Little Boost: Why automakers are going for small gas turbo engines
Small engine, big output. Is that good?
I heard the term 'turbo boost' for the first time in the 80s TV show ‘Knight Rider’. Pardon the super ‘tito’ moment, but that is the truth. You can Google what the show is, or I can simply tell you. It was mainly about a highly advanced 1982 Pontiac Trans Am that was like the James Bond of sports cars and could go extremely fast using its, you guessed it, turbo boost function.
In real life, that sports car came with a naturally-aspirated 5.0L V8 engine that sent it from 0-100 km/h in 12.2 seconds. In its role as a TV super car, it used a “turbo” that let it accelerate from 0–100 km/h in just 2 seconds. Of course, whoever wrote that in did not seem to know what a turbocharger is; from the description, they were probably thinking of nitrous.
Tito moment over, what is a turbo? And why do we see so many in tiny gasoline engines doing the job of larger four, six, or even eight-cylinder mills?
The Humble Turbine
The turbocharger is nothing but an air compressor hooked up to both your exhaust and your intake system. It uses a vehicle's exhaust gas to spin a turbine which in turn drives the compressor. It's like using waste to give you more power.
The air sucked in is converted into a high-pressure, low-velocity stream and pushed into the engine, forcing it to burn more fuel and make more power. That is why it is also known as 'forced induction.'
For curious minds wondering why diesel engines almost always have a turbo, the reason is that a turbo minimizes the disadvantages of a diesel. Those engines have low power, but high torque. A turbo allows for more power, giving the vehicle the best of both.
If you have ever heard the term supercharger, it is just like a turbo but instead of using exhaust gases, it has a belt that takes power from the crankshaft to turn the compressor, which then does the same thing a plain turbo would do. The difference here is that where turbos typically have lag and then a kick-in boost, a supercharger is smoother all the way because it is belt-driven. In mechanical terms, a supercharger is typically more complex (and costly) to install than a turbocharger, and that's why more manufacturers use turbos.
Combined with an intercooler (to lower the temperature of the air when it passes through a hot turbine), turbochargers and superchargers allow all kinds of engines to produce more power.
Small Gasoline Engine + Turbo: The Perfect Formula?
Now that we clarified what a turbo is, we can now get into the nitty-gritty: why are more carmakers using small turbo gasoline engines with low displacement and fewer cylinders in place of larger engines with more cylinders?
The answers are many, but relatively clear: technology, weight, emissions, efficiency, and cost-effectiveness.
Due to its lightweight properties and efficiency, automakers are turbocharging three-cylinder engines for use on multiple platforms, and Ford actually led the way early on. The EcoBoost system has gained worldwide recognition for how small it has gone without sacrificing performance. Both have a 1.0-liter three-cylinder turbo engine version used in subcompact models and other turbocharged engine sizes ranging from 1.4-liter to 2.0-liter for compact sedans and crossovers.
In the right vehicle segment, reducing the number of cylinders improves fuel economy and decreases CO2 emissions. But this comes at the cost of lower power output. Using a turbocharger fixes this problem.
A turbocharger, assuming all things are equal, will theoretically add 50% more power to your engine. How? Your naturally-aspirated engine gets 14.7 PSI (pounds per square inch) of air pressure at sea level. If you add a regular turbo, which has an average boost of about 6-8 PSI, that’s about 50% more pressure to push 50% more air and gas to the engine for 50% more power.
I’m sure by now, either you own one or have ridden in one, and chances are, you wondering what other pros there are on turbocharging a small engine, especially three-cylinder models, and if there are any disadvantages.
One of the biggest concerns about this setup is ‘turbo lag’. In old turbos, this is the delay before the power kicks in as pressure builds up to spin the turbine. Today, with better turbo technology and lighter materials, lag has been all but eliminated. Smaller turbos also spool up much faster. These are the types used by today’s compact vehicles to get rid of lag and properly power their downsized engines.
