[ZR1] Inside the LS9 Part 1
09-16-2009, 06:37 PM
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Inside the LS9 Part 1
The July 2008 issue of Hot Rod magazine had an in-depth article on Chevrolet's LS9 engine.
Starting with this thread I'll try to share details found within that article. I found details previously unknown to me...hopefully other CF members will find the article informative.
First off credit is due to Bill McGuire, Detroit editor of HRM. Photography for the article was provided by David Freers and GM.
Also want to give credit to the LS9 engineering team who brought the 638 HP LS9 engine to reality:
*Yoon Lee, designer of the intake manifold for the LS3 & LS7. He is responsible for the LS9's compact blower, manifold, and charge cooler.
* Tom Briolat, application engineer.
* Mike Siegrist, design system engineer.
* Ron Meegan, asistant chief engineer.
* Jim Cremonesi, team leader for the crank, flywheel, damper, rods, pistons and bearings.
* Gerry Clark, technical specialist, engine performance and valve train analysis. Gerry performed the computer simulations that proved the LS9 concept before it ever saw a dyno. He also designed the camshaft.
* Tom Stephens, GM Executive V-P, GM Global Powertrain and GM Global Quality. (responsible for approximately 37,000 engines and 33,000 tranmissions produced world wide daily at GM!
Through careful engineering 76% of the LS9 components are carried over from the LS7. Many of the improved pieces that were developed for the LS9 will now be back-fitted to the LS7 and other small block V8 engines.
BRB...time for dinner!
Starting with this thread I'll try to share details found within that article. I found details previously unknown to me...hopefully other CF members will find the article informative.
First off credit is due to Bill McGuire, Detroit editor of HRM. Photography for the article was provided by David Freers and GM.
Also want to give credit to the LS9 engineering team who brought the 638 HP LS9 engine to reality:
*Yoon Lee, designer of the intake manifold for the LS3 & LS7. He is responsible for the LS9's compact blower, manifold, and charge cooler.
* Tom Briolat, application engineer.
* Mike Siegrist, design system engineer.
* Ron Meegan, asistant chief engineer.
* Jim Cremonesi, team leader for the crank, flywheel, damper, rods, pistons and bearings.
* Gerry Clark, technical specialist, engine performance and valve train analysis. Gerry performed the computer simulations that proved the LS9 concept before it ever saw a dyno. He also designed the camshaft.
* Tom Stephens, GM Executive V-P, GM Global Powertrain and GM Global Quality. (responsible for approximately 37,000 engines and 33,000 tranmissions produced world wide daily at GM!
Through careful engineering 76% of the LS9 components are carried over from the LS7. Many of the improved pieces that were developed for the LS9 will now be back-fitted to the LS7 and other small block V8 engines.
BRB...time for dinner!
09-16-2009, 08:33 PM
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The engine was first conceived as an "up-front analysis." That means the LS9 was conceived, tested and proven as a concept before it ever made its first dyno pull. Using advanced simulation and modeling software, Gary Clark, and his team built the engine in the computer and made sure it could get the numbers, only then did the project proceed. The key question for designers was, can you make a total package with the power, torque, excellent driverability, fuel economy, emissions, noise and minimal vibration...they did over 300 dyno runs analytically before they ever began the real engine. One key element in the LS9's civilized manner is the camshaft design, which like everything else, was performed on a computer. Closely based on the LS7 lobe profiles, the LS9's cam was carefully tweeked to optimize the pumping cycle and maximize idle quality -- its lobe-separation angle is a whopping 122.5 degrees.
The block was cast in 319-T5 aluminum, the LS9 cylinder case is 20% stronger in the main bearing webs than previous small blocks. Deck plates are installed for boring and honing. For 2009, all 6.2L V8's will be upgraded to this block casting.
Integral piston squirters in the crankcase oil galleries were essential in making the LS9 live under prolonged high boost. Says Jim Cremonesi "We see a significant drop in piston dome and pin boss temperatures. It's the best way we know to pull the heat out of the piston when making this much power."
