If you recall from Part 1 of "Inside Information" (May '11), we introduced you to the talented and highly trained Design Responsible Engineers (DREs) who oversee the design, development, validation, and continuous improvement of the components that constitute the Corvette's LS3 engine.
It's easy to see why the DREs' jobs are so important. More than 38,000 LS3s have been factory installed in Corvettes since the powerplant's introduction in 2008, and these core product engineers' undivided attention to their individual components gives Vette owners a feeling of complete confidence every time they engage their cars' start buttons.
"The DREs make critical decisions to improve the performance, quality, and longevity of Corvette," GM Technology Communications, Powertrain spokesperson Tom Read says. "They have a broad range of resources available to them to make important decisions on LS3 parts as well as parts for other engines. Design and development assets in use by the DREs allow parts to be created with unimaginable attention to detail, for pure performance, durability, and efficiency.
"For instance, adjacent to where most Powertrain DREs sit is GM's $463 million engineering-development center, which is, overly simplified, the highest-tech dyno lab on the planet. A pipeline of information feeds DREs around the clock with engine-performance data so they design in quality from the beginning. They also access CAE engineers and state-of-the-art simulation and computer software that tells them things like where a part needs to be beefed up for strength, where some grams can be taken out for speed, or precisely where an oil passageway can be tweaked for better flow.
Corvette's engine Design Responsible...
Corvette's engine Design Responsible Engineers (DREs) work out of GM's Powertrain Engineering Center in Pontiac, Michigan. Their desks are located in the center building, and they tap the resources of GM’s $463 million engineering-development center, located in the two wings to the left of the parking area.
"DREs attend technical design education classes that MIT professors would love to sit in on," Read continues. "The classes reinforce sound engineering principles, retain and convey lessons learned—the Chevy small-block alone has more than 55 years of these—and provide technical insight from experts. They also often consult brilliant advanced-engineering personnel on their innovative projects to improve or advance their own designs. GM's Powertrain Advanced Engineering group in Pontiac, Michigan, and R&D at our Technical Center in Warren are like Ph.D. warehouses. The resources at our DREs' disposal are almost as endless as GM's reach. After all, competent core-product engineering is a must to make the best vehicles. Without question, DRE resource expenses are not spared to make sure our Corvette customers end up with some of the finest-engineered and precision engines in the world."
Though the Corvette's DREs are actively involved in the LS3 engine program, many of them are also responsible for the components that go into the LS7 and LS9 programs (and worked on the LS1, LS2, and LS6 in the past). Likewise, expect many of these DREs to be involved in GM's Gen V small-block engine program, which will power the Corvette model line in the near future.
You met four DREs last month—the ones responsible for the LS3 cylinder block, piston assembly, crank, and oil pump. This month you'll meet four more of them—the men responsible for the LS3 cylinder heads, head bolts and fasteners, camshaft (cam drive), and intake manifold.
Cylinder Heads
Name: Dennis Gerdeman
Title: Design Responsible Engineer
Years with GM: 31
Other experience: Cylinder Head Casting Process and Tooling Engineer
What LS3 parts are you responsible for? Cylinder heads and head gaskets
What LS7 and LS9 parts are you responsible for? Same
What other Corvette parts have you been involved with in the past? I was also design responsible for the LS1, LS6, and LS2 cylinder heads shortly after they were released for production. I came into the small-block engineering family after these head designs were initially developed, and then integrated various changes and upgrades through their life.
Why do you think your LS3 part is the most important part on the engine? The cylinder heads are the key to achieving the maximum performance and output of the engine. A Corvette engine won't make the horsepower if you can't flow big-time air. And these cylinder heads flow big air for a production piece with as-cast ports and chambers. We were able to achieve maximum valve-lift airflow of more than 168 grams per second (g/s) for the inlet ports, and more than 123 g/s in the exhaust ports. There have never been production small-block heads that flowed as much air as the LS3 intake and exhaust ports, or valves as large as the LS3's—except, of course, for the monster LS7 CNC-ported heads.
What is a focus area you watch when designing the LS3 part, especially knowing it is for a Corvette engine? The LS3 was the natural progression for the small-block cylinder heads. We had to push the envelope from a head-packaging standpoint by using the strengths of the new 103.25mm bore. Precision manufacturing requirements restrict what you can do, but we worked hard to widen the intake ports in order to get the floor of the ports as high as possible, without sacrificing cross-sectional area. Keeping the air attached to the floor of the ports at high valve lifts is crucial to minimizing turbulence and flow restrictions.
The machined angles and widths of the valve seats have to be perfect in order to maintain that huge airflow from the intake ports to the combustion chambers. Countless hours were spent on the CAD tube adjusting the machined valve seats, and also perfecting the transition from the machined seats into the combustion chambers. When the cylinder heads are going into Corvettes, you can never spend too much time in these areas.
