At the time I wrote this, Jim Schindler had the top LS3 number on “The List.” Jim is always reliable so I chose to stick with his numbers because I also used his chassis dyno information.
LS2 – 400+ Horsepower?
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 29 horsepower under the newer certified method. The Cadillac STS-V with its Northstar V8 gained 29 horsepower when re-rated under the new protocol.
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, owned both LS2 and LS3 equipped cars and ran the quarter-mile in 12.49 seconds at 114.9 mph in his 2005 LS2, manual shift, Z51 coupe and 12.409 seconds at 114.7 mph with his 2008, 436 horsepower LS3, manual shift, Z51 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. Chevrolet performance numbers are derived from an average of numerous runs made under controlled conditions and then adjusted for standard day temperature and density altitude (DA). 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 MTI’s 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.
Observed 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 365 horsepower. It is impossible to tell where most numbers are concentrated within the range because of unreported results and my inability to gather all chassis dyno figures that were reported. When the range varies by at least 25 to 27 horsepower it becomes apparent how unreliable chassis dyno numbers are as a predictor of true engine horsepower. These variations are due to dynamometer type, dynos being out of calibration, operator input, tire pressure, engine temperature, hood open or closed, correction factor error, fuel octane, drivetrain wear, tire size and wheel weight, etc. It is obvious that using chassis dyno numbers to back calculate true engine horsepower is unreliable at best.
Range of LS2 rwhp
witnessed by LG Motorsports--See this post:
Range of LS3 rwhp
--See the following posts:
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. Calculating drivetrain loss between cars with different horsepower ratings has constant, linear, and exponential components but is closer to a constant number assuming peak power occurs at equal rpm and cars are equipped with the same transmission, differential, wheels, tires, tire pressure, etc. Beginning with the C4 Corvette and continuing with C5 and C6 Corvettes with T56 transmissions, the commonly accepted drivetrain loss was 60 horsepower or 15%. Those losses are no longer valid for LS3 Corvettes mainly because of a completely new and redesigned TR-6060 transmission. LS3s are experiencing drivetrain losses of roughly 50 horsepower or 11.5%.
Higher rpm results in more friction loss, especially when the whole drivetrain is involved. When comparing cars where peak power occurs at different rpms, friction loss can be adjusted in a strict linear relationship—the predominant term when comparing loss at varying rpms. This results in close to a one horsepower advantage at the rear wheels for the LS3 Corvette. A 100 rpm friction loss based on a 60 horsepower drivetrain component (difference between flywheel and rear wheel horsepower, otherwise the complete drivetrain) is calculated as follows: 6,000 rpm – 5,900 rpm = 100/6,000 = 1.67% and 60 x 1.67% = 1.002 horsepower lost to additional friction.
Corvette changed from the Tremec T-56 to TR-6060 manual transmission in 2008 Corvettes. That transmission has internal changes, which result in a different friction factor than the T-56. A statement that Dave Hill made during a Corvette Action Center interview with Hib Halverson indicates the effect drivetrain components can have on performance: “There's three different types of gear rattle, neutral, shutdown and driveaway. We had some hardware that was going to get rid of all three but and we decided to reverse one of them, because the solution was costing too much acceleration. That was a dual-mass clutch and it would have eliminated all of the driveaway rattle but it would have cost us 2/10ths sec. in 0-60. We said, 'Even for driveaway gear rattle, that's too much of a performance price to pay because it was a significant amount of what we gained with the 400hp.' So we eliminated the neutral gear rattle, the shutdown gear rattle and got more than half of the driveaway gear rattle. That is the only thing that I wanted to get that I didn't.”
This shows that the TR-6060 transmission could be having a significant effect on drivetrain frictional loss. http://www.corvetteactioncenter.com/...05/final5.html
Wheel weight and new differential gear oil also become factors in drivetrain power loss. The new forged wheel option is reportedly from 1.6 to 3 pounds lighter in weight for the front and from 2 to 4 pounds lighter for the rear wheels. This results in less rotational mass, which gives an advantage on an inertia type chassis dyno. For model year 2008, Corvette differentials were filled with a new gear oil (Dexron LS Gear Oil 75W-90) resulting in less power lost to friction in this drivetrain component.
It is not hard to understand why LS3 Corvettes are experiencing less parasitic drivetrain losses taking into account a new TR-6060 transmission, peak horsepower occurring at a lower RPM, lighter weight forged wheels and a new gear oil with better lubricating properties.
I had the pleasure of talking to a Tremec transmission representative at the 2013 Corvettes at Carlisle show. He verified that the TR-6060 transmission was not only stronger than the T-56, it is also more efficient and presents less parasitic losses in the drivetrain. I specifically asked him if that included the straight-through 4th gear—the gear used during chassis dyno testing. His answer was: “Yes...there is less 4th gear friction in the TR-6060 than in the T-56, resulting in more power to the wheels."
GM publication, Corvette Quarterly, had an article titled “Takin’ It to the Limit” in the Winter 2008 issue. In this case “Limit” did not refer to top speed performance, but to getting the best gas mileage possible in a base model LS3 Corvette. The fact that the car traveled 549 miles on one tank of gas with an average fuel economy of 30.6 miles-per-gallon is not what attracted my attention. There was one small sentence that stood out like a Boeing 747 on a radar screen—“Continual reductions in internal friction also pay dividends at the fuel pump.”
The article also stated, “A third reason for the Corvette’s efficiency is its powertrain. Taken as a complete unit, it’s hard to beat.”
Those sentences amount to a subtle statement that the LS3 drivetrain is more efficient than the previous LS2’s. Tadge Juechter, Corvette Chief Engineer, talked to the author before the article was written. I’m sure he explained some of the finer details of drivetrain efficiency.
Reduced drivetrain parasitic losses are a definite factor in LS3’s inordinately higher rear-wheel-horsepower numbers when compared to an LS2 that is rated at 406 Net or 411 Certified horsepower.
Calculating Drivetrain Power Loss For LS2 and LS3 Corvettes
Average rear-wheel-horsepower (based on low and high numbers, not the full range)
Note: These numbers do not represent an average of all chassis dyno numbers but should be ballpark figures.
