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2009 CTS-V Engine details


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2009 “LSA” 6.2L V-8 SC (LSA)

2009 Model Year Summary

All-New Gen IV Small-Block V-8 for 2009 Cadillac CTS-V

Gen VI Supercharger with Twin Four-Lobe Rotors

Integrated Air-to-Liquid Intercooler

Enhanced Gen IV Cylinder Block

Hypereutectic Aluminum Pistons with Oil-Spray Cooling

Lightweight Reciprocating Assembly

Lower Lift, Low Overlap Cam

High-Flow Rotacast Cylinder Heads

Center-Feed Fuel System

Direct-Mount Ignition Coils

E67 Control Module

Upgraded Oiling System

Revised Accessory Drive

High-Moly Cast Iron Exhaust Manifolds with Close-Coupled Catalysts

Acoustic Engine Cover

Full Description of New and Updated Features

All-New Gen IV Small-Block V-8 for 2009 Cadillac CTS-V

The 556-hp 6.2L Supercharged Gen IV V-8 (RPO LSA) is installed longitudinally in the CTS-V, and available with either GM Powertrain’s Hydra-Matic 6L90 six-speed automatic or the twin-disc Tremec TR6060 six-speed manual transmission. This engine is assembled in Silao, Mexico.

With 556 horsepower at 6100 rpm and 551 pound-feet or torque at 3800 rpm, certified by the Society of Automotive Engineers, the supercharged LSA V-8 is the most powerful production engine in Cadillac’s 106-year history. It makes the CTS-V one of the fastest four-door automobiles in the world, with at least 23 percent more horsepower and 24 percent more torque than benchmark competitors such as the Audi RS4, BMW M3 and Mercedes-Benz C63 AMG, according to published figures.

As significantly, the LSA delivers an excellent balance of low-rev torque and high-rev horsepower, with the smooth, refined operation expected in a luxury brand. The new 6.2L Supercharged LSA takes Cadillac’s tradition of outstanding power, performance and impressive refinement to new levels.

Gen VI Supercharger with Twin Four-Lobe Rotors

A state-of-the-art supercharger is key to the 6.2L LSA’s remarkable performance. This Gen IV small-block V-8 is equipped with Eaton’s Twin Vortices Series (TVS) supercharging technology, which represents the sixth generation of joint Eaton/GM Powertrain supercharger development. The LSA supercharger displaces 1.9 liters and generates maximum boost pressure of 9.0 pounds per square inch (0.62 bar).

A supercharger is essentially an air pump driven by the engine’s crankshaft. It forces more air into the engine’s combustion chambers than that engine could otherwise draw on its own. The increased volume of oxygen allows the engine to efficiently process more fuel, and thus generate more power.

The TVS takes supercharging technology to new levels of refinement and efficiency. Each of its two rotors has four distinct lobes, or spiral-shaped vanes that intermesh precisely with those on the other rotor as they spin at high speed. Efficiency gains with the four-lobe rotors are substantial, compared to comparably sized, previous-generation superchargers: Approximately 20 percent more airflow, with an improvement in thermal efficiency up to 15 percent. Moreover, parasitic power loss—the amount of power the engine uses to operate the supercharger—is reduced 35 percent. That improves both the supercharger’s response time and the engine’s overall efficiency.

With the TVS supercharger, the 6.2L LSA delivers nearly 1.5 horsepower per cubic inch of displacement and specific torque that’s at least 18 percent higher than any of its primary competitors. Yet impressive output figures tell only part of the story. The supercharger’s large displacement expands its effective range, building power more quickly at low rpm. Its four-lobe rotors spin at over 15,000 rpm, or about two and a half times the engine’s rotation speed, to sustain its benefits at high engine speeds, when many superchargers lose their effectiveness. There’s no high-rev power drop-off with the LSA.

Nor is there typical supercharger whine—the high-pitched, whizzing sound emanating from a supercharged engine as the rotors spin furiously. The four-lobe rotors help lower noise radiating from the supercharger case as much as 10 decibels, and sound pressure is nearly identical whether or not the supercharger is generating boost. During CTS-V development testing on Germany’s 13-mile Nurburgring race course, onlookers were convinced that the LSA had no supercharger, even when it was running at wide-open throttle.