What are the current trends with your LS3 part? Where is it going? Of course, more power and refinement are always considerations for future Corvette programs, and the cylinder heads are at the heart of the discussion. We are always looking at different casting methodologies and new machining processes. You name it; if it makes it stronger, lighter, and flows more air, we're tuned in and probably trying it out.
Compare your part with aftermarket parts of the same item. What makes yours better? The LS3 cylinder heads have more structural analysis, component testing, and engine validation than any other aftermarket cylinder heads you will find. The specifications built into the GM analysis and validation provided a level of structural integrity that isn't present in any aftermarket head castings. The other advantage we had was our ability to interact with the C6.R racing team during the LS3 cylinder-head development, which actually helped drive our LS3 valve sizes and airflow targets.
Do you own a Corvette, a classic car, or have a related hobby? I'm a major Corvette fan, and someday I hope to own a C6, preferably with the LS3. I've loved this body style ever since it came out. I did let my small-block passion overflow into my finished basement, a good portion of which I have decorated in Corvette memorabilia.
Head Bolts
Name: Eric Nordling
Title: Design Responsible Engineer
Years with GM: 11
Other experience: Six years of finite-element analysis prior to GM, eight years as Lead Analysis Engineer for overhead-cam engines, and three years as the Small Block Assembly Sealing and Fastening Design Responsible Engineer
What LS3 parts are you responsible for? Engine fasteners, seals, and joints
What LS7 and LS9 parts are you responsible for? Same
What other Corvette parts have you been involved with in the past? None
Why do you think your LS3 part is the most important part on the engine? What holds your LS3 together can't fail, period. Fasteners that come loose allowing the joint to fail can be catastrophic to the engine, so we use proven design practices and rigorous test schedules to ensure the joint maintains clamp load at all times.
The LS3 head bolts were designed to seal the head gasket under very aggressive driving conditions. The head bolts provide the clamp load required to seal coolant, oil, and combustion gas from leaking out of the engine at the head-to-block interface. To ensure the head gaskets will always survive, we study the engine loads under all ranges of operation and design the head and block structures to the worst-case thermal and pressure loads. We use dyno testing and analytical techniques to predict and apply these conditions to the engine. We also avoid overloading the joint, because too much load can create high stresses in the head and block, and increase bore distortion. In the case of the LS3, the head bolts have been designed and rigorously tested to provide optimum sealing performance while minimizing the stress on the aluminum structure. [This increases] the overall durability of the engine.
All GM head bolts are torque-to-yield. This means the bolts are stretched a little past the yield strength, so when thermal loads relax the joint, the retained load is sufficient. Torque-to-yield fasteners should never be reused, because they are slightly stretched during the assembly process and can't produce the same load or bolt safety factors the second time they are torqued.
What is a focus area you watch when designing the LS3 part, especially knowing it is for a Corvette engine? The strength of the block in the water jackets adjacent to where the head bolts attach is a critical area for development. Block engineers are consulted to ensure the stress resulting from the bolt loads in this area is correctly managed. Also closely managed is the placement of threads and counter-bore depth to minimize bore distortion while maximizing bulkhead strength. Proper thread engagement on the head bolts minimizes load loss in the joint due to thread relaxation.
What are the current trends with your LS3 part? Where is it going? As horsepower and torque increase in the future, new head bolts may be required, but for now there is plenty of room to up-level power in the current LS3 design.
Compare your part to aftermarket parts of the same item. What makes yours better? When working on engines, it's important to know how the structure affects your clamp load. We use small-block heads, gaskets, and blocks to develop the torque-angle strategy—a more precise way of controlling bolt clamp force—in our fastening lab here in Pontiac, Michigan. The torque-angle strategy is unique for each critical fastener, and it really depends on the structure as much as the bolt. Our head bolts are the best, not only because we control the fastener's yield point very closely, but also because the torque-angle strategy we specify ensures that we achieve the right clamp load in the joint without over-stretching the bolt or over-stressing the aluminum structure.
Do you own a Corvette, a classic car, or have a related hobby? I enjoy building and riding custom motorcycles with my father. I like to help my father-in-law work on his vintage-car collection. I helped him work on his '67 Corvette 427 convertible and, more recently, a '59 Impala. I appreciate the historic significance of working on small-block engines and being able to build upon and improve their great reputation by doing all I can to increase their durability.
Camshaft (Cam Drive)
Name: Shane Smith
Title: Design Responsible Engineer
Years with GM: 9
Other experience: Project Engineer—GM Racing and Performance Parts (with NHRA Pro Stock teams) and Lead Mechanical Engineer for dynamometer development
What LS3 parts are you responsible for? Camshaft, lifters, valves, valvesprings, timing drive, rocker arms, and pushrods
What LS7 and LS9 parts are you responsible for? Same
What other Corvette parts have you been involved with in the past? None
Why do you think your LS3 part is the most important part on the engine? The camshaft is what sets the personality of the engine. The LS3 cam design runs smoothly and efficiently during cruising, and delivers the wide torque band and big power numbers, too. The lobes and timing are optimized for that balance. The intake-side specs of 0.550-inch lift and 204-degree duration at 0.050-inch give the engine the air it needs all the way up to redline. The hollow-stem intake valves are a must-have to keep this valvetrain in control with that cam profile.
