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InIt’s been over two years since Chevrolet floored the automotive world with the first-ever supercharged production Corvette. In the waning months of ’07, the Corvette rumor mill was heating up with tantalizing images and reports of something hot from the Corvette development team. A cell-phone video from a passerby of an odd-looking Corvette in traffic provided a juicy audio clue to what was under the hood. As I’ve been following drag racing since I was a kid, I immediately recognized that distinctive supercharger “whizz” sound. When the wraps came off, sure enough, the new Corvette was blown, and its name was ZR1!
The Corvette tuner crowd is a pretty sharp group of enthusiasts with a long history that goes all the way back to the ‘60s, when Joel Rosen was building 500-plus-horsepower big-block Corvettes. Back then, they were known as “specialty car builders,” with a tradition that went all the way back to the “coachbuilt” 1911 Mercer Runabout and the 1914 Stutz Bearcat. When a production sports car with a built-in supercharger producing 638 hp hit the showroom floor, it was only a matter of time before someone took apart a ZR1 to see if Chevrolet left any untapped power in the 376ci, all-aluminum LS9 engine. Enter the very talented team at Lingenfelter Performance Engineering. And oh, they found quite a rich vein of power.
Right off the showroom floor with just pump gas, the new ZR1 is capable of 0-60 in just 3.5 seconds, the quarter-mile in 11.2 seconds, and a restricted top speed of 205-mph. The LPE team established their parameters: how much quicker can we make the ZR1 without going totally crazy, and using only bolt-on parts? As we move forward with the story, keep this in mind: No weight was taken out of the car, and none of the ZR1’s creature comforts were disabled. Aside from a TR6060 Z06 gearset, the entire drivetrain is stock, including the ZR1’s dual-disc clutch setup.
The basic ZR1 LS9 engine and drivetrain are so stout that there wasn’t anything to change. About 95 percent of the project focused on stuffing more frigid, compressed air into the LS9. The only change to the exhaust system was the addition of a “mild to wild” device that holds the flappers on the exhaust tips open. Even the rear differential gearing is stock. The dramatic increase in power came mostly forward of the Eaton 2-rotor, 4-lobe supercharger.
LPE installed an 8.5-in-diameter harmonic balancer and a 2.60-in supercharger pulley to increase the supercharger speed. The stock supercharger’s air-intake snout has a bend in its inner port. LPE designed a new casting that straightens out the bend that’s worth an extra 60 hp when combined with the other enhancements. A Lingenfelter S&B air filter and a ported stock throttle body complete the intake part of the setup. The intercooler is an essential part of the ZR1 system. LPE doubled the capacity of the ‘cooler and increased the capacity of its reservoir. The intercooler’s supercharger inlet was also modified. The above-mentioned modifications, with a sharp tune and 109-octane racing gas, netted 739 rwhp and 739 rwtq. Talk about finding horsepower!
While Corvettes have never been designed for drag racing, the quarter-mile is an excellent standard by which to measure a car’s performance. Running 345/35R18 Mickey Thompson ET Street Radials on the rear and M&H Racemaster 185/50R18 front tires—all mounted on CCW aluminum wheels—the car was ready for some track testing. On July 3, 2009, at Muncie Dragway, the LPE-modified street ZR1 ran a 10.03 at 141.50 mph. Then, on December 9, the car made a best-ever run of 9.813 at 145.74 MPH. After the test runs were complete, the LPE team packed up the ZR1 and trailered the car back to the shop.
Let’s put some perspective on this amazing Corvette. The Astoria-Chas L88 ‘67 roadster had a best-ever run of 10.47, and in 1970 Grumpy Jenkins and Ronnie Sox were running 10.0s with their all-out Pro Stock race cars. Granted, those cars weren’t supercharged, but they couldn’t be driven home either. LPE proved what an astonishing car the ZR1 really is. I’m certain that other tuners will follow. LPE also hinted that a standing-mile top-speed test might be in the works. And lastly, all of the parts used on this car are available—that is, if your ZR1 isn’t quick enough for you. - KST
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Illustrated Corvette Series No. 143 - 2009 Production Corvette
"Is the C6 Corvette Finished?"
In the summer of 1966, when Chevrolet showed the automotive press its upcoming ’67 model line, the Corvette was still supposed to be a production version of the Mako Shark II show car. It turned out that transforming the show car’s over-the-top styling into something you could actually live with was a major challenge. The C3 “shark” Corvette was instead released as a ‘68 model, and the rest is history. Many years later, some Corvette historians began referring to the ’67 model as “the finished Sting Ray.” In its day, it looked as if Corvette designers had done everything they wanted with the Sting Ray design before it was time to move on. A somewhat similar situation occurred in ’01. Only this time, Corvette engineers really had done all they wanted to do with the C5 platform, so the decision was made to start designing the C6. The new ’05 Corvette hit the ground at nearly top speed and just kept rolling along each year with special-edition models and the Z06.
