsepower and 400-lb.ft. torque rated LS2.
Using a percentage such as 15% to calculate loss of power between the flywheel and rear wheels is somewhat common even though it is incorrect. Drivetrain loss between cars with different horsepower ratings is much closer to a fixed number assuming peak power occurs at equal rpm and both cars use the same transmission, differential, wheels, tires, tire pressure, etc. The Corvette LS2 seems to lose, on average, 50 horsepower (400 – 50 = 350 rwhp and *363 + 338 = 701/2 = 350.5 rwhp) between the flywheel and rear wheels. Drivetrain loss for the LS3 is likely to be less than for the LS2 mainly because it reaches peak horsepower at 5,900 rpm rather than 6,000 rpm. Higher rpm results in more frictional loss, especially when the drivetrain is involved. Calculating frictional loss in strict linear relationship, results in close to a 7 horsepower advantage at the rear wheels for the LS3 Corvette. (6,000 – 5,900 = 100/6,000 = 1.67%--400 x 1.67% = 6.68 horsepower) If we use LS3 as the base, the advantage is even greater (100/5,900 = 1.695%--436 x 1.695% = 7.39 horsepower). A mechanical engineer would probably say that using a linear calculation is not accurate for determining drivetrain frictional loss. However, I use this only as an example to show that the LS3 Corvette has a definite advantage on a chassis dyno. Another factor may be weight of the rear wheels. Forged wheels on 2008 cars are lighter than the cast wheels that were on the 2005 to 2007 cars. Rear wheels with less weight but same diameter result in less rotational mass and therefore an advantage on the chassis dyno. The combination of less frictional loss from peak power occurring at a lower rpm and lighter forged wheels give LS3 cars, especially those with forged wheels, a distinct power advantage on a chassis dyno as compared to LS2 cars.
Chassis dyno numbers for factory stock, manual shift, NPP exhaust, LS3 Corvettes have ranged from 374 to 399 horsepower. *Numbers for factory stock manual shift LS2 Corvettes range from 338 to 363 horsepower and twice I have seen claims of 365 hp posted for an LS2. Comparing the ranges, excluding the 365 numbers, we come up with a difference of 36 horsepower at both ends of the scale. It sure looks like Chevy was right on target with their ratings.
.
____________________
Chevrolet gives Corvette LS2 engines a 400 horsepower rating at 6,000 rpm and LS3 engines a 430 horsepower rating at 5,900 rpm. When equipped with the optional NPP exhaust system, LS3 is rated 436 horsepower at 5,900 rpm. LS3 was rated using the updated SAE J1349 procedure and then certified under SAE J2723. LS2 was only rated under the previous SAE J1349 standard, however, GM engines that were rated under both SAE procedures gained from 1 to 5 horsepower under the newer certified method except for the Cadillac STS-V. Its Northstar V8 gained 29 horsepower when re-rated under the new method.
According to Chevrolet testing, a LS2 equipped C6 Corvette with Z51 performance option and manual shift is able to go from 0 to 60 mph in 4.1 seconds and the quarter-mile in 12.5 seconds at 115 mph. Chevrolet states that the LS3 Corvette with Z51 option and manual shift is able to run from 0 to 60 mph in 4.1 seconds and the quarter-mile in 12.4 seconds at 117 mph. Corvette forum member Jim Schindler presently has the best quarter-mile elapsed time for a stock LS3 Corvette on “The List”. He owned both LS2 and LS3 equipped cars and ran the quarter-mile in 12.49 seconds at 114.9 mph in his 2005, manual shift, Z51 coupe and 12.409 seconds at 114.7 mph with his 436 horsepower manual shift, Z51, 2008 coupe. However, Jim had a top speed of 117.03 mph on one of his seven runs at Houston Raceway Park. Overall, it looks like he matched the Chevy performance spec with both cars, but he believes with a little more seat time he would be able to improve his time in the LS3. Chevrolet performance numbers are derived from an average of numerous runs adjusted for standard day temperature and barometric pressure. Also, corporate professional drivers drive the cars. All of this results in a consistency difficult to duplicate outside of corporate testing.