Integrated Air-to-Liquid Intercooler

An advanced intercooling system increases the 6.2L LSA’s performance and extends its supercharger’s benefits. The engine’s charge cooler is integrated in the supercharger case just above the rotors, with a single air-to-liquid cooling “brick” that substantially lower the temperature of air used in the combustion process.

Intercoolers are familiar features on supercharged and turbocharged engines. Similar in concept to an engine’s radiator, intercoolers cool the air pumped by the charging device into the cylinders. Cooler air is denser air, which means there is more oxygen in a given volume, resulting in optimal combustion and more power. Traditionally, intercoolers look like small radiators mounted somewhere outside the engine, with air fed into the engine through a plumbing network.

The LSA’s intercooling system raises the bar in both packaging and efficiency. It uses a single aluminum tube-and-fin heat exchanger mounted above the rotors in the supercharger case. Air pumped by the supercharger flows directly through the brick and down to the intake ports on the cylinder heads. The intercooler brick is cooled by its own coolant circuit, with a remote pump and 3.02-liter reservoir mounted in front of the CTS-V’s radiator.

Bottom line: The temperature of air fed to the LSA’s cylinder heads is reduced 158 degrees F (70 degrees C), substantially increasing the amount of oxygen available for the combustion process. The intercooler design also contributes to the supercharger’s quiet operation. The cooling brick helps dampen sound radiating from the supercharger case, while ribs cast into the top of the intercooler housing add strength and reduce vibration.

Enhanced Gen IV Cylinder Block

The 6.2L Gen IV small block has been further refined for the LSA. It’s cast from 319-T5 aluminum and fitted with cast-iron cylinder liners

Bulkheads in the LSA engine block have been strengthened 20 percent by optimizing the size of the bulkhead “windows” to take advantage of material thickness in the bulkhead. This is additional improvement beyond a 20% gain obtained in the naturally aspirated 6.2L LS3 V-8 by increasing the radius of the hone over-travel fillets from three to 10 millimeters. The enlarged bulkhead windows also improve bay-to-bay breathing by managing airflow inside the engine more efficiently, thereby decreasing pumping loss, or reducing resistance to the pistons’ downward movement.

Bulkheads are the structural elements that support the crank bearings. In the LSA, they accommodate six-bolt, cross-threaded main-bearing caps that limit crankshaft flex and stiffen the engine’s structure. The caps are nodular iron, specified for its strength, rigidity and minimal vibration.

The cylinder liners are cast into the LSA block and machined with a deck plate installed over the cylinder bores. The deck plate simulates the pressure and minute dimensional changes that occur when the cylinder heads are bolted to the block. The process enhances assembly quality and fit, ensuring precise head sealing, perfect piston ring fit and peak performance as the engine accumulates miles.

Block enhancements initiated with the LSA will be applied to all 6.2L Gen IV engine blocks, including those used for the new LS9 in the 2009 Chevrolet Corvette ZR1, the LS3 Corvette V-8 and truck applications. While the Gen IV block shares its 90-degree cylinder angle and 4.4-inch bore centers with GM’s original small block V-8, it applies design, casting and machining technologies that were unfathomable when the original was introduced in the 1950s.

The Gen IV block debuted in 2005 as the foundation for the 400-hp LS2 V-8 in the Chevrolet Corvette, Cadillac CTS-V and Pontiac GTO. It was developed with the latest math-based tools and data acquired in GM’s racing programs, and it provides an exceptionally light, rigid foundation for an impressively smooth cam-in-block engine. Its deep-skirt design helps maximize strength and minimize vibration, and its aluminum construction reduces weight approximately 100 pounds compared to a conventional cast-iron cylinder block.

Hypereutectic Aluminum Pistons with Oil-Spray Cooling

Superior piston design sets the tone all of the 6.2L LSA’s internal components. The engineering objective? Lighter, stronger and smoother.

The pistons themselves are aluminum—cast from a high-silicon alloy developed for its combination of strength and heat-management properties. Casting reduces noise-generating potential, compared to other high-performance piston materials such as forged aluminum, and is specified when NVH control is a priority. The hypereutectic pistons are also lighter than conventional steel, which translates to less reciprocating mass inside the engine. Less mass means greater efficiency, high-rpm capability and a feeling of immediate response as the engine builds revs.

