Torque Ratings

mowernutNovember 19, 2012

I have a question that hopefully someone here can answer. I was just looking at the commercial mowers on Snapper's website. Can anyone tell me the difference between GROSS torque, and NET torque? They offer the B&S engine with 8.5 gross torque, and the Honda engine with 7.1 net torque @ 2500 RPM. Just curious which is really the stronger engine. Also, maybe its been a while, but I thought the usual engine RPM setting for mowers was closer to 3000 with 3200 being the absolute maximum. Have safety ratings brought the RPMs down?

Thanks!

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bill_kapaun

Blade tip speed regulations are what controls the engine RPM.
I can't remember the exact number, but I think it's about 17-18000 feet/min.

You are correct about the 3000-3200 RPM number.
Fact is though, max torque is at a lower RPM, thus the lower torque RPM number.

Not sure what the difference is between gross & net torque, but if it's like the old HP ratings, it means "accessories" like cooling, charging, muffler etc. aren't included in the gross rating.

    Bookmark   November 19, 2012 at 10:47PM
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bsmith717(6)

I'd say that the gross ratings are measured with just the engine on a dyno and the net ratings are what the measurable TQ is with the machine on the frame all hooked up and with the propulsion system running. I'm thinking its like engine HP and wheel HP ratings. On a car you can expect the wheel ratings to be 20%-30% lower than what is measured at the engine standing alone. I'd go with the Honda personally! ;)

    Bookmark   November 22, 2012 at 1:21PM
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bill_kapaun

From the Briggs website-
"The gross power rating for individual gas engine models is labeled in accordance with SAE (Society of Automotive Engineers) code J1940 (Small Engine Power & Torque Rating Procedure), and rating performance has been obtained and corrected in accordance with SAE J1995 (Revision 2002-05). Torque values are derived at 3060 RPM; horsepower values are derived at 3600 RPM. Actual gross engine power will be lower and is affected by, among other things, ambient operating conditions and engine-to-engine variability. Given both the wide array of products on which engines are placed and the variety of environmental issues applicable to operating the equipment, the gas engine will not develop the rated gross power when used in a given piece of power equipment (actual "on-site" or net horsepower). This difference is due to a variety of factors including, but not limited to, accessories (air cleaner, exhaust, charging, cooling, carburetor, fuel pump, etc.), application limitations, ambient operating conditions (temperature, humidity, altitude), and engine-to-engine variability. Due to manufacturing and capacity limitations, Briggs & Stratton may substitute an engine of higher rated power for this Series engine."

    Bookmark   November 23, 2012 at 3:31AM
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mowernut

Thanks for all the great explanations. I'm thinking Honda on this one.

    Bookmark   November 25, 2012 at 9:28PM
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bill_kapaun

I think you you're right.

Something NOT mentioned is how "flat" is the torque curve? It may have a very narrow "peak" that has been "tuned" to 3060 RPM.

    Bookmark   November 25, 2012 at 10:11PM
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rcmoser

another thing to consider or thought is the amount of weight being thrown at certain RPM. Few Good examples would be JD A, Bs, and 60s tractors, two cylinders with huge flywheel. Took along time to wind up, but Once it wound up lots of useable torque due to the amount of weight in movement. Hard to Kill A once it got wound up. That's why the popped all them wheelie's if you weren't careful pushing the clutch in.

    Bookmark   November 29, 2012 at 5:56AM
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riotgrip

One thing with the snapper, the briggs will be easier to get parts for. The briggs you mention has a cast iron sleeve and that ninja deck and blade is a good design. If you are a homeowner looking for a great mower the snapper commercial is awesome. I have the same style with a kawasaki engine on it, I'll say that is tough as anything with great power, but parts can be a pain in the butt. If they made a briggs with a cast iron sleeve when I purchased my mower I'd have went with the briggs. That being said you certainly couldn't go wrong with the honda.

    Bookmark   May 9, 2013 at 12:46PM
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bill_kapaun

Since you are resurrecting a "zombie thread"-
The Briggs is more likely to need parts!

    Bookmark   May 9, 2013 at 7:28PM
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bsmith717(6)

You can also look at it like your income. The gross is what you make total before deductions (taxes, 401 plan, insurance, etc) the net is what you can actually put in your pocket.

I just recently cut my lawn with a neighbors brand new mower with the b&s 7.75hp engine. This mower also had only self propel and none of the other accessories my HRX217HXA has. Even though my Hondas advertised at ONLY 6.5 HP it felt much more powerful than the Briggs big boy and don't get me going on the lack of fuel efficiency or complete void concerning idle quality.

Ill take my Honda with a lower advert rating any day of the week!

    Bookmark   May 9, 2013 at 10:30PM
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