Engineering timelines are longer than those of media scandals, which has given Honda a predicament with its all-new i-DTEC diesel engine. The company’s decision to develop a next-generation ultra-clean turbo-diesel was made well before Volkswagen was caught getting its cheat on, but the finished 1.6-liter inline-four reviewed here in the Honda Civic is reaching its target market in Europe just as demand slumps for compression-ignition engines, thanks in large part to the Dieselgate scandal.
Too bad for Honda, which has been suffering in Europe for years. Sales on the Continent fell to just 140,000 last year, more than 50 percent below the peak reached in 2007 and less than a tenth of what the brand manages in the similarly sized U.S. market. But it’s also a shame because the new engine could well be seen by historians of late-era internal combustion, looking back decades from now, as representing the pinnacle of diesel technology.
the Audi SQ7 and the diesel Bentley Bentayga, an engine that has been heralded as another pinnacle of the compression-ignition craft. In the Euro-spec Civic hatchback, the i-DTEC’s headline figures are 118 horsepower and 221 lb-ft of torque, with Honda claiming a 9.8-second sprint from zero to 62 mph and a 125-mph top speed. The only gasoline Euro-spec Civic that the i-DTEC has a chance of beating in a stoplight showdown is the base turbocharged 1.0-liter three-cylinder (yes, that is a thing). For reference, the 2.2-liter i-CTDi turbo-diesel that Honda considered selling in the United States (and which we tested) a decade ago produced a superior 138 horsepower and 251 lb-ft of torque.
But the new engine isn’t about firepower, instead focusing on efficiency and emissions. And on those measures, it is almost unbeatable. Europe’s NEDC fuel-economy figures are notoriously optimistic, so the Civic DTEC’s official figure of 67 mpg combined (when converted to U.S. gallons) is best seen as a means of comparison with other cars rather than an indicator of real-world performance. That number is identical to the one Toyota claims for the 2018 Prius, and it does make the Civic one of the most efficient cars available in Europe.
More impressive is that the Civic is already able to pass the stringent new Euro 6D TEMP emissions standard—a year ahead of its implementation. That standard uses real-world testing to ensure emissions of NOx and particulates don’t go above 2.1 times the permitted laboratory values during everyday use. For reference, a report from 2015 suggested that some diesels emit up to 14 times their official NOx levels out on the road.
Honda has managed to achieve this target without the added cost or complexity of a urea-injection system. Instead, the i-DTEC gets a close-coupled NOx storage catalyst and diesel particulate filter in the exhaust. These capture undesirable particulates and burn them off using forced regeneration through added fuel if the exhaust temperature isn’t sufficient. The new engine also has had its efficiency boosted with the use of steel pistons rather than aluminum to improve heat dispersion, a low-friction timing chain, a high-efficiency variable-geometry turbocharger, and smoother cylinder bores thanks to two-stage honing. The die-cast aluminum block has been designed to be stiffer than the previous-generation engine, because it moves the resonances to lower frequencies and reduces noise by a claimed 3 decibels at 2000 rpm.
It’s no diesel hot hatch, as the i-DTEC feels markedly less enthusiastic than the 1.5T Civic, despite a fatter torque curve—at least below 4000 rpm. But the Civic easily kept up with Italian traffic on our drive route near Rome, with a free-flowing stretch of the autostrada freeway confirming that it will sit happily at an indicated 90 mph without breaking a sweat. We didn’t drive far enough to run our own fuel-economy numbers, but after 60 miles the test car’s trip computer reported 45 mpg. Given our rapid progress, that probably represents a worst-case scenario.
There is little chance that Honda will sell its new engine anywhere outside Europe; company executives admit that it likely will be the last diesel it will develop. Diesels still made up 45 percent of European passenger car sales last year, but that percentage is falling rapidly and is disproportionately made up of cars bigger than the Civic. Within a technology generation, the case for spending the money necessary to develop another all-new diesel for a minority player like the Civic will almost certainly be gone. But it is fitting for such an engineering-led company that, despite its modest output, this little diesel should be remembered as one of the pinnacles of its genre.