DGS49
Diamond Member
Turbocharging and supercharging are ways that an ICE can '"pretend" that it is bigger than it is. A 2 liter engine can act like a 4 liter engine by forcing air-fuel mixture into the cylinders (rather than allowing it to get into the cylinders under merely atmospheric pressure), thus creating a bigger "bang." In fact, there is almost no limit to the effect. Some manufacturers are producing 2-liter engines getting almost 400HP by either turbocharging (Porsche) or a combination of turbo and supercharging (Volvo).
The advantage of those two strategies is that when you are not "pushing" the car, it acts like the smaller displacement engine, thus getting better fuel economy than a larger displacement engine of the same power. Hence, on the EPA's fuel economy cycle, where the car is driven like a Granny would drive, it gets "good" gas mileage - better than the larger displacement engine of the same HP.
But there are also disadvantages that are rarely discussed. Charged engines are more complex, get hotter, and are subject to much higher stresses, and must include coolers for not only the engine block but also the turbocharger itself. The long term viability of these high-performance turbos (when compared to larger-displacement "regular" engines) is still undetermined.
It is a disputed matter whether turbocharged engines actually do get better mileage than larger engines of the same power. Some say that the "base" power in a turbo is so pathetic that the driver unconsciously pushes the car all the time, just to get the performance of the larger engine. The only time when it is clearly beneficial is on the highway at constant speeds - which could be overcome by higher gearing with a larger engine.
But are turbocharged engines cheaper to manufacture than larger-displacement engines of the same power? How could they be? The incremental cost of adding displacement is minimal.
I think the turbo craze is just manufacturers using this strategy to make their fuel economy look better than it actually is (due to the EPA testing protocol), at the expense of REAL fuel economy and longevity.
But what do I know?
The advantage of those two strategies is that when you are not "pushing" the car, it acts like the smaller displacement engine, thus getting better fuel economy than a larger displacement engine of the same power. Hence, on the EPA's fuel economy cycle, where the car is driven like a Granny would drive, it gets "good" gas mileage - better than the larger displacement engine of the same HP.
But there are also disadvantages that are rarely discussed. Charged engines are more complex, get hotter, and are subject to much higher stresses, and must include coolers for not only the engine block but also the turbocharger itself. The long term viability of these high-performance turbos (when compared to larger-displacement "regular" engines) is still undetermined.
It is a disputed matter whether turbocharged engines actually do get better mileage than larger engines of the same power. Some say that the "base" power in a turbo is so pathetic that the driver unconsciously pushes the car all the time, just to get the performance of the larger engine. The only time when it is clearly beneficial is on the highway at constant speeds - which could be overcome by higher gearing with a larger engine.
But are turbocharged engines cheaper to manufacture than larger-displacement engines of the same power? How could they be? The incremental cost of adding displacement is minimal.
I think the turbo craze is just manufacturers using this strategy to make their fuel economy look better than it actually is (due to the EPA testing protocol), at the expense of REAL fuel economy and longevity.
But what do I know?