Why Huge Difference in HP.....Vintage VS Modern....

[Rbertalotto]

I look at old Wheel Horse, IH, John Deere tractors and I'm seeing 8- 18 HP garden tractors......Pulling implements and doing ground engagement work.

Now I see lawn mowers with 22-25 HP!.......

What happened? Did they change the HP ratings?

Years ago my family had a Panza Tractor with 8HP and it was used with pull behind shovel to dig our houses foundation hole!

 

[kmcconaughey]

I seem to recall a similar discussion years ago on here. I believe it came down mostly to marketing. But there could be torque ratings and EPA emission regulations involved as well.

 

[snicklas]

In a quick search I found an explanation of the more recent change (2013), but I’m sure the change in the older engines was something similar...

But I understand your question. Why can I run a 50 inch deck on a 14 HP or even 12 in an IH Cub Cadet, but a 50 inch on a Box Store Cub is 25+ HP.... But one other reason may be the fact the newer decks are much higher vacuum/airflow creating. That why a newer mower really “whirs” and the IH decks you hear are more quiet or mechanical noise, rather than air noise. Moving air takes power. The old mechanical engine cooling fans take measurable horsepower to run. That’s why the viscous fan clutches and then the electric fans came along.

 

[mgonitzke]

The newer decks pull hard, and today's V-twin engines don't have as much torque.

 

[mfrade]

And don't forget the hydro eats up a few horsepower.

 

[kashaver]

Several things happened. Very few if any engines are flat-head any more. What really drove the change to overhead valves was EPA emissions. All the manufacturers went to overhead valves because they could control emissions better. They also had to make the engines run much leaner now than in the old days to make them meet emissions. Running leaner also limited the amount of 'lugging power' the engine could develop. To compensate, They basically made the engines bigger so they would not have to run with a load that was that close to the peak hp they could produce. Meaning, if the rpm didn't fall off a lot, the emissions stayed where the EPA wants them to be.

Then there was the lawsuit where Briggs and Stratton (and possibly other MFGs.) was sued because the decal on the engine claimed more HP than the engine actually was producing.

 

[dijohnson]

Is this the reason they went to CC's for small engines instead of HP?

 

[dschwandt]

Blade tip speed is probably much higher on these newer decks as well.

 

[zkoester]

Several things happened. Very few if any engines are flat-head any more. What really drove the change to overhead valves was EPA emissions. All the manufacturers went to overhead valves because they could control emissions better. They also had to make the engines run much leaner now than in the old days to make them meet emissions. Running leaner also limited the amount of 'lugging power' the engine could develop. To compensate, They basically made the engines bigger so they would not have to run with a load that was that close to the peak hp they could produce. Meaning, if the rpm didn't fall off a lot, the emissions stayed where the EPA wants them to be.

Then there was the lawsuit where Briggs and Stratton (and possibly other MFGs.) was sued because the decal on the engine claimed more HP than the engine actually was producing.

I remember this lawsuit lol

 

[tlavalette]

The newer decks pull hard, and today's V-twin engines don't have as much torque.

As what?

 

[mgonitzke]

As what?

As earlier comparable flathead engines.

 

[dschwandt]

It takes a lot of torque to pull a 10" plow through a lot of Steve's bean stubble.
My 128 did very well 2 years ago and really pulled hard but just kept on barking!!

 

[tlavalette]

As earlier comparable flathead engines.

You sure about that? I have re-powered many garden (and lawn) tractors with OHV engines. Not trying to start a war but the OHV engines are far and away above the older flatties in performance and fuel economy. I have no issue with the older ones. I still have some myself. My AC 620 I re-powered with a 16hp Vanguard. Way better performance on about 40% less gas. With that being said the new (big box store) mowers are pretty much throwaway units and these engines are cheaply built and do have issues.

As earlier comparable flathead engines.

 

[Rbertalotto]

Here's one for you. I recently got involved in "Of-Road / Overlanding"....Built a rooftop tent camping trailer ( www.rvbprecision.com) and to heat it I bought a self contained Diesel fuel hot air heater.

I have a CO detector in the garage and wanting to see how much CO the heater put out, I ran it for a while with the door closed. The detector never went off even when placed three feet from the exhaust pipe. I then put the CO detector in a open box of other stuff I use in the trailer.

Yesterday I did some rewiring on my CC782 and to be sure I didn't screw anything up, I started the tractor and let it ruin well under a minute in the closed garage. I then shut down the shop and went into the house.

A few minutes later my wife said she was hearing an alarm going off in the garage.

The CO detector was about 15 feet from the tractor, in a box with other stuff on top of it!

These old motors are REAL putting out the CO...................Be careful!

 

[mgonitzke]

You sure about that? I have re-powered many garden (and lawn) tractors with OHV engines. Not trying to start a war but the OHV engines are far and away above the older flatties in performance and fuel economy. I have no issue with the older ones. I still have some myself. My AC 620 I re-powered with a 16hp Vanguard. Way better performance on about 40% less gas. With that being said the new (big box store) mowers are pretty much throwaway units and these engines are cheaply built and do have issues.

Yes. Wish I could find them, but somewhere I have torque curves for the Kohler Magnum 18 (horizontally-opposed flathead twin) and Kohler Command 18 (OHV V-twin), and the torque curve for the Magnum is much flatter. It will hang in there if you lug the engine down a bit. I put a Command 18 in my 1872 (and removed the throttle stop screw on the carb, effectively making it a 20 hp). It performs well if you keep the RPMs up, but if you lug it down too much, it falls flat on its face. It does use less fuel then the Magnum, but this difference became smaller after I rejetted the carb on the Command to get the exhaust gas temps down. The better fuel economy on the newer engines is partly due to them being run almost dangerously lean from the factory. That said, I prefer the newer engines, and my 782 will be getting one too once another good used engine comes my way.

I'm going to be replacing the K321 in my loader tractor with a single cylinder Kohler Command 15 hp, so it'll be interesting to see how those two compare.

 

[exSW]

Interesting. My 782 is repowered with a Mag 18. Pulls the tiller quite well. Not sure if a peaky newer motor would please me.

 

[kmcconaughey]

Matt, all, here's a link to a discussion we had some time back Steve B., posted a torque curve chart for the K series #241, K301 and K321 plus a bunch of specs from 82 series brochures:

Torque Info

 

[tlavalette]

Yes. Wish I could find them, but somewhere I have torque curves for the Kohler Magnum 18 (horizontally-opposed flathead twin) and Kohler Command 18 (OHV V-twin), and the torque curve for the Magnum is much flatter. It will hang in there if you lug the engine down a bit. I put a Command 18 in my 1872 (and removed the throttle stop screw on the carb, effectively making it a 20 hp). It performs well if you keep the RPMs up, but if you lug it down too much, it falls flat on its face. It does use less fuel then the Magnum, but this difference became smaller after I rejetted the carb on the Command to get the exhaust gas temps down. The better fuel economy on the newer engines is partly due to them being run almost dangerously lean from the factory. That said, I prefer the newer engines, and my 782 will be getting one too once another good used engine comes my way.

I'm going to be replacing the K321 in my loader tractor with a single cylinder Kohler Command 15 hp, so it'll be interesting to see how those two compare.

If thats what works for you go for it. I'm not a purist on old tractors/equipment. The stuff I have has to work for a living. I know most want their stuff to be as delivered from the factory and I do appreciate that and like seeing them. I do know from my experiences the OHV engines easily out perform the flatties. Keep us posted on the 15 command conversion.