While it would be foolish to think that one approach to engine design is objectively “better” than the other, it’s interesting nonetheless to realize that these two disciplines of racing – F1 and NASCAR – aren’t all that different, in terms of performance, when observed closely. That being said, their spirit of design and real-world implementation are quite distinct. For simplicity’s sake, we’ll compare the last generation of Formula 1 V8 to the contemporary NASCAR spec V8, as the current V6 Turbos are completely different.
Obviously, the NASCAR and Formula 1 engines are made to generate the most usable power within the framework of the rules, but they go about this task in different ways. The heavier, bulkier stock car is a monster which can exploit all its power and torque somewhat easily because of the consistently-high speeds; the driven wheels are not as traction-limited. Comparing this to the demands placed on an F1 car, the driven wheels are subjected to serious forces but aren’t asked to bring the car from low speeds to high speeds as often.
Additionally, NASCAR engines are intended, at least superficially, to have a common link with road-going machines. This is evident from the way their bodies are styled, though in reality, they have very little to do with the V8 found in a Corvette.
In general, it’s the NASCAR engine which is subject to a plethora of restrictions, though some might think it’s the other way around. They use a roller/lifter setup, and are fairly advanced as far as these kinds of motors go, but they are staunchly restricted in regards to minimum weights and materials used.
In NASCAR, the engines have to be made from iron blocks that are (nominally) production-based. In essence, this means their cylinder banks are angled at 90 degrees, and they displace 358 cubic-inches, or 5.86 liters. They can’t be made from aluminum, and they have to use the original, production castings. The bore spacing is set at 4.5 inches thanks to its purpose-built design.
The 358 cubic-inch engines in America’s premier racing category use shorter rod ratios. This means more forces are exerted on the cylinder walls, which translates to more vibration and friction, increased coolant and oil temps. However, that also means big torque and improved response thanks to a greater vacuum pull – and that churning force helps get the 3,500-pound stock cars up to speed rapidly, and keep them there. That approach has its drawbacks, though.
Unfortunately, that massive low-end torque can mean problems with wheelspin. Bill Guzenski, former engine builder for Roush, explains, “We used to build a 298 cubic-inch motor for shorter tracks so that we could put the power down more effectively. If we tried to use it at Daytona, we’d get swallowed up, but because we were torque limited at the comparatively-lower speeds, it gave us a huge advantage.”
Large bore, short stroke engines are good for road racing and high-RPM performance. Both NASCAR and F1 are built to these standards, but the short stroke distance in a Formula 1’s 2.4-liter V8 engine — only 1.566-inches — is what allows it to rev to 20,000 rpm! The stroke-to-bore ratio is only 0.4, which is about half that of a basic production car, and piston speed is 5,248 feet per minute. Additionally, the F1 engine uses a pneumatic valvetrain to help with the incredible engine speeds.
Despite the seeming differences and the advanced technology used in a modern Formula 1 engine, the brake mean effective pressures (BMEP) are strikingly similar to those of the NASCAR engine. At their peak torque figure, the last generation of normally-aspirated F1 engines developed 15.17 bar of BMEP, and at peak torque, the NASCAR engines make an astounding BMEP of 15.12 bar – just 0.3% difference! Similarly, mean piston speed is less than 3% slower in the stock car.
The differences between the NASCAR motor and the F1 motor aren’t just limited to technology, either. Their implementations outside the sport are quite different, too, as Frank Honsowetz of Ed Pink’s Racing remarks: “NASCAR auto manufacturers are not learning about technology that can be applied to the future passenger car, but they’re learning about the methodology; the process they can use to design a passenger car.” Because of the tight deadlines and massive pressure faced in the hustle and bustle of NASCAR, Honsowetz notes, “they’re developing people in motor racing.”
It’s the people that take front stage in NASCAR. For reasons of sportsmanship and mechanical parity, NASCAR engines are “more constrained,” according to Honsowetz, “so the differences are minute.” This means a closely-packed field and a good thirty cars that stand a chance of winning a race, and it’s the fans which benefit from the technology. After all, racing is supposed to be a show.
In contrast, Formula 1 draws crowds largely because it’s seen as the epitome of big-budget racing technology, and while the motors are closely watched, the leading teams still manage to find advantages in power output and delivery. Perhaps, these teams are less concerned with the idea of close competition and more interested in technologies which give some teams an unfair advantage, and the way those technologies can be transferred into the everyday commuter car. F1, by comparison, is much more concerned with the machinery, and sometimes errs into the “science fair” end of the racing spectrum, rather than simple entertainment.
Dave Rebello of California’s Rebello Racing remarks on how F1 engines make “an incredible amount of power for such a small engine, and with such a small amount of fuel.” The size of the engines do mimic the typical production car engine size in Europe, and place a similarly-high demand on fuel economy. Perhaps this is why they use longer rod ratios, which help with efficiency. This is because holding compression for half a degree of crankshaft rotation longer at Top Dead Center improves combustion efficiency and squeezes a little more power out of the air/fuel mixture. Typically, an engine with a higher rod ratio will produce a little more power from mid-range to peak RPM. In Formula 1, where efficiency is tantamount to a quick lap time, this goes a long way — no pun intended.
Plus, the peaky engine, matched with a relatively-small displacement, allows for that power to be put down with some regularity; these engines are designed to be tractable, as well as light. Both schools approach these goals quite differently, but they both shed light on the spectrum which encompasses pure spectator sport at one end, and multinational technology race at the other. While it’s obvious which camp sits where, their place on the spectrum does change slightly from time to time. Perhaps they could both learn a bit from each other.