To handle the higher cylinder pressures, a heavier, thicker domed piston was required-- 539 grams vs 482 grams for the LS7. Compression ratio is 9.1:1. To offset the increased piston mass, Pankl titanium con rods (152.15 mm long, 445 grams) were selected along with tapered wristpins. The LS9 piston has a polymer skirt coating. GM is planning on using this coating on their engines across the board.
LS9 piston forging employs a 1.5 mm moly-filled steel top ring, a 1.2 mm nocular iron second ring and a 3.0 mm oil ring assembly.
The LS9 head is similar to the L92 (I believe they meant LS2) but includes airflow wings in the intake ports to promote mixture motion. The head is rotocast in 356 T6--molten aluminum is pored into a slowly rotation mold to optimize casting density. Intake valves are titanium, exhaust are stainless steel.
High combustion pressures cause the LS9's cylinder head to pulse up and down on the block deck, requiring a seven layer head gasket and 12 mm stainless head bolts (11 mm bolts are standard on the 6.2l block) to keep the cylinders sealed.
The Roots blower is an Eaton piece that displaces 2.3 liters and turns at 2.3 times crank speed. At max engine output, around 70 hp is used to drive the unit, which produces 10.5 psi of boost. An 11 rib belt drives the blower, p.s pump, and water pump.
Stay tuned for Part II.
Zippy
The block was cast in 319-T5 aluminum, the LS9 cylinder case is 20% stronger in the main bearing webs than previous small blocks. Deck plates are installed for boring and honing. For 2009, all 6.2L V8's will be upgraded to this block casting.
Integral piston squirters in the crankcase oil galleries were essential in making the LS9 live under prolonged high boost. Says Jim Cremonesi "We see a significant drop in piston dome and pin boss temperatures. It's the best way we know to pull the heat out of the piston when making this much power."
To handle the higher cylinder pressures, a heavier, thicker domed piston was required-- 539 grams vs 482 grams for the LS7. Compression ratio is 9.1:1. To offset the increased piston mass, Pankl titanium con rods (152.15 mm long, 445 grams) were selected along with tapered wristpins. The LS9 piston has a polymer skirt coating. GM is planning on using this coating on their engines across the board.
LS9 piston forging employs a 1.5 mm moly-filled steel top ring, a 1.2 mm nocular iron second ring and a 3.0 mm oil ring assembly.
The LS9 head is similar to the L92 (I believe they meant LS2) but includes airflow wings in the intake ports to promote mixture motion. The head is rotocast in 356 T6--molten aluminum is pored into a slowly rotation mold to optimize casting density. Intake valves are titanium, exhaust are stainless steel.
High combustion pressures cause the LS9's cylinder head to pulse up and down on the block deck, requiring a seven layer head gasket and 12 mm stainless head bolts (11 mm bolts are standard on the 6.2l block) to keep the cylinders sealed.
The Roots blower is an Eaton piece that displaces 2.3 liters and turns at 2.3 times crank speed. At max engine output, around 70 hp is used to drive the unit, which produces 10.5 psi of boost. An 11 rib belt drives the blower, p.s pump, and water pump.
Stay tuned for Part II.
Zippy
09-16-2009, 10:44 PM
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Part II
Gerry Clark: "We couldn't find any more power with this cam, but we were able to reduce the parasitic load of the blower so it didn't have to work so hard." Along with decreasing the blower load, the camshaft strategy also improved idle stability and driveability. "Combustion variability is a pretty strong function of valve overlap." Along those lines, one reliability indicator of idle stability is a metric called standard deviation of net mean torque. By that measure the LS9 is 11 percent smoother than the LS7, despite producing 133 more hp. Of course, we can thank the big blower and charge cooler for all that hp. "We knew we needed a bigger compressor than what was then on the market, says Yoon Lee, who headed up the supercharger program. The Gen 6.2L Eaton blower is approximately 35% more efficient than traditional Roots blowers, thanks mainly to its four lobe, 160 degree twist impellers. "There used to be significant advantages in the twin screw Roots. It's not really there anymore." Lee says of the sophisticated rotor design. The integral charge cooler further increases the system's efficiency. Lowering the intake air charge 140 degrees F at max output. Which brings us to the part of the project LS9 team members call the biggest challenge. Making all that power was easy; fitting in into the car was difficult. The blower and drive system made the LS9 both taller and longer than the LS3 or LS7 and thus a very tight squeeze under the Corvette's hood. Some clever engineering of the accessory drive system took care of the length problem, but there was one requirement on which GM corporate suits refused to budge: a "four-degree-down-vision" standard, which meant no big hood blister blocking the driver's forward view. (personal comment: perhaps that's part of the reason for the hood window?)