In 2007, the Corvette rumor mill went into hyper-drive with speculation about a super-Vette that was supposedly in the works. The Net was buzzing with possible names that included “Blue Devil,” “Corvette SS,” “C6 Grand Sport,” “Zora Corvette,” and a few others. Perhaps the boys at GM saw the financial storm clouds that were over the horizon and decided on an early release for the new model. In December 2007, Chevy officially announced “The Return of the King—the ‘09 ZR1.” The following month, the much-talked-about supercar was shown to the public—a full seven months ahead of the normal new-car-announcement schedule.
When the ’05 Corvette was released, its new LS2 engine produced 400 horsepower. By ‘08, the base Corvette’s LS3 was packing 430 horses. Remember, Corvette fans, this is “net” horsepower, not the “gross” power ratings of the old days. A gross-power figure for the new LS3 would be well into the mid-500 range—in the base Corvette! As we rolled into ’09, the C6 Corvette was in an interesting position. Right after the ZR1 debuted, the rumor mill picked up on talk of the C7 Corvette, with a lot of speculation that the car might use a mid-engine configuration. As summer and fall approached and those financial storm clouds started to become visible, talk of the C7 quickly vanished. And considering the current financial state of affairs at GM, it looks like the C6 will be around for some time.
Unlike the transition of C3 to C4, when Corvette performance was at its lowest, the performance of the C6 couldn’t be much better. For buyers with very deep pockets and a lot of nerve, there’s the ZR1, GM’s first 200-mph production car and the first Chevy to cost over 100 grand. A few ticks below the ZR1 is the tried-and-true Z06, and just a tick or two below that is the base model Corvette. Each version has a distinctive personality, but the performance of the three models is surprisingly close.
The ‘09 Z06 distinguishes itself with the same wheels we saw in ’08 on the 427 Z06 Special. The base 2009 Corvette has slightly restyled wheels and some very minor changes in interior trim; otherwise, it is a carry-over from ’08. In ‘08 power went up to 430 hp, and the Z06’s Dual Mode exhaust was a new option that yielded another 6 horses while lending some added bark and rumble to the car’s persona.
Despite a power spread of nearly 200 hp between the base Corvette and the ZR1, real-world performance is relatively close, making the entry-level ‘09 with the Z51 and Dual Mode exhaust options the performance bargain of the decade. The base Vette runs 0-60 in just 4.1-seconds, with the Z06 and ZR1 running the same sprint in 3.6 and 3.4 seconds, respectively. Quarter-mile times are close as well: 12.4 @ 117 mph for the base Corvette, 11.7 @ 124 for the Z06, and 11.5 @ 128 for the ZR1. Top speed is 186 mph for the base car, 198 for the Z06, and 205-plus for the ZR1. Interestingly, for the price of one ZR1, you could get two base cars with the Z51 and Dual Mode Exhaust options. According to road tests, the driving experiences among the three cars are very different. The ZR1 is civilized all the way up to its limits. The Z06 is a wild, edgy ride at its extreme. The Z51-optioned base Corvette is fast, crisp, and just a breath behind its bigger brothers.
So, is the C6’s evolution finished? With the C7 Corvette now projected out to 2014 or beyond, what might Chevrolet do with the Corvette for the next four or more model years? Right now, the grump list is pretty slim, but there’s plenty of time to address two issues. Two consistent complaints center on the steering being somewhat vague and the interior being second rate. Perhaps the steering system of the ZR1 or Z06 will trickle down to the base car, and the $8,055 leather interior option will be made standard. Then the C6 will truly be finished. After all, one reviewer has already summed up the base Vette this way: “This is as much Corvette as I need.” ‘Nuff said. - K. Scott Teeters
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Illustrated Corvette Series No. 134 - 2009 ZR1 LS9 Engine
"GM's Civilized Monster-Mouse"
It’s not just about the numbers, folks. Sure, if you compare the famous big-block 427 ZL1 with the 376ci LS9, the conclusion is obvious. The ZL1 never had accurate published power ratings (estimates were in the 550hp “gross” range) and would have never passed current durability requirements, much less EPA certification. The new LS9 does all of the above and produces significantly more power considering that its (minimum) 620hp rating is a more accurate “net” figure.
But the LS9’s superiority is about more than just numbers. In the old days, when big-blocks were bold, if Duntov wanted more power, all he had to do was add a little more of everything. That meant more cubic inches, extra compression, hotter spark, colder air, and/or additional carburetion. It was all a juggling act between maximum power, driveability, and durability. And we won’t even get into fuel economy.
