LT6 Engine Deep Dive: Everything You Need to Know about the Corvette Z06 Flat-Plane-Crank V8
We met with the engineering team responsible for the LT6 engine and learn everything there is to know about this modern marvel.
The 2023 Corvette Z06 is remarkable for many reasons. However, at the heart of it all is the all-new LT6 engine. You already know the basic specs. 5.5L DOHC flat-plane-crank V8 that revs to an 8,600 rpm redline. 670 horsepower. 460 pound-feet of torque. The LT6 is the most powerful naturally aspirated V8 ever engineered into a production car. That is all very exciting indeed. However, there’s a lot more to the LT6 story you probably don’t know.
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This week, GM hosted a press event with every engineer on the LT6 team, including Corvette Chief Engineer, Tadge Juechter. Before this LT6 deep dive event even began, we were impressed with what we knew about this engine. Now, having spent three and a half hours with the engineering team, we’re completely blown away. Here’s what we learned…
GM Literally Bought a Wrecked Ferrari to Study Flat Plane Crank Engines
The new Z06 needed an exotic engine. It had to be designed specifically for the Corvette and nothing else. From a priority perspective, the engine needed to be naturally aspirated for consistent track performance. It needed to be something that would thrill the Z06 driver by its sound, its feel, and even just by looking at it. Above all else, it needed to have exhilarating performance. It needed to perform as well or better than the most exotic cars in the world. To make sure it achieved that, the LT6 team benchmarked cars from Porsche, McLaren, and Ferrari. They even went so far as to buy a wrecked Ferrari 458 off eBay so they could study the inner workings of the engine.
NASA Inspiration
GM developed the LT6 under the codename Project Gemini. This was as a nod to the space program and the American astronauts love of Corvettes. It was also in reference to the fact that this was a moon-shot engine program. Gemini is also Latin for twins. As in twin intakes and throttle bodies, dual fuel pumps, etc. Want some other fun Gemini facts? There are 54 Gemini rockets throughout every LT6 engine, both inside and out. Some of these rockets are even functional as they act as assembly directional arrows for the engine builders.
The LT6 is Only **2Lbs** Heavier than the Base C8’s LT2
GM wanted to keep the LT6’s overall weight down and they succeeded. Consider these stats.
- The LT6 is only about two pounds heavier than the LT2 in the regular Stingray while making 175 more horsepower.
- Compared to the LT4, the LT6 is a whopping 30 pounds lighter while making 20 horsepower more.
- The forged titanium connecting rods in the LT6 weigh about half as much as the rods used in the LT5 from the last ZR1.
- The forged aluminum pistons used in the LT6 come from the same supplier that provides the pistons for the race engine.
- The crankshaft in the LT6 is 33 percent lighter than the LT2’s crankshaft.
This team took weight savings very seriously.
GM Kept the LT6 a Secret for 7 YEARS!
Building a world-beating engine is not done overnight. Here’s a rough timeline of the engine’s developement.
- 2014: The LT6 project starts
- September 2015: First prototype engines
- February 2017: Project Gemini Team build refined prototypes with production materials
- October 2018: First production-intent engine builds are ready. Time for the next testing phase
- March 2020: COVID forces all engine reviews to become virtual
- March 2021: Excercise production build process begins
The Rumors Were Right; The LT6 is a Race Engine
The LT6 and the LT6.R are basically twins… Except the LT6.R in racecars makes LESS power. The cylinder block, heads, valvetrain, and fuel system are shared between the street and race engine. However, due to racing regulations, the race car makes 150 fewer ponies thanks to a restricted air intake. These engines were co-developed and if you ever say that your Z06 has a race engine in it, you are not really that far off.
