HP ratings of small engines

[LD1]

When it comes to lawn mowers, it is about blade speed and ground speed.:thumbsup:

Those older mowers that didnt have the HP, couldnt match the ground speed of todays mowers, especially ZTR's.

Even the riding mowers with 26HP and ~52" decks can still get a good quality cut without lugging too bad at a MUCH faster ground speed than the older mowers. Problem is most peoples yards are too rough, ot they just dont ever try mowing in a higher gear.

 

[oldyellr]

I seem to see the same in cars and trucks. I had a stock 351 Clevand engine in a 1970 Ford Torino that supposedly had only 275 HP but would smoke the biggest tire made at the time and hide the needle (120 MPH) in less than a half mile, over 85 MPH in a quarter mile and now we have 4 cylinders with claims to that much hp and more that wont do half (well maybe half) as much in performance.

Over the years, car manufacturers lied both ways about horsepower. In the 1960s they grossly exaggerated horsepower, but when GM made the 302 engine for the Z/28 Camaro, they only called it 295 hp just to pacify the insurance companies, even though it could put out 400. The auto industry have always been shysters about horsepower and performance. You also must realize that automobile engine horsepower is measured at the flywheel with no accessories. All the accessories and a slushbox transmission eat up a lot of that before it gets to the drive wheels.

Things like outboard motors, tractors and mowers have been a lot more honest about horsepower over the years, until, of course, the marketers figured they could gain an advantage by lying, leading to the class action suit.

 

[oldyellr]

Being able to just melt tires in a RWD with 125 HP and having a FWD econobox with nearly 300 HP being unable to do so really shows how far the technology has come.

Well, you won't really find an "econobox" with 300 hp, but a Subaru WRX or Mitsubishi EVO will give a Corvette a good run, but you have to know how to drive and keep it in the narrow power band.

A tractor engine is completely different. It needs a very flat horsepower and torque curve so the governor can react to any increase in load without losing RPM.

 

[scrappy isb67]

alot has to do with the engine.
Dad has a 982 that has been re-powered with a 25 hp V-twin and it pulls down in heavy grass. My deere has 1 hp less and doesn't pull down unless I am trying to break the mowing speed record in HEAVY grass and I am running the same size deck as he is

 

[BethesdaEC]

Well, you won't really find an "econobox" with 300 hp, but a Subaru WRX or Mitsubishi EVO will give a Corvette a good run, but you have to know how to drive and keep it in the narrow power band.

A tractor engine is completely different. It needs a very flat horsepower and torque curve so the governor can react to any increase in load without losing RPM.

Car engines rarely spend a significant amount of time wide open throttle, mostly they are rolling down the highway at 2000 RPM putting out maybe 20 HP. A mower spends it entire life at WOT putting out max power.

 

[Will_C]

I'm not a techie when it comes to knowledge about horsepower, but I do believe epople want to mow faster. I used to mow my mother's yard with a 18hp Case tractor with a 60" deck-it took 2 hours going as fast as I could go with the power it had. I did it with a BX 2200, 60" deck, and it took me 1.5 hours-plenty of power, the limiting factor was comfort of the ride.

I now mow with a Toro 52" commercial ZTR with a 23 hp engine-I can do the same job in around an hour with a better cut-but if the grass gets ahead of me, I wish for 25 or 27 hp on that machine.

Will

 

[brokenot]

I could also get 19 mpg running over 75 miles per hour with that Torino

I've got to believe your fond memories of the car are causing you to remember things a little differently. How did you manage that kind of mileage back in the good ol' days of carburetion, no computer-optimized ignition timing (or any other instantaneously tweaked-on-the-fly parameters), a simple transmission without one, (or two) overdrive ranges, no locked-up torque converter, a third member gear ratio that *probably* had the engine singing at 3500 rpm or so at that road speed....etc. etc.

Just wondering out loud, 'cause I had several similar vehicles that would never approach that mileage number unless I was traveling downhill. And....while they were "fast" in their day, they would most certainly be soundly trounced by today's performance machinery.

 

[MessickFarmEqu]

one other factor here is that these over rated engines don't have torque like they used to. Older tractors could lug, new ones start to die under even a moderate load.

 

[LD1]

one other factor here is that these over rated engines don't have torque like they used to. Older tractors could lug, new ones start to die under even a moderate load.

That is mostly due to engine speed.

HP is simply a mathmatical calculation using RPM and torque. More of either results in more HP.

Old engines didnt tur many RPM's. But had a lot of torque.

New engines dont have a lot of torque but turn way more RPM's.

For example, the old ~25HP 8n's only ran ~2200RPM. A new kohler 25HP on a ZTR runs 3600RPM's. SAME HP, no two ways about it, but the 8n had more torque to get that RPM # at a much lower RPM, the new kohler uses RPM's to achieve the HP.

 

[tractorsanmore]

Years ago I owned a 1970 mach 1 351 cleveland 4v , 4 speed , dual exhaust , 300 hp. all stock and drove it to florida driving 65 or 70 mph . Was getting around 20 mpg . The car had close to 100,000 miles on it at the time .