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2009 Toyota Corolla CE

Bill Petro/Toyota

New cars are using turbocharger technology to improve fuel economy. Will adding a turbo charger to my 2009 Corolla improve its gas mileage? Is the improvement in fuel efficiency enough to merit the modification (for example, a 2 per cent improvement versus a 20 per cent improvement)? I am curious what the benefits and drawbacks are? – Jeremy

Ah, if only it were that easy.

Turbocharging and supercharging force more air into the engine. This added pressure results in more power per unit of displacement.

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The turbocharger has two sides, one placed in the exhaust stream and the other on the intake side. The exhaust gasses forced out of the engine following combustion turn an impeller, causing the other side to spin as well. This forces more air into the engine.

Superchargers are driven by a pulley at the end of the crankshaft, like the alternator, power steering pump and air conditioning compressor. As it spins, it forces more air into the intake stream.

In both cases, the intake air is compressed, making it hotter. It is common to use an intercooler to bring that temperature back down. The intercooler is simply another radiator designed to cool air. Because the air is being forced into the cylinders the resulting explosion is greater when the mixture is ignited. This added force pushes the piston down harder resulting in more torque or power.

But here is the rub – those added forces and more powerful combustion place a greater strain on the engine internals, everything from the piston and rings to the crankshaft and bearings.

The added power and compressed air create more heat so added cooling is required for both the turbocharger itself and the engine itself.

To avoid blowing the engine apart, extremely accurate fuel delivery and ignition timing are required. Sensors are used to detect a wide variety of parameters and report to a powerful and fast engine control computer, which adjusts the fuel and spark. And let's not forget the added power requires a stronger transmission, axles, etc. All of this, when included from the design stage, can be incorporated in a drivetrain.

You might be able to find a shop that would install a turbocharger on your Corolla but that could be accomplished in one of two ways:

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  1. An aftermarket kit with no internal modifications at a cost of a few thousand dollars and accompanied by a strong likelihood the engine would self-destruct fairly quickly or ...
  2. A complete swap for an engine designed to work with a turbocharger and the accompanying equipment – we’re past the $10,000 mark at this point and the 2 to 5 per cent improvement in fuel economy would make recouping your “investment” a rather lengthy process.

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