NASCAR is a true racing series where there is no balance for performance or any kind of penalty the sanctioning body puts on engines that over perform. For that reason, from an engine development standpoint, NASCAR is one of the top arenas for engine builders. Whoever can make the best engine is going to have the advantage come race day.
At the Monster Energy NASCAR Cup level, it’s no secret that the competition is fierce. Every little thing matters from the driver to pit stops to one of the most important aspects – the engine. Engine Builder recently got an inside look at engine development at Earnhardt Childress Racing (ECR) from Andrew Randolph, ECR’s technical director. He gave us the scoop on the Chevrolet engine in Cup called a R07.2 and all that goes into maxing out its performance every week.
The R07.2 is a 5.8L two-valve per cylinder V8. Its roots are in the small block Chevy era from 50-plus years ago. However, over time it’s been refined, and that is the engine the folks at ECR put out on the track each week.
“The basic architecture [of the engine] as far as bore spacing, bore sizes, two valves, push rods, etc. has stayed the same,” says Randolph. “What has changed is the materials, tolerances, surface finishes, masses, and things such as that so these engines, which are naturally aspirated, can turn 10,000 RPM and make over 850 hp when unrestricted.”
Each participating vehicle manufacturer (Chevrolet, Ford and Toyota) must provide a NASCAR-approved block, cylinder head and intake manifold casting. The team, engine shop or engine builder can then modify that casting however they prefer to maximize performance, within prescribed limits of total displacement and cylinder bore size as well as some minimum masses and dimensions on various components.
“The box that you have to operate in and what you can do is actually quite large,” Randolph says. “If you look at engines from different teams you’ll see they are very different and their performance characteristics are very different. It’s a pretty awesome environment for engine development. It’s a huge playground that is fun when you’re doing well – when you’re not doing well it’s more like work.”
Everything at this level of racing and engine building is purpose-designed. The advantage builders like ECR have in the racing world over the production world is knowing exactly how the engine is going to be used.
“We know how long is has to run for, the temperature it’s going to run under, the distance it’s going to run, and the engine speed range,” Randolph says. “We can customize the engine for each racetrack for each week based on the particular engine speed characteristics and throttle characteristics of the track and even the driver who is going to be driving it, to make sure that the power curve is optimized to produce minimum lap time at that specific event.”
These engines only have to last for one race, so the objective is to have an engine that has good durability for race distance plus one mile. After the race, the engine is going to come back and be totally disassembled. Many of the parts will never be used again, but some of them will be such as the crankshaft, cylinder head and engine block. Each part is serialized and has a prescribed lifetime to it.
“Wherever we find a performance advantage by making a part that might not last as long but still get us through the race and produce better performance, the incentive is there to do that,” he says.
ECR does everything it can to make each engine run and get as much power out of it as possible. Beginning with the castings, the first thing ECR does is lighten everywhere it can.
“We want to make things as light as they can possibly be, but still be stiff where stiffness is required and still have enough structural integrity to last through the event without any failures,” Randolph says. “For example, an intake manifold casting that comes in the door will weigh 35-40 lbs., and a finished intake manifold that goes on one of these engines will be in the 12-15 lb. range. There is that much aluminum sitting on the floor when we are done.”
These performance enhancements that ECR creates is all part of the team’s engine development philosophy, which is not to develop the engine as an 8-cylinder engine, but rather as eight one-cylinder engines.
“We instrument each cylinder with cylinder pressure so we can determine the power contributions of each of the eight cylinders individually,” he says. “Then we will design the cam timing, the exhaust systems, the intake geometry and even sometimes the compression ratio, although we have a maximum compression ratio of 12:1. We design each cylinder individually such that when you add the eight cylinders together you get a power curve that’s optimized for the specific track you’re going to.”
It’s a unique way to develop engines – essentially eight one-cylinder engines that happen to share the same crankshaft – but ECR has been able to make engines light and optimized for specific tracks quite successfully.
