HP and quality of todays vs. older equipment?!

Knute · Jul 27, 2003

I've been thinking about this and I wonder if the issue isn't HP but rather torque. Engines can be built for high HP numbers or high torque, or sometimes both. I wonder if the real differnece between these is the amount of torque - pulling power - these engines generate.

It could be that your friends Sears does have twice the HP, but maybe has LESS torque than your smaller JD.

Since HP is what's advertised it could be they're building engines with high HP numbers and sacrificing torque for the marketing advantage of quoting higher HP numbers.

Schultz · Jul 28, 2003

This I copied & edited it from a previous Power Trac post, some of you may have already seen this but it's my take on the HP vs torque of many small engines.
To convert torque to hp the formula is:
hp=torque*rpm/5252

I think engine "peak" HP & Torque values can be very misleading. A better number to use is the continuous hp & torque values. Unfortunately, not all manufactures provide this info on their web sites, and some may be more conservative than others about these continuous values. As you are likely aware not all 22 or 25 or 30 hp engines are created equal, some have brooder power bands than others, especially diesels, but the peak values may not show this. This is where torque rise from maximum hp comes into play. If an engine has high torque rise then it's able to generate nearly the same hp over more rpm. Look at the power curves for Kawasaki 23hp kaw 23hp compared to the B&S 23 hp b&S 23hp . The Kaw when heavily worked at 3600 rpm won't loose rpm's or bog down like the B&S. Notice the huge torque rise on the Kaw vs B&S

If you really want to know how much available power there is, the area under the hp/rpm curve will give you a total available power number, but none of the manufactures provide this information. This would be great then all we would have to look at is one number to determine if one engine was more powerful than the next @ the same rated HP. A crude estimation of the area under these power curves for B&S 23hp engine would be 30,200 and 33,150 for the Kaw, about 10% more total power. Then if you compare this to a Kubota diesel of the same HP the difference is even greater.

Slamfire · Jul 28, 2003

If the formula for deriving hp is torque x rpm/a constant, I guess that explains how hp goes up while torque falls off.

rdln · Aug 6, 2003

I'll be able to reply to this post using experience soon when my new 18hp deere has some hours on it but I have been cutting the grass for 3 years with my 1965 10hp cub cadet and attest to the over built theory.

Also a factor with higher hp requirments on new tractors is that hydrostatics loose power before its applied to the wheels. IMO

slowzuki · Sep 22, 2003

There is also another concept discussed here, drawbar hp is a measure based on how much power can be put to the ground.

A 25 hp lawnmower that weighs 300 lbs is fine but any old low hp tractor that is heavier will win a tug of war!

Not to contradict, but I find the newer high hp rigs can handle grass cutting better than the older rigs, as long as you can stand the racket when they are reved out to get that hp.

Our mid 60's 12 hp tractor could chug all day but it burned up the pto clutch mowing heavy stuff.
Ken

F350driver · Nov 23, 2003

Hi, Me I like the older equipment too!

My lawn tractor is a 63 Suburban 600. It has an old one cylinder cast iron B&S with an oil bath breather. I'm a simple guy so a simple little tractor to play with works good.

I just finished "spiking" my little .28 acre yard with my antique hooked to a home depot special implement. Kinda halfway makes me feel like I'm driving my big tractor down on my farm as I put-put around the yard.

I'll be restoring this little workhorse so if anybody knows where I can get the light blue implements or an appropriate 3pt hitch please let me know.

Happy Holidays,
Jim

Joe1 · Nov 24, 2003

This is kind of an old post.

I'd be curious to see if those tough old tractors would do even better with a modern newer engine of higher rated HP. They did well with the one lungers, but might be even better, all other things equal, with a modern OHV engine.

The new engines certainly are more efficient from an emissions standard, and probably are more economical. I can't believe an old flat head can make the same HP and torque as an OHV engine with electronic ignition, and it would burn more fuel doing it.

My father's 54 Pomtiac had a 266 cu in flathead straight 8 that put out 127 Gross HP. My 99 Cherokee with a 244 cu in pushrod OHV put's out 190 Net HP, and it's pretty understressed, and is already out of date.

I don't subscribe to the conspiracy theory that all the manufactures got together and decided to build junk just so they could sell more in the future.

MossRoad · Nov 24, 2003

Don't foget that a lot of those HP tests were done by different standards, too. /forums/images/graemlins/wink.gif

art · Nov 24, 2003

I can't say that I worked on the real old stuff, or is a farmall M old? The newer engines are better built for higher torque rise and more fuel efficient. Can't say the old stuff lasted any longer that I'm aware of, just felt longer sitting in a steel pan seat and out in the cold. I only had the pleasure of bringing one customer (an old bear) into a cab tractor. He was funny, plowed all nite for two days when he first got it, a six pack of beer and a couple of Dolly Parton tapes and see you for chores in the morning!