Engine-Rating Rip-Up

The Society of Automotive Engineers announces at its annual World Congress last month significant new updates to improve the accuracy of the test standard auto makers have used for more than 30 years to rate the power and torque of light-vehicle engines in North America.

Equally important, the SAE also is introducing an all-new, voluntary test procedure designed to ensure power figures derived from the new standard are more reliable and common across the industry.

David Lancaster, General Motors Corp. technical fellow-GM Powertrain, and chairman of the SAE committee responsible for revising the standards, says engines tested under the new 2-stage system will list horsepower and torque figures with a new qualifier: SAE “Certified.”

Since 1971, engine horsepower ratings have been published by auto makers as “SAE net.” Lancaster says the “old” SAE standard that set forth the procedures for measuring horsepower — J1349 — has been updated to “remove ambiguity” in its language that left certain loopholes that could be exploited to exaggerate engine power.

In some past cases, manufacturers have taken advantage of J1349's loopholes to generate horsepower ratings that could be achieved under the rarefied conditions of an ideal testing environment — but were unlikely to be replicated in the real world.

Last August, the SAE finalized an updated version of J1349 that more precisely defines certain engine-operation parameters used when testing an engine to rate its horsepower and torque.

These stricter definitions, Lancaster says, close J1349's loopholes and ensure “a realistic condition the customer will actually see in the vehicle.”

In concert with the updates to the J1349 engine-testing standard comes an important new component: a voluntary test procedure — witnessed by an independent third party — that must be undertaken to earn the new “Certified” rating. The voluntary certification test — SAE standard J2723 — was finalized March 31.

GM says it has the world's first production engine to bear the SAE “Certified” label for its horsepower and torque figures: the all-new LS7, a 7L OHV V-8 that powers the ultra-high-performance Corvette Z06 coming later this year.

It is unclear, however, how many manufacturers will perform the voluntary new J2723 certification test, or if they do, what strategy will apply for selecting which engines in an auto maker's existing powertrain portfolio will be selected to undergo the certification process.

GM, for one, is intensely committed.

“Within a couple of years, the vast majority of our engines will be SAE certified,” says Lancaster.

Ford Motor Co. participated in the committee that updated the J1349 standard, and Frank Sadni, Ford director of V-engine engineering, and Jerry Beamer, Ford engine performance development manager, say Ford is testing a variety of '06 model engines in compliance with the new J1349 standard, but currently has no plans to put engines through the voluntary J2723 certification test. Ford, Beamer says, “is confident that our (internal) process for rating engines is very robust,” and sees no need to have horsepower and torque figures verified by a third party.

Rating engines with the newly revised J1349 could cut at least a few horsepower from an engine's current rating. The new J1349 standard “says you have to (test the engine with) the same hardware that's in the vehicle,” says Lancaster. That means, among other things, the hydraulic power steering pump now must be attached to the test engine — usually at the cost of a couple horsepower.

For that reason, most auto makers are likely to continue to publish ratings for existing engines derived via the “old” J1349 standard whenever practicable.

“When J1349 was originally written, we were running with carburetors and (mechanical) distributors,” says Lancaster. And, he adds, “the standard never said the intent (of J1349) was to give a customer a representative number. Having good, solid (engine power and torque) numbers provides a lot of benefit to us in the industry.”