cc to torque to hp Conversion Update!

Five years ago the power output of every snowblower sold here in the United States was measured in hp or horsepower. It was a nice simple measurement that everyone was used to.

Four years ago they changed the rules and started selling snowthrowers with the power measured in gross torque. Of course no one understood what this meant and even though companies like Briggs & Stratton tried to explain it, it still didn’t make much sense.

Then they changed the rules on us again.

So we just start to get used to measuring an engine’s output in torque and now for the 2009/2010 season a lot of the snow blower manufacturers are dropping the torque measurement and only giving us engine size in cc’s.

I spent a great deal of time researching this and I’m not going to spend time trying to explain why the engine manufactures have changed their terminology. Instead I’m just going to show you a formula you can use to figure it out yourself.

Here’s the formula I used from the Briggs & Stratton website (rpm x torque / 5,252) The engine manufacturer’s used 3600 rpm most of the time to rate the engine’s horsepower so I will use that number in the formula. I also used the torque ratings from the Briggs & Stratton website for their motors to keep this chart simple. Other manufactures (like Powermore) may have different torque ratings for their motors.

If you are trying to get exact hp measurements you should research the torque ratings for the specific brand.

1x1.trans cc to torque to hp Conversion Update!

For 2009/2010 MTD has dropped all torque ratings on snow throwers. The engines are only labeled in cc’s.

Here is a simple chart of approximate cc to torque to horsepower conversions. It’s not exact, but it will give you a better idea of how big the new engines are. I used 3600 rpm in the formula for this comparison. Assume that your new snowblower motoe runs at less rpm.
123 cc = 4 hp
179 cc = 5 hp
208 cc = 8 to 9 Gross Torque = 5.5 to 6 hp
277 cc = 11 to 11.5 Gross Torque = 7 to 8 hp
305 cc = 13.5 to 14.5 Gross Torque = 9 to 10 hp
342 cc = 15.5 to 16.5 Gross Torque = 11 to 12 hp
357 cc = 14 hp
420 cc = 15 hp

To me cc’s is not a good comparison from one motor to another. It is also not a good comparison from one manufacture to another. For example, a 190cc Briggs & Stratton side valve motor will not have the same power as a Honda 190cc overhead valve motor. cc’c don’t give you a good measurement of what the engine is capable of. True, an overhead valve motor from a specific manufacture should have more power with more cc’s but there are a lot of other factors that go into determining how much power is available for you to use. The true power of a motor is determined by engine type, (overhead valve/side valve) carburetor (naturally aspirated/fuel injected/turbo) rpm you use it at (2750/3100/3650) and many other factors. I hope this helps.

Here is an explanation of torque from Briggs & Stratton

Explanation of Torque from B&S

 

Here is an original article on this issue:
Horsepower loses its grip on mowers. In terms of engines, talk turns to torque
By Rick Barrett
McClatchy Tribune
Published on: 02/23/08

When you buy lawn and garden equipment this spring, a familiar old term —- horsepower —- will be missing from many engines.

Blame it on lawyers, or engine makers who might have fudged the numbers, but horsepower is no longer the gold standard for small gasoline engines.

Sears, for example, advertises some lawn mowers rated by horsepower, others by torque, and still others by cubic centimeters. And some mowers have no such designation at all.

“Unfortunately, we are not giving consumers the answers they want,” said Bill Rotter, an owner of National Ace Hardware stores in the Milwaukee area.

There’s no longer a horsepower rating for many Briggs & Stratton engines. Last year, Briggs chose torque as its rating system for push mowers, snow throwers, pressure washers and generators.

In basic terms, torque is a measure of the force needed to turn something like a wrench or a lawn mower blade.

“We think it’s a better measurement of a mower’s ability to cut grass,” said Rick Zeckmeister, North American consumer marketing director at Briggs & Stratton, the world’s largest manufacturer of small gasoline engines.

Horsepower, on the other hand, evolved from a measure of the rate at which a horse could pull coal up a mine shaft into a more technical measurement related to watts. Although most people don’t know its technical meaning, many have found it useful in comparing the power of engines.

So now, consumers may face confusion over how torque equates to horsepower. There isn’t a practical conversion chart because torque and horsepower are two different things.

“Torque doesn’t mean much to the consumer,” Rotter said. “And it’s more complicated for us because it’s almost impossible to try and explain what gross torque means” to someone buying a lawn mower.

Rotter said he wouldn’t be surprised if, down the road, engine manufacturers return to horsepower ratings.

