Got the VW TDI Blues? Turbo 4-Cylinder Gas Engines Will Save The Day

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Compact cars have grown up.  New turbocharged gasoline engines are making them fun, fast, and frugal, and they have as much to offer as small turbocharged diesel engines.

A recent test we conducted of the new 2016 Honda Civic EX-T With Honda Sensing revealed that the Civic’s 1.5-liter, four-cylinder, turbocharged engine is going to change everything in this class.  The Civic is the sales leader in the compact sedan class and being all-new and sporting this punchy but practical engine almost guarantees it will stay that way.  What drivers will find is that this new breed of small turbo engines and their more modern transmissions deliver a mature feeling of power around town, great passing ability, and now also amazingly good fuel economy.  Here’s why.

elantra torque curve red

Turbocharged engines have one main advantage over engines without turbos, torque. And importantly, that higher torque is available to drivers basically at idle.  That means that when the driver first applies throttle, the feeling is that of a very powerful engine.  The small turbos are actually not as powerful as other engines may be, but it is where and how they feel powerful that matters.

Engineers love to make graphs and curves to explain things and all engines have what is called the torque and power curve like the one above from the new Hyundai Elantra.  In non-turbo engines (called normally-aspirated), the peak power is available only at the very high RPM range.  So on paper, an engine may be advertised as having 142 hp like the Corolla’s engine.  However, most drivers never use the high RPM ranges of their engine, so they only use a fraction of the engine’s available power around town.

Turbocharged engines have a much flatter torque curve.  Look at the part of the curve above that we marked in red.  In the new Hyundai Elantra 1.4 Turbo, the engine delivers the maximum available torque between just 1400 RPM to 3600 RPM.  That’s 1,000 rpm from idle, and it’s the exact spot in the engine’s RPM range we all drive around using.  The net effect is a feeling of strong push when we accelerate.  The new Civic’s torque curve has that same profile.

Civic 16 engine comparison chart

Honda went to great lengths in the Civic’s design to enhance the feeling of power.  Both its new 2.0-liter normally-aspirated engine and the new 1.5-liter turbo have great fuel economy and power for their class.  However, the torque from the small turbo is what makes it feel strong to a driver.  In our testing, the turbo engine and constantly variable transmission had no feeling of turbo-lag either.  That brief flat spot many larger turbos have was absent.

civic 16 part throttle curves


The charts above are interesting because they don’t just show the feeling and performance of the new Civic with its turbocharged engine at full throttle, but rather, part throttle as well.  Historically, enthusiast magazines like Car and Driver and Road and Track (whom we greatly respect) have focused on how a car performs and feels when flogged by a hot-shoe tester.  They rank the cars based on these extreme results and the “losers” would often be pegged as “boring.”  However, Honda and other automakers are aware that 90% of car shoppers never treat their car the way the semi-professional racers at these enthusiast magazines do.  So, without any pretense, Honda and others are now providing automotive writers with information showing how the actual target audience will experience the cars they make.  The graph above on the left shows clearly that the feeling of the 1.5 turbo is stronger than the “7DCT competitor” across the full range of throttle except at almost full throttle.  What does this mean?  If you buy the small turbo, it will feel stronger to you.  It will also top the fuel efficiency of modern diesel engines.  The 2015 Volkswagen Jetta diesel automatic was EPA rated at 34 MPG Combined and 42 MPH Highway (before it was removed from the market for polluting). The 2016 Civic 1.5T has earned a 35 MPG Combined and 42 MPG Highway rating.

Having not tested the just-launched Elantra we reached out to a colleague who has just returned from the Elantra press launch.  Patrick Rall is a muscle car fan who owns multiple V8 drag racers.  What did he say about the new batch of small turbos entering the compact class segment?  He told BestRide, “Turbo technology can only help the compact segment. Compacts have always focused on fuel economy, but in the past, those fuel friendly engines forced buyers to compromise power in a big way. The induction of turbo technology to compact vehicles has improved fuel economy, but the forced induction setup also yields new sensations of power combined with MPGs.”

If you are one of the very few drivers in America familiar with diesel engines in small cars none of this information is new to you.  Diesel engines have used turbos for many years to create this strong torque and strong feeling of push from the cars they are in.  Diesels have many trade-offs due to their inherently-dirty combustion cycle that are starting to limit their use in the U.S.  The great news is that all the advantages they have offered are now found in small gasoline powered cars.  Down the road, the electric vehicles we will be driving in greater numbers will have this same feel.




John Goreham

John Goreham