GM's LS9 Engine - King Of The Hill

It was almost three years ago when GM introduced the 7L LS7 engine as the most potent mill ever turned out by the General. At 505 hp 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 it hoped to surpass the world-class performance of the Z06, GM knew it would need something special under the hood.

The LS9's dual aluminum-brick intercooler will have its own dedicated cooling system, with a 3.62-liter reservoir mounted in front of the radiator.

Displacement Drops
The new LS9 exceeds the LS7 in every area except one: displacement. The main reason for the drop in displacement is strength. GM's plan for the LS9 included a supercharger, and it 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 Powertrain: "All the blocks benefited in '08 with a 20 percent increase because of the LS3 improvements. Therefore, since '07, the bulkhead area strength has increased 40 percent. That's something to keep in mind when the 6.2L blocks start showing up in the boneyards, 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.

The Eaton TVS supercharger is all about pumping out power, while staying as compact as possible. Inside the supercharger is a new, four-lobe rotor pair that tops 15,000 rpm, thus helping sustain airflow at high engine rpm.

Forging Ahead
Exotic titanium will continue to be used in the engine's rods as per the still-continuing LS7, 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 The Power
For the first time ever, the new ber 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, including blower displacement. The larger displacement of the new Gen VI 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 a maximum boost of 10.5 psi.

Air To Water Intercooler
The new air-to-liquid, tube-in-fin intercooler will help lower inlet temps by up to 140 degrees F. 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 ZR1 Vette.

The blower rotors have a 160 degree twist versus the last generation's 60 degree design. A special coating on the rotors allows them to self machine when run the first time.

Other 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. This 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 engine handling 30 percent more g-force. This increase in oil capacity will also be integrated into the LS7 engine in the Z06.

Bottom Line
While GM didn't give the final power number of the LS9, GM Powertrain's Sam Winegarden told PHR: "There's no way it's leaving Wixom with less than 620 horsepower and 600 lb-ft of torque!" That would equal an output of 100 hp 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. And at least one aspect of manufacturing has been made 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 more than 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.

The rotocast aluminum heads are works of art. Porosity has been virtually eliminated, and the design provides more consistent density. The strength has also been improved by 12 percent. The valves are the same titanium intake and hollow-stem sodium-filled exhausts found on the LS7.	Coated, forged pistons are an improvement over the hyper-eutectic pistons used in the LS7. Titanium rods keep weight to a minimum.	This graph compares the output of the new LS9 relative to the LS7, and more importantly, the 8.4L Viper V10, and 6.2L LS3.
The LS7's dry-sump system has been retained in the LS9, but improved with the addition of an oil cooler assembly. Tank capacity has been increased 33 percent to 10.75 quarts. Mobil 1 synthetic will continue on as the factory-recommended fill.	The 2009 ZR1 Corvette is the recipient of all the LS9's goodness-at least for now. Note the plexiglass cover on the hood, which gives gawkers a window into the engine room, a l Ferrari.

For more detailed photos of the LS9, log on to www.popularhotrodding.com.