Ah turbo engine, I still remember in the 90s, where everybody and their grandmother in the car modding scene wants to turbocharge their cars. It was truly a wild time with many Japanese sports cars of the era are using turbochargers such as Lancer Evo, WRX, RX-7, Supra, GT-R and many others. Seems like if you don’t have turbocharger, then you’re not a sports car (well, the NSX begs to differ, but NSX is an exotic car rather than a pure sports car). Fast forward 3 decades today, turbocharged engines are everywhere in cars. Many European brand cars are turbocharged, and mostly they are small cars too, so what happened? Are all of those small cars are sports cars? Well no.
Turbochargers today is no longer in the domain of performance cars and more into the domain of efficiency booster. As government all around the world tries to curb green house emission, they introduce more and more stringent emission law that require engineers to utilize turbochargers on 4 wheel automotive products. Turbocharged engine works by forcing air into the engine to produce more power. As most cars operates at low engine speed, in reality cars do not need big engine. However, speed is not just the domain of making shorter time to a destination, but also a safety feature for example to pass a slower car. As speed necessitate the use of power, thus bigger engine, automotive engineers uses turbocharger to increase power. As traditional internal combustion engine relies on burning air and fuel mixture, forcing more air in is the easiest way to produce more power. As performance booster, turbocharged engine can extract more power from a smaller displacement engine that rivals or even exceed bigger displacement engine. The forcing of air however is not without risk, as the keyword here is forcing.
To produce more power than the same engine of the same displacement, turbocharged engine produces more temperature and pressure inside the engine, and one typical result from this is knocking. Knocking happens when pressure inside the cylinder is so great, it combust the air fuel mixture before the spark plug (for gasoline powered engine) can fire. This is why turbocharge engine mandate the use of higher octane fuel to minimize or even eliminate knocking from pressure. In modern engine, onboard computers have the ability to detect and prevent knocking by decreasing efficiency by retarding the ignition timing which also makes the engine produces less power. The one thing about engine knocking, especially on turbocharged engine is that with increased engine rotation, as power is demanded by the user, the temperature and pressure inside the engine increases. One way to alleviate this issue is to enriching air fuel mixture, by simply adding more fuel into the cylinder that acts partly as coolant to reduce temperature. For naturally aspirated engine, simply by having lower pressure and temperature inside the cylinder, they can rev higher, produce more power at the higher rotation engine speed and with using less fuel than turbocharged engine.
The use of turbocharged engine in modern cars for efficiency involves the dual nature of the engine equipped with turbochargers. In the simplest term, turbocharged engine feels like two engine in one, a small displacement engine, and a bigger one. Turbocharged engine does not force air all the time, instead it operates in two scenario just like traditional combustion engine, low load and high load. At low load scenario, for example driving at cruising legal speed on highway, the engine literally operates close to naturally aspirated engine with the turbocharger working in an off boost fashion . For example in our topic is Toyota Raize engine, at low load scenario it operates like any three cylinder 1.0L engine. Compared to Honda WR-V engine at low load scenario as it is a four cylinder 1.5L engine, the Toyota engine offers technical efficiency based on physics alone.
However, one does not simply drive a car only on low load scenario, which is cruising speed unobstructed on highway alone. The combination of low and high load scenario like stop and go driving in city, complete with traffic jam and having to speed up to pass another driver means that turbocharged engine is always on boost at any typical driving condition. The ideal way to drive small displacement turbo engine cars like Raize is to drive slow, with the occasional half open throttle to pass a car only. This is how small turbocharged engine is intended to be used, as the engineers wants the user to revert to off boost and low load scenario immediately to reap the benefit of efficiency from a small displacement turbo.
I can already imagine if I post this content on youtube, every Raize owner probably already typing angry about how their car makes more power early and everything well… Thing is…
Yes, Toyota Raize makes torque early but that’s during on boost condition at high load scenario. At off boost low load scenario, Raize engine still needs to spin up and makes torque similar to Honda’s larger engine. Also, at the end of the day, Honda WR-V engine simply makes higher power. The debate for horsepower vs torque is tale as old of time. Yes horsepower figure is calculated from torque x RPM divided by a constant, or simply power is the function of applying torque. So both is important, one cannot do without the other. The only thing that matters is application of torque and horsepower. You want to move things a lot? Then look for high torque figure, you want to go fast? Look for power figure.
At the end of the day, Honda WR-V and Toyota Raize are both good cars on their own right. A compact SUV that delivers results in a different way. Honda going traditional with naturally aspirated “large” internal combustion engine and Toyota going with turbocharged small block internal combustion engine. The use of turbocharge engine allows for Toyota Raize to offer slightly gusty performance on slow to medium speed, and when somebody can utilize hypermiling technique, potentially delivers a more efficient fuel consumption. Honda WR-V simply decimates Toyota Raize at all driving condition but at higher fuel consumption as it makes more power. Can I get good fuel consumption from WR-V, possibly, but it will be easier to do so on Raize. Just pick what you like, nobody dictates your life.