While the knock on 70s-era three-piston engines was the palpable amount of vibration, you’ll barely feel it today because of modern equipment and design. Engines with an odd number of cylinders (e.g. 3 or 5) tend to have vibration because the movement of one cylinder isn't being canceled by an opposing cylinder. To mitigate this, some automakers use a balancer shaft that adds weight to the vehicle but cancels out unbalanced forces by rotating in the opposite direction. Ford avoids the encumbrance by designing an unbalanced flywheel and pulley system that shifts the vibration to a transverse orientation for better absorption by the engine mounts. Some even use enhanced engine mounts to minimize vibrations transferred to the engine.
The only question left now is, can these small engines take the mechanical stress created by the turbocharger that forces them to make more power? Short answer, yes. All engines undergo the same design simulation and optimization before getting cast in aluminum. After that, the prototype spends countless hours of testing before being green-lit for production. The last step before installation, all engines must pass the rigorous final endurance and durability testing under the most extreme conditions. That’s why out of the 78 million vehicles sold every year, only an average of 150,000 are lemons (not all of them are even engine problems). That’s less than 1% of the total global auto sales.
Which Cars Use Small Gas Turbo Engines?
Aside from Ford and General Motors, many other marques have turned to turbocharging to reduce their carbon footprint and fuel consumption. Chinese auto brand Geely has five small-displacement turbo engines called G-Power. Four are gasoline, one is diesel, but all are under 2.0 liters.
Japanese automakers are following suit. From the compact Nissan Almera with its 1.0-liter turbo mill to Honda’s executive-sized Accord that uses a 1.5L Earth Dreams Technology VTEC turbo banger, unlike that Alphaville song, these engines are not ‘big in Japan’ anymore.
Ford didn’t stop with their compact cars and crossovers either. Their mid-sized SUVs and even muscle cars have all been ‘ecoboosted’ with engine sizes ranging from the Mustang’s 2.3L EcoBoost to the Explorer’s 3.5L EcoBoost.
This new trend isn’t exclusive to mass-market vehicles as well. Audi has a 2.0-liter engine on the A3, Mercedes-Benz has a similar one in the A220, and Mini’s Clubman S also uses the same size engine.
Sports cars are in on it too. Fiat’s 124 Spider comes with a 1.4-liter turbo engine, Kia gave the Stinger a turbo-and-intercooled 2.0-liter banger, and the Alfa Romeo 4C went small with a 1.7-liter engine. Even Ferrari went this route decades ago. Remember the F40 with its 2.9-liter engine or the much older 308 GTB using a 2.0-liter?
Future: Downsized Engine + Turbo + Hybrid
You know what they say, the future is now, which is why even the pinnacle of motorsports, Formula 1 has embraced the change. In 2014, all F1 cars dumped their big V8s for 1.6-liter V6 engines. It uses a hybrid turbocharger (also known as an e-turbo) and a couple of electric motors. One takes kinetic energy from the brakes while the other is takes excess heat from the exhaust and stores it in a battery for later use.
What makes it special? Instead of using the exhaust gasses, the hybrid turbo takes one of its two motors and uses it to spin the turbine up to speed creating an instant boost.
Turbo makers have been espousing this idea for years. The auto industry's first electric turbo made by Garrett Motion actually won an award last year, and competitor Borg-Warner also has a similar electrically driven compressor called the eBooster.
Pretty soon, it will not be a pipe dream anymore as you will see this technology in ordinary passenger vehicles.
Conclusion
Today you’ll find a downsized turbo engine in just about every vehicle category from subcompacts, sedans, crossovers, trucks, and on all sizes of SUVs. It is partly due to government pressure on automakers to boost Corporate Average Fuel Economy (CAFE) to an average of 19 km/l by 2025. Quite a tall order because on these engines right now, we’re only at 10-12 km/l at best.
Small-displacement engines, especially the three-pot type, aren’t what they used to be and neither are today’s turbochargers. Thanks to modern tech and raw materials, both are vastly improved to address the demand for higher efficiency and reduced emissions while keeping the vehicle’s performance at par with customers’ expectations.
If you’re still on the fence about getting a vehicle with this setup, go for it. See how you’ll save more gas money and be more environmentally friendly too. Just don’t expect super car-level performance because your ride isn’t KITT, and you’re no Michael Knight.
