Turning to Turbo
March 28, 2008

By Kate McLeod

The clock is ticking loudly toward 2011. That's when Corporate Average Fuel Economy (CAFE) regulations will mandate increased miles per gallon for light trucks and passenger cars.

We know automakers are working all the angles to meet these new higher fuel economy goals. Diesels are tough because Detroit doesn’t make them and the Japanese don’t like them — although diesels that comply with 50-state regulations promise to be on sale later this year.

Hybrids have proven they work, but they are a costly solution to the problem. There’s a third option: the turbo-charged gasoline engine. It is cheaper than diesels — which are themselves all turbocharged — or hybrids.

Welcome Back, Turbo
Turbos use exhaust gases to turn a compressor that pumps a greater volume of air to the engine's intake manifold. Increasing the density of the intake charge allows the engine to burn more fuel, boosting power and torque. A turbocharger can temporarily cause a smaller, more fuel-eficient engine to act larger when needed, usually during acceleration or to sustain higher speeds.

This technology is relatively cheap and proven. In the 1970s, many manufacturers sold cars with turbocharged engines, including BMW, Porsche, Buick, Mercedes, Saab, Ford and Audi. Ford and GM turned to "downsized" turbocharged engines during the gas crunch in the '70s. Chrysler became a big manufacturer of turbocharged engines in the '80s. But when gasoline once again became cheap and plentiful, the turbo’s popularity faded.

“Turbochargers combined with engine downsizing seems to be one of the strategies that OEMs are considering to get fuel economy,” said Paul Lacy, manager of technical research for Global Insight, an international consulting firm. “We will see turbo penetration jump over the next 10 years and almost double in the next six to eight years.”

Ford has already announced its Ecoboost program. The first Ecoboost engine, a 3.5-liter twin-turbocharged V6, will be in the 2009 Lincoln MKS. It will produce the power and torque of a V8 with the fuel efficiency of a V6. Ford boasts the engine’s estimated 340-horsepower and more than 340 lb.-ft. of torque will make the MKS the most powerful and fuel-efficient all-wheel-drive luxury sedan in the market.

General Motors, which is backing off the development of a new premium V8, is most likely going to announce a similar commitment to turbo with its 3.6-liter V6.

Turbo-diesel vs. Turbo-gas
The turbo market is really two markets: the more-costly but longer-lasting diesels, which will be sold in larger numbers in the U.S. from model year 2009, and the growing wave of gasoline engines that use turbos to mimic the power of a larger engine.

Said George Peterson, president of automotive consultant AutoPacific, “People still think they should hate diesels but very few people in America have experienced the modern diesels. When they drive them they will start to think maybe they should like diesels.”

“Automakers have met the 50-state (emissions) regulations for diesel,” said Michael Timmerman, vice president of communications for turbocharger manufacturer Honeywell, “so you’re going to see diesels coming into the U.S. market. But, you’re also going to see a lot more gasoline engines boosted by one or two turbos. Turbocharging engines will help manufacturers with fuel economy, weight and emissions. It’s a practical solution to have a V6 rather than a V8.”

Turbo-enhanced diesel gives excellent performance (un-turbocharged diesels rev too slowly) with a 20 to 40 percent increase in fuel economy; turbo-boosting gasoline engines will get more power out of a smaller engine. Downsizing the engine and injecting fuel right when it is needed results in a 10 to 15 percent savings in fuel.

Turbos used to suffer from turbo lag: you’d hit the accelerator and not much would happen for a long second, until the greater rush of exhaust gas could begin to spin the turbocharger's compressor in earnest. Today, lag is barely perceptible because advanced components that quickly get the compressor up to speed and the use of clever twin-turbo designs; the average driver is unlikely to notice much delay.

Honeywell has seen its turbo business steadily grow since the 1990s when Europe turned to diesel. “Business grew 10 to 15 percent throughout the '90s in Europe,” said Timmerman. “If the same growth happens in the U.S. that happened in Europe during the last decade, we can ramp up to meet demand. In the U.S. it will be on both fronts — diesel and gasoline.”

Turbo, Timmerman said, is easily applied to smaller engines. “You can use turbo boosting on any engine that has an internal combustion system. In Europe, Toyota sells a turbo-diesel version of the Yaris which gets about 52 miles to the gallon and Smart used turbo to boost a 700cc engine. If Tata brings out the Nano, part of the plan is to introduce a diesel version. It works well on small engines.

"Take the Prius as an example: I have no idea if Toyota plans to use turbo, but if you took the regular 1.5-liter engine with an electric motor — that is the kind of thing that would be ideal to boost.

“We’re talking to some manufacturers about doing a hybrid diesel that will get a projected 70 to 80 miles per gallon. The technology keeps getting better. And if you consider weight, a turbo weighs a lot less than a big (hybrid) battery pack.”

He says total global production of automotive turbochargers last year was about 18 million units.

What will it cost the consumer to save fuel? It’s tough to tell,” said Peterson, “because of the way people are pricing these things so far. Battery and diesel are substantially more expensive than a modern turbocharged (gasoline) engine, but it is hard to tell how much. Toyota, so far, is eating the cost of the batteries in their hybrids. I would speculate around $3,000 for a hybrid and $5,000 with all the technology necessary to meet emissions standards for diesel. I thought diesel and hybrid would be about even but I think diesel is more.”

Turbocharged engines may save manufacturers money, but they still typically require the engine to use premium fuel. Consumers could see those 10 to 20 percent gains in fuel economy fade away in actual fuel-cost per gallon, which is between 20 and 40 cents higher with premium, depending on various factors.

Kate McLeod is a New York City-based writer and frequent contributor to Edmunds' AutoObserver.

Photos from Honeywell
1 — Turbocharger undergoing testing on a test stand.
2 — Cutaway view of a turbocharger.

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