Final Inspection

Turbos, Blowers and Real-World Fuel Economy


If the public gets the idea auto makers are trying to pull a fast one, it could cripple one of the hottest technologies in the automotive industry.

Just in case you hadn't noticed, auto makers around the world are jumping on the boosted engine bandwagon in a big way.

By replacing bigger engines with smaller ones, then boosting them to get the needed power, manufacturers are coming up with quick fuel-efficiency improvements. But they also are running into some real-world fuel-economy problems. More on this in a minute.

The market for turbochargers is growing so fast auto makers are encouraging more suppliers to get into the business. They don’t like it when a handful of companies dominate the global market for a critical technology.

Currently, the global turbo market for light-passenger vehicles largely is the domain of BorgWarner, Garrett (Honeywell) and IHI. But Continental and Bosch and Mahle have joined the fray. And yet there doesn’t seem to be any problems with too much capacity because demand is booming and will be for years to come.

Of course, turbochargers are not the only play in this game. Eaton’s superchargers are coming on strong, thanks to several innovations. Up until recently, superchargers mainly were on relatively large displacement V-6s and V-8s for high-performance cars. Not anymore.

Eaton now makes a tiny supercharger for the 1.2L Nissan Micra. It also has a supercharger on the hybrid version of the Nissan Pathfinder. And it will announce a diesel supercharger application for an unnamed OEM in the near future.

The knock against superchargers is that because they are belt-driven, they cause parasitic power losses on an engine. But Eaton is coming out with a clutched supercharger that only engages when needed, eliminating most of those losses. It’s also working on an electric supercharger that would need no belt at all.

So far, Eaton is the only player when it comes to mass-producing superchargers for passenger vehicles. But the OEMs will not tolerate that for long.

I’ve got to believe several purchasing departments are actively prodding other Tier 1 suppliers to start manufacturing superchargers.That would give them the leverage to hold the lid on prices just in case superchargers really strike the fancy of car buyers, thanks to the instant throttle response blowers provide.

A word of caution to those in the forced-induction world: In my experience, boosted engines smaller than 2.0L may deliver terrific fuel economy on dynos in the lab but are not so good in the real world.

Little engines simply must labor too hard to keep up with traffic, meaning you are in boost mode most of the time, and that kills fuel economy.

So far, consumers are enamored with the impressive mileage numbers they see on dealer showroom stickers, but prepare for a backlash if too many consumers are disappointed by what they actually achieve in everyday driving. Maybe some public education is in order, or maybe the OEMs need to keep real-world, not test-cycle calibration, at the forefront of their efforts.

If the public gets the idea auto makers are trying to pull a fast one, it could cripple one of the hottest technologies in the automotive industry.

John McElroy is editorial director of Blue Sky Productions and producer of “Autoline” for WTVS-Channel 56, Detroit, and “Autoline Daily,” the online video newscast.

Discuss this Blog Entry 9

on May 9, 2013

All passenger car diesels are turbo-charged and return amazing fuel consumption. There is no reason these days why a gasoline turbo shouldn't do the same especially with GDI. We have moved on since the turbos of the 1980s.

on May 10, 2013

I think the author is trying to convey that with all the new tech that is going around the OEM's, (turbo's, etc.), that will be targeted as issues with the EPA test cycle vs. real world fuel efficiency comes to a head. It will be the boosted cars that will be sacrificial lambs as real-world conditions will have them in boost more often than not. Let's face it, driving in boost is fun. The EPA test cycle probably does not have them in boost, or if they do, it's not for long. With lawsuits coming forth (Honda, Hyundai/Kia) over fuel economy complaints, it will be this generation of downsized, boosted motors that will unfortunately get blemished. That's what the article is truly saying or worried about.

Maybe the window sticker should give the fuel economy estimate but also mention, "if 8-12psi puts a smile on your face when you mash the pedal, your fuel economy will be between X and Y."

on May 10, 2013

Well said is228979. Most all the new gasoline GDI turbos are getting roasted by consumer activistsfor for disappointing real-world fuel economy. A very light foot is required to come close to advertised numbers and that spoils all the fun.

on May 10, 2013

That's very true. I think automakers should try to talk a bit more about being in boost, as the average consumer doesn't know how a turbocharger even works. A light foot is hard to come by when all it takes to smile is the distance from your foot to the floor.