– Range 338 to 365 Average – 351.5 rwhp
– Range 374 to 399 Average – 386.5 rwhp
Power lost in drivetrain
– 400 SAE Net hp minus 351.5 rwhp = 48.5 horsepower
(12.125% Drivetrain Loss)
– 406 SAE Net hp minus 351.5 rwhp = 54.5 horsepower
(13.42% Drivetrain Loss)
– 411 Certified hp minus 351.5 rwhp = 59.5 horsepower
(14.48% Drivetrain Loss)
– 436 Certified hp minus 386.5 rwhp = 49.5 horsepower
(11.35% Drivetrain Loss)
LS2 Corvettes are exhibiting a loss of about 10 more SAE Certified horsepower--due to drivetrain parasitic loses and "knock retard" engine management--than LS3 Corvettes. Loss difference will probably change somewhat if a more complete average set is used.
LS2, with a 54.5 horsepower drivetrain component, loses .91
more horsepower to friction as a result of peak power occurring 100 rpm higher than LS3.
(54.5 hp x 1.67% = .91015 hp)
LS2, with a 59.5 horsepower drivetrain component, loses .99
more horsepower to friction as a result of peak power occurring 100 rpm higher than LS3.
(59.5 hp x 1.67% = .99365 hp)
Why LS2 Is Not Perceived To Be The Rocket Ship It Really Is
Most performance cars exhibit the feeling of “coming on the cam,” or that someone just turned on the afterburners. A Corvette LS2 does not feel that way because its power curve is smooth and linear. LS2 has great torque and power at low as well as high rpm.
, writing for Corvette Action Center's web-site, did a number of in depth articles about the C6 Corvette when it was a new model. In an interview with Jordan Lee, GMPT Small-Block Chief Engineer, who worked on the LS2 program, Lee said, “At the bottom end, the LS2 is so much fatter than the LS6. There is one thing you gotta be cognizant of: a lot of people think, when they drive very high-performance sport cars, they’re tuned only for high rpm. People perceive that because the bottom end is so weak. You step in the throttle at low rpm and the engine’s flat, but then, all of a sudden, it feels like it’s coming on the cam.” http://www.corvetteactioncenter.com/...5/sequel5.html
“The LS2 has a fat, broad torque curve so it’s very satisfying down low, but you never have that rapid, flip-the-switch type of feel at higher engine speed. For my taste, and I think the majority of sports car drivers agree, it’s more satisfying to have all that responsiveness and still have all the top end.”
Halverson’s response, “I’m with Jordan Lee on the “satisfying” thing (and the C6’s acceleration numbers are with him, too), but I’m not so sure all Corvetters will agree with us because the erroneous belief that “comin’ on the cam” is demonstrative of a powerful engine is so pervasive amongst urban legends in the car hobby. Reality is: if a normally-aspirated engine really has that on-off or on-the-cam feeling, it’s either a race engine or a production engine with poor air flow management, either of which kind of suck on the street.”
“Conversely, the LS2’s bulked-up, low-end adds to its LS6ish top-end to make a torque curve that’s flatter than freakin’ Kansas. Its lack of peakiness makes the car easier and more fun to drive. It idles nicer than an LS6 and has a tiny edge in throttle response. All this comes under the heading of “refinement.”
mentioned this a number of times when comparing his 2005 LS2 Corvette to a friend’s modified C5 Z06: “When I got my first C6, a friend who has a 2002 Z06 with headers, tune, etc. (382 rwhp) came over and we drove each others cars. His FELT like it would run off and leave my C6 for dead. But a funny thing happened side-by-side. Even with his mods, they were damn near equal—his only advantage was slight at higher speeds.”
had a similar experience: “When I bought the C6, I was pretty sure it was noticeably slower than my Z. Since I still had it, I got a friend to drive and we did some highway pulls from 45 or so. To my surprise, the C6 was right there with the Z through 120. It was interesting, the C6 would pull on the Z at the low end of each gear and the Z06 would catch it back on the top end of the gear. The C6 was Z51 so same gearset. As an experiment, we swapped rear wheels. The Z could no longer pull. So I'd conclude that the 6.0L is a pretty stout motor if it can move a heavier car that well despite have same HP. Also, the C6 tune, as you know, is a dog. After Shawn's tune, my LS2 has that same razor-sharp response the LS6 had.” http://forums.corvetteforum.com/c6-c...post1558790425
Shortly after LS2’s introduction in the C6 Corvette, a major auto publication, in news-clip format,—I believe it was Motor Trend
—made a direct comparison between LS2 and LS6 engines. Identical Cadillac CTS-v cars, with different engines, were used in testing. The LS2 car out-accelerated the LS6 Cadillac, leading the magazine to conclude that LS2 was the stronger engine.
LS2 Corvettes do not feel as fast as they really are.
Another problem the LS2 has is spending too much time in low, “knock retard,” timing tables. Corvette LS2 engines have a 10.9:1 compression ratio and are designed to run on 93 octane gas in optimal conditions.
Hib Halverson wrote the following: http://www.corvetteactioncenter.com/...5/sequel7.html
“General Motors’ 2004 media Product Information Guide, or PIG (“media pig”-hidden meaning, perhaps?) says 93-octane gasoline is “recommended” for use in Corvettes. Owner’s Manuals for ’04 say to use ”…91-octane or higher for best performance.” While there seems to be a difference between what GM tells media and what it tells owners (certainly not the first time that’s happened), most people will run LS2s on whatever premium unleaded they find. Generally, this means 93-octane along the East Coast and parts of the Midwest and 91-octane in most of the rest of the country.”
“LS2, like all Corvette engines since 1982, has computer-controlled spark timing and part of that is a feedback loop which eliminates detonation which can damage the engine. When the knock sensors signal the engine controller that detonation is occurring, in milliseconds, the controller retards timing—we call this “knock retard”—until detonation stops and, once it stops; timing is restored. This feedback process goes on constantly such that spark timing is always at the optimum level for best performance, highest fuel economy, lowest emissions and the octane of the gasoline being used.”
