A 2015 Golf TDI Clean Diesel has set a new Guinness World Records achievement for the “lowest fuel consumption—48 US contiguous States for a non-hybrid car” with an 81.17 mpg (2.9 l/100 km) performance. Traveling 8,233.5 miles (13,251 km) around the US in 16 days on $294.98 of Shell Diesel fuel, the Golf beat the previous mark of 77.99 mpg (3.01 l/100 km) by more than 3 mpg, and also beat the hybrid vehicle record of 74.34 mpg (3.16 l/10 km) by more than 6 mpg. The 2015 Golf TDI carries an EPA-estimated highway fuel economy rating of 45 mpg (5.22 l/100 km).
The record-setting Golf TDI, sporting Volkswagen of America’s 60th anniversary emblem, as well as logos from sponsors Shell, Goodyear, LG, Garmin and Linear-Logic, departed from Volkswagen of America’s headquarters in Herndon, Va., on 22 June. It returned on 7 July, having visited all 48 contiguous states.
Wayne Gerdes, automotive journalist and founder of cleanmpg.com, was the primary driver. His co-driver was Bob Winger, an electronics engineer long involved in energy and conservation projects. Gerdes is an expert hypermiler who has set mileage records in more than 100 vehicles. In 2013, Gerdes set the prior Guinness World Records title for “lowest fuel consumption—48 US states for a non-hybrid car” in a 2013 Volkswagen Passat TDI, with 77.99 mpg.
For the attempt, the Golf TDI used Shell ultra-low-sulfur diesel fuel and Goodyear Assurance Fuel Max tires which feature a fuel-saving tread compound to help increase fuel efficiency. The record-setting Golf TDI was also equipped with a Linear Logic ScanGauge II to precisely measure fuel economy, G4 smartphones by LG and a Garmin nüvi 57 LM GPS navigator to meet Guinness World Records tracking requirements.
The 2015 Golf TDI features Volkswagen’s EA288 diesel engine. The EA288 is based on the Volkswagen MDB, its modular diesel engine toolkit (Modularen Diesel Baukasten) (earlier post).
The EA288 in the Golf is a 2.0-liter, four-cylinder turbocharged and direct-injection diesel engine, a thorough update from the powerplant in the previous Golf. Despite the similarity in basic specifications, the only aspect that carries over from the previous EA189 unit is the cylinder bore spacing.
The new engine produces 150 hp—10 more than before—at 3,500 rpm, as well as 236 lb-ft (320 N·m) of torque at 1,750 rpm. The engine, when combined with the manual transmission, carries an EPA estimated rating of 30 mpg in the city and 45 mpg on the highway (combined 36 mpg/6.53 l/100 km), an improvement of 1 mpg in the city and 3 mpg on the highway over the previous EPA numbers.
The compact EA288 engine has the intercooler for its turbocharger system integrated directly into the intake manifold, which serves a two-fold purpose of increasing throttle response and performance as well as helping lower emissions.
The engine block is cast iron, with a forged steel crankshaft that runs in five main bearings and has four counterweights. In order to counteract engine vibration and maintain smooth operation, the EA288’s crankshaft is connected to two gear-driven counter-rotating balancer shafts that spin at twice engine speed. Friction has been reduced by about 15% in the engine, through the use of roller bearings for the drivetrain side camshaft, increased piston-to-wall clearance, and lower piston-ring tension, among other measures.
The aluminum-alloy crossflow cylinder head has a number of unique features. First, the camshafts are integrated into a separate housing by a thermal joining process, ensuring a very rigid camshaft bearing while keeping the weight low. Second, each overhead camshaft operates one intake valve and one exhaust valve per cylinder (as opposed to one camshaft for intake valves only and one for exhaust), allowing for greater air delivery and swirl. The engine features variable cam phasing on the intake and exhaust valves.
The EA288 Clean Diesel TDI engine places strong emphasis on thermal management, which is evident in the cylinder head’s two-section coolant jacket, as well as a three-part cooling circuit and switchable coolant pump. Compared to the previous engine, emissions are reduced by up to 40%, helped by siting the exhaust after-treatment module close to the engine and by the use of a low-pressure exhaust gas recirculation system.