Volvo’s T6 Engine Part of Bold Powertrain Strategy

Wards 10 Best Engines competition has recognized outstanding powertrains for 22 years. This installment of the 2016 “Story Behind the 10 Best Engines” series looks at the development of Volvo’s groundbreaking 2.0L turbocharged and supercharged 4-cyl. 

Anyone not paying attention could be forgiven for discounting Volvo as a serious player since Ford sold the company to Chinese automaker Geely six years ago. But the Swedish automaker has re-emerged and been on a roll lately, largely due to breakthrough interior design and the pleasing performance and efficiency of its all-new Drive-E 4-cyl. engines.

WardsAuto editors honored the 240-hp T5 turbocharged Drive-E I-4 that now powers Volvo’s midrange S60 sedan, V60 wagon and XC60 CUV as one of its 2015 Wards 10 Best Engines, and now bestow another 10 Best trophy on this unique 316-hp turbocharged and supercharged T6 version in the larger XC90 CUV and ’17 S90 luxury sedan. This surprising twin-charged 2.0L surely is one reason the ’16 XC90 was named North American Truck/Utility of the Year at January’s Detroit Auto Show.

In just the last couple of years, Volvo has transitioned almost everything it builds to Drive-E powertrains. The all-new, all-aluminum, turbocharged and direct-injected engine family eventually will include four 2.0L gasoline I-4s, four 2.0L diesel I-4s and a gasoline 1.5L I-3, all sharing the same 0.5L cylinder displacement and common components.

The T6 twin-charged 4-cyl., mated to an equally new Drive-E 8-speed automatic, boasts a healthy 295 lb.-ft. (400 Nm) of peak torque and impressive EPA economy ratings of 20/25 mpg (11.8-9.4 L/100 km) city/highway and 22 mpg (10.7 L/100 km) combined, best-in-class for a gas-powered all-wheel-drive 7-seat luxury CUV.

“The idea of 2.0L engines taking over for powerful V-6s in premium 7-passenger CUVs...seemed like a stretch...,” writes WardsAuto editor Drew Winter, “until Volvo introduced its superb T6 4-cyl. in the XC90. By adding the low-end grunt of a supercharger to the already strong turbocharged T5 2.0L that took home a Wards 10 Best Engines trophy last year, Volvo has created an engine that can match big naturally aspirated V-6s in power and torque and also cream them in real-world fuel efficiency when powering big vehicles.”

The XC90 weighs more than 4,600 lbs. (2,087 kg) yet never feels underpowered, Winter says. “There is no waiting for thrust when you need it in a hurry to pass on a 2-lane country road.”

“Smooth and refined, especially considering it’s a 4-cyl. doing the work of a big 6-cyl. or small V-8,” adds editor Bob Gritzinger.

“I’m a big fan of this engine, and the XC90 is the perfect fit for this high-tech power-puncher,” chimes in editor James Amend.

All Drive-E engines feature continuously-variable valve timing, “intelligent” heat management with an electric water pump, low-friction camshaft ball bearings, brake regeneration and stop/start with an electric transmission oil pump that maintains pressure when the engine is off.

All are designed to be teamed with electrification in hybrid vehicles. Upgrades to the T6 version over the T5 include a high-strength aluminum cylinder-head and double-water-jacket cooling to better handle the additional heat of double boosting, a lower-backpressure catalyst and an improved air-intake system that reduces supercharger noise.

Its block and crankshaft are new, and the main bearing diameter is reduced from 60 mm to 53 mm for lower friction. These changes also prepared it for plug-in hybrid duty with a 9.2 kWh Li-ion battery and rear electric drive in the XC90 T8 PHEV. The T8 designation refers to its V-8-like 400-hp performance, while the turbocharged T5 and twin-charged T6 offer performance similar to the old turbo I-5 and I-6 they replace. Denso supplies the Drive-E fuel injection and ECU. Eaton supplies the supercharger and Borg-Warner the turbocharger.

Replacing Old Ford Engines

The Drive-E family’s mission was to replace Volvo’s previous (mostly Ford-based) powertrains with a more efficient and commonized lineup, “so we would have only one installation per car for all variants, which would reduce our investment quite a lot,” says Volvo Powertrain Vice President Michael Fleiss.

“One thing was getting rid of the diversity in our powertrain lineup, and the second was to make very efficient powertrains with lower friction, variable-cam timing and lightweight materials. We also wanted the lowest possible cost of ownership for the customer when it comes to servicing the engine,” Fleiss says.

The modular, scalable design shares a common lower end with “unique top parts for petrol and diesel,” adds Volvo Powertrain Engineering program management director Johan Hallneus.

“We are using a common process in our engine plant, where the petrol and diesel engines go through the same flow and a common engine-management system so we can focus on delivering technology rather than different engine variants and installation processes.”

One major challenge was the transition from old powertrains to new Drive-E powertrains in such a short time. “Since the beginning of 2015 we have had only our own powertrains, diesel and gasoline, in all Volvo vehicles,” Fleiss says. “I don’t think any other car company has changed all powertrains in all of their vehicles in two to three years.”

“We had to do that because it was in the contract when Volvo was sold to Geely,” Hallneus says. “But there were two very positive side effects. One, the fuel consumption of our fleet was drastically reduced. And two, some of our cars that were not new were transformed into essentially new cars by the new powertrains. For example, last year we sold the most XC60s ever, and that car has been in production for five years.”

Volvo is not first to team supercharging with turbocharging. Volkswagen has done it with a 1.4L 4-cyl., says Fleiss, “but we have enhanced it quite a bit. The VW supercharger went up to 2,300 rpm, while ours goes to 3,500 rpm, and we use it more than they do.”

Hallneus points to the extraordinary attention to detail that was paid to friction reduction, “not with one breakthrough technique but by taking many small steps with ball bearings on camshafts, improved surfaces on the crankshaft and cylinders, machining refinements and a fully variable oil pump. All these things together build up to best-in-class friction reduction, which really pays off in performance and fuel consumption.”

The other major element, Fleiss adds, is the combustion system. “Friction and the combustion chamber are the keys to fuel consumption and emissions, and we were in the lucky situation that we had to do everything new to get away from our legacy powertrains.”

Fleiss also confirms there is more to come. “We are happy to have a great foundation with our first-generation Drive-E, so now we can improve that and further surprise the industry. My team is busy working on the next-generation Drive-E powertrains with further improvements in friction and combustion, increased injection pressure and some new technologies that will make our engines even more efficient, but not less powerful.”