The Turbocharger – Boosting Performance of a Car Near You

By Kevin Gordon

12.23.2008

Cut away Garrett Turbo

Of all the things about cars, including those things in and on them, my favorite part is the turbocharger. The name could have come from a toddler – albeit a smarter one than the inventor of the name supercharger – this device’s potential is all grown up. Also known as a turbo for short, this exhaust gas powered compressor can turn an ordinary car into an extraordinary car. In today’s automotive marketplace it appears as if this technology has gathered strong and steady support. Over twenty manufactures use them in their vehicles. To clarify, this is cars and SUVs, sold in the U.S., and does not include diesels.

I am guessing that you are saying to yourself. “Big deal; a lot of cars have “turbos.” What’s the point?” Well, the turbocharger can have benefits beyond free extra power from your engine.  The benefits range from the ability for manufacturers to use a single engine model across a variety of model lines (without the penalty of bloated and underpowered models), smaller engine displacements, less weight, increased fuel economy, and most important to the automotive enthusiast, easy end-user tuning.

For the uninitiated, turbochargers are a type of forced induction. Please understand, I do not intend to write a complete and/or detailed explanation of how a turbocharged engine, but a quick description seemed valuable. Turbochargers take incoming air, compress it to levels higher than atmospheric pressure, and force additional air and fuel into each combustion cycle of an engine. This compressed air volume is generally referred to as boost. In order to compress the incoming air, the exhaust gas of a car’s engine is used to turn a turbine or impeller, which in turn spins a compressor wheel. This compressor wheel draws incoming air from the intake and passes it into the intake manifold. Since the power output of an engine is ultimately determined by how much, and how efficiently, air and fuel is burned, turbochargers can allow a smaller engines to perform like larger engines.

This is not a new concept. The idea of compressing the air that is entering the motor is almost as old as the four cycle combustion engine. The first working example of a supercharger can be traced back to 1885. The idea of using exhaust gas to turn a compressor dates back to 1905, and turbos frequently appeared on large diesel motors in the 1920s. Still, there is no greater example of what could be accomplished with a turbocharger than the Offenhauser Indy cars of the 60’s and 70’s. These cars often exceeded 1200hp from their small displacement four cylinder motors, in the 1970s.

OK. Enough history, back to the present day. When I noticed this trend, I had in it my head that there were a large number of cars that contained turbocharged engines, but after a little research I was shocked with the raw numbers. Twenty-one manufacturers, not including those I would consider exotic manufacturers, use turbochargers, or will in the very near future. From these manufacturers over 50 different models. The chart below contains current, and some of the future models that have a turbocharged motor on their options list:

Manufacturer Model(s)
Acura RDX
Audi A3, A4, A5, TT, TTS
BMW 1 Series, 3 Series, 5 Series, 7 Series, X5 (f), X6, Z4 (f)
Chevrolet Cobalt SS, HHR SS
Chrysler PT Cruiser
Dodge Caliber SRT4
Ford Mustang (f), Edge (f), Flex (f)
Hyundai Genesis Coupe
Lincoln MKS (f)
Mazda CX-7, MAZDASPEED MAZDA3
Mercedes 600 Series, 65 Series
MINI Cooper, Cooper Clubman
Mitsubishi Lancer Ralliart, Lancer Evolution
Nissan GT-R
Pontiac Solstice GXP
Porsche 911, Cayenne Turbo
Saab 9-3, 9-5
Saturn Sky Redline
Subaru Forester, Impreza WRX, Impreza STI, Legacy, Outback
Volkswagen CC, Eos, GLI, GTI, Jetta, Passat, Tiguan
Volvo C30, C70, S40, S60, S80, V70, XC70

*(f) – A future model

Audi 2.0T FSI

Many manufacturers use small four cylinder turbocharged engines to power a large variety of models. The best example of this is Volkswagen. They have taken their marvel of a motor, the 2.0T FSI, and placed it all over their, and Audi’s product line. This motor provides copious amounts of early-arriving torque, returns more miles per gallon compared to its naturally aspirated competition, and has proven bulletproof when being tuned to over 380 horsepower. This motor is in eleven different models, and is so capable that there are rumors that they keep it down in horsepower in order to charge more money for V6 models. Want an example? Drive a 2.0T Audi A4 back-to-back with the V6 A4. In day-to-day driving it is tough to justify the premium for the V6.

