Today’s automotive landscape has supercars achieving insane performance milestones that only dared occupy anyone’s wildest dreams two decades ago. And to double down on the impressiveness of those achievements is that many of them are being accomplished with only six cylinders.
Case in point, the twin-turbo V6 engine in the latest generation of the Acura NSX. “Looking at GT3 rules, all you have to have is a mass-production-based bock and heads,” says Ted Klaus, President of Honda Performance Development. “The NSX GT3 is the only car in the field that has a bone-stock engine.”
Designed from the outset to be a road-going race engine, a “bone-stock” 3.5L V6 engine powered Acura’s GT3 and GTD efforts in 2017 and 2018 and ultimately won the championship in 2019. While Acura as a company, and the NSX in particular, are no strangers to racing, when designing this generation of powerplant, the team took a different route.
Heritage or Technology
The original NSX engines — the C30A and C32A — were based on the production Acura Legend engine at the time. A company of tradition, a modified, specialized variant of a production engine was the first option considered when originally designing the new supercar.
“We started asking, ‘Could a production-based engine be special enough for the NSX?’” Klaus recalls. “Is it better to have something already linked to the brand – a special version of another engine? Or should NSX have its own engine?” Ultimately, the answer was that as the flagship of Acura Performance, the NSX should have a bespoke engine, unlike anything else in the lineup.
Built at the Anna Engine Plant in Anna, Ohio, the NSX engine production facility is a 4,000 square-foot facility at the center of the 2.5 million-square-foot high-volume engine plant. While the standard high-volume lines produce about 4,500 engines a day, the NSX engine takes about five hours each to complete.
The Bespoke Jewel
The engine itself is a unique creation, with each component and design feature chosen for a specific purpose. For example, the 75-degree cylinder angle in the aluminum block keeps the engine compact enough to mid-mount the engine, allows enough room under the cylinder head to properly mount a turbocharger, and keeps the overall height of the unit to a minimum. So much so, that the top of the cylinder head, when mounted in the car, is level with the top of the tire.
The slightly oversquare engine has a 3.600-inch bore with a 3.500-inch stroke allowing it to carry its 500-horsepower peak from 6,500 to 7,500 rpm. A 10.0:1 compression ratio allows for efficient combustion across the map and works well with the dual fuel injection layout (both port- and direct-injection).
The four-valve-per-cylinder, dual overhead cam cylinder heads utilize Honda’s latest and most advanced version of the venerable VTEC — i-VTEC with Variable Timing Control (VTC) which allows the engine to not only have multiple camshaft lift and duration profiles but also allows the camshafts to be electro-hydraulically advanced and retarded as needed.
The size of each of the single-scroll turbochargers isn’t noted anywhere, officially, but if we had to make a guess based on a part number and some quick cocktail-napkin math, we’d wager they are in the 58mm range. The turbos are electronically gated to 15.4psi maximum manifold pressure, and the engine also features a six-rotor dry-sump oiling system with segregated scavenge areas for maximum performance in all conditions.
As noted in the video above, Acura is proud of its mix of traditional hand-crafted engine building as well as the modern assembly technology they have incorporated into the process. There are 547 fasteners on the NSX engine, and each one is started by hand. However, in order to ensure a perfectly even cylinder head deck, a multi-spindle nut-runner is used, so that not only is the correct torque applied every time, but that torque is applied to the fasteners simultaneously.
Once assembled, each engine undergoes an hour-long computer-controlled break-in process. Again, mixing traditional and modern tech, besides being monitored by a huge bank of sensors during the process, a technician uses a mechanic’s stethoscope to listen to the engine during the process.
Finally, once broken in, the engine receives a final balance. This is done with the engine fully assembled and filled with oil and at operating temperature. Balance is measured at each end of the crankshaft, and perfect balance is achieved through the use of specially weighted flywheel bolts.
This new generation Acura NSX engine is an amazing piece of engineering, making 143 horsepower-per-liter out of the gate, with the ability to hold its own in an international racing class like GT3, while also handling the day-to-day rigors of rush-hour traffic in the middle of summer. This engine truly is an engineering marvel.