“In nominal atmospheric conditions, 93-octane is adequate for the LS2 to perform optimally with minimal knock retard to control detonation, however, some of my chassis dyno testing of pump gasolines leads me to speculate that, to run detonation-free under the worst conditions, i.e.: wide-open-throttle, heavy load, low humidity, sea level (or near so) pressure, high intake air temperature and high coolant temperature—the LS2 probably needs about 95-octane.”
“With the engine calibrated for 93-octane, that extra last bit of performance during severe duty requiring perhaps as much as 95-octane, Corvetters in a fair amount of the country stuck with 91 and a few errant owners trying to use regular; feedback spark control and knock retard are what allows the engine to produce highest-performance on good gas but not be damaged by detonation when running on gasoline of less than 93-octane.”
Corvette forum member, TTRotary
, commented on the effect knock retard engine management has on his LS2 Corvette in hot weather—“Now for the caveat: for some reason (perhaps aggressive engine management due to high compression ratio), the LS2 in the C6 just falls apart on a hot day. 68-75F, the thing is a monster—I like it better than the LS6. But give it 95F and turn on the AC, and it becomes a DOG.” He also commented on knock retard being mistaken as torque management (TM)—“The good news is I have never encountered TM on my car, even when temps are cool and I rip the 1-2 shift hard. Maybe engine management is what people have confused with TM. If ever a car needed cold air intake and a tune, it’s this one.” http://forums.corvetteforum.com/c6-t...post1552336590
Corvette forum member, Yawlak80-86
, made excellent posts on octane requirements for LS2: http://forums.corvetteforum.com/c6-t...post1579509447
. He said, “The problem is especially bad with LS2s as they have too much timing combined with too high a compression ratio from the factory. They spend most of their time on the low tables when using 91 and still ping. . .When I go to the track, I run a blend of 100 octane race fuel w/ 91 octane pump gas making at least 95 octane so I can run adequate timing." He also mentioned the LS3—“The owners manuals are not gospel. LS3s have a slightly lower compression ratio than the LS2 and LS7. They also have much better heads than the LS2 (perhaps the quench zone is relocated in the cylinders as a result—I’m not positive). Perhaps these are some of the reasons they say the LS3s are good with 91-octane but I can tell you with certainty, they are not, at least not in my neck of the woods. I can also tell you that I had no pinging issues on the East Coast with premium top tier fuels, (except for Shell).”
Corvette forum member, Tommy D
, made a post which supports the contention that knock retard engine management is not as intrusive on the LS3—“Remember that torque management cannot be tuned out on launch and is not as intrusive on the later C6s.” http://forums.corvetteforum.com/c6-t...post1577287695
On page 6 of “C6 Naked and Exposed – The Sequal; Finally . . . We Drive It!!!," GMPT engineer Jordan Lee states, “When you bump the compression, you need better combustion efficiency, so you're less prone to knock
(underline my emphasis); but if you do get knock; you need a control system which can react very quickly so that it’s unobtrusive to the driver.” http://www.corvetteactioncenter.com/...5/sequel6.html
On page 5 of “Ruthless Pursuit of Power: 2008 Edition,” Hib Halverson had this to say about LS3 combustion quality: http://www.corvetteactioncenter.com/...ls3_page5.html
“The best combustion quality occurs when the air fuel mixture in the chamber is distributed uniformly, or is “homogenous”, throughout the chamber. The process of becoming homogenous, or as close to it as possible, occurs in the latter stage of the intake valve event and continues once the valve is closed and the piston starts upward. Not only does the upward piston movement compress the air-fuel mix but it also causes it to swirl and tumble and that further mixes it up making it more homogenous. The LS2/LS6 chamber had great swirl but not very good tumble. The air fuel mix needs to be doing both if the goal is homogeneity right when the spark comes.” A bulge added to LS3’s combustion chamber caused the mixture to tumble as well as lowering the compression ratio.
Combustion quality along with a lower compression ratio allows LS3 engines to spend less time in “knock retard” than LS2. This is why LS3, in combination with a somewhat more efficient drive-train, shows better numbers on many chassis dynos than an LS2 engine with only 20 less horsepower.
Anthony @ LGMotorsports
did a back-to-back comparison of a LS2 Corvette, LS3 Camaro and a 5.0 Mustang. Here it is: http://forums.corvetteforum.com/c6-t...post1576411472
LS3 Camaro Max power was 374.35 RWHP; LS2 Corvette was 358.99 RWHP. Difference is 15.36 HP. Camaro LS3 Certified HP is 426; LS2 Certified HP should have been 411. That is a 15 HP difference. I believe a back-to-back comparison means all dyno runs were done at the same time. It looks like LS2 was on the right timing table.
LG Motorsports’ back-to-back comparison shows that the power differential between LS2 and LS3 is greater in midrange rather than at peak power rpm levels. LS3 surpasses the 15 horsepower difference at about 3500 rpm . This continues until peak power is reached at 5900 and 6000 rpm where there is a 15 horsepower difference. The chart also seems to show LS3 losing power more rapidly than LS2 after peak power levels are reached. Projecting LS3’s power curve to 6600 rpm, it looks like LS2 and LS3 power levels will be practically the same. But don’t forget, this is for the 426 HP LS3, not the 430 HP Corvette LS3.
GM’s Corvette power and torque chart shows that, unlike LG Motorsports, the greatest power differential between LS2 and LS3 is reached at peak levels. Scroll down the following link to see the GM chart (http://www.corvetteactioncenter.com/...ls3_page6.html
). This chart shows that LS2/LS3 power and torque are nearly the same until about 3500 rpm, where LS3 starts climbing at a faster rate. LS3 power and torque change their angle of ascent, whereas, LS2 continues rising at a steady rate. LS3 acts more like an LS6, so “coming-on-the-cam” is a noticeable sensation.
How LS2 made 20+ HP over ’01 LS6 and LS3 made 20 HP more than LS2
Dividing ’01 LS6’s 385 horsepower by its 346 cubic-inches results in 1.1127167 HP per cubic-inch. Multiplying that figure by LS2’s 364 cubic-inches results in 405 HP. Both engines use the same cylinder heads and camshaft, but LS2 has a power-increasing higher compression ratio (10.9:1 advertised – 10.87:1 actual) than LS6 (10.5:1).