In 2007, BMW released their 3.0 liter twin-turbo motor in the 3-series coupe. This motor had the automotive press claiming that the M division had just made themselves obsolete. Early reports were that BMWs with this motor installed were severely underrated. BMW underrated their performance not only in horsepower, but in factory claimed performance benchmarks. The 335i coupe outperformed every M3 that came before it; at least it would in a straight line. Since that time, this wünderbar engine has found its way into the 1-series, 5-series, the X6, and in the near future, the X5 and Z4.  It is true; manufacturers have been using the same engine across product lines for as long as the car has existed. But now, using these turbocharged motors provide no penalty when they end up in larger and higher-end models. I remember driving a 3.0 liter naturally aspirated 5-series a few years ago, and while its dynamic characteristics were good, I could not stop thinking that it was an underpowered car for the price. Recently, I had the chance to drive a 535i, with the twin-turbo motor, and I could not stop wondering why anyone would buy the 550i with a V8.

Cut away version of the 335 motorThere has been some technological advancement that has allowed for this surge in counts of turbocharged cars. First, the actual turbochargers have become far more advanced. Today, many modern turbochargers have the ability to change the angle of their impeller blades, or have a special valve to increase the velocity of the incoming gas when the volume of that gas is low. Other interesting techniques have been used as well. Take the twin-turbo BMW motor I referenced earlier; it has two small turbos, and each one boosts three cylinders independently. This is important because turbochargers are driven by the exhaust gas of your car, and as a result it takes a significant volume and velocity to spin at a rate that causes boost. The second major advancement, variable valve timing, has become commonplace. Remember when you used to see the term VTEC on Hondas and it meant something special? Today, this ability to vary how long valves are open during a combustion cycle is almost ubiquitous. This capability has drastically improved torque while maintaining top-end horsepower. Finally, the introduction of direct injection – the ability to directly spray fuel into the cylinder – has allowed for cars to keep relatively high compression and much improved fuel economy. These three advancements have moved the turbocharger to the mainstream.

This trend does not appear to be slowing down. Ford has been working on their EcoBoost V6 since 2002. Despite the name, the last time gas was this cheap was… well I think you get the point. This motor takes the basic block from a run of the mill Ford V6, adds two Honeywell turbochargers, and the result is the modern short block motor for the masses. The quick statistics:

  • 340 HP – 340 Ft/Lbs of torque
  • 20% Fuel savings over a comparably powered V8
  • Significant weight savings over its V8 counterparts
  • A cost difference of only $700 compared to similar non-boosted V6s
  • A true differentiator for those many mid-size SUVs and minivans that clog the marketplace

The final favorite thing, about my favorite thing, is the easily accessible extra horsepower. Most turbocharged cars are built with industry accountants constantly beating the engineers with sticks in order to keep warranty costs down. This results in most turbocharged cars have quite a bit in reserve from the factory. Earlier, I mentioned that the VW 2.0T FSI motor can reliably produce 380hp with some modifications. You’ll notice I did not say that the transmission, clutch, or half shafts reliably deal with this much power. Well, 380hp may require some more drastic changes than the average driveway mechanic can manage, but 50-60hp gains can easily be had with only changes to the car’s brain. Either replacement Electronic Control Units (ECUs), or piggy back control units modify the way the car thinks about what is going on, and generally allow it to run more boost and make more horsepower and torque.