The Z06 Can Run All Day On a Track with the A/C On and Ambient Temps at 100F
John Albert, LT6 Vehicle Systems Engineer, explained that the Corvette Z06 has a 50 percent increase in engine cooling capability over the Stingray Z51. To keep the LT6 cool there are five radiators. This includes a new center radiator and an additional auxiliary radiator. The front fans are 50 percent more powerful, and the larger side opening makes for a 20 percent increase in airflow. If you drive this car on the track as it is intended, you can even remove the front aero panel. This will increase the center radiator grille opening by over 75 percent. All these improvements do not come at the expense of customer features. The size of the frunk is the same as the Stingray. And thanks to a 20 percent larger AC compressor the air conditioning in the Z06 is even better than in the base car.
Fun fact. The engineering team was tasked with making the Z06 capable of running all day at the track with ambient temperatures of 100 degrees Fahrenheit with the air conditioner on. Both the engine and the driver need to stay cool.
First-Ever Continually Variable Exhaust Valves
The sound of the LT6 is critical to the experience. As such the exhaust on the Z06 features the first-ever use of continually variable (as opposed to just open/closed) valves. These valves can be tuned in 2-degree increments for varying positions within each drive mode. The exhaust was tuned to sound aggressive at startup. It needed to have a bark to it when it was fired up. Global Chief Engineer Jordan Lee said that when he first heard it startup, he thought it was almost too loud even for him. There is a mode to control this if you don’t want to get into fights with your neighbors. And as good as the system sounds it is also about performance. There is a 21 percent reduction in back pressure compared to the system in the C7 Z06. And the muffler is 25 percent lighter than the two-mode “suitcase” exhaust used with the C8’s LT2.
The LT6 Doesn’t Drink Oil… On or Off Track
The Z06 is a track car pure and simple. Juechter said it was the most robust car ever for the track. It was tested at the Nürburgring, VIR, Willow Springs, and other tracks around the world. The LT6 has to not just survive the punishment of track driving but thrive in that environment. Robert Monchamp is the Lead Engine Calibrator for the LT6, and he said that this was calibrated for the racetrack. It will of course perform day-to-day driving duties just fine, but the whole purpose of this engine was to make it responsive and powerful in track driving situations. During testing, they observed no additional oil consumption from track use compared to street use.
Get Your 1-4-3-8-7-6-5-2 T-Shirt Ready
Some fun numbers related to the LT6 engine. The engine has seven oil pumps. And the fifth camshaft drives its two fuel pump. A team of over 20 engine calibrators worked on the LT6 to set the over 41,000 tunable calibration values. It took 12,606 engineer-hours to develop the LT6. 1-4-3-8-7-6-5-2 is the firing order for the LT6.
Building Each LT6 Takes 3 Hours (& You Can Build Yours!)
The LT6 is assembled at the Performance Build Center in Bowling Green. Each engine is hand-assembled by a single builder. It takes roughly three hours to assemble one engine. A plaque called the builder’s badge bridge is installed on the intake of every LT6 and it displays the name of the specialist that assembled that engine.
As with the previous generation, Z06 Chevy will give buyers the option to build their own engines. That option is not immediately available for the LT6. However, the plan is to bring that back. You will eventually be able to build your own LT6 under the supervision of a master builder. If you partake in this option, your name will be placed on the builder badge bridge.
Don’t Call it the Small Block Gemini
The team was quite clear that this is not the next-generation small block. Despite the fact that the LT6 has the 4.4-inch bore spacing that is the trademark of the Chevy small block. The team would prefer the LT6 be referred to as the small block Gemini. It may be splitting hairs, but the team wants to be clear that this bespoke engine for the Z06 is not the start of a new generation. This is a special piece of equipment.
Low Maintenance? That’s the Goal
Another goal of the LT6 engine team was to develop an exotic engine with the accompanying exotic sound and performance. But not the accompanying exotic maintenance routine and cost. When asked about maintenance Lee said to change the oil and filter and after 100,000 miles check the spark plugs. That’s it.
The new Corvette Z06 is a moonshot of a car with a moonshot of an engine. Everyone that spoke about the LT6 mentioned how honored they were to be a part of such a special project. They also mentioned how special the car is to drive. We can’t wait to get our chance at that someday soon.
Images: Chevrolet
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