LS2 has a single catalytic converter mounted right after each exhaust manifold rather than the close-coupled converters—known as pups—that were combined with the under-car converters on the ’01 LS6. Having one converter on each side reduced back pressure by 2-inches of mercury, which on its own is worth about five horsepower. Along with exhaust manifolds that flow 4% better and exhaust pipes with smoother bends, LS2 benefits by having longitudinally-mounted mufflers with larger internal volume resulting in 10% less restriction than the transverse mufflers with four, 90-degree tube bends that were mounted on all C5 Corvettes. These improvements resulted in a total of 20% less back pressure in the exhaust system.
A redesigned induction system (air box and duct) resulted in 31% better airflow. Most of this increase was the result of C6 Corvettes becoming both front-breathers, air entering through the grill, and bottom-breathers, air entering from the bottom of the car—split 60% front; 40% bottom. Base C5 Corvettes were bottom-breathers only, but the Z06 LS6 had additional air ducted directly to the air-filter box from openings in the front fascia—C6 air flow was an improvement over the Z06. LS2 uses the same mass-air-flow sensor (MAF) as the '02 to '04 LS6, but with the honey-cell flow straightener found in the '01 LS6. Throttle body size went from 76-mm on the LS6 to 90-mm on LS2. Fuel injector capacity increased to 32.5 lb/hr. (4.1 g/sec.) from LS6's 28.5 lb/hr. (3.6 g/sec.).
LS2’s intake manifold was produced using the vibration welded process. It is glass-filled and made out of Nylon 6 rather than Nylon 66, which was used in LS6’s lost-core-process manifolds. The bell-mouth is larger and runner geometry has been optimized for a six-liter engine. The combined result of all intake/induction system improvements is an air flow increase of 15%.
Vibration welding has resulted in seams that allow crosstalk—air passing between runners—which is detrimental to smooth air flow and results in some lost power. GM went back to the lost-core process for the LS3 engine but used Nylon 6. John Rydzewski, Assistant Chief Engineer for Small Block Passenger Engines: “A vibration-welded intake has different shells. One port can be a combination of an upper portion and a bottom portion with the runners welded together on the side. It’s a pretty good seam, but there might be a little crosstalk (port-to-port leakage) which can rob you of some power. We had seen that in some applications, so we went to a lost-core intake (on LS3).” http://www.corvetteactioncenter.com/...ls3_page6.html
Vibration welding was also used in the production of LS7 intake manifolds; however, at some point the seams were sealed to prevent crosstalk. I doubt that sealing was ever used on LS2 intakes.
LS2’s pistons have a true flat-top design with all three rings having lower tension than LS1 and LS6 rings. Lower tension reduces friction to free up horsepower. The pistons also have full floating wrist pins that help reduce the piston slap noise that’s common on Generation III engines (LS1, LS6). Gen IV engine blocks (LS2, LS3) have siamesed cylinder bores, meaning that a water slot between bores is unnecessary for adequate cooling and that all bores have a solid, uninterrupted connection. This resulted in a stronger block that is less prone to heat distortion in the cylinders. Less bore distortion means less friction and pumping losses.
Both intake and exhaust airflow are better on LS2 Corvettes than the 2001 LS6. LS2 uses the same cam and heads as the ’01 Z06. With a higher compression ratio, 18 more cubic-inches, induction/intake and exhaust flow better than 2002 to 2004 LS6 engines and various internal modifications that decreased friction and pumping losses, LS2 should have been rated at the 406 or 407 SAE net horsepower that Tony Holloway told me LS2 engines produce. In applications using the LS6 385-horse cam, torque equals horsepower, so LS2 torque should match its horsepower rating.
LS2 never received an official certified rating under the new, for model year 2006, SAE J1349 procedures. But GM, knowing that the new protocol was coming, rated LS2 using the new methods long before the engine received its official 400 horsepower rating. Under SAE certified protocol, LS2 rated between 410 and 415 horsepower. If the new rating system had been ready for the 2005 model year, LS2 would NOT have been rated at 400 horsepower.
The 2002 version of LS6 and 2008 LS3 made 20 horsepower more than their predecessors. Both engines used the same cam intake profiles, but LS3’s exhaust profile is the same that was used in the ’01 LS6 and LS2 cams. Along with more aggressive cams, power gains were derived from exhaust back pressure reductions on the '02 LS6 and better flowing heads on LS3.
The following six paragraphs were taken from an article titled 2002 LS6 Engine – The Ruthless Pursuit of Power: The Sequel
by Hib Halverson, from the January, 2002 issue of GM High-Tech Performance magazine: http://www.gmhightechperformance.com...e/viewall.html
According to LS6 camshaft engineer, Jim Hicks, in comparing the ’01 LS6 cam to the ’02 cam: “You can do a direct A/B comparison and there’s an easy 8-10 HP there, whether you change the back pressure or not. There are other changes in the ’02 package—exhaust system and induction system—which increase the power more. The overall power increased about 20 HP and the cam was half of it. Again, that’s because it’s a short-duration design with low overlap so it’s not really affected that much by back pressure.”
Corvette Chief Engineer, Dave Hill said, “We never set out to obsolete the 2001 LS6. The horsepower increase was possible only after we completed a lengthy development of a new catalyst. I want to set the record straight: the 2001 was the best Z06 we could possibly make and 2002 is better because new catalyst technology let us get the back pressure down, increase the breathing and make that power increase.”
Assistant Chief Engineer for Gen III Passenger Car Engines, John Juriga, added, “In 2000 we had to meet the LEV standard here in California, so we added close-coupled converters up front on the California package, our ‘pups’ as we call ‘em. In 2001 we carried those pups across the board, including on the LS6. Even while we were implementing that, we were working on a design that would eliminate those pups. This reduced back pressure by two inches of mercury. On its own, that was worth about 5 HP. That seems not much, but if you reduce back pressure by even small amounts, you can make a bigger gain with improvements on the induction side, especially with the cam.”
More airflow from the new cam and less back-pressure from the new cats drove some other improvements on the induction side. For MY02, LS6 gets a new air filter assembly. It’s similar to the ’01 unit in that it has an additional air intake opening on its cover, but the extra opening is larger. GM also did what GMHTP readers have been doing for years with MAFs--remove the air flow straightener screen. This allowed for a less restrictive path through the sensor.