The combustion surface of the LSA pistons, or the top land, lacks the valve-relief pockets typical on high-performance engines with relatively high-lift valves. Rather, the LSA top lands are sumped, with a saucer-shaped indent that dips gradually from the outer edge of the piston. This design promotes a thorough mixing of air and fuel, and along with other durability enhancing features, allows a 9.1:1 compression ratio: higher than a conventional supercharged or turbocharged engine, for improved combustion efficiency.

The durability enhancements include an anodized top land, which reduces wear and helps deflect heat generated during combustion away from the LSA’s bottom end. To further reduce wear, the piston skirt is coated with a polymer material, which limits bore scuffing, or abrasion of the cylinder wall over time from the piston’s up-down motion. The polymer coating also dampens noise generated by the piston’s movement. The wrist pins, which attach the piston to the connecting rod, were developed for maximum durability, with a large outer diameter and a tapered inner diameter. These pins “float” inside the rod bushing and pin bores in the piston barrel. Compared to a conventional fixed pin assembly, in which the connecting rod is fixed to the piston’s wrist pin while the pin rotates in the pin bore, the floating pins reduce stress on the pin. They allow tighter pin to pin-bore tolerances and reduce noise generated as the piston moves through the cylinder. The benefit is less engine wear, improved durability and quieter operation.

Finally, the 6.2L LSA represents the first line of small block V-8s equipped with oil-spray piston cooling. Eight oil-squirting jets in the engine block drench the underside of each piston and the surrounding cylinder wall with an extra layer of cooling, friction-reducing oil. The oil spray reduces piston temperature, promoting extreme output and long-term durability. The extra layer of oil on the cylinder walls and wristpin also dampens noise emanating from the pistons.

Lightweight Reciprocating Assembly

Careful analysis applied to the pistons extends to other reciprocating parts inside the 6.2L LSA V-8. Whenever possible, GM Powertrain has trimmed mass, increased strength and reduced friction, enabling the LSA’s high-rpm capability, improving overall performance and working to ensure durability.

Within the LSA’s cylinder block spins a balanced, dropped-forged steel crankshaft with an eight-bolt flange to mount the flywheel. The eight-bolt pattern increases clamping strength compared to naturally aspirated 6.2L Gen IV V-8s, which use a six-bolt crank flange. At the front end of the crank, the torsional damper is secured with a keyway and friction washer for an added element of security, given the LSA’s exceptional torque. The crank design reduces noise a single decibel—small in itself, but significant to overall refinement in a true high-performance luxury sedan.

Forged powder-metal connecting rods mate the crank with the pistons. These rods are forged under extreme pressure from alloy metals reduced to powder, rather the melted to liquid, for a balance of low mass and high strength. They reduce pressure on both the rod-end bearings and main bearings, compared to conventional rods, and allow the bearings to be optimally sized for the least amount of friction.

Lower Lift, Low Overlap Cam

A refined camshaft helps balance the 6.2L LSA’s remarkable output with silky, tractable low-rev operation.

The camshaft operates the engine’s valves, and its design is crucial to both power and smoothness. The torque enhancing benefits of the supercharger allowed GM Powertrain engineers to develop a “softer,” lower-lift camshaft for the LSA, compared to the typical high-rev, high-power super-sedan engine. The LSA cam delivers maximum lift of 12.2 mm for both the intake and exhaust valves. Moreover, the cam lobes are profiled to reduce the amount of time that both intake and exhaust valves are partially open at the same time. Valve overlap is reduced compared the previous, LS2-powered CTS-V, despite the substantial increase in output. The result is smoother operation at low speeds, and particularly at idle.

The cam design also reduces operating noise compared to the naturally aspirated 6.2L Corvette LS-3 V-8 by one decibel. While the change might not seem significant by itself, it combines with similar incremental improvements through the LSA that reduce interior noise in the 2009 CTS-V substantially compared its predecessor

High-Flow Roto-Cast Cylinder Heads

The 6.2L Supercharged LSA cylinder heads are similar to those used on the naturally-aspirated 6.2L LS3 Corvette V-8, with enhancements for supercharged induction and maximum durability.

The LSA heads feature a unique “wing’’ cast into each intake port to promote a swirling motion that blends the pressurized air-fuel charge. The heads are also cast from a premium A356-T6 alloy, which better manages the heat generated in a supercharged engine. A356-T6 pays particular dividends in the thin bridge area between the intake and exhaust valves, where effective heat dissipation is crucial to both performance and long-term durability. Finally, the LSA heads are rotacast. This process rotates the head mold as the molten alloy cools and essentially eliminates porosity, or microscopic pockets of air trapped in the casting. Rotacasting delivers a stronger part that helps maintain performance and structural integrity over the life of the engine.