Schindler had his LS3 Corvette tested on a chassis dynamometer by MTI in Houston, Texas. The best dyno run resulted in SAE corrected numbers of 390.5 horsepower and 380.5-lb.ft. of torque. Jim asked what a stock LS2 rates on MTIs chassis dyno. MTI pulled a typical stock LS2 dyno sheet showing 353.7 horsepower and 354.3-lb.ft. torque. The difference between Schindler’s LS3 and the LS2 was 36.8 horsepower and 26.2-lb.ft. torque. That is a nearly perfect match for Chevy’s rating for both engines. Chevrolet numbers show the LS3 with NPP exhaust has a 36 horsepower and 28-lb.ft. torque advantage over the 400 horsepower and 400-lb.ft. torque rated LS2.
Using a percentage such as 15% to calculate loss of power between the flywheel and rear wheels is somewhat common even though it is incorrect. Drivetrain loss between cars with different horsepower ratings is much closer to a fixed number assuming peak power occurs at equal rpm and both cars use the same transmission, differential, wheels, tires, tire pressure, etc. The Corvette LS2 seems to lose, on average, 50 horsepower (400 – 50 = 350 rwhp and *363 + 338 = 701/2 = 350.5 rwhp) between the flywheel and rear wheels. Drivetrain loss for the LS3 is likely to be less than for the LS2 mainly because it reaches peak horsepower at 5,900 rpm rather than 6,000 rpm. Higher rpm results in more frictional loss, especially when the drivetrain is involved. Calculating frictional loss in strict linear relationship, results in close to a 7 horsepower advantage at the rear wheels for the LS3 Corvette. (6,000 – 5,900 = 100/6,000 = 1.67%--400 x 1.67% = 6.68 horsepower) If we use LS3 as the base, the advantage is even greater (100/5,900 = 1.695%--436 x 1.695% = 7.39 horsepower). A mechanical engineer would probably say that using a linear calculation is not accurate for determining drivetrain frictional loss. However, I use this only as an example to show that the LS3 Corvette has a definite advantage on a chassis dyno. Another factor may be weight of the rear wheels. Forged wheels on 2008 cars are lighter than the cast wheels that were on the 2005 to 2007 cars. Rear wheels with less weight but same diameter result in less rotational mass and therefore an advantage on the chassis dyno. The combination of less frictional loss from peak power occurring at a lower rpm and lighter forged wheels give LS3 cars, especially those with forged wheels, a distinct power advantage on a chassis dyno as compared to LS2 cars.
Chassis dyno numbers for factory stock, manual shift, NPP exhaust, LS3 Corvettes have ranged from 374 to 399 horsepower. *Numbers for factory stock manual shift LS2 Corvettes range from 338 to 363 horsepower and twice I have seen claims of 365 hp posted for an LS2. Comparing the ranges, excluding the 365 numbers, we come up with a difference of 36 horsepower at both ends of the scale. It sure looks like Chevy was right on target with their ratings.
.
I read the whole thing, but I am not sure what the bottom line is.
Please break it down for me. At the end of the day, what are you saying?
When I go through and I read:
.......According to Chevrolet testing, a LS2 equipped C6 Corvette with Z51 performance option and manual shift is able to go from 0 to 60 mph in 4.1 seconds and the quarter-mile in 12.5 seconds at 115 mph. Chevrolet states that the LS3 Corvette with Z51 option and manual shift is able to run from 0 to 60 mph in 4.1 seconds and the quarter-mile in 12.4 seconds at 117 mph. Corvette forum member Jim Schindler presently has the best quarter-mile elapsed time for a stock LS3 Corvette on “The List”. He owned both LS2 and LS3 equipped cars and ran the quarter-mile in 12.49 seconds at 114.9 mph in his 2005, manual shift, Z51 coupe and 12.409 seconds at 114.7 mph with his 436 horsepower manual shift, Z51, 2008 coupe. However, Jim had a top speed of 117.03 mph on one of his seven runs at Houston Raceway Park. Overall, it looks like he matched the Chevy performance spec with both cars, but he believes with a little more seat time he would be able to improve his time in the LS3. Chevrolet performance numbers are derived from an average of numerous runs adjusted for standard day temperature and barometric pressure. Also, corporate professional drivers drive the cars. All of this results in a consistency difficult to duplicate outside of corporate testing.