To get the blower and charge cooler stack safley tucked under the hood, components were painstakingly shaved down "one millimeter at a time," says Tom Briolat, applications engineer. As the liasion between the power train and platform teams, he was tasked with horse-trading the millimeters back and forth between the two groups, but he's sure it was worth it.
The dual-brick heat exchanger unit was incorporated into the charge cooler to keep the unit's height to a minimum. A small radiator at the front of the car processes the system's 3.6 liters of coolant.
The four lobe rotors (Eaton TVS, Twin Vortices Supercharger) with a 160 degree twist take smaller, smoother gulps than traditional two and three lobe impellers, reducing blower whine and improving pumping efficiency,
GM says the LS9 successfully completed more than 6,800 hours of dyno testing, including a simulated 24 hours of LeMans race. Unlike the performance engines from many of the exotic carmakers, the Corvette LS9 was held up to passenger car durability standards--more than 100,000 miles.
Don't know about anyone else, but I have a greater appreciation for GM and Eaton engineering for this remarkable powerplant, which will go down in history as one of the greatest internal combustion engines ever!
Gotta love America!
Zippy
Gerry Clark: "We couldn't find any more power with this cam, but we were able to reduce the parasitic load of the blower so it didn't have to work so hard." Along with decreasing the blower load, the camshaft strategy also improved idle stability and driveability. "Combustion variability is a pretty strong function of valve overlap." Along those lines, one reliability indicator of idle stability is a metric called standard deviation of net mean torque. By that measure the LS9 is 11 percent smoother than the LS7, despite producing 133 more hp. Of course, we can thank the big blower and charge cooler for all that hp. "We knew we needed a bigger compressor than what was then on the market, says Yoon Lee, who headed up the supercharger program. The Gen 6.2L Eaton blower is approximately 35% more efficient than traditional Roots blowers, thanks mainly to its four lobe, 160 degree twist impellers. "There used to be significant advantages in the twin screw Roots. It's not really there anymore." Lee says of the sophisticated rotor design. The integral charge cooler further increases the system's efficiency. Lowering the intake air charge 140 degrees F at max output. Which brings us to the part of the project LS9 team members call the biggest challenge. Making all that power was easy; fitting in into the car was difficult. The blower and drive system made the LS9 both taller and longer than the LS3 or LS7 and thus a very tight squeeze under the Corvette's hood. Some clever engineering of the accessory drive system took care of the length problem, but there was one requirement on which GM corporate suits refused to budge: a "four-degree-down-vision" standard, which meant no big hood blister blocking the driver's forward view. (personal comment: perhaps that's part of the reason for the hood window?)
To get the blower and charge cooler stack safley tucked under the hood, components were painstakingly shaved down "one millimeter at a time," says Tom Briolat, applications engineer. As the liasion between the power train and platform teams, he was tasked with horse-trading the millimeters back and forth between the two groups, but he's sure it was worth it.
The dual-brick heat exchanger unit was incorporated into the charge cooler to keep the unit's height to a minimum. A small radiator at the front of the car processes the system's 3.6 liters of coolant.
The four lobe rotors (Eaton TVS, Twin Vortices Supercharger) with a 160 degree twist take smaller, smoother gulps than traditional two and three lobe impellers, reducing blower whine and improving pumping efficiency,
GM says the LS9 successfully completed more than 6,800 hours of dyno testing, including a simulated 24 hours of LeMans race. Unlike the performance engines from many of the exotic carmakers, the Corvette LS9 was held up to passenger car durability standards--more than 100,000 miles.
Don't know about anyone else, but I have a greater appreciation for GM and Eaton engineering for this remarkable powerplant, which will go down in history as one of the greatest internal combustion engines ever!
Gotta love America!
Zippy
09-18-2009, 02:16 AM
#7