There were no changes to either the LS6’s intake manifold or its cylinder heads. John Juriga: “The intake manifold was already pretty darn good. We designed it to handle additional flow rates and not require retool the very next year because composite intakes are very expensive to retool and develop. We made sure it would flow more air than we needed in the first year. The same was true with the heads.”
A change in engine air flow significant enough to provide 20 more horsepower also demanded a small change in the engine’s fuel and spark curves. This was done with slight changes in the PCM calibration. There was no change in injectors or fuel pressure.
Low hanging fruit had already been picked for the LS2 engine to come up with 20+ more horsepower than the 385-HP LS6, so LS3 needed a significant upgrade for an equal increase in power. LS3 had no changes in the exhaust system after leaving the cylinder head exhaust ports and there wasn't a great difference on the induction side before air entered the intake manifold. LS3’s intake manifold was again made using the lost-core process and flowed 2-3% better than the LS2 intake. To add 20 more horses, there had to be a major upgrade in the cylinder heads along with the new cam. LS3 did not have the advantage of eighteen more cubic-inches (5.2% more than LS6) and the higher compression ratio that LS2 had over the LS6. LS3 was only twelve cubic-inches or 3.3% larger than LS2 and its compression dropped from LS2’s 10.87:1 to 10.7:1.
A Corvette Action Center article titled Ruthless Pursuit of Power: 2008 Edition
by Hib Halverson http://www.corvetteactioncenter.com/...ls3_page1.html
describes the improvements that increased LS3 power:
Assistant Chief Engineer for Small Block Passenger Engines, John Rydzewski, talks about improvements in the intake manifold: “We also reshaped it for better flow. Yoon Lee, who’s been on the program for a few years, did the development. Compared to LS2, he reduced restriction by 2-3% at 13.5mm lift. It’s just a smoother path, right down to the head.”
Compared to LS2/LS6 cylinder heads, LS3 heads flow much better. According to Lou Oniga, Design Responsibility Engineer (DRE) for Small-Block Cylinder Heads, “The flow numbers are (average) 17% improvement on the intake and 6.2% on the exhaust.”
LS3's camshaft was improved with a 405-HP, LS6 intake lobe profile--exhaust lobe profile from the 385-HP LS6/LS2 cam was retained.
LS3 fuel injectors come from LS7 and flow 5-gram/sec.--LS2 injectors flow 4.1-gram/sec. The throttle body carries over from the LS2. There are no functional changes to the positive crankcase ventilation (PCV) system. The induction system ahead of the throttle body is from the Z06, but with some quarter-wave tuners added to attenuate certain frequencies of intake noise. The exhaust manifolds are similar to the units introduced in 2005 on LS2, but have a slight change in each exhaust runner where it bolts to the head to match the revised exhaust port exits. Exhaust pipes after the manifold are the same as the LS2, but when the NPP option is included, a flap in each muffler opens allowing exhaust gases to flow more freely...adding 6-horsepower.
There are improvements in the LS3 block: Main bearing webs are about 20% stronger and windows, which enhance “bay-to-bay breathing” in the interest of oil control and reduced parasitic loss, have been somewhat enlarged. LS3's ring package has once again been changed: The top two compression rings have the same tension as LS2 rings; the bottom, oil ring tension was increased. All rings have a .25-degree increase in grove tilt. Increased grove tilt and oil ring tension improved oil control, but more tension adds friction, which is a drag on power.
LS2 vs ’01 LS6
) (Corvette: Sports Car Super Star
by the Auto Editors of Consumer Guide, 2005, Publications International, Ltd., page 391) (The Complete Book of Corvette: Every Model Since 1953
by Mike Mueller, 2006, Motorbooks – MBI Publishing Company, page 328)
LS2 Exhaust System – New exhaust manifold is capable of four-percent better flow; back pressure reduced by 2-inches of mercury with a single catalytic converter attached to exhaust manifolds rather than close-coupled pup-cats and under-car converters; smoother exhaust-pipe bends; 10% less back pressure with the elimination of four, 90-degree tube bends at mufflers and less restrictive larger internal volume mufflers. In total, the reduction in exhaust back pressure is 20% over the 2001 base system.*
LS2 Intake System – Significant improvement was made because C6 Corvettes became both front- and bottom-breathers. Intake manifold: runner geometry optimized for six-liter displacement; larger bell-mouth; crosstalk causes slight power loss. Throttle-body size increased from 76-mm to 90-mm; induction system (air box and duct) redesigned for lower restriction—31% lower restriction than LS1 induction system.* Overall, intake/induction system airflow has been improved by 15%. *Note: Beginning with the 2001 production year, LS1 and LS6 engines used the same intake and exhaust manifolds, MAF sensor, and throttle body.
Cylinder heads and cam – Heads are same as 2001 to 2004 LS6; cam is same as 2001 LS6
Engine – Compression ratio increased from 10.5:1 to 10.87:1; displacement increased by eighteen cubic-inches or 5.2%; lower tension piston rings free up horsepower; siamesed bores result in a stronger block and cylinders with less bore distortion, friction and pumping losses.
LS3 vs LS2
LS3 Exhaust System – no change from LS2
LS3 Intake System – Intake manifold restriction reduced by 2-3% and made with lost-core method—no lost power; throttle-body same as LS2; induction system same as Z06, but with quarter-wave tuners.
Cylinder heads and cam – Significant cylinder head upgrade with intake flow increased by 17% and exhaust increased by 6.2%; cam intake profile same as ’02 LS6, exhaust profile same as LS2.
Engine – Compression ratio dropped from 10.87:1 to 10.7:1; displacement increased by twelve cubic-inches or 3.3%; reduced parasitic loss from increased bay-to-bay breathing; higher tension oil rings result in increased friction and lost power.
