It was almost three years ago when GM introduced the 7-liter LS7 engine as the most potent mill ever churned out by the General. At 505 horsepower and 470 lb-ft of torque it surpassed everything else in GM's stable and most of the engines put out by the competition. But today, it's no longer the meanest dog in the kennel. That distinction has officially been passed to GM's latest creation-the LS9.
The LS9 engine was developed to motivate GM's latest supercar, the ZR1 Corvette and, if they hoped to surpass the world-class performance of the Z06, GM knew they would need something special under the hood.
Displacement Drops
The new LS9 exceeds the LS7 in every area except one, displacement. The main reason for the drop in displacement was strength. GM's plan for the LS9 included a supercharger and they felt the 427 cubic-inch block wasn't strong enough to reliably hold up to the intended boost. Instead, a beefed up 6.2-liter LS3 block will be used. Starting in '09, all 6.2L blocks, including truck blocks, will feature this 20 percent increase in bulkhead strength. According to Tom Reed, of GM, "All the blocks benefited in '08 with a 20 percent increase because of the LS3 improvements. Therefore, since 2007 the bulkhead area strength has increased 40 percent. Something to keep in mind when the 6.2L blocks start showing up in the bone yards, way down the road." The 319-T5 aluminum block, with forged steel bearing caps, will also be deck plated, bored, and honed. The LS9 will also feature eight block-mounted oil squirters. These squirters will keep chamber temps down and lessen drivetrain noise. This is the first time GM has used oil squirters in a small-block application. By sharing the casting across the LS3 line, costs will be kept down.
Forging Ahead
The use of exotic titanium will continue to be used in the engines rods, but GM has moved to forged 9.1:1 compression pistons. The floating pin- pistons are anodized on the top and the skirts are polymer coated. Turning it all will be a forged steel micro-alloy crankshaft.
Boosting Up The Power
For the first time ever the new super 'Vette will come from the factory with a supercharger under the hood. The Eaton Gen VI Twin Vortices Series (TVS) supercharger exceeds the previous Gen V supercharger in several key areas. The main area is in blower displacement. The larger displacement of the new Gen VI unit expands the range of the compressor's effectiveness, building power more quickly at lower rpm and sustaining it through higher rpm. The 2.3L displacement of the Eaton will provide maximum boost of 10.5 psi.
Inside the supercharger is a new, four-lobe rotor arrangement that tops 15,000 rpm, thus helping sustain airflow at high engine rpm. Also, the intermeshing design of the lobes helps quiet the supercharger, even at high rpm. In fact, the new Gen VI four-lobe blower design provides up to 10 dBa less case-radiated noise than the Gen V blower.
Air To Water Intercooler
The new air to liquid tube-in-fin intercooler will help to lower inlet temps by up to 140 degrees Fahrenheit. The dual aluminum brick intercooler will have its own separate dedicated system with a 3.62-liter reservoir mounted in front of the radiator. One of the most impressive feats of this new system is how it's packaged into such a compact form. GM engineers were tasked with keeping the overall dimensions of the new LS9 in line with the LS7. This way, no huge bulge will be needed on the new ZL1 'Vette.
Other Improvements And Details
To keep the engine as low as possible, GM opted to run a two-belt system on the LS9. The air conditioning and alternator will run on a separate 6-rib belt while the blower, power steering, and water pump will run off an 11-rib belt. To handle the extra strain, the water pump bearing was beefed up.
Oil capacity was increased for the system since the ZR1 has an expanded performance envelope compared to the Z06. The result is a 33 percent increase in oil capacity. That means you'll need 10.75 quarts of oil instead of the previous 8 quarts when you do an oil change. The increased oil supply will result in the mill handling 30 percent more g's. This increase in oil capacity will also be integrated into the LS7 engine in the Z06.
The Bottom Line
While GM didn't give the final power number of the LS9, Sam Winegarden stated that: "There's no way it's leaving Wixom with less that 620 horsepower and 600 lb-ft of torque!" That would equate to an output of 100 horsepower per liter of displacement, making it the most powerful production vehicle engine in GM's history. Equally important to GM, was the LS9's refinement, driveability, and durability. Despite having 23 percent more power over the LS7, the LS9 delivers an 11 percent improvement in idle performance over the LS7. The GM engineers have also increased the thermal efficiency by 15 percent and lowered parasitic loss by 35 percent over the last generation supercharger. Manufacturing has been easier since 76 percent of the parts in the LS9 carry over from other GM small-blocks. In terms of durability, the LS9 has already been validated to over 100,000 miles. That's 6,800 hours on the dyno with more than 100 of them at WOT. This is a good thing since we bet these new engines will be spending quite a bit of time clawing at the upper rpm.