The performance profile of the turbo four may have doomed it to being merely a footnote in Honda's illustrious history.

The RDX sold just over 15,000 units in 2011.

Hopes that the power-dense four-cylinder might find its way into other Honda products has also been dashed.

When the 2013 Acura RDX launches this spring, Honda will quietly close down a spur line of its Anna, OH, plant. Since 2006, it had been building the 2.3-liter four-cylinder engine used in the first-generation RDX there. These engines were unique, the company's first to be fitted with a turbocharger from the factory. But the redesigned 2013 RDX will be available only with a V6, and with no other application for the turbo four, Honda's most impressive performance engine will die an ignoble death.The 2.3-liter turbo was a variation of the 2.4-liter four used in the Honda Accord and the Acura TSX . Rated at 240 horsepower, it was the 260 lb-ft of torque that made things special. Honda's traditional approach to engine design had favored high-revving, small displacement engines that made generous power thanks to variable valve timing technologies – but at the expense of torque output. So when Honda announced that it would be producing a turbocharged engine for the first time, it seemed to herald the next wave of Honda performance. Finally, some torque to match the howling VTEC power. But sadly, it was the performance profile of the turbo four that may have doomed it to being merely a footnote in Honda's illustrious history.The RDX , one of the first compact luxury crossovers , was envisioned as a sporty model that would attract the sorts of drivers that might wish they owned a Porsche , but wouldn't find a true sports car practical. Alas, those buyers never materialized – the RDX sold just over 15,000 units in 2011."The buyers of two-row crossovers are not quite what they appeared to be," said Honda spokesman Chris Naughton.Naughton told us that the knife-edged nature of the turbocharged engine, with its narrower powerband compared to the smooth V6, wasn't embraced by crossover buyers. The other factor that likely kept the RDX from being parked in more driveways was its fuel economy – only 19 miles per gallon combined – and a penchant for premium fuel. The RDX was initially offered with a five-speed automatic with paddle-shifters that Acura called "Sequential SportShift," as well as Acura's "Super Handling" all-wheel-drive system. The redesigned model has a six-speed automatic and a simpler, lighter-weight all-wheel-drive system like the one found on the Honda CR-V With the 2.3-liter turbo going out of production, hopes that the power-dense four-cylinder might find its way into other Honda products has also been dashed. Honda uses a similar 2.4-liter four, though naturally aspirated, in other models, including the forthcoming Acura ILX . We imagine the turbo four might have served as a decent base for building a performance version of the Accord or a lighter but still powerful TSX . Even a turbo-four-powered CR-V is something we could embrace, giving some character to that ubiquitous people mover.Applications in even smaller Honda vehicles – yes, we're stupidly imagining Civics and Fits with grapefruit shooter exhausts – might be a stretch, but we wonder if Honda's first attempt at turbocharging ending this way won't have bad implications for the future? Just as seemingly every manufacturer on earth is offering turbocharged engines, even in entry-level cars like the Chevrolet Sonic , Honda has prematurely abandoned them. Then again, as Honda's Naughton said, "We now have that expertise."Here's hoping Honda uses it , once again.