A lot of things have taken place in the last couple of years that have could heralded the death knell of the performance V-8 in a factory-built car. Ever tightening emissions standards, brutal government mandated increases in CAFE (Corporate Average Fuel Economy) requirements, skyrocketing gas prices, and a sluggish economy are not on the side of an automaker keeping a big V-8 in its production lineup. Thankfully we have those at GM who relish a challenge against the most iconic engine platform ever, and take pure pleasure in defeating the enemies of factory V-8 performance in brutal smack downs of horsepower and cubic inches.
In the mid-'90s, many in the industry thought the folks at GM/Chevrolet were crazy in sticking with "archaic" pushrod technology instead of following the overhead cam craze of other brands. Just another example of GM's stubbornness in clinging to outdated technology and not keeping up with modern times. Well, the Gen III and Gen IV "LS" series V-8 left many a doubter lying on the floor with its great fuel efficiency, power output, compact size, light weight, low production costs, and overall versatility. For the 21st century small-block, the engineers behind the Bow Tie seem to have done it again.
Since the pending announcement of the new Gen V small-block hit the internet, there've been a lot of rumors and erroneous details about the new engine that left no real clear picture about what the new Mouse was going to be, outside some sort of V-8. Overhead cams, twin in-block camshafts, three valves per cylinder, 5.5 liter or smaller displacement, factory turbos—the rumors were all over the place.
Well, we went to Michigan when GM unveiled the Gen V engine, which will be introduced first in the all-new '14 Corvette. When the cover was lifted, all the rumors vanished, and in their place was a brand-spanking-new 6.2 liter, all-aluminum, direct injected, constant variable valve timing-equipped V-8, with a name all Chevy enthusiasts remember with both fondness and derision: LT1.
LT1? Judging from the reactions when we first posted the new designation to our Facebook page, reactions were mixed. Negative or positive, it doesn't matter. The new engine shares only four parts with the LS series (more on that later), promises great out of the box horsepower, even greater potential for more, and is probably the best rebirth possible for one of the more storied engine names in Chevy's RPO list. So, leave the Opti-fail jokes in the back seat of your '94 Z28, and get ready for what could be the best small-block to ever leave Detroit.
According to one GM spokesman we spoke to, the name still resonates inside Chevrolet. The original from 1970-'72 is considered by many to be the best small-block ever—big-time horsepower like the fuel-injected V-8s that came before it, but with lots of bottom-end torque. When the second-gen LT1 was introduced in 1992, it was the first high-performance V-8 to produce 300 hp since 1971 and was seen as the second coming of all-out performance in the modern era. Because the new engine is being introduced 22 years after the Gen-II small-block (which came 22 years after the first LT-1) it seemed only logical to Chevy to call it this.
Here's the overview: 6.2 liters, direct injection, 11.5:1 compression, specially-designed pistons for maximum combustion efficiency, a lower profile intake, constant variable valve timing, cylinder deactivation (V-8 to V-4), 450-horsepower (perhaps more), the lowest emissions from a large displacement V-8 to date, and the promise of unequaled fuel economy. And it's all wrapped up in an aluminum package.
"The Holy Grail for developing a performance car is delivering greater performance and more power with greater fuel economy, and that's what we've achieved," said Tadge Juechter, Corvette chief engineer. "By leveraging technology, we are able to get more out of every drop of gasoline, and because of that we expect the new Corvette will be the most fuel-efficient 450 horsepower car on the market."
Only 450 hp? That's just 14 more than the current Vette's LS3 with the dual-mode exhaust, isn't it? Well, don't be surprised if that number goes up. The 450 HP rating given to us is a preliminary estimate from early testing, and once full testing is finished up with the usual amount of tuning and tweaking from the engineers, that rating will probably go up. Though the new LT1 is only months away from production, there's a little more development work to be done. And as we've seen from the LS3, this number could be seriously underrated.
Something else we noticed when checking out the front accessory drive on the new LT1 … no power steering pump. The engineers didn't say anything, but we can only surmise this means the C7 will feature electric power steering. Another interesting item is the cast iron exhaust manifold. Its construction and outlet flange, which mimic that of the current LS7 V-8, look conspicuously ready to accept an exhaust driven power adder of some sort. Could the next ZR1 have a turbo or two? Just a guess based on observations, so we'll be forced to wait and see till this time next year.
Here's what the engineers have to say:
"The Corvette LT1 represents the most significant redesign in the small-block's nearly 60-year history—building on its legacy to make one of the world's best engines even better," said Sam Winegarden, vice president of Global Powertrain Engineering. "More than just great horsepower, the LT1 has been optimized to produce a broader power band. Below 4,000 rpm, the torque of the Corvette LT1 is comparable to that of the legendary 7.0L LS7 out of the current Corvette Z06. The LT1 is a sweetheart of a powerplant, and drivers will feel its tremendous torque and power at every notch on the tachometer."
