Due to stricter emission norms and demand for more power and higher fuel efficiency, the automotive world continues to move away from naturally aspirated engines.
With naturally aspirated engines becoming rarer, the number of turbocharged gasoline engines is increasing by the day. And we are not talking about two or three-liter engines, but small-capacity turbo engines that are used in Hot Hatches and compact sedans.
Before we get to the ‘perils’ of small-capacity turbocharged gasoline engines, let’s understand why they are becoming so popular and why almost every auto manufacturer is spending millions on R&D to refine their turbocharged gasoline engines.
It’s the Need of the Hour
With stricter emission norms and the environmental impact of internal combustion engines, downsizing has become the need of the hour. That is the reason why car manufacturers are replacing their large-capacity naturally aspirated engines with smaller turbocharged engines.
As they say, “there’s no replacement for displacement”, but modern technology has found a way to churn out similar or higher power figures from a smaller turbocharged engine as compared to their naturally aspirated counterparts. The loss of displacement is compensated by adding a turbocharger.
To give you a perspective, a 1.2L 4-cylinder naturally aspirated engine can produce 80-90 bhp and 110-120 NM of torque. On the other hand, a 1.0L 3-cylinder turbocharged engine is capable of delivering up to 120 bhp and 170 NM of torque. The difference is staggering, and hence explains the radical shift from NA to turbocharged engines.
The benefits of small-capacity turbocharged engines are significant. You get a power boost in the mid-range, which will definitely put a wide grin on your face. Plus you get better fuel economy, provided that you don’t drive beyond 3000 RPM. However, the low-end is not that great until the turbo spools up.
On the surface, a small turbocharged engine is all bells and whistles, and it might give you cheap thrills in the initial years. But it has certain downsides, like everything else in the world.
First off, these are 3-cylinder engines, which means balancing is going to be an issue. Although manufacturers are trying their best, it’s quite difficult to balance a 3-cylinder engine, which leads to cabin vibrations and the engine gets vocal as you go past 3000 RPM.
A turbocharger is an expensive and sensitive component. The turbines may get damaged if not handled properly during the service. If you or your mechanic breaks the turbocharger, it’s going to set you back by a couple of hundred dollars. Also, maintaining a turbocharged engine is expensive in general.
Turbocharged engines may give you overheating troubles down the road, especially if you are going hard on gas on the New Jersey I-95. Not only are you highly likely to get New Jersey traffic tickets for speeding, but the excessive heat might cause some serious damage under the hood. They may tell you that a turbocharged engine is fun to drive, but you can’t push it hard every day.
Small turbocharged engines have reliability concerns. They are less durable than their naturally aspirated counterparts; the reason being they are made to work harder and push beyond their physical limits by forcing extra air into the cylinder to produce more power. As a result, the pressure and temperature inside the cylinder are higher than in NA engines. Although manufacturers are making every effort possible to make small turbocharged engines as robust and reliable as possible, that often leads to higher manufacturing costs, which trickle down to the consumer.
That said, if you are going to buy a turbocharged gasoline engine, be ready to shell out extra dollars for the technology and the power boost.
On the other hand, naturally aspirated engines are more sought after among car enthusiasts and people who place reliability above performance.
High-performance turbocharged engines suffer more wear and tear if driven consistently at higher RPMs. Also, if you are not careful with the maintenance and drive your car beyond the service interval, you are knocking years off your engine’s life. We often hear about naturally aspirated engines clocking quarter or half a million miles. No big deal. But that may seem like an overarching dream with a turbocharged engine unless it is robustly built like a turbocharged diesel.
Inconsistent throttle response
Now, this is something that may require getting used to if you are buying a turbocharged vehicle for the first time. For example, the 3-cylinder 1L turbocharged engine performs like a regular 3-cylinder 1L engine until the turbo spools up, which is beyond 2000 RPM in most cases. As a result, the engine feels really dull and sluggish between 1000 – 2000 RPM. You will have to work the gearbox continuously to keep the RPM above 2000 in order to enjoy the power boost. This makes the throttle seem inconsistent, unlike the linear throttle response exhibited by a naturally aspirated engine.
Lower Fuel Efficiency
This may sound contrary to what turbocharged engines are designed to do. Of course, turbocharged engines offer better fuel economy when driven gently, but as soon as the turbo kicks in, the fuel economy goes out the window. Here’s a simple explanation for this peculiar behavior. Although small engines are more fuel-efficient, a turbocharger puts more pressure on the block, which leads to higher temperature and engine knock. To combat this issue, the engine must maintain a lower compression ratio, which means dumping more fuel to meet the power demand and maintain the necessary fuel-to-air mixture to protect the engine.
Inconsistent Torque Curve
A turbocharged engine has all the meat in the mid-range. For instance, a 1L turbocharged engine will drive like a 1L engine in the low end but performs like a 1.6 or 2L in the mid-range and 1L again in the top-end. On the other hand, a naturally aspirated engine pulls linearly from the low end to all the way up to the redline.
If you are planning to buy a small-capacity turbocharged petrol vehicle, keeping these points in mind will help you manage your expectations and make an informed buying decision.