LS2 improvements resulted in a 21 or 22 horsepower increase over the 385-HP LS6 and LS3 improvements resulted in a 20 horsepower increase over LS2. Compared to LS2, LS3 had no increase in exhaust flow after exhaust gases left the heads and intake flow increases were relatively minor. LS3’s cam was not as significant an improvement as the 405-HP LS6 cam was over the 385-HP version. The 405-HP LS6 cam gained from 8 to 10 HP, so in my opinion, LS3’s cam gained somewhat less. To get another 11-14 horses, LS3 needed a major flow increase from its heads (17% intake - 6.2% exhaust), especially considering that LS3's compression dropped compared to LS2 and it had a one-third less increase in cubic-inches in comparison to LS2’s increase over LS6. LS2's largest power gains came from increases in compression and cubic-inches, but significant air-flow upgrades--15% on the intake side and 20% on exhaust--were the drivers of more power and torque at both low and high rpm levels without using a bigger cam.
During engine development, Corvette's Chief Engineer and Vehicle Line Executive, Dave Hill, wanted LS2 power to be where the Z06 LS6 was (405 HP) without the premium hardware (longer, hollow-stem valves with potassium-sodium filled exhaust stems), although LS2 did get the stiffer '02 - '04 LS6 valve springs for high rpm stability. I bet he was satisfied with the outcome. GMPT’s Executive Director of Engine Engineering, Sam Winegarden: “Chief engineer Dave Hill said he would really like to take all standard Corvettes to where the Z06 was, and we said that jived with where we saw our competitors, from an engine perspective, going in terms of horsepower. We continually benchmark our engines against our competitors and look at the trends.” (Corvette C6
by Phil Berg, 2004, Motorbooks International, page 63)
Power Progression: LS6 – LS2 – LS3
LS6 heads were originally designed with more than enough air flow to accommodate a 405 horsepower LS6 engine. So, identical LS2 heads (243 castings) already had enough air flow to feed 406 or 407 HP as measured with the original SAE J1349 rating procedures used by all U.S. auto manufacturers from 1972 through 2005. When Chevy rated the preproduction LS2 with what became the new, for model year 2006, SAE certified protocol, it measured between 410 and 415 HP. All GM engines that were rated under both standards had higher horsepower numbers with the new certified protocol.
A redesigned C6 platform allowed for better induction and exhaust air flow than was possible with the C5 platform, including the C5 Z06. LS2’s increased air flow, compression and cubic inches resulted in a stronger engine than the 2002 to 2004, 405-HP LS6.
Two sets of heads were developed for the LS7 engine. The first heads were ultimately rejected because they couldn’t produce the desired power. After some additional work, these heads were used on the LS3. LS3’s fuel injectors and induction system ahead of the throttle body (MAF sensor, air box and duct) also came from the LS7—these parts flowed more fuel and air than necessary, but since they were already inventoried, using them eliminated extra engineering, development, production, and inventory costs. LS3’s throttle body and exhaust system, except for a small change in the manifold to match the head’s reshaped exhaust ports, were from the LS2. Using off-the-shelf parts was a cost effective way to reach 430 SAE certified horsepower in a normally aspirated, overhead valve, 6.2-liter engine.
Evaluation Of Information Presented
Advertised manual shift LS3 performance (12.4 sec. @ 117 mph) was arrived at with a Z51 equipped coupe that most likely included the dual-mode exhaust, 436 horsepower engine. At the 2008 National Corvette Museum Birthday Bash event, Chevrolet's power point presentation stated manual shift performance figures were arrived at with a Z51 optioned car. Base car performance probably was 12.5 seconds @ 116.5 mph.
From conversations with GM personnel at the 2007 National Corvette Museum Birthday Bash event, Corvette Forum member talon90
stated that “…the best times possible were presented.” The only way to come up with "the best times possible" would be to use cars equipped with Z51 and a rating of 436 hp. This makes good marketing sense, enabling advertising to report a greater differentiation with LS2. LS2 was underrated at 400 horsepower, so by using a performance-optioned car, LS3 power difference looked to be more than it actually was. There was really only a 20 horsepower difference and that is what advertised performance numbers show. Twenty-five horsepower is needed for a 2 mph quarter-mile speed advantage (436 – 25 = 411) so 20 horsepower is needed for a 1.5 mph advantage for the base LS3 (430 – 20 = 410). LS2 should have received a 410 or 411 Certified horsepower rating.
Comparing the performance numbers:
Base manual coupe – 12.6 seconds @ 115 mph (Chevrolet advertised)
Z51 manual coupe – 12.5 seconds @ 115 mph (Chevrolet unadvertised)
Base manual coupe – 12.5 seconds @ 116.5 mph (Estimated)
Z51, NPP manual coupe – 12.4 seconds @ 117 mph (Chevrolet advertised)
GM states there is a .2 second and 2 mph difference in quarter-mile performance between LS2 and LS3 Corvettes rather than the actual .1 second elapsed time difference between the Z51 equipped cars used in testing. Chevrolet had to do this because the LS2-Z51 elapsed time of 12.5 seconds was never used in general advertising except for Corvette Quarterly magazine, a limited GM publication. Therefore, it was necessary to use the LS2 base car time of 12.6 seconds in performance comparisons with the LS3. This resulted in the advertised .2 second time difference. Quarter-mile speed differences between a non-NPP equipped LS3 and one with that option were too insignificant to make a difference in advertised performance numbers.
It appears that when the LS3 Corvette was first introduced at its 2007 Corvette Museum unveiling, Chevrolet’s power point presentation purposely omitted showing that Z51 and NPP exhaust optioned cars were used in performance testing. Also, LS3 power was compared to the 395 horsepower Trailblazer SS LS2. Apparently this was done to make the new model Vette look like a bigger improvement over the previous LS2 car than it actually was. This was a poorly done marketing ploy. The following year’s power point presentation made a small but significant correction showing that manual shift performance figures were derived with a Z51 equipped car—the 436 horsepower option was still not mentioned. Surprise!...Finally!...At the April, 2009 National Corvette Museum C5/C6 Bash, Tadge Juechter, Corvette Chief Engineer, admitted that performance times for LS3-Z51 cars were obtained with the 436 horsepower engine. Another mistake was made at the 2007 information session: The new LS3 Corvette was given credit for a 7:56 time at Germany’s Nurburgring. That time was actually run by the C5-Z06…Chevrolet never ran an LS3 Corvette at the Nordschleife. It was common knowledge that a 2006 LS2 Corvette had already established a time of 7:59 at the “Ring.” Why did Chevy slant their 2007 presentation of the new LS3 Corvette with wrong and misleading information? I believe it was to cover the fact that the LS2 had been underrated—showing a greater performance differentiation would accomplish that.
should have received a 406 SAE Net horsepower rating
when it was first used in the new 2005 C6 Corvette. The only reason this did not happen was Chevrolet’s concern about offending C5-Z06 owners by having an equal or more powerful engine in the new base Corvette. The following year, LS2 would have been re-rated at 410 or 411 SAE Certified horsepower
under the new standard if LS3 had not already been planned as its 2008 replacement.