Increased power and efficiency were made possible by an unprecedented level of analysis, including computational fluid dynamics, to optimize the combustion system, the direct injection fuel system, active fuel management, and variable valve timing systems that support it. More than 10 million hours of computational analysis were conducted on the engine program, including 6 million hours (CPU time) dedicated to the advanced combustion system.
Direct injection is all-new to the engine architecture, and is a primary contributor to its greater combustion efficiency by ensuring a more complete burn of the fuel in the air-fuel mixture. This is achieved by precisely controlling the mixture motion and fuel injection spray pattern. Direct injection also keeps the combustion chamber cooler, which allows for a higher compression ratio. Emissions are also reduced, particularly cold-start hydrocarbon emissions, which are cut by about 25 percent.
Active Fuel Management (AFM)—a first-ever application on Corvette—helps save fuel by shutting down half of the engine's cylinders in light-load driving. At cruise speeds and in light load driving, the LT1 will shift from a V-8 to a V-4.
Continuously variable valve timing, which GM pioneered for overhead-valve engines, is refined to support the LT1 AFM and direct injection systems to further optimize performance, efficiency and emissions.
These technologies support the all-new, advanced combustion system, which incorporates a new cylinder-head design and a new, sculpted piston design that is an integral contributor to the high-compression, mixture motion parameters enabled by direct injection.
The LT1 head features smaller combustion chambers designed to complement the volume of the unique topography of the pistons' heads. The smaller chamber size and sculpted pistons produce an 11.5:1 compression ratio, while the head features large, straight rectangular intake ports with a slight twist to enhance mixture motion. This is complemented by a reversal of the intake and exhaust valve positions, as compared to the previous engine design. Also, the spark plug angle and depth have been revised to protrude farther into the chamber, placing the electrode closer to the center of the chamber to support optimal combustion.
The pistons unique top design was optimized via extensive analysis to precisely direct the fuel spray for a more complete combustion. The contours of the piston heads are machined to ensure dimensional accuracy, essential for precise control of mixture motion and the compression ratio.
But 11.5:1 compression? The last production engine to leave the factory with that much squeeze was the ZL-1 427 at 12:1. But while that fire breathing monster needed high-octane race juice so it didn't sound like a diesel, the new LT1 does it on 93-octane or less. That's right, if you feed the LT1 (we're gonna keep saying LT1 until you finally stop picturing the '90s mill) regular gas, it'll keep going without detonating a piston out the side of the block. It might not smoke the tires like when 93 is in the tank, but it'll still make the new C7 move like lightning. It's entirely possible that thanks to direct injection and the unique combustion chamber design, the compression could go up even higher in the future.
"The engine requirements for a production car and a race car are remarkably similar," said Jordan Lee, small-block chief engineer and program manager. "In both cases, you want an engine that is powerful and efficient, compact, lightweight, and durable. That combination is what made the original small-block so successful. Today, the introduction of state-of-the-art technologies and engineering makes one of the best performance car engines in the world even better."
As an example, the new LT1 engine is 40 pounds lighter than BMW's twin-turbo 4.4L, DOHC V-8 with similar output. That weight savings not only improves the Corvette's power-to-weight ratio, but also contributes to a near-perfect 50/50 weight balance for enhanced steering response and handling. The new LT1 is also four inches shorter in overall height than the competitive DOHC V-8. That also improves handling by lowering the center of gravity while enabling a low hood line – contributing to the Corvette's iconic profile, as well as ensuring exceptional driver visibility.
"The power and efficiency of the small-block V-8 are hallmarks of Corvette performance," said Lee. "But, the compact size and great power-to-weight are just as important for the overall driving experience. The all-new LT1 will play a huge role in making the all-new Corvette a world-class sports car, in terms of technology, performance, and refinement."
The original LT-1 debuted in the '70 Corvette (370-hp) and Camaro Z28 (360hp), and was the most powerful carbureted small-block ever installed in a production car.
Engine Features and Highlights
All-Aluminum Block and Oil Pan
The Gen V block was developed with math-based tools and data acquired in GM's racing programs, providing a light, rigid foundation for an impressively smooth engine. Its deep-skirt design helps maximize strength and minimize vibration. As with the Gen III and Gen IV small-blocks, the bulkheads accommodate six-bolt, cross-bolted main-bearing caps that limit crank flex and stiffen the engine's structure. A structural aluminum oil pan further stiffens the powertrain.
The block features nodular iron main bearing caps, which represent a significant upgrade over more conventional powdered metal bearing caps. They are stronger and can better absorb vibrations and other harmonics to help produce smoother, quieter performance.
