Mid-engine History of The Future

Highlighting the many benefits of a century-old vehicle layout whose golden era is with today’s performance cars.

April 1, 2020

Lindsay Brooke

Last year’s blockbuster film “Ford vs. Ferrari” grossed over $225 million and earned two technical Oscars, but its real star was the Ferrari-thumping Ford GT racecar shown in cutaway illustration here. SAE readers who want the full lowdown on this mid-engine LeMans-winning legend can download the five SAE Technical Papers originally published on the car in the 1960s. Go to sae.org/publications/technical-papers and search for: The Ford GT Sports Car, 670065 (Roy Lunn’s masterpiece paper); Mustang 1 development, 611F; Ford GT Engine, 670066 and 670067; Ford GT Electrical and Ignition, 670068; Ford GT Transaxle, 670069; and Ford GT Driveshafts and Brakes, 670070. Where else but at SAE can you find this stuff?

What do a 1901 Curved-Dash Oldsmobile, a 1936 Auto Union Grand Prix car and the 2020 Acura NSX Hybrid and the new 2020 Chevrolet Corvette have in common?

Their engines are located between the front and rear axles, behind the driver. The so-called ‘mid-engine’ drivetrain layout has found favor in passenger cars, mostly at low volume, since the beginning of the automotive age. It’s been popular in various transit and school buses and fire apparatus as well.

Leading-edge racecar engineers, such as those at Auto Union and Mercedes-Benz in the 1930s, chose mid-engine over alternative powertrain layouts to minimize the vehicle’s polar moment of inertia (or rotational inertia)—a physical object’s resistance to rotation about any axis. In cars, a larger polar moment of inertia is typically created by a large distance between the vehicle’s major masses. In such layouts, higher forces are required to stop and start any turning maneuver. The vehicle is less agile as a result.

Introduced with a conventional 3.0-L V6 powertrain in 1990, the Acura NSX proved that mid-engine high-performance sports cars don’t have to be costly, high-maintenance exotics. Honda’s packaging brilliance shines in the NSX Hybrid launched in 2016, boasting lowest-in-class Cg and super-compact drivetrain.

By adopting mid-engine layouts, handling, braking and acceleration are improved via substantially increased rear tire loading — as GM engineers note in our C8 Corvette development feature on page 30. There are weight distribution and cooling benefits in some applications, too. By contrast, mid-engine commercial vehicle designs offer packaging benefits.

Mid-engine mania was slated to be a highlight of WCX 2020, until the event was cancelled due to the COVID-19 pandemic. What potential SAE show-goers missed was the SAE Mobility History Committee’s “History of the Future: Mid-Engine Revolution” — an engaging showcase of early-to-modern mid-engine vehicle examples.

“Although mid-engine vehicles have recently been in the news, our display demonstrated that this design configuration is not new, and perhaps the original drivetrain layout,” noted Len Kata, the MHC chair. The WCX display, he said, aimed to “enlighten visitors regarding the history of mid-engine technology,” spanning 1903 to the present. Vehicles to have been displayed included a 1903 Olds chassis; 1909 Buick Model F; 1948 Citroen Traction Avant; 2006 Ford GT; 1970 Porsche 914, and an extensive Acura NSX Hybrid display with a chassis and full vehicle.

“As always, our mission is to present the history of mobility in a manner that engages interest and inspires further study and interpretation of our heritage,” Kata said.