“For example, take Daytona – when we race at Daytona, the engine speed over the course of a lap will vary from a minimum of 8,700 RPM to a maximum of 9,000 RPM. So it’s a 300-RPM-wide power band, so we want a very narrow, but peaky power curve for that application,” he says. “When we race at Martinsville, which is a very flat, half-mile track that is like a paperclip – tight corners followed by straightaways – our engine speed range at wide open throttle goes from 5,000 RPM to 10,000 RPM. There we want a much different-shaped power curve. We want a broad power curve, very drivable with no big peaks or valleys so it’s easier to maintain traction. That’s a much different engine content for all the pieces – cams, headers, intake manifolds, and differences in the individual cylinders.”
If you design a single-cylinder engine, it’s inherently going to have peaks and valleys where it comes in and out of tune.
“We design all the cylinders different so that the valley of one cylinder will be augmented by the peak of another cylinder to help you provide this flat power curve over the engine speed range that you desire,” he says.
In order to reach this height of performance, ECR relies on a number of aftermarket companies for quality engine parts from head gaskets and pistons to valves, connecting rods and crankshafts.
“Valve springs are a very challenging part of these engines,” Randolph says. “A coil valve spring at 9,000 RPM has to get compressed all the way down until the coils are essentially bound to one another and then sprung back open again, but it has to do that 75 times a second and it has to do it for 4 hours. So you can imagine the stress that’s on that part. It’s a very expensive and very challenging part to do.”
Piston rings are another critical part due to the RPMs that ECR engines turn and the bore sizes that they have, which require a lot of development. Of course, oil at this level is also critical and a large part of developing the best performance possible.
Every engine after a Cup race comes back and gets torn down fully. Every part gets inspected whether it will be reused or not to ensure there is no excessive wear or impending failure which might be the symptom of another issue. Then, parts that will be reused – crankshafts, cylinder heads, blocks – undergo a variety of tests to make sure they have no cracks or any other issues.
“It’s a fairly extensive evaluation to prepare an engine to be run a second or third or fourth time,” Randolph says. “Every part in the engine has a life assigned to it, and every part is serialized with QR codes so we can see what the history on that part is. We can tell how many races it’s run, where it ran, how many miles, what temperature, what batch it was in from the manufacturer, and what date it was received.
“A block is the longest-lasting part that we use, and will be used for as many as 16 events. If you average 500-600 miles, that’s 8,000-9,000 miles on a block. The block is compacted graphite cast iron, which for NASCAR starts with a cast iron base and has metal additives that increase the strength of it dramatically.”
All that development comes down to horsepower on race day. If ECR doesn’t find one or two horsepower a month, it won’t be long before its teams are falling behind.
“It’s a constant search for power and it’s amazing some places where you find it,” Randolph says. “It’s just a constant pressure to look at everything, and we spend a lot of money on instrumentation now because it’s very difficult to find one- or two-horsepower improvements. Now we’re down to finding half-horsepower improvements. We need to have systems in place where we can find those reliably. You’re going to find 10 half-horsepower improvements before you find one 5-horsepower improvement.”
Depending on the track the team is going to of course, there may be restrictor plates used on the intake to keep speeds under control. The result at Daytona and Talladega,for instance, is wide open thottle all the way around.
“This last trip to Daytona, we were making just barely over 400 hp thanks to restrictor plates, yet we were still running over 200 mph constantly,” Randolph says. “If they didn’t restrict the engines, cars would be going in the 250 mph range and they worry about saftey issues. But every time NASCAR changes plate rules, that drives us to go back and redesign our cam, headers, tuning characteristics, valve events, etc. Every time you change something as simple as an air restrictor, it changes everything that’s in the engine. Fortunately, we know for the year what the different formulas are for the different tracks.”
ECR Engines designs, develops, and builds Chevrolet engines for the Monster Energy NASCAR Cup Series, XFINITY Series and Camping World Truck Series teams campaigned under the RCR banner. The company also has an engine leasing program for other teams in NASCAR’s top three divisions.
In addition to its NASCAR engine programs, ECR also designs, develops, and builds engines for other forms of motorsports on various levels, including the 6.2L LT-R engine powering the Cadillac DPi-V.R. campaigned in the IMSA WeatherTech SportsCar Championship.
Article courtesy Engine Builder.