Low-friction hydraulic roller lifters actuate the LSA’s valves, with unique offset rocker arms for the intake valves. On the inlet rocker, the valve tip is offset six millimeters from the pushrod. This configuration allowed Powertrain engineers to locate the intake port for a more direct air-fuel flow into the combustion chamber.

Valves are among the most heat-stressed parts in an engine, and their wear resistance is crucial to long-term durability. Those in the LSA are manufactured from a high-chromium steel alloy called SilChrome 1, with thicker heads than most other Gen IV V-8s. They promote heat transfer away from the valve face and valve guide to the cooler end of the stem, where it more readily dissipates. This maintains a lower, more uniform valve temperature, reducing wear on the valve guide for better alignment and a consistent seal between the valve seat and valve face over the life of the engine. The intake valves measure 55 mm in diameter and the exhaust valves, 44 mm.

Given the LSA’s pressurized induction, Powertrain engineer focused special attention on sealing. Head gaskets are extra-robust, four-layer stainless steel, ensuring gasket sealing under the high combustions pressures generated by the LSA.

Center-Feed Fuel System

The 6.2L LSA’s fuel system was developed to deliver adequate fuel volume precisely, consistently and quietly.

To ensure appropriate fueling in all conditions, from casual cruising to race track-type wide-open throttle, Powertrain has equipped the LSA with a dual- pressure fuel system. The system delivers 250 kPa (about 36 psi) at idle or low speeds. Yet the electronic throttle management system can almost instantaneously increase fuel pressure to 450 kPa (65 psi) for sustained high-speed operation or wide-open throttle. The dual-pressure system reacts according to throttle application, and presents several advantages. It limits the energy used by the fuel pump at low speeds, for maximum efficiency, and it reduces operational noise. It also ensures adequate fuel delivery when the LSA demands its maximum flow rate of 50 grams per second.

The LSA also employs a new center-feed fuel rail that delivers gasoline to the center of the injector rail on each bank. The delivery point is roughly equidistant to each of the injectors, which have a maximum flow rate of 6.52 grams per second at 400 kPa. Fuel pressure variation among the injectors is reduced, and so is noise. The rapid ticking sound often generated by fuel injectors is alleviated.

An 87-mm, single-bore throttle body draws air into the engine. The electronic throttle maps have been optimized for excellent response and modulation in a multitude of driving scenarios.

Direct-Mount Ignition Coils

The 6.2L LSA’s coil-on-plug ignition features advanced coils developed for the 7.0L LS7 V-8 in the Corvette Z06. These coils are smaller and lighter than those used on previous small-block V-8s. An individual coil for each spark plug delivers maximum voltage and consistent spark density, with no variation between cylinders.

The LSA ignition system is unique nonetheless, as the coils mount directly on LSA-specific rocker covers. Those on the naturally aspirated 6.2L LS3 and LS7 are joined by a bracket. The individual LSA coils provide a cleaner look and a shorter lead between the coil and the iridium-tip, center-electrode spark plug.

E67 Control Module

An advanced controller manages the multitude of operations that occur within the 6.2L Supercharged LSA V-8 every split second. The E67 is the high-line controller in GM’s family of three engine control modules (ECM), which was developed to direct nearly all the engines in Powertrain’s line-up. It features 32-bit processing, compared to conventional 16-bit processing, with 32 megabytes of flash memory, 128 kilobytes of RAM and a high-speed CAN bus. The E67 synchronizes more than 100 functions, from spark timing to cruise control operation to traction control calculations, and it has more computing power than the typical desktop PC 20 years ago. It works more than 50 times faster than the first computers used on internal combustion engines in the late 1970s, which managed five or six functions.

The family strategy behind GM’s ECMs allows engineers to apply standard manufacturing and service procedures to all powertrains, and quickly upgrade certain engine technologies while leaving others alone. It creates a solid, flexible, efficient engine-control foundation, freeing engineers to focus on innovations like the LS9‘s advanced supercharging technology, and to get them to market more quickly. Powertrain creates all the software for the three ECMs, which share a common language and hardware interface that’s tailored to each vehicle.