Compared to the Gen IV engine, the Gen V's cylinder block casting is all-new, but based on the same basic architecture. It was refined and modified to accommodate the mounting of the engine-driven direct injection high-pressure fuel pump. It also incorporates new engine mount attachments, new knock sensor locations, improved sealing and oil-spray piston cooling.
Advanced Oiling System with Available Dry-Sump System
The LT1 oiling system—including oil-spray piston cooling—was also optimized for improved performance. It is driven by a new, variable-displacement oil pump that enables more efficient oil delivery, per the engine's operating conditions. Its dual-pressure control enables operation at a very efficient oil pressure at lower rpm coordinated with AFM, and delivers higher pressure at higher engine speeds to provide a more robust lubrication system for aggressive engine operation.
Standard oil-spray piston cooling sprays the underside of each piston and the surrounding cylinder wall with an extra layer of cooling oil, via small jets located at the bottom of the cylinders. For optimal efficiency, the oil jets are used only when they are needed the most: at start-up, giving the cylinders extra lubrication that reduces noise, and at higher engine speeds, when engine load demands extra cooling and greater durability.
An available dry-sump oiling system promotes exceptional lubrication performance during aggressive driving maneuvers and high cornering loads. It includes two stages: a pressure stage and a scavenge stage. The pressure stage includes the new, dual-pressure-control and variable-displacement vane pump.
Dexos semi-synthetic motor oil, with a 5W30 specification, helps reduce friction to further enhance the LT1's efficiency.
New Tri-Lobe Camshaft
As with the Gen IV engine, the camshaft remains in the same position relative to the crankshaft and is used with a new rear cam bearing, but it now features an all-new "tri-lobe" designed lobe which exclusively drives the engine-mounted direct injection high-pressure fuel pump, which powers the direct-injection combustion system. The cam's specifications include 14mm/13.3mm (0.551/0.524-inch) intake/exhaust lift, 200/207 intake/exhaust duration at 0.050-inch tappet lift, and a 116.5-degree lobe separation angle.
New Cam-Driven Direct Injection Fuel Pump
The direct injection system features a very-high-pressure fuel pump, which delivers up to 15Mpa (150 bar). The high-pressure, engine-driven fuel pump is fed by a conventional fuel-tank-mounted pump. The direct injection pump is mounted in the "valley" between the cylinder heads under the intake manifold, and is driven by the tri-lobe at the rear of the camshaft. This location ensures any noise generated by the pump is muffled by the intake manifold and other insulation in the valley.
PCV-Integrated Rocker Covers
One of the most distinctive features of the new engine is its domed rocker covers, which house the (patent-pending) integrated positive crankcase ventilation (PCV) system that enhances oil economy and oil life, while reducing oil consumption and contributing to lower emissions. The rocker covers also hold the direct-mount ignition coils for the coil-near-plug ignition system. Between the individual coil packs, the domed sections of the covers contain baffles that separate oil and air from the crankcase gases—about three times the oil/air separation capability of previous engines.
Intake Manifold and Throttle Body Assembly
The LT1's intake manifold features a "runners in a box" design, wherein individual runners inside the manifold feed a plenum box that allows for excellent, high-efficiency airflow packaged beneath the car's low hood line.
Acoustic foam is sandwiched between the outside top of the intake manifold and an additional acoustic shell to reduce radiated engine noise, as well as fuel pump noise.
The manifold is paired with an electronically controlled throttle body, featuring an 87mm bore diameter and a "contactless" throttle position sensor design that is more durable and enables greater control.
Four-into-One Exhaust Manifolds
The LT1 uses a cast version of the "four-into-one" short-header exhaust manifold design used on the Gen IV LS7 engine. The cast header passages enable consistent exhaust flow into the "wide mouth" collector at the converter.
Cooling System, Humidity Sensor and More
Additional features and technologies of the Gen V engine include:
- A revised cooling system with an offset water pump and thermostat for more efficient performance
- Air induction humidity sensor ensures optimal combustion efficiency, regardless of the surrounding air's humidity
- 58X ignition system with individual ignition coil modules and iridium-tip spark plugs
- All-new E92 engine controller.
Rebirth of the Horsepower Factory
To produce the new LT1, GM invested millions of dollars in modernizing the Tonawanda Engine Plant, the birthplace of tens of thousands of high-performance engines during the muscle car era. Now in the 21st century, it will be reborn, just like the LT1 name, and crank out what should be millions of Gen V small-blocks. The LT1 is just the first in a new line of efficient, powerful, American V-8s that easily outclass their competition.
Tonawanda first opened in 1938, and will celebrate its 75th birthday in 2013.