THE TURBO EQUATION
Mazda's CX-5 and Mazda6 models feature an interesting quirk in their engine choices, in that both of them feature two different 2.5 Litre, four-cylinder engines available. One of them makes 187 horsepower, and the other makes 250. With the same displacement and cylinder count, how does one engine make 25 percent more horsepower?
The answer is the magical, mythical turbocharger.
Turbos have been around in passenger vehicles since the 1960s, and many people associate them with high-performance sports cars, or big diesel trucks. However, with the advent of more stringent fuel economy standards worldwide, combined with the desire to not lose performance when achieving these standards, many car manufacturers are turning to the turbo as the solution.
But how do turbochargers work their magic? By harnessing wasted exhaust gas energy to make more power. Internal combustion engines are similar to an air pump, sucking in air (and fuel), igniting it, then pushing the spent gasses out the other side and through the exhaust. On a "normally aspirated" engine, aka one without a turbo, this exhaust gas energy is unused and wasted. It flies out the exhaust pipe like a river flowing down a mountain, unchecked.
To utilize this exhaust gas energy to their advantage, engineers place what is essentially a small turbine into the exhaust flow. This turbine is connected to a shaft, that connects to another turbine that is placed in the intake tract. The exhaust gas energy turns the first turbine, which spins the second turbine, and essentially pumps more fresh air into the engine. The more air pumped in, the more fuel can be added, the more power is made.
Like damming up the aforementioned mountain river and using turbines to generate electricity, the turbo is placed in the exhaust tract to push more air into the engine. The same engine displacement and cylinder layout that makes 187 horsepower with no turbo, can make 250 prancing ponies with one.
But turbochargers are not without potential drawbacks. Without careful engineering, turbocharged engines can suffer from poor performance lower in the rev range ("turbo lag"). At low RPM, the exhaust gasses are not flowing fast enough to get the turbine spinning fast enough to pump a significant amount of air into the engine. Without proper tuning, the engine will feel flat until the revs rise and the turbo spins up.
Mazda counters the possibility of turbo lag by using their exclusive "Dynamic Pressure Turbo" system. At low RPM, valves in the exhaust system restrict the flow of gasses in order to increase their velocity and spin up the turbo. If you open your mouth up wide and try to blow a pinwheel, it will only spin slowly. You can speed up the pinwheel by closing your lips and directing a thin stream of fast air at it. The amount of air does not change, just the velocity.
As the engine revs up, the Dynamic Pressure Turbo valves open full up, to give maximum velocity and volume.
Want to see the effect for yourself? Come on by County Mazda to test drive a Mazda Dynamic Pressure Turbo engine today. Our test route surrounding New Glasgow helps to demonstrate the versatility and performance of the engine, while also showing off the suite of Mazda exclusive Skyactiv technology that sets their vehicles apart from the rest.
County Mazda in Pictou County has an extensive inventory of new and used vehicles, financing for any credit situation, and our service department is equipped for any make or model of vehicle. Visit us now at 391 Westville Rd, New Glasgow, Nova Scotia, B2H 2J6.