ZR1 Corvette production is scheduled for only 2,000 units, beginning in July of 2008. All LS9 engines are hand-assembled at the GM Performance Built Center in Wixom, Michigan. This powerplant was three years in development and makes major advancements through the use of cutting-edge engine-management systems. These “black box” electronic wonders help balance out the radical hardware while ensuring emissions compliance and respectable fuel efficiency.
Those willing to pony up 100-plus grand will get prodigious output along with a relatively mild cam grind that makes for a very stout but tractable vehicle. After all, the ZR1’s stated goal was to be a docile pussycat around town and a track-day tiger. At 1,000 rpm the LS9 is already making 300 hp and 320 lb-ft of torque, with maximum readings of at least 620 hp and 595 lb-ft coming at 6,500 and 4,000 rpm, respectively. Incredibly, ninety percent of the LS9’s peak torque is available from 2,600 rpm to 6,000 rpm. For an EPA- and GM-durability-certified engine, that’s damn impressive!
Let’s go through the basics and see how this mouse roars from beginning to end. The LS9 displaces 6.2 liters, with bore/stroke measurements of 4.06 x 3.62 and a 9.1:1 compression ratio. The engine is a pushrod, 2-valve-per-cylinder design with a 12-quart dry-sump oiling system. The block and cylinder heads are aluminum, but the heads are spun-cast from A356-T6 alloy for higher heat tolerance.
The LS9’s block is essentially the same as the base LS3’s, but nearly all other components are either completely new, upgraded LS3, or LS7 parts. Reinforced bulkheads improve block stiffness by 20 percent. The LS9 uses six-bolt steel main caps with high-strength steel bearing caps, a new forged-steel micro-alloy crankshaft, and a new 9-bolt flywheel mount. The head-gasket design is unusual, too. The gaskets are cut to the same shape as the LS3 units but have four layers of steel instead of two. Also, the intake tract incorporates a “swirl ring” to improve the air/fuel mixture.
I know what you’re thinking: Why didn’t they just use the 427ci LS7 to start with? Designed for use in the naturally aspirated Z06, the LS7 block was rejected because its thinner cylinder walls prompted durability concerns with the added pressure from the supercharger. Maybe we’ll see that setup in the C7 Corvette.
When it comes to making power, it all begins with copious amounts of compressed, cooled air. That air enters the intake tract and travels straight into a new Eaton R1900 2-rotor supercharger nested between the cylinder banks. Each of the blower’s rotors has four lobes, making it both efficient and quiet. Using a 2.3:1 pulley ratio, the Eaton unit pumps out 2.3 liters of compressed air per revolution and achieves a maximum boost level of 10.5 psi.
The compressed air is transferred to a “dual brick” Behr air-to-liquid intercooler capable of reducing intake-charge temperatures by as much as 140 degrees F. It is then blown through valves that are the same size as the LS3’s but use titanium construction on the intake side and sodium-filled stainless steel on the exhaust. The pistons are forged aluminum instead of cast, and the connecting rods are machined out of titanium.
Standard LS3 ignition coil packs mounted to the rocker covers ignite the pressurized mixture. A unique, electronic fuel-pressure regulator switches between 87.0 psi and 36.3 psi settings based on engine speed, while an 11-rib V-belt runs the supercharger, power steering, and water pump.
Keeping a high-pressure, high-temperature engine such as the LS9 engine alive requires enhanced oiling capabilities. In addition to its dry-sump system, the LS9 is the first small-block Chevy to use oil squirters to boost cooling and reduce engine noise. The exhaust system of the LS9 is identical to the Z06’s, with manifolds and catalytic converters designed to meet 150,000-mile durability tests. No official EPA fuel-mileage ratings have been published to date, but the LS9 may fall victim to the gas-guzzler tax.
The ZR1’s drivetrain has also been enhanced with a twin-disc Luk clutch that has dual 260mm discs. It boasts more clamping power than the Z06’s single 290mm unit, with no extra pedal effort. Power then runs through a revised TR6060 six-speed manual gearbox with dedicated ratios, including a steep First gear that helps launch the car and a shorter Sixth gear to enable the ZR1’s 200-plus-mph top speed.
