v10 torque vrs diesel

the silverback wrote:
I am a retired Engineer also and designed engines. You can not argue with the equations above. they work for both gas and diesel,in fact any engine.
Let's keep it simple!! Go to any NASCAR race or drag strip. See that they are talking about weight/HP not torque to make there machines do something faster.
It also works for Motoehomes!!!

the silverback wrote:
I am a retired Engineer also and designed engines. You can not argue with the equations above. they work for both gas and diesel,in fact any engine.
Let's keep it simple!! Go to any NASCAR race or drag strip. See that they are talking about weight/HP not torque to make there machines do something faster.
It also works for Motoehomes!!!

Perhaps, you can see why I don't like to be lumped in with typical RV buyers.

jmtandem wrote:

Well yeah, but they don't want to discuss the real world of selecting/buying a motorhome. They want to simply quote the horsepower formula, and then repeat it several times for good measure,......as if it's more than we can understand.
What nobody seems to understand is that the manufacturers use a gasoline engine if it's appropriate, and the same for a diesel.

Cloud Dancer,

You are correct as the manufacturer's select the best engine, trans, suspension, rear end ratio, axles and tire sizes for the coaches they sell constrained by performance and cost. And buyers can usually rest in the knowledge that what they are purchasing has been carefully selected to provide very satisfactory performance (except perhaps Chinese tires) at a cost that is not prohibitive.

However, there are a few of us here that like to think through the issues and banter around some and have fun discussing how things work and why. It revolves around theory, premise, conclusions and real world experiences. And that is OK, too. No harm no foul.

It is real easy for anybody that does not want to participate in the discussion to just skip it and go purchase the coach that has the floor plan that best suits them.

Javi1 wrote:

DanTheRVMan wrote:

Javi1 wrote:
Torque is a measure of the ability of an engine to do work. It's a component of, but not the same as, the horsepower of the engine, which is the rate at which work can be done. In an automotive engine, power and torque are related by a simple equation that considers torque, engine speed (in revolutions per minute), and a conversion factor of 5252
Torque x RPM / 5252
In this equation, torque is expressed in terms of ft-lbs, the engine speed is given in revolutions per minute, and 5252 is a conversion constant. An engine's horsepower, then, isn't constant, but rather varies with its speed.
Here’s the problem with horsepower... it is the potential or speed at which work can be done while torque is the ability to work....
While it is possible to take two 350 hp engines and make the same speed pulling the same load up an incline the one with the most torque at the lowest rpm is going to get there cheaper and usually faster because the other will require more gear reduction to produce the same forward force... Which will result in higher rpm’s needed, more fuel burned and more heat produced of which requiring more cooling which adds weight which requires more power (torque) or decrease in payload..
An example is my 6.7 liter diesel which produces 400 HP at 2800 rpm but 800 ft-lbs of torque at 1600 rpm... using the above equation one can see that the 6.7 produces 800 x 1600 / 5252 = 243.72 hp at 1600 rpm, far from the potential peak hp of 400 at 2800 rpm... Although in looking at the torque curve of the 6.7 it is apparent that the 800 ft-lbs is nearly constant through the range of 1600 to 2800 giving the 6.7 a very high work range.
The Ford V-10 gas engine produced 457 ft-lbs of torque at 3250 and 362 hp at 4750 using the above equation one can see that the V-10 produced 457 X 3250 / 5252 = 282.79 hp a gain of 39.07 HP but at the cost of more than twice the revolutions... to produce slightly more than ½ the torque of the 6.7 diesel.
While the design of the gas V-10 is aimed at higher RPM the life expectancy of an engine turning at well over twice it’s normal operating range is almost certainly going to be reduced by some factor if one expects it to produce the same work ability through increased rpm.. and gearing..

You are right about the shape of a gas engines torgue curve, but gas engines are lighter not heavier than diesels.

Speed is determined by weight/hp and gas MHs are generally much lighter than diesels MHs so for the same HP a gas MH will be faster in spite of the worse shape of torque or hp curves.

As for the life of the engines you are correct the diesel should last lots longer. But since gas will last over 100k and most people wear out the house first this is not a good reason for many people to blow their budget and buy a diesel so the fourth owner can go a few more miles.

Yes, generally a gas engine is found in a smaller coach, however the original question was (I think) about the same size coach just gas or diesel powered.. in which case unless it was one of the smaller coaches.. the diesel will win, especially if you base winning on longivity X power / fuel expense.

Well yeah, but they don't want to discuss the real world of selecting/buying a motorhome. They want to simply quote the horsepower formula, and then repeat it several times for good measure,......as if it's more than we can understand.
What nobody seems to understand is that the manufacturers use a gasoline engine if it's appropriate, and the same for a diesel.

uncleluap wrote:
we can banter back and forth till the cows come home,use 5252X whatever
Use whatever formula u were taught.I have no knowledge of such stuff
I absolutely know one thing for sure.There is not a V8 or V10 in production today that come,s even close to being able to feasable propel a 40+Ft 4 slide 34K motorhome down the road and up mountain passes and if there was we would be seeing them.thats why we only see engines like the 425 8.9L cummins doing the job and not ford V10.thats my opinion