RATINGS: HP vs TORQUE

[KennyV]

Dee now this is exactly what I have been missing...
Glad to be back.
I am wondering if the torque ratings are peak torque or the actual torque at the proper RPM... most small engines on lawnmowers are set up to run around 3600 RPM... Hmmmmmm... :smile:KennyV
:smile:OH did I mention I have really missed everyone here....:smile:

 

[JDgreen]

Dee now this is exactly what I have been missing...
Glad to be back.
I am wondering if the torque ratings are peak torque or the actual torque at the proper RPM... most small engines on lawnmowers are set up to run around 3600 RPM... Hmmmmmm... :smile:KennyV
:smile:OH did I mention I have really missed everyone here....:smile:

Good question...I have always wished there was a small tachometer, a CHEAP one, that you could buy to measure rpm of a small engine...I have seen some advertised with a digital readout for an ATV but they were very costly.

 

[handirifle]

Hi all, first post here. I am posting on this one cause I ran into this issue on a couple different fronts, in the last year. The first, was when i bought a tiller, and noticed the rating of 9lbs torque, hmmmmm.

I agree on the issue of what is really doing the work, it is torque, not hp, but it's all a numbers game. Auto makers went for MANY years without publishing HP or torque figures, because of lawsuits. Their needs to be tolerances they are allowed, as I'm sure everyone is aware, no two engines will produce the same HP, even when built identical.

The second was when I bought a used Murray 20HP (B&S) Garden Tractor, with 52" cut, to mow my 3 acres. I ran it a total of 2 hrs, before it floated an exhaust valve seat, shutting the engine down. The interesting part came when contacting B&S about replacement parts/engine, the recommended replacement was a 26hp Vtwin to replace my 20hp flat twin. His reply was even though the hp of newer engine was higher, mine had greater displacement (and I suspect greater torque) and this was what would work.

 

[rer]

Speaking of hp and torque rating I actually did some sizing up today. A big wheel I have has a Briggs and Stratton 6.75lb/ft torque rating, but further examination found it is the exact engine as my older 5.5hp right down to the float bowl. All parts were the exact match Bore and stroke measured exactly the same. Also that same 6.75 is also 9.14 newton meters.:biggrin:

 

[jeff]

H.P. will have a lot of variables with the same displacement engine due to little things like valve timing and lift, carb jetting compression, etc. Ask anyone who has hotroded a small block chev.

 

[txyank1]

OK, new member here. I've read the thread and didn't see exactly what I was looking for. I haven't bought a mower (rotary, push mower) since the rating change to torque. It's time to replace my Craftsman 6.25 HP and I want something with as much and preferably more power. What do I look for?:confused2:
Thanks

 

[doug9694]

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Since the new adopted ratings, a new replacement will be listed as cc so that shouldn't be a problem.

But just in case you opt for an older replacement engine this link should give you all the information you would ever need.

Convert cc to hp or horsepower to cu.in. cc or cu.cm metric conversions

I use 1hp per every 1.5 PT (foot per torque per rpm) It is based on the formula of 1hp = 1 PT at 5,252 RPM. Since most mower and equipment engines are rated near 3600, you need more torque to equal the 5,252 ft lbs. That cc per hp rating does not make since.
OHV engines have more hp than flat heads for the same size cc. Also compression ratios will change the hp rating. Next I expect all the ratings to be switched to metric. KW or MN or ???. Then we will have to learn all over again.
I would like to see them give both. TP and hp in parentheses at least.