WASHINGTON -- After years of touting ever higher horsepower numbers to win new customers, Toyota Motor Corp., Honda Motor Co. and possibly other automakers are now backtracking on some of those claims.
Strict new tests developed by the industry's top engineering group are prompting the carmakers to roll back horsepower estimates on several key vehicles, including the Toyota Camry, America's best-selling car, and Honda's luxurious Acura RL.
For the 2006 model year, Toyota says its Camry equipped with a 3-liter V-6 engine generates 190 horsepower. In 2005, Toyota said the same car with the same engine had 210 horsepower.
The revised ratings comply with new Society of Automotive Engineers standards designed to eliminate subjective interpretation in establishing horsepower claims.
While Toyota and Honda are retesting their entire vehicle lineups, other automakers generally are retesting only cars and trucks with updated powertrains.
Over time, most automakers are expected to comply with the new guidelines, and horsepower ratings for other vehicles could be revised.
Detroit's automakers say they have been conservative in calculating horsepower and don't expect to have to reduce horsepower ratings on many vehicles. In fact, after retesting, the Big Three have revised horsepower ratings upward on several vehicles.
The changes are likely to raise questions among customers.
"Horsepower is a big draw," said Jim Sanfilippo, an automotive marketing expert at AMCI Inc.
"This is at best difficult to explain," he added.
"Toyota and the other companies better have a good answer when customers ask questions about what happened."
The Camry has been a best-seller for years and a linchpin in Toyota's strategy to increase sales in North America.
Honda is reducing horsepower ratings across its Acura brand. The flagship RL sedan will lose 10 horsepower, to 290 from 300. The popular MDX SUV will fall from a rating of 265 to 253. Less powerful models such as the Honda Civic will see smaller reductions.
"From what we've seen so far, this is going to affect the Japanese and the Europeans a lot more than the domestic manufacturers," said Mark Brueggemann, senior market analyst for Kelley Blue Book.
Brueggemann said engines have not changed, so car shoppers won't notice any drop-off in performance during test drives. But consumers look at horsepower when they're deciding which models to test drive and buy.
For example, the 190-horsepower Camry will compete against a new Hyundai Sonata that advertises 235 horses under the hood. "This could have a possible effect of eliminating a car from consideration," he said.
The changes are already having an impact among die-hards who prowl Internet chat rooms like AutoWeek's Combustion Chamber, Edmunds Town Hall and GM Insidenews. In a recent posting on AutoWeek's site under the heading, "Acura hurt by new SAE hp standard -- numbers were inflated," one chatter said: "Bottom line is if you sell me a car with the promise of say 300 hp, I want my 300 hp!"
Toyota had to advertise based on the new SAE testing procedures because of a California state law, said company spokesman Bill Kwong. The company then decided to use one set of ratings for all of its U.S. ads.
"We hope it won't be confusing," Kwong said. "If you drive a 2006 or 2005, it drives the same. It's the same car. Customers are not getting anything less or anything more."
Honda spokesman Mike Spencer predicted it would take a few years for customers to understand the changes, but eventually all manufacturers will be using the new SAE tests.
"We've been using SAE procedures all along, it's just that SAE changed their procedures," he said.
The news is better for General Motors Corp. and Ford Motor Co. Some models such as the Chevrolet Corvette and the Ford Fusion sedan are faring better under the new testing procedures, which could give them a much-needed edge in the marketplace.
The Cadillac STSV luxury sedan roadster with a Northstar engine saw its horsepower rating go from 440 to 469.
"We have confidence that our customers will get the power they pay for," said GM spokesman Thomas Read. "It's going to give the consumer a better rating for their engine."
As the new testing procedure is phased in, it may be tricky for consumers. For example, the Ford Five Hundred sedan is rated at 203 horsepower for 2006, the same as the 2005 model. But the 2006 rating does not reflect the new SAE testing procedure, because Ford is not going to the expense of retesting its existing engines, said company spokesman Nick Twork.
The company will use the new SAE test only when it overhauls a powertrain, as it did for next year's Explorer, Twork said.
But Twork said Ford does not expect significant drop-offs in horsepower as the new test is phased in. When Ford unveiled its midsize Fusion sedan in January, it projected 210 horsepower. When it was tested under SAE's official protocol, the engine received a 221 horsepower rating, Twork said.
"We typically like to underpromise and overdeliver," Twork said. "We feel we've been pretty conservative, and we don't anticipate any major changes."
DaimlerChrysler is using the new SAE procedures on any model with changes in its powertrain, said spokesman Cole Quinnell. He said the company expects new ratings to be within 3 percent of the old ratings, with some going up and some going down. DaimlerChrysler is making a special effort to test high-performance models, like the Dodge Viper V-10. The Viper now tests at 510 horsepower, up from 500 in 2005.
"We've wholeheartedly embraced the new procedures," Quinnell said. "We hope it shows our credibility."
When an engine doesn't measure up to its advertised performance, it can hurt. Mazda Motor Corp. reintroduced the rotary engine with its RX-8 sports coupe a few years ago. It had a high horsepower rating. But when drivers got inside, they discovered weak low-end torque, meaning that the rocket-like acceleration they'd expected was missing.
Ford pulled its high-performance Mustang Cobra from the market a few years ago when enthusiasts complained the engine did not live up to its billing. Ford tweaked the engine before selling it again.
SAE says it tightened its horsepower rules when engineers noticed some elements in the old test were prone to interpretation.
"We tried to tighten language that was open to interpretation," said Dave Lancaster, a technical fellow at General Motors Corp. who chaired the SAE committee that wrote the new requirements.
Under the old testing procedures, there were small factors that required a judgment call: how much oil was in the crankcase, how the engine controls were calibrated and whether a vehicle was tested with premium fuel. In some cases, the little adjustments added up to a big change in horsepower ratings. The new SAE procedures allow less wiggle room.
John Di Pietro, road test editor at Edmunds.com, said the drop in horsepower ratings for '06 models they have tested are not especially dramatic. For vehicles such as a midsize family sedan, the reputation of the manufacturer will likely be more important, Di Pietro said.
"It will be up to the salesman to ensure they understand the engine hasn't actually lost any power," he said.
Vehicle 2005 2006
Acura MDX 265 253
Acura RL 300 290
Acura RSX 160 155
Chevrolet Corvette LS7 500 505
Cadillac XLR 440 469
Ford Explorer* 210 210
Honda Civic 200 197
Lexus LS430 290 278
Pontiac G6 200 201
Toyota Corolla 130 126
Scion xB 108 103
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