Beginning in 2006, GM policy was to rate all new engines along with existing engines that were continuing in production to the SAE Certified standard. Corvette’s LS7 was the first engine to receive a rating under the revised protocol. It was initially rated at 500 horsepower under the old J1349 standard, but gained 5 horsepower under the new. If LS2 had also been given a certified rating, Chevy would have been forced to advertise LS2’s true numbers. I’m sure marketing played a part in the decision not to rerate. The engine was only one year old in 2006, still too close to the 2004 C5-Z06, and being able to advertise a 30 horsepower increase in the C6’s fourth production year (2008) would be a great selling point at just the right time. Also, rerating the LS2 to 410 or 411 Certified horsepower in 2006 would have been a large power increase for an existing 400 horsepower engine, proving that LS2 was intentionally underrated at its introduction in 2005
It is common knowledge that GM monitors Corvette Forum, providing an easy and low expense method for taking the pulse of Corvette owners. On occasion, company personnel make anonymous comments on the forum if they believe input is needed. For example: A slide show presentation at the 2007 National Corvette Museum Birthday Bash event, showcasing the brand new 2008 Corvette, included information stating that LS2 made 395 horsepower. This caused a stir on the Forum. Eventually Harlan Charles, Corvette product manager (forum name 1990z51
), entered the fray by stating, “An engineer told me the 395 rating is for the Trailblazer SS.” Without identifying himself, he attempted to head off a developing storm where forum members began doubting that the Corvette LS2 was a 400 horsepower engine.
Concerning true LS2 horsepower numbers, another attempt to “get the truth out” was made by Forum member Crush1
, who apparently is either a Corvette insider or has access to inside information. After reading his post, it becomes obvious that he knows what he is talking about. Here are two posts by Crush1
. Read both of them and judge for yourself if you think this man is credible.
To write so effortlessly about Corvette horsepower and the relationship between methods used to measure that power, requires an intimate and working knowledge of the subject. Everything Crush1 stated is correct except for the 1971 net to gross horsepower ratios for Corvette engines that he mentioned in the 2nd post. He said they range from “about .75 to .83.” They actually range from .7647 for the LS-6 engine to .8333 for the LT-1, so I guess he was close enough (ratios are for the 1971 engines, not the 1992-1996 LT1 and 2001-2004 LS6). Everything else was exactly right. This man knows what he is talking about and I for one believe him when he says that the C6 LS2 was measured “with the new specs in the range of 410-415 HP”, especially when my own calculations match that perfectly.
I have no doubts about the accuracy of my conclusions because they were based on information from GM personnel or people that have direct access to those who design and build the Corvette. Also, my calculations were made from Chevrolet’s own numbers. As Crush1
stated, “…the base C6 measures, with the new SAE specs, in the range of 410-415 HP
.” If Chevrolet had introduced the LS2 in 2006, when the new rating system became available, it would have been rated at the low end of that range. Otherwise, LS2 would have been rated at 410 or 411 SAE Certified horsepower
Because Chevrolet assigns horsepower numbers from the bottom of the range of tested engines, I believe they would have given LS2 a 406 horsepower rating under the old standard and 411 under the new. LS2 most likely would have received these ratings if Chevy had not been concerned about upstaging the C5-Z06 with its 405 horsepower LS6 engine. They also wanted a significant power increase for the planned 2008, mid-model upgrade. Rating LS2 at 400 HP allowed for a 30 HP increase, which was much more attractive than a 19 or 20 horsepower increase. 400 HP killed two birds with one stone.
*The following posts lead me to believe Chevy’s test cars had all the performance options, including NPP exhaust, for the “best times.”
LS2 Power in Australia
LS2 engine in a 2005 Chevrolet Corvette
was introduced as the Corvette's new base engine for the 2005 model year. It produces 400 hp (298 kW) at 6000 rpm and 400 ft·lbf (542 N·m) at 4400 rpm from a slightly larger displacement of 6.0 L (5,967 cc/364.1 CID). It is similar to the high-performance LS6, but with an improved power peak and more torque throughout the rpm range. The LS2s in the E-series HSVs are modified in Australia to produce 412 hp** (307 kW)
and 412 ft·lbf** (559 N·m)
An all-new Holden Commodore chassis, known as the VE was unveiled in July 2006. Following this, a new range of "E" Series HSV models were released in August 2006.
Changes to the exhaust system yielded a 10 kW (14 PS; 13 hp) increase in power (see below) for the LS2 to 307 kW (417 PS; 412 hp**).
The power and torque measurements have changed from the stricter ECE method in the Z series to the DIN method for the E series. The use of 98 RON* fuel is also now recommended over 95 RON. Thus the actual power increase is likely to be less than 10 kW (14 PS; 13 hp)
, however, the exact amount cannot be determined without testing data. DIN horsepower
is the power measurement protocol in the German DIN standard 70020. It is sometimes abbreviated as "PS
", which stands for Pferdestärke, which is the German word for horsepower. DIN hp is measured at the engine's output shaft, and is often expressed in metric (Pferdestärke) rather than mechanical horsepower.
*Australia's 98 RON fuel is equal to fuel that is rated at 93 RON+MON/2 in the United States. The two countries use different methods of rating fuel octane.
The kilowatt (kW) was wikipedia's base unit used to measure engine power. Kilowatts can be converted to SAE net horsepower by dividing the kW unit by .7457. SAE net horsepower, in turn, is converted to DIN (PS) horsepower by multiplying by 1.0139. The E-Series LS2 is rated at 307 kW. Dividing 307 kW by .7457 gives 411.6971 or 412 SAE net
horsepower and multiplying 411.6971 times 1.0139 gives 417.41625 or 417 PS (DIN)
horsepower. SAE net and DIN are two different methods of measuring engine horsepower, but vary so little in their procedures that they are nearly identical and are easily converted to one another.
