How Low Can You Go?

The engine downsizing trend sweeping across the global powertrain community need not apply exclusively to hulking V-8s and high-powered V-6s.

No, even 4-cyl. engines can be squeezed for higher efficiency, and powertrain engineering specialist FEV Inc. has developed a 0.7L turbocharged 3-cyl. engine concept intended to replace powerplants twice its size.

Simply named Extremely Downsized Engine, the direct-injection gasoline concept delivers 134 hp/L and is capable of 12% better fuel efficiency than a naturally aspirated 1.5L 4-cyl., says Henning Kleeberg, FEV's department manager-spark ignition engines.

On display for the first time in the U.S. at this year's SAE World Congress in Detroit, the EDE concept arrives in anticipation of stringent new emissions mandates in Europe and the U.S.

The European Smart car's high-performance Brabus engine, with two spark plugs per cylinder and conventional port fuel injection, serves as the base for the 0.7L concept. To boost efficiency, FEV replaced PFI with direct injection and removed one of the spark plugs in a significant redesign of the head.

“As we go to smaller combustion chambers, the challenge is to get direct injection in there, to get the fuel mixed and to get away from the low-speed pre-ignition problem that DI engines have,” Kleeberg tells Ward's.

So the reconfigured SOHC valvetrain incorporates a longer camshaft and dual independent cam phasing, allowing for fully variable valve timing and overlap on both the intake and exhaust ports, with a control valve for each.

FEV collaborated with fellow suppliers Mahle GmbH and Hydraulik-Ring GmbH on the valvetrain, which has two valves per cylinder.

Without the ability to phase between two cams on the same shaft, the EDE concept would lack low-end punch.

“We have the same low-end torque as with a larger naturally aspirated engine,” Kleeberg says. “With the large valve overlap, you can create quite significant torque improvement at low speeds.”

The small turbocharger allows for rapid spool up of inertia, which further helps overcome “turbo lag.”

Compared with a naturally aspirated 1.5L 4-cyl. typically found in subcompacts, this concept delivers 32% more torque at only 1,500 rpm, Kleeberg says.

The concept delivers 100 hp for an impressive specific output of 134 hp/L, as well as 103 lb.-ft. (140 Nm) of torque.

With a bore diameter of 66.5 mm (2.6 ins.), FEV says the EDE would be the smallest powertrain in the market.

FEV says the concept engine would be ideal for B- and C-segment cars.

There are cost benefits, as well. Removing a fourth cylinder and related hardware means material costs can be cut by a quarter. Even after adding cam phasing, direct injection and turbocharging, Kleeberg says he believes the system is cost-competitive.

Gary Rogers, president and CEO of FEV, is optimistic about finding a customer to adopt the EDE concept.

“The question in many people's minds is, how low can you go? At what point does (downsizing) no longer make any sense?” Rogers tells Ward's.

“If you want to get into another 15% fuel-economy improvement without hybridization and the cost of batteries and all that, another step on the path that you can go is yet smaller.”