The E67 also applies a rate-based monitoring protocol sometimes known as run-at-rate diagnostics. Rate-based diagnostics improve the robustness of the Onboard Diagnostics System (OBD II) and ensure optimal performance of emissions control systems. The software increases the frequency at which the ECM checks various systems, and particularly emissions-control systems such as the catalytic converter and oxygen sensors. Rate-based diagnostics more reliably monitor real-word operation of these systems, and allow regulatory agencies to more easily measure and certify emissions compliance. With the E67, the CTS-V’s environmental performance matches its race-track potential.

Upgraded Oiling System

To ensure peak, low-friction efficiency, and to promote durability during extended high-rpm operation, the 6.2L Supercharged LSA has a more powerful oil pump than the naturally aspirated 6.2L LS3. Pump capacity increases to 33.8 gallons per minute. The LSA’s six-quart oil pan is fitted with a liquid-to-air oil cooler.

Revised Accessory Drive

The 6.2L LSA’s accessory drive system accommodates the supercharger with a third track on the crankshaft pulley. The supercharger is operated by its own belt, which is wider than a conventional belt (eight ribs) to turn the rotors without slip. The other drive belts are conventional five-rib widths, with one operating the air conditioning compressor and another operating the water pump, power steering pump and alternator.

Cast-Iron Exhaust Manifolds with Close-Coupled Catalysts

The 6.2L LSA exhaust manifolds are fabricated from a premium high-silicon, high-moly iron alloy. The material delivers excellent heat management properties, and the design ensures the high flow volume required of an engine with the LSA’s capability. Moreover, cast iron radiates less noise than other materials such as stainless steel, making it the preferred choice in a luxury sedan.

Immediately downstream, the exhaust manifolds are fitted with a pair of close-coupled catalytic converters that heat quickly, achieving light-off temperature and closed-loop operations in seconds. The primary catalysts are further downstream under the vehicle floor.

Acoustic Engine Cover

The LSA is trimmed with special engine cover surrounding the intercooler and supercharger case, which is visible under the CTS-V’s hood. The cover has "SUPERCHARGED LSA" script on each side, with the V-spec logo and classic Cadillac laurel emblem front-and-center.

The engine cover helps isolate high-frequency sounds emanating from the engine, and it’s attached with ball-stud mountings that more effectively limit vibration transfer than conventional twist-in fasteners. It’s also lined with dense acoustic foam.

Overview

The 6.2L Supercharged Gen IV LSA V-8’s credentials speak for themselves. It’s the most powerful production engine in Cadillac’s storied history, with 556 horsepower, high-rev capability and higher specific torque than any of its competitors. It makes the Cadillac CTS-V one of the world’s fastest, most capable sedans.

A Cadillac, of course, demands smooth, refined operation, and the LSA delivers here, too. Measured by interior noise levels at cruising speed and wide-open throttle, the 2009 CTS-V is substantially quieter than its highly successful predecessor, with cabin noise measurements that meet or beat Europe’ best ultra-performance luxury sedans.

Measured by cost-to-performance ratio, the LSA might also be considered a relative bargain. The elegant simplicity in the small-block V-8’s DNA means cost-effective development and production, and that translates to value, for customers and the corporation. Yet an emphasis on value overlooks one significant point. The LSA is one of the best high-performance sedan V-8s in the world, regardless of price.

GM Powertrain’s 90-degree small-block car engines remain unique in the automotive world: high-tech, aluminum-intensive, ultra-high-performance cam-in-block V-8s. The LSA adds a supercharger to the mix, and pushes the combination of impressive low end torque and free-breathing, high-rpm horsepower to a new level.

The starting point for the LSA was the first engine built for the sixth-generation Corvette—the Gen IV 6.0L LS2 V-8. The LS2, in turn, had built on two milestone engines: the LS1 and LS6 V-8s developed for the C5 Corvette. Those Gen III engines had introduced a host of leading-edge technologies to the grand tradition of GM’s small block, starting with all-aluminum construction, a thermoplastic intake manifold and drive-by-wire electronic throttle. With them the engineers and analysts who claimed cam-in-block engines could not meet the performance demands of a new millennium--or increasingly stringent emissions standards—were proven patently wrong.