Before modifications, the Australian LS2 made 297 kW (404 PS; 398 SAE net)
on 95 RON fuel
. Corvette’s LS2 makes 303 kW (412 PS; 406 SAE net)
on 93 RON+MON/2 fuel
, which is the equivalent of Australia’s 98 RON.
Power increase from using 98 rather than 95 RON fuel can be found at this web address: http://www.drive.com.au/Editorial/Ar...rticleID=18747
. Even though improvements were made to the L76 engine, the 10 kW power increase is the same as the LS2 engine experienced with the same modifications. Quotes from the article:
“Holden says the engine, codenamed L98 is almost identical to the L76 version launched in Commodore late in 2005. The fitment of a dual exhaust system with quad outlets raises peak power 10kW to 270kW and torque 20Nm to 530Nm.
The dual exhaust lowers back pressure by 12 per cent and also increases that trademark burble favored by V8 drivers.
There’s also another catch with fuel; 270kW and 530Nm can only be achieved using more expensive 98-octane unleaded.
Using regular unleaded, power will drop about 7 kW (to 263kW in total) and torque drops 22Nm to 508Nm.”
A 7 kW power increase from using higher octane fuel translates to 9 SAE net horsepower (7/.7457 = 9.387). The Holden LS2 made 398 SAE net horsepower before calibration to use 98 RON fuel and the addition of a performance exhaust increased power to 412 SAE net. That amounts to a 14 horsepower increase, 9 coming from the octane boost, which means the remaining 5 horsepower came from exhaust improvements.
Those 5 horsepower closely match the 6 horsepower increase LS3 engines experience with the optional NPP exhaust system. Corvette LS2 engines were rated using 93 octane fuel, the equivalent of Australia’s 98 RON fuel. It seems that the only difference between the Corvette LS2 and its Australian cousin, which is rated at 297 kW (404 PS; 398 SAE net) using 95 RON fuel, is the octane fuel that the engine was rated with. If we add the 9 horsepower gained with higher octane fuel to the 398 rating that Holden gave its LS2 the result is 407 SAE net horsepower
. That is a perfect match with what Tony Holloway, Crush1
and what a high level Corvette powertrain engineer stated LS2 rated on GM’s engine dynamometers. Holden then added 5 more horsepower with a better exhaust system. The following quotes describe the better flowing exhaust:
“Engineering and technology
Under the bonnet the unique-to-HSV 6.0 litre LS2 V8 now produces 307kW @ 6000 rpm (up from 297kW @ 6000rpm) and 550Nm @ 4400rpm (from 530Nm @ 4400rpm) thanks to a revised intake and exhaust system (including new smooth flowing 'four-into-two-into-one' tubular extractors) and a 24 month program to refine the engine calibrations, positioning Grange as one of the fastest luxury/sports limousines in the world.”
“Holden says the engine, codenamed L98 is almost identical to the L76 version launched in Commodore late in 2005. The fitment of a dual exhaust system with quad outlets raises peak power 10kW to 270kW and torque 20Nm to 530Nm.”
Holden’s L98 and LS2 engines have a true quad outlet—two on each muffler, but without a dual-mode flap that can be had as Corvette option NPP. The standard Corvette exhaust has a single outlet on each muffler, which then splits into quad tips. Holden’s HSV LS2 has short tube extractors (four-into-two-into-one) rather than the Corvette style (four-into-one) cast iron exhaust manifold. From the quoted information, it is difficult to determine what the exact exhaust difference is between the Holden 297 and 307 kW LS2 engines—what we do know is that there was a 10 kW power increase from using higher octane fuel and exhaust changes. That 10 kW increase is the exact increase experienced by the L76 engine because of higher octane fuel requirements and exhaust improvements. I think it is reasonable to assume that power increases in both engines can be apportioned similarly, meaning that both engines experience an eight or nine horsepower increase from the use of higher octane fuel and a five or six horsepower increase from exhaust changes.
Because Corvette’s LS2 and HSV's 307 kW LS2 were rated using the same octane fuel, Holden’s E-Series exhaust is the reason that the Australian LS2 (412 SAE net hp) makes five or six more horsepower than Corvette’s version (406 SAE net hp), just as Corvette’s NPP exhaust adds six horsepower to the LS3 engine.
Why didn’t Chevy advertise the 405 to 408 SAE net horsepower that the Corvette LS2 actually rated considering that Holden was truthful with their advertised ratings? Answer: Because Chevy was concerned about offending C5-Z06 owners by advertising the true power rating for LS2. Holden did not have those concerns because they do not sell Corvettes in Australia.
The following autoblog article calls into question the 412 lb-ft of torque
mentioned by wikipedia in the first paragraph, stating that the HSV LS2 makes 412 horsepower and 406 lb-ft of torque
. Wikipedia also contradicts the 412 figure, stating that the E-Series LS2 makes 550 N-m or 410 lb-ft of torque
at this address: http://en.wikipedia.org/wiki/Holden_...0-litre_V8_LS2
is not a method of measuring horsepower, it is a different unit of measure and can be converted to SAE net horsepower by dividing the kW value by 0.7457. An explanation of SAE net horsepower, DIN horsepower and Kilowatt measurement can be found at this web address: http://neptune.spacebears.com/opine/horsepwr.html
– This is a standard, DIN 70020, for measuring horsepower that very closely matches SAE net. The conditions of the test vary slightly, but the required equipment on the engine and the point of measurement (flywheel) remains the same. Because the test conditions are so similar, it is safe to divide DIN horsepower by 1.0139 to arrive at SAE net. This value is so close to equal that for all but the most technical purposes DIN and SAE net are interchangeable.
—Factors .7457 for kilowatts and 1.0139 for DIN horsepower convert to the original SAE J1349 standard for determining SAE net horsepower. These factors do not convert to the revised SAE J1349 with SAE J2723 certification, which was first used to measure horsepower for the 2006 Corvette Z06 LS7 engine. LS7 was initially rated at 500 SAE net horsepower before being rated at 505 SAE Certified horsepower with the new method.