But if I had a choice, I'd take the small diesel because I'd have the torque and efficiency, even when mashing the pedal.

on May 13, 2013

The article is a bit misleading IMO. Fuel economy is based on many factors, but most things being equal a turbo charged engine is more efficient making "X" hp than a similar engine which is normally aspirated. If a normally aspirated car gets better mileage in "real world" driving, it's because it makes less power than the turbo version (less power = better mpg...that's thermodynamics of an ICE). I love turbocharged cars because at least you have the OPTION of going fast while still getting decent fuel economy the remainder of the time.

on May 13, 2013

Again, I think it all goes back to the EPA test cycle at the end. Most of the gas savings on a turbocharged engine is in the design stage with the engine being made smaller and "lighter". A properly sized and tuned turbo will not be in 'boost' at low to mid-throttle. You could see improvements in fuel economy at anything under half-throttle, but there's so many other factors that are different between a forced-induction 2.0L and a NA 2.0L. The fuel maps/spark tables programed into the ECU are not the same between those 2 engines. Is the turbo engine using an intercooler to keep IAT's down? Could it be the ECU programming that gets the better fuel economy and not the turbo or smaller engine seperately? These cars can't possibly spend much time during the EPA test cycle in boost and let alone they run 100% gasoline.

The average consumer see "turbo" in a car ad, and they want to thrash it when they drive. The see the estimated EPA fuel economy numbers and they expect it 100% regardless. You can't have your cake and eat it too. You can get better mpg's when not in boost, but those gains will disappear in boost. It can't be apples to apples IMHO, as the average consumer will probably flog the turbo engine more than the NA engine just for the mere fact that they associate turbo with aggressive driving.

on Sep 3, 2013

Unless you're in city traffic most of the time, try a 2005 Camaro SS with a manual for fuel economy. You may be uncomfortably surprised.

on Aug 30, 2013

Forced induction is now light, reliable and presents zero drivability issues, plus it's more fuel efficient than natural aspiration and it can adapt to climate and altitude.

What I want to see is a credible study to compare 91 RON capable engines with engines that are purpose tuned to 93 or higher octane ratings. I think the oil industry should be compelled to quit 91 and move up to at least 93, maybe 95 as an across the board standard and forget altogether this nonsense of selling 87 and 89 as some sort of "savings" because they have "choice."

on Jan 28, 2017

"Forced induction is light/reliable/zero drivability issues/altitude compensated"...YES. "more fuel efficient"...NOT-NECESSARILY, sir.

The stupid trend, is not going turbocharged, but GOING TOO SMALL and then claiming real world fuel economy will be realized. There is a definite limit, a WEIGHT LIMIT.
As a long time driver, owner, DIY-maintainer and modifier of Turboed cars, I can attest that no amount of electronic wizardry can compensate for an excessively heavy car. Cases in point: the New Dodge Dart was equipped with a 1.4L Turbo engine, the other one is the Chevrolet Malibu Turbo 2.0L. I've driven both. Both are not only boring to drive, but fail to reach advertised fuel economy in daily driving by a large margin. We are at a very high location: 7360 Ft. asl AND at a warm, 25C temperature, so we have an effective pressure-altitude equivalent to more than 10,000 to 11,000 ft of altitude, thus we really put to good use turbocharged engines. Personally I've found that a 3,200 pound midsize 4-cyl Turbo sedan NEEDS at least a 2.3 liter engine, otherwise, forget to have both the "turbo" oomph AND the promised fuel economy. In order to fulfill both promises, that turbo car will need an extra system: Water or water methanol injection, as no amount of gimmicry or electronics will allow the needed boost level, and that is why Turbo engines from the 90's never achieved any real economy, because they had to resort to excessive gasoline injection to avoid detonation at higher boost levels and realistic octane number, as a proper intercooling demands unavailable space and cost allowances. Real-life turbos on smallish engines below that ratio of weight/displacement/boost become gas guzzlers when pressed to move a heavy sedan. And I'm sure of this because I've resorted to having to modify my 3 turbo cars, after finding that even in the 90's, the Factory did not produce the best balance, much less today, and that is by far. Amclaussen.

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What's Final Inspection?

WardsAuto editors share insights and observations on the global auto industry.


David E. Zoia

As Editorial Director, I oversee much of what goes into, enjoying a ringside seat that lets me observe up close just about every facet of the industry worldwide. I have covered the...

James M. Amend

James Amend is an associate editor at, covering day-to-day business and product news at General Motors. He also leads coverage of regulatory and environmental issues, as well as the...
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