The Tech That Was Going To Save The Internal Combustion Engine Was A Lie
...downsizing is a very simple idea: turbocharging a small engine would give you the power of a larger engine while retaining the fuel efficiency of a smaller engine. It meant that a VW Golf that might have been powered by a two-liter engine would be just fine with a 1.6, a 1.6 could be replaced by a 1.4 or 1.3, and you could continue to scale down the sizes of your engines in this downsizing regime.
The auto industry bought into the plan like mad, and a few years after that lecture in early 2010, we were seeing 1.0 liter engines in small family cars across most European manufacturers. Even here in the land of the Big Gulp, downsizing became standard. Just about everything comes with a two-liter turbo four now, even when a few years ago 2.5-liter naturally-aspirated fours, with 3.0 liter V6s above them were the norm.
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The most extreme case of downsizing was executed at Fiat. It managed to fit a 0.9 liter, two-cylinder engine into its smallest 500 and Panda hatchbacks.
Fiat called it the TwinAir and it came with some very interesting hydraulic valve technology in addition to its turbocharging to extract the highest level of efficiency and power from the teensy little powerplant. The results looked spectacular. Fiat advertised the car with a stunning 67.3 mpg average fuel consumption. The thing won awards left and right.
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Not long after the car debuted, reviewers and owners found themselves rarely able to come even remotely close to Fiat’s claimed mileage figures. One particularly notable test from CAR Magazine saw a TwinAir Fiat Panda barely cresting 30 mpg in ordinary driving. Other reports cited by Reuters found these TwinAir cars to regularly return 40 percent less economy than claimed, making them very worst offenders on the market.
And this is where the lie of the thing comes though; downsized engines might provide the fuel economy of a small engine while returning the power of a larger one, but they’ll never do both at the same time.
This is because of the trick of turbocharging. You only get the power advertised once the turbocharger kicks in. Once you’re in boost, the turbocharger is forcing air and fuel into your engine, wildly raising the amount of gas you’re burning. You might be making the power of a larger engine, but you’re sucking fuel like one, too. So with a downsized engine, you can get the economy of a small engine, but only at the lowest levels of the rev range, before the turbocharger kicks in.
When does this happen? Not when you’re driving like a normal person, as owners quickly discovered. No, the conditions for downsized engines just so happen to perfectly match up with those of government tests for fuel economy and exhaust emissions. These tests are easy enough that downsized engines can complete them while rarely, if ever, dipping into the gas-guzzling boost they need to work in the real world.
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http://jalopnik.com/the-tech-that-was-going-to-save-the-internal-combustion-1788662897