That is not where the fun ends. Some of these programming changes will allow you to take a car that only ran on premium fuel and run it on regular gas. Even though it will run on the cheap stuff it will still make the same power that your car had when it came from the factory. Others allow you to control which settings you would like based on conditions. I have had the opportunity to own one of the turbocharged Subarus, and COBB tuning completely changed the character of the car. Not only was it a beast, its driving characteristics were remarkably improved. In early versions of this motor, there was an odd fluttering of power as boost was applied. COBB tuning not only fixed that, but if you drove the car like a normal human being, the gas mileage improved.

In this world of attempting to squeeze every last bit out of power out of a drop of fuel, technologies like turbochargers can only help. The real benefit is the ability to keep the fun in motoring while keeping the dirty hippie environmentalists at bay. I say, the next time you’re out shopping for a new car, look for one with a turbo attached to the intake. No matter your automotive priority, boost makes everything a little better.

COPYRIGHT Autosavant – All Rights Reserved

Author: Kevin Gordon

Kevin is Autosavant's owner and Editor-in-Chief, responsible for setting the overall strategy and editorial direction of Autosavant. He's also the primary contributor to Autosavant's YouTube channel (youtube.com/autosavant) where you can find a comprehensive library of new-car reviews.

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5 Comments

  1. You can view a turbocharged engine as a variable displacement engine. When the turbo boosts the intake pressure more gas can be sent into the cylinder as if it is a bigger cylinder. There are two problems to be observed. Turbos introduce durability issues because you have higher pressures and forces that would not normally be there on a naturally aspirated engine. Second, the gas consumption can be higher if you use the turbo boost a lot. The driver has a larger range of engine “displacement” but if higher boost is used – the gas consumption goes up!

  2. I’ve driven vehicles with a few of the engines you have mentioned, and it’s AMAZING how different they feel from the turbos of yore (like the 1988 Grand Am I owned, that blew a hole in its block during college…oops). But anyway, the BMW 3.0 TT six, GM 2.0 DI Turbo, and VW 2.0T FSI are all outstanding engines with great responsiveness and fuel economy. The BMW engine in particular (in a six speed manual 135i coupe) could pull strongly in any gear – even better than a V8 probably would. What a sweetheart of an engine…

  3. I think part of the problem is that the concept of the turbo-supercharger is largely malleable in Western culture. A lot of “non-car-people” can guess that the word “turbo” indicates something faster, because the word has been applied in capital letters on everything from computers to men’s razors, and even intangible things like internet service. And thanks to advancements in technology and materials engineering, those same people probably wouldn’t be able to tell you if they had a turbo or supercharger under the hood of their own cars. That’s great and all, but it doesn’t give people the total picture about why forced induction is so awesome.

    Now that the integration between forced induction and the internal combustion engine has become more seamless, NOW is the time to kick out a memorable marketing campaign, something that tells people the ways in which a turbocharged engine is better than a naturally aspirated mill of the same size.

  4. Dave, Thanks for the comment.

    It may be true that durability issues could arise from the added pressures of turbocharging, but modern turbocharged cars have computers controlling the total amount of pressure/boost available to the engine. Fundamentally, there is only so much squish allowed inside the cylinder (AKA compression ratio) and today’s turbo charged cars monitor all of the variables so instantaneously, they keep everything in safe ranges.

    To your point about fuel economy, you are absolutely correct. More boost, more fuel. But, fuel economy of these cars comes down to how you drive them. A good example is the motor in the Civic Si vs. the VW motor referenced in the article. Both engines make comparable horsepower. The EPA estimates that the Civic returns 24mpg (combined cycle), a VW GTI, 24mpg (combined cycle), all while weighing almost a 1000 pounds less than the VW. So the naturally aspirated car requires (about) the same amount of fuel to make 200hp, while giving up 68 ft/lbs of torque.

  5. I am not a believer.When I sold Isusu turbos in the 80s I don’t think one ever lasted 100,000 miles,40 was more normal.Yes,they are better now but will they last 250,000 miles?I have seen fours from nissan and toyota last this long without a rebuild.The new 2.4 ecotec from G.M. looks like a good engine with gdi and 182h.p. and 175torque in a cobalt will give much superior mpg to the VW, be cheaper,simpler,and I think longer lasting.

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