Are large gas motor Rv's underpower?

Mr.Mark wrote:

rgatijnet1 wrote:

Mr.Mark wrote:

rgatijnet1 wrote:

Mr.Mark wrote:

the silverback wrote:
I designed engines for 35 years. It is about horsepower and weight of the Motorhome. NOT TORQUE!! Except the more torque means more horsepower. So if a gas MH has a good horsepower to weight ratio it will do just fine.

Mr. Silverback, I'm certainly not questioning your advice because you probably have forgotten more than I'll ever know about engines.

But, you are the first person I've seen that says 'not torque' is not a major component to power an engine. All the diesel converstaion I've read about engines is torque, torque, torque.

For instance, on the new motorhome that we have ordered, the engine has been replaced from a Detroit with 515 hp and 1,650 lb. ft. of torque to a Volvo 500 hp with 1,750 lb. ft. of torque. The Prevost guys say that I should be able to tell a difference on the increase ability to climb steep hills. That's what they are telling me if I understood them correctly.

MM.

Torque at the rear wheels, which is all that really matters, is a function of gearing, which is why a hand held 1" air ratchet can produce 2000+ foot pounds of torque in a truck shop. Plenty of torque with the air ratchet but it won't get you up a hill very fast. :B
Then you talked to a salesman and there is the old adage about if his mouth was moving he was lying.

Honestly, I don't know what that means about the air ratchet compared to a diesel engine. The info I got is from the Prevost sight where all the gear-heads hang out, they are not salesman but very intelligent folks (apparently, they have me fooled) LOL!

MM.

What it means is to ask about the gear ratio on the different rigs. Same engine and same amount of engine torque can climb hills much differently depending on the rear axle ratio. If one coach is geared for mountains and the other is geared for top speed, the engine can be the same and the one that is geared for the mountains will beat the other to the top every time. One axle ratio can give you much better mileage and another gear ratio can give you much better hill climbing ability, all with the same engine horsepower and torque. The axle ratio changes the amount of power that is available at the rear wheels.

Rgatijnet1, yes, I understand what you are saying about the gear ratio. I've never seen it as an option on any coach, but I could be wrong.

I saw a video of a new John Deere (?) diesel farm tractor on a pull-off contest with an old steam engine farm tractor. The steam engine tractor pulled the four wheel drive John Deere with the JD going at full throttle (they were attached back to back). The torque on the steam engine was unbeatable. The guy said the steam engine gear ratio had to be set for pulling OR speed.

MM.

Your example fits perfectly with my statement of:
- torque determines if you can get up the hill.
- HP determines how fast.

Most likely, the steam tractor simply had more torque at the wheels via lower gears but it probably never attained any significant speed.

There also may have been secondary issues. Old steam tractors are typically very heavy and it probably had excellent traction even if only 2wheel drive. If the JD's wheels started spinning, it may have lost due to traction not because it didn't have more pulling power.