It wasn’t long ago that even racing Corvettes didn’t have this much cool hardware. But then again, there’s never been a $100,000-plus Vette available from your local Chevy dealer. If you haven’t yet placed your order, you just might have to wait for the ‘10 model. Will the ZR1 coast through the rest of the C6 run unchanged as the flagship Corvette, or does Chief Engineer Tadge Juechter have a few more tricks for the ZR1? Stay tuned! - K. Scott Teeters
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Illustrated Corvette Series No. 133 - 2009 ZR1 Corvette
"Chevy's World-Class Supercar"
The Internet rumor mill worked three shifts for nearly two years on the recently introduced 2009 ZR1. Fuzzy spy photos kept fans stoked, while all sorts of colorful names were bandied about. The buzz was that the Corvette team was hard at work on a new super-Vette. The only solid information was that the car would be based on the existing Z06. Everything else was up for delicious speculation. Automotive bloggers and magazine writers taunted us with names such as “Blue Devil,” “Stingray,” “Corvette SS,” and “Z08.” Then, in December ‘07, Chevrolet stopped torturing us and announced the return of the king: The ZR1 was back!
The new ZR1 is arguably the most aggressive production Corvette ever made. As we wrote last month, the ZR1 name was originally a racing option from ’70-1/2 to ‘72. The ’90-‘95 ZR-1, with its jewel-like LT5 engine, was a terrific machine, but it didn’t look that much different from a regular Corvette. Such is not the case with the latest ZR1. One has to go all the way back to the ’65-’69 big-blocks—with those amazingly loud side-mounted exhaust pipes—for more visual testosterone. The ‘09 ZR1 bears a strong resemblance to the L88 Corvettes, with their flared fenders and race-car-inspired details.
But unlike the earlier super-Vettes that were intended for track use only, this is a mega-muscle machine you can live with everyday. Forty years after the L88 and ZL1, we now have a Corvette that delivers unimagined performance in every area. Let’s draw some comparisons.
The new ZR1 packs 620 horsepower and 595 pound-feet of torque. The L88 and ZL1 engines never received accurate published power ratings, but real output was estimated to be close to 550 gross hp. The new ZR1’s LS9 engine is rated in net hp. It also passes emissions tests and is capable of over 20 mpg on the highway. The beasts of old got 8-10 mpg and had no emissions controls whatsoever. The new ZR1 also has a suspension that won’t hammer out your fillings and brakes that don’t have to be hot to work. Yes, 40 years of development have paid off big-time.
The ZR1’s stunning good looks are obvious from every angle. While the Z06 is a very aggressive-looking car, the ZR1 takes things to the next level. The entire front end and the roof section are made of carbon fiber. Chevy decided to show off the exotic material by using a $60,000-a-gallon clearcoat over the new chin spoiler, rocker panels, front fenders, and roof. The new hood is one inch taller than a regular Vette’s, bears a slight resemblance to the C3 big-block hoods, and features a Plexiglas window that shows off the LS9’s engine cover. The front and rear fender flares are the same as the Z06’s, but the front fenders have larger, more aggressive vents. The back end is finished off with a short, full-width spoiler. The only things missing are the side-pipes, rendered unnecessary by the car’s ultra-efficient conventional exhaust system. New ZR1 badges adorn the front fenders and rear bumper cover.
The new ZR1 couldn’t have much more exotic hardware. The all-aluminum LS9 engine is not only supercharged, it has an intercooler, port fuel injection, a 10.75-quart dry-sump oil system, and a LUK dual-disc clutch. The TR6060 six-speed transmission has been beefed up, and the gear ratios are closer than those in the Z06.
Now let’s talk about those wheels and brakes. The Speedline forged-aluminum wheels measure 19x10 inches in the front and 20x12 inches in the rear. For the first time since ’77, a Corvette will not be wearing Goodyear tires. The Michelin Pilot Sports measure 285/30-19 on the front and 335/25-20 on the rear. The brake system uses Brembo carbon-ceramic rotors that are vented and cross-drilled. They measure 15.5x1.6 and 15x1.4 inches fore and aft, respectively. Six-piston calipers are employed in the front, and four-piston units are used in the back. The brake pads are twice the size as those used on the Z06 and will last the car’s lifetime in street use. The basic Z06 suspension is modified with next-generation Delphi Magnetorheological (MR) variable shocks, softer springs, larger anti-roll bars, and revised rear-suspension geometry.
The interior has only slight addThe interior has only slight additions. The seatbacks feature “ZR1” embroidery, a boost gauge and “ZR1” tach face plate spruce up the instrument cluster, and the door-sill plates also bear the car’s model designation. And so you don’t forget how fast the ZR1 can take you, the speedometer goes up to 220 mph!
The interior has only slight additions. The seatbacks feature “ZR1” embroidery, a boost gauge and “ZR1” tach face plate spruce up the instrument cluster, and the door-sill plates also bear the car’s model designation. And so you don’t forget how fast the ZR1 can take you, the speedometer goes up to 220 mph! - K. Scott Teeters
Illustrated Corvette Series No. 155 - Lingenfelter's 9-Second ZR1