......Schindler had his LS3 Corvette tested on a chassis dynamometer by MTI in Houston, Texas. The best dyno run resulted in SAE corrected numbers of 390.5 horsepower and 380.5-lb.ft. of torque. Jim asked what a stock LS2 rates on MTIs chassis dyno. MTI pulled a typical stock LS2 dyno sheet showing 353.7 horsepower and 354.3-lb.ft. torque. The difference between Schindler’s LS3 and the LS2 was 36.8 horsepower and 26.2-lb.ft. torque. That is a nearly perfect match for Chevy’s rating for both engines. Chevrolet numbers show the LS3 with NPP exhaust has a 36 horsepower and 28-lb.ft. torque advantage over the 400 horsepower and 400-lb.ft. torque rated LS2.
......Drivetrain loss for the LS3 is likely to be less than for the LS2 mainly because it reaches peak horsepower at 5,900 rpm rather than 6,000 rpm. Higher rpm results in more frictional loss, especially when the drivetrain is involved. Calculating frictional loss in strict linear relationship, results in close to a 7 horsepower advantage at the rear wheels for the LS3 Corvette. (6,000 – 5,900 = 100/6,000 = 1.67%--400 x 1.67% = 6.68 horsepower) If we use LS3 as the base, the advantage is even greater (100/5,900 = 1.695%--436 x 1.695% = 7.39 horsepower). A mechanical engineer would probably say that using a linear calculation is not accurate for determining drivetrain frictional loss. However, I use this only as an example to show that the LS3 Corvette has a definite advantage on a chassis dyno. Another factor may be weight of the rear wheels.
......Forged wheels on 2008 cars are lighter than the cast wheels that were on the 2005 to 2007 cars. Rear wheels with less weight but same diameter result in less rotational mass and therefore an advantage on the chassis dyno. The combination of less frictional loss from peak power occurring at a lower rpm and lighter forged wheels give LS3 cars, especially those with forged wheels, a distinct power advantage on a chassis dyno as compared to LS2 cars.
......Chassis dyno numbers for factory stock, manual shift, NPP exhaust, LS3 Corvettes have ranged from 374 to 399 horsepower. *Numbers for factory stock manual shift LS2 Corvettes range from 338 to 363 horsepower and twice I have seen claims of 365 hp posted for an LS2. Comparing the ranges, excluding the 365 numbers, we come up with a difference of 36 horsepower at both ends of the scale. It sure looks like Chevy was right on target with their ratings.
.....Considering that SAE Certified procedures verify the accuracy of a 436 horsepower rating for a NPP equipped LS3, I wonder what LS2 would have rated using the same procedure, especially since it loses more power in the drivetrain
On the one hand, it sounds like you are saying that the reported difference in the power ratings is accurate. But on the other hand, it also sounds like you are saying that the stated difference in power might be exaggerated or boosted because of the weight of the wheels, and the point in the RPM range where peak HP is measured.
Last edited by '06 Quicksilver Z06; 03-22-2008 at 12:59 AM.
03-22-2008, 12:58 AM
#11
Burning Brakes
Thread Starter
Many posters on this forum feel that chassis dyno numbers for the LS3 indicate more than a 36 horsepower difference when compared to the LS2. I believe this is a result of using a straight percentage to calculate the difference between crank and rwhp. What I am pointing out here is that the percentage is not an accurate tool, especially when considering that LS3 is losing less horsepower through the drivetrain as a result of reduced friction and in some cases wheels with less mass. I don't believe those factors have ever been considered here. This results in a smaller difference between LS2 and LS3 crank horsepower than prevously thought and also a smaller difference between crank and rear wheel power in the LS3. LS3 has a significant advantage at the rear wheels partially because less horsepower is lost in the drivetrain.