What is a focus area you watch when designing the LS3 part, especially knowing it is for a Corvette engine? The challenge is to make the power target and run strong through hundreds of hours on the dyno, and in real-world track testing at the very highest engine speeds. The Corvette customer likes power, but we can't sacrifice driveability. Anyone can throw in a lumpy cam and develop power, but that doesn't make for a good car to drive all the time. The LS3 cam's behavior was critically reviewed for all aspects of driveability by a select number of folks who know what Corvette owners want.
What are the current trends with your LS3 part? Where is it going? Cam development is highly proprietary. What I can share is that we're always looking for ways to be more aggressive in the profile department, for obvious reasons. We must, however, preserve a certain acceptable level of NVH and emissions.
Compare your part to aftermarket parts of the same item. What makes yours better? The LS3 camshaft is designed to pass durability tests that aftermarket companies don't have to think about. We use the latest technology in laser equipment to measure what the valves are doing at all different running conditions. We work to minimize the velocity of the valve right before it closes against the seat in the head, and the height of the valve bounce right after it closes. This is a key area to watch when you design for long life.
Do you own a Corvette, a classic car, or have a related hobby? My first experience with small-block Chevy cams was in high school. My friend and I spent a whole weekend changing the cam and adding headers to his 350ci '71 Chevelle. The thing ran about the same as it did before all the work, so I can't call it a success.
Outside of work, my hobby is playing with old Mopars. It all started when I bought a '66 Coronet at age 14, and spent a year-and-a-half getting it ready for the road. I bought my '71 Challenger right after I was hired by GM in 2001. My daily driver to the office is a '77 New Yorker.
Intake Manifold
Name: Tim Carr
Title: Design Responsible Engineer
Years with GM: 34
Other experience: Quality Control/Gauge Design Engineer at the GM V-6 3800 engine plant in Flint, Michigan; Design Responsible Engineer for intake manifolds for the 3.1 and 3.4 V-6 engines; and Design Responsible Engineer for the small-block V-8 truck engine intake manifolds
What LS3 parts are you responsible for? Intake-manifold assembly
What LS7 and LS9 parts are you responsible for? LS7 intake-manifold assembly
What other Corvette parts have you been involved with in the past? Design Responsible Engineer for the LS2 intake manifold
Why do you think your LS3 part is the most important part on the engine? Airflow is critical in order for the Corvette engine to meet its performance targets. The LS3 intake manifold has a precise balance of extremely low airflow losses, good cylinder-to-cylinder flow balance, and optimum runner length for engine tuning. At peak valve lifts, the LS3 manifold flows more than 155 g/s. The LS3 and LS7 share a common architecture; however, the LS3 runners are sized for the lower peak horsepower speeds of the engine. The LS3 manifold has 89 percent of the flow capacity of the LS7 manifold. This is significant considering the LS7 engine develops about 70 more horsepower. [It's also] accomplished in a very tight vehicle-packaging environment.
What is a focus area you watch when designing the LS3 part, especially knowing it is for a Corvette engine? Airflow is the primary concern with developing the intake manifold for Corvette. Extensive analysis is performed to reduce flow losses, and [to develop] package-runner geometry that provides the torque and power the Corvette driver expects. The composite material used on the Corvette intake manifold is very light, and its smooth surface finish reduces flow losses. Appearance and noise are also considerations. The textured manifold noise cover reduces the high-frequency sound, which most Corvette owners would consider objectionable.
What are the current trends with your LS3 part? Where is it going? The future trends for the LS3 manifold include providing even better airflow performance, with less packaging space underhood than in the current Corvette. We are not leaving any stone unturned in the development of future manifolds. We are analytically pursuing many design iterations to find every additional cfm possible and we have many resources dedicated to this pursuit of additional efficiency and power.
Compare your part to aftermarket parts of the same item. What makes yours better? Many aftermarket manifolds achieve better performance only by compromising features on the production part. One example of this type of compromise is to fabricate a larger, taller manifold to increase plenum volume. While this might improve performance, it is likely that the manifold would contact the hood, or that noise would be [increased]. It's difficult to provide a better manifold and still meet emissions regulations, provide sufficient clearance to other components, and function reliably for the life of the vehicle.
Do you own a Corvette, a classic car, or have a related hobby? I enjoy car shows during the summer. My favorite classic Corvettes are those from '58-'62. I enjoy family time, downhill skiing in the winter, and boating during the summer.