Wondering about horsepower.

[99ls1ta]

The past few weeks I'd been looking at lawn tractors and it really got me thinking. Whats with all these huge hp power plants on small lawn tractors? I have limited knowledge on equipment but I know my grandfathers jd 214 only has 14hp my other grandfather has a cub series 2000 with a 12.5hp, dads Kubota 18hp all from the mid 90s early 00s. Now the smallest engine I found on the $1000 box store machines puts out 17.5hp why is that much required on small machines? Is there a different rating system in effect now? I know for a fact in the 70s there were tractors with only 8-10 hp running around doing a fine job, 25hp v-twin on a $1700 42in deck lawn tractor seems a bit overkill does it not? Or is 25 hp today = less back then (but then why are the jd x500s only around the 25hp mark)?

Also in the same subject I noticed there seems to be no hp ratings on the push mower engines anymore, They are now going on torque ratings (which makes more sense when you think about it) but one would think they could still give the hp rating as well (and give the torque rating for the tractors as well as hp). Just a few observations that got me wondering.

 

[PoorPlowboy]

Torque is the real measure of work and today's 24hp twin puts out about the same torque as an old iron 12hp.

 

[Baby Grand]

I don't know what happened, but I had the same experience. My mother in law's old, 12hp MHD didn't seem to be any weaker than our new, 2007 21hp Craftsman did. After many mechanical issues with that Craftsman we found an older 14hp Kubota G5200, which could mow circles around it. I think PoorPlowboy is right - it's torque that gets the job done. Torque over a wide range of engine speed is what makes the machine keep working, even when the revs drop under heavy load.

 

[MikeInEburg]

It's much like buying a pickup truck, once you decide to buy one, you'll start thinking "maybe I should go a bit bigger just in case". If 17HP is good, 20HP is better. It spirals up from there.

 

[oldballs]

Same wonderment here. Now some wise guy is displaying small engine sizes in "cc". Geeze...why not gives us all the numbers? and in French/Spanish/German/ Swahili too.:laughing:

 

[Gary Fowler]

Todays engines are just not as strong per HP as yesterdays. I had a 332 JD with 14 HP that pulled a 54" mower fine. I bought a used Troybuilt 17.5 HP that wouldn't pull a 42" mower in high grass even in 1st gear. I gave it to my daughter who still uses it to trim spots that her Kubota B2920 might miss with belly mower. I then bought a Craftsman with a B&S engine 26 HP and it cuts well, but it doesn't have any more power than my 23 HP Ferris with Kawasaki engine. I think it is all hype in the engine ratings now days.

 

[LD1]

Torque is the real measure of work and today's 24hp twin puts out about the same torque as an old iron 12hp.

If that were true, it would mean that todays engines have to spin twice the RPM to get double the HP number.

Either way, HP is just a number derived from the torque and RPM. So more HP either means more speed, or more torque.

HP is how fast work can get done. That is the important one. Not sure why small people say that small engines of yesterday feel more mowerful than ones of today? I dont have any experience with small consumer level mowers. But I had a JD 240 that was 12 or 14 HP. I now have a ZTR with 25HP kohler. And yea, it can cut grass about twice as fast. Which is spot on with having twice the HP.

And I dont mean its faster just because its more maneuverable. It will pull its 61" deck through thick grass much faster than the 240 would with a 46" deck without bogging.

 

[prosperity]

It's all about marketing. To the average consumer bigger is better, right?

Joe homeowner is looking at box store lawn tractors. Model 'A' is 18hp 50" cut for $3000.00. Model 'B' is 20hp 50" cut for $3500.00. Bigger has to be better so Joe buys the $3500.00 model It probably costs the manufacturer $40 more for the bigger engine so that means $460 more profit.

 

[zzvyb6]

My old '70s Craftsman magnesium case push mower had a big block 454 Chevy in it. Used about a gallon of fuel per month. Once it went to full throttle and hovercrafted itself into the side of the garage.

I think the motors and emission rules of today require the extra size rating, or maybe the hp ratings are actually accurate now.

 

[99ls1ta]

So I am correct in my thinking that the 25hp box store twins are still less "powerful" (torque/able to get work done) than the 22-24hp twins in the X5 deeres for example? Not talking anything tractor or quality related just power output engine to engine. Sort of like a Honda civic si engine vs a late 90s 350 v8 both make just north of 200hp but the v8 can work twice as hard.

I wish it was a little more like truck buying, here is the hp, torque, displacement, payload/towing cap etc right in the spec sheets. I know they are not all accurate but at least we have a ballpark on what we are getting unlike the power equipment world. If my above thinking is correct that hp number is so misleading since the torque is what is most important and dispite the same or higher hp rating its a weaker engine (again not quality just power output).