Last edited by Marina Blue; 03-22-2008 at 03:55 AM.
03-22-2008, 01:03 AM
#12
Many posters on this forum feel that chassis dyno numbers for the LS3 indicate more than a 36 horsepower difference when compared to the LS2. I believe it is assumed, when comparing those numbers, the LS3 has already lost more horses between the crank and wheels than LS2 because a straight percentage to calculate the difference is used. What I am pointing out here is that the percentage is not an accurate tool, especially when LS3 is loosing less horsepower through the drivetrain than does LS2. I don't believe that has ever been considered. Therefore there is less difference in power at the crank than most people believe. At the wheels it is a different story. LS3 has a bigger advantage there because less horsepower is lost in the drivetrain.
03-22-2008, 01:08 AM
#14
Who cares? The LS3 makes a lil more power. Ok. If LS2 guys are getting envious then they should mod the car or stop being hung up. I'm not sure what all the hype is about. Ok, GM made a stronger motor in the LS3. They also did with the LS7. I'm happy GM is making stonger motors. I AM worried the LS3 cars make more power than me so I built a stroker for the 05.
Other than that its a well written post. I'm just not so sure why people are getting all uptight about it.
Other than that its a well written post. I'm just not so sure why people are getting all uptight about it.
03-22-2008, 01:18 AM
#15
Burning Brakes
Thread Starter
The message is somewhat mixed.
On the one hand, it sounds like you are saying that the reported difference in the power ratings is accurate. But on the other hand, it also sounds like you are saying that the stated difference in power might be exaggerated or boosted because of the weight of the wheels, and the point in the RPM range where peak HP is measured.
On the one hand, it sounds like you are saying that the reported difference in the power ratings is accurate. But on the other hand, it also sounds like you are saying that the stated difference in power might be exaggerated or boosted because of the weight of the wheels, and the point in the RPM range where peak HP is measured.
Whatever the case, LS3 cars have significantly more power at the wheels and in the end that is what counts.
Last edited by Marina Blue; 03-22-2008 at 03:29 AM.
03-22-2008, 01:22 AM
#16
Team Owner
03-22-2008, 01:24 AM
#17
Melting Slicks
03-22-2008, 01:25 AM
#18
Team Owner
03-22-2008, 01:29 AM
#19
Melting Slicks
Who cares? The LS3 makes a lil more power. Ok. If LS2 guys are getting envious then they should mod the car or stop being hung up. I'm not sure what all the hype is about. Ok, GM made a stronger motor in the LS3. They also did with the LS7. I'm happy GM is making stonger motors. I AM worried the LS3 cars make more power than me so I built a stroker for the 05.
Other than that its a well written post. I'm just not so sure why people are getting all uptight about it.
Other than that its a well written post. I'm just not so sure why people are getting all uptight about it.
It's kinda like Pe^I$ envy for some. They'll nevur git ovur it 
03-22-2008, 01:37 AM
#20
Safety Car
Member Since: Nov 2007
Location: Tarpon Springs FL
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Who cares? The LS3 makes a lil more power. Ok. If LS2 guys are getting envious then they should mod the car or stop being hung up. I'm not sure what all the hype is about. Ok, GM made a stronger motor in the LS3. They also did with the LS7. I'm happy GM is making stonger motors. I AM worried the LS3 cars make more power than me so I built a stroker for the 05.
Other than that its a well written post. I'm just not so sure why people are getting all uptight about it.
Other than that its a well written post. I'm just not so sure why people are getting all uptight about it.
But he forgot ONE thing. The drag co-effecient of a freshly waxed LS3 with Zanio....I believe Zanio provides a unfair advantage to all LS3 cars. Based on my calculations the Zaino equipped LS3 vette will take milliseconds off of the 1/4 mile ET.