Lawsuit spurs change

The shift away from horsepower ratings came after a lawsuit in Illinois claimed that engine manufacturers were overstating the horsepower of lawn mower engines.

In some cases, the lawsuit alleged, identical engines were labeled with different horsepower ratings, misleading consumers into believing they were getting more power by purchasing more expensive models.

Briggs advertised one engine as having 6.75 horsepower and yet told the Environmental Protection Agency the same engine had 3.6 horsepower, an 88 percent overstatement, according to the lawsuit.

Since at least 1997, engine manufacturers Briggs, Tecumseh, Kohler, Toro and Kawasaki have reported horsepower ratings to the EPA that were significantly lower than the ratings advertised to the public, the lawsuit said.

For Briggs, it wasn’t an attempt to mislead anyone, according to Tom Savage, a senior vice president at the company.

There are different testing protocols for the EPA than for the general public, Savage said. The EPA ratings are based on a “composite” of test results at different engine loads, while results for the general public are based on an engine’s full power capabilities.

An Illinois judge dismissed the suit last March, but it may resurface.

“It’s still not totally resolved because the judge did not tell us what portions of the suit he dismissed with prejudice or not. So in effect, it allows the lawyers to come back,” said James Brenn, Briggs’ chief financial officer.

The suit included plaintiffs from across the nation, including Susan Barnard, a librarian from Green Bay, Wis.

Barnard bought a Yard Machines mower for $263.70 that was supposed to have a 5-horsepower Briggs engine. Although she was happy with the mower, she was miffed when lawyers involved in the lawsuit contacted her and told her the engine was less powerful than billed.

“I said, ‘Those dirty buggers. You get them to stop doing that. Put me on the lawsuit,’” she said in an interview.

‘Horsepower sells’

Over the years, manufacturers in the intensely competitive small-engine business have used horsepower ratings as a marketing tool.

“Horsepower sells,” said Jeff Hebbard, a vice president at Ariens Co., a Brillion, Wis.-based manufacturer of lawn tractors and other outdoor power equipment. “It doesn’t always sell for the right reasons, but it does sell.”

The horsepower race sounds like what has occurred with electric motors, where power claims have been embellished, said Kevin Brady, a Minneapolis attorney and engineer not affiliated with the horsepower lawsuit.

“You can exaggerate a bit and not get in trouble,” Brady said. “It’s called puffing.”

In reporting to the EPA, engine manufacturers have some leeway to fudge horsepower ratings by about 15 percent.

Sometimes, the same engine is advertised as having different horsepower ratings depending on how it’s sold.

“There are slight adjustments that get them there, but it’s the same engine,” Hebbard said.

Ariens buys engines from Briggs, Kohler, Honda and other manufacturers.

It has been challenging for the engine makers to find a rating system that works, said Dan Ariens, company president.

“Americans are very familiar with horsepower. It’s a number they kind of understand,” Ariens said.

It’s uncertain which power standard the small-engine manufacturers will settle on, if they agree at all.

“Some guys like to have cubic centimeters as their standard, some like torque, and some like horsepower,” said Savage of Briggs & Stratton. “I don’t know if there will be a one-size-fits-all solution.”

SHOPPER’S GUIDE

What to look for, according to Peter Sawchuk, a Consumer Reports power equipment expert.

Ignore: horsepower, torque or engine displacement

Pay attention to: The mower’s cutting width and overall performance, rather than engine statistics.

Look for: An engine with an overhead valve system. It might be more expensive, but it will last longer.

GLOSSARY OF ENGINE TERMS

Torque: Briggs & Stratton says torque is the best way to rate an engine that powers a push lawn mower, snow thrower, pressure washer or other equipment where the engine is turning something. Torque, in basic terms, is a twisting force that causes rotation.

Horsepower: Engine manufacturers typically measure horsepower by operating a “bare” engine, not equipped with accessories or installed in power equipment, at a given engine speed. In technical terms, a unit of horsepower is equal to 745.7 watts, another measurement of power.

Since torque and horsepower are two different things, Briggs says it can’t do a direct comparison.

Cubic centimeters: The volume of the engine’s cylinder chamber. An engine with more cubic centimeters should produce more power. But that could be affected by other features of the engine, including its fuel injector or carburetor.

Here is a link that might be useful: AJC Article

3 Comments

  1. John February 21, 2014
    • Paul Sikkema February 21, 2014
  2. Joe E Goodart April 7, 2014

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