Within this evolution, and a data base only tradition can provide, rests the cornerstone of small-block value. The performance in the LSA comes with 76 percent carryover parts from other small-block V-8s, while 25 percent of the new parts are common to the supercharged LS9 V-8 for the 2009 Chevrolet Corvette ZR1. The value is enhanced by GM Powertrain’s advanced application of math-based computer tools. Powertrain engineers created 370 different power simulations to optimize the LS9 and LSA. One simulation takes 24 hours, while one engine build takes nine weeks. Both the LS9 and LSA V-8s met power requirements out of the box. It’s value without compromise, in performance, emissions or customer satisfaction.

Or quality and durability. The 6.2L Supercharged LSA has been validated beyond 100,000 miles and accumulated more the 6,400 hours of dynamometer testing. It has run over 270 consecutive hours at wide-open throttle without a failure. It’s been road tested in the world’s extreme climates and track-tested under racing g loads on some the world’s most demanding circuits. It has completed actual and simulated 24-hour track tests.

And if its output and high-speed potential seem to suggest otherwise, the LSA nonetheless requires minimal maintenance. Its advanced iridium-core spark plugs and Dexcool coolant are validated to 100,000 miles of operation, with the same level of performance at 90,000 miles as they deliver at 10,000. The LSA also features GM’s advanced Oil Life System. This technology measures stress on the engine and calculates oil life based on real-world use--whether it’s profiling or extended, no-limit autobahn blasting--rather than a predetermined mileage interval. The Oil Life System eliminates unnecessary oil changes in vehicles that are driven in light-duty conditions.

For all the improvements and advanced technologies built into the 6.2L Supercharged LSA V-8, the bottom line still counts most. This is an ultra-high performance engine, with capabilities suited to one of the best performing sedans in the world.

Bruce

2023 Cadillac CT4-V Blackwing

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ironic that GM has come out with an even more gas guzzling motor for the cts-v. well they are pushing the performance envelope and the total sales figures for that car will be minimal for sure. maybe 5k per year? i know the sts-v gets lousy mileage too. i wonder if the fuel/air ratio is 10:1 like it has been posted at other websites. i guess they don't want to run into a lean condition with a blown motor.

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Very nice information on the CTS-V! I did an LSA lookup and found a number of nice images.

While I prefer the early STS's, the powertrain in the 2009 CTS-V is very impressive.

The timing with expensive fuel is bad, the cost is out of my range, but.....WOW!

-George

Drive'em like you own 'em. - ....................04 DTS............................

DTS_Signature.jpg

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ironic that GM has come out with an even more gas guzzling motor for the cts-v. well they are pushing the performance envelope and the total sales figures for that car will be minimal for sure. maybe 5k per year? i know the sts-v gets lousy mileage too. i wonder if the fuel/air ratio is 10:1 like it has been posted at other websites. i guess they don't want to run into a lean condition with a blown motor.

Do you mean compression ratio at 10:1?

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no, i meant air/fuel. i read some posts by a guy who had his sts-v tuned and it was around 10:1 during initial dyno runs. maybe at non-boost conditions it is closer to normal, 12.7 or is it 13.7? of course i have no idea how GM is going to tune a ls-v motor since they are not really available to the public yet.

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no, i meant air/fuel. i read some posts by a guy who had his sts-v tuned and it was around 10:1 during initial dyno runs. maybe at non-boost conditions it is closer to normal, 12.7 or is it 13.7? of course i have no idea how GM is going to tune a ls-v motor since they are not really available to the public yet.

Hmm this is an area that I am unfamiliar with, I always thought that the air/fuel ratio was a sliding scale that strove to maintain the ideal 14.7:1 stoichiometric balance for gasoline. When you say 10:1 do you mean on average throughout the range or at maximum output to stop from leaning out the engine? Wouldn't emissions be increased if less than 14.7:1 is permitted to occur?

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it was during the dyno run so it was full throttle. i think the computer lets some things slide during those conditions. the guy did not say what his a/f ratio was during part throttle cruise conditons. i just saw the horsepower show this weekend where they used a power tuner on a new Z06. i am sure the mixture and advance settings were tweaked to gain more power. and there will probably be a tuner for the 09 cts-v and ZR1 that is coming out.

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One of the things to keep in mind is that there are other factors to consider. As I recall the northstar runs a bit rich under full throttle because that ensures the piston temperature will stay within an acceptable range if you are staying full throttle to max velocity.

Bruce

2023 Cadillac CT4-V Blackwing

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