Dodge announces a diesel half-ton...

[chpthril]

i agree with maintaining objectivity. Thats why I have a problem with comparing a forced induction engine to a normally aspirated. Comparing a gas v-8 in a half ton to a diesel in a 3 qtr ton. Kinda like comparing the wake of a 21i "Tiges dont need ballast" to a 24ft x-star with 3k of ballast.

now, I havent looked at the retail price new v's the market used price of comparable trucks yet.

[Timmy!]

Resale value also has to do with the laws of supply and demand.

[Timmy!]

Here are 2012 sales figures for 1/2 ton vs "HD". Ford sold 343,000 + 1/2 tons and only 117,000+ HD trucks just to give you an idea.
http://news.pickuptrucks.com/2013/02...s-in-2012.html
http://news.pickuptrucks.com/2013/02...s-in-2012.html

BTW - who would have guessed that GM (Chevy and GMC combined) was the champ on 3/4 ton trucks?!?!? I feel like all I see are F250's everywhere and very few Chevy/GMC's. Chevy/GMC combined still get killed by Ram! I guess what you see on the road also has to do with the market you are in. Seems like around here that the majority of dually's doin work are Dodges.

[JohnnieMo]

I don't know what this means. But it does lead me to suspect that there are two rating systems for engine power.

I don't have all the answers for you, but what I do know is this.

To measure the performance of an engine (in horsepower or in watts), you need to measure it with something. To do that we use engine dynamometers, or chassis dynamometers. The best real world use case is to put the vehicle on a chassis dyno and measure the power output. Power is the rate at which work is performed (also called joules per second)

So by putting the vehicle on the dyno, we can determine how many joules of force is created in each second. Torque on the other hand is the force applied at a lever arm distance (we won't get further into that)

The best dyno's are the ones that actually measure your power whilst under the same load as driving. These give you the best measurement. So you rotate a mass with the wheels that is the same weight as the vehicle itself. This doesn't come quite as close to the real world because of a lack of wind resistance, but you get close. The resulting number is your measure of power. In the case of your minivan it would be a lot more than 35HP, but not nearly as high as 335HP. Generally, those published SAE numbers for horsepower are measured at the engine before you take into account the resistance of the transmission, drive shaft, rear axle and wheels. In a 4x4 truck you are looking at about a 20% loss. In a minivan maybe 15%. So if your minivan is truly making 335HP at the engine, then it should be putting 285HP out at the wheels.

As for your bobcat, remember the measurement is the RATE at which work is performed. Work is defined as Force x Distance. Through gearing, you can make your power do a lot more work, just in a slower way. You certainly aren't digging that hole with the bucket moving at 60MPH. So the rating is less.

You could use the engine on your minivan to dig that hole too, but it wouldn't really be designed for it.

[IDBoating]

Through gearing, you can make your power do a lot more work, just in a slower way.... You could use the engine on your minivan to dig that hole too, but it wouldn't really be designed for it.

Yes, but ultimately an engine is designed to generate a given amount of shaft horsepower (or watts, or joules/sec, or whatever figure of merit you wish). It still escapes me how two pretty substantial diesel engines can have horsepower ratings that differ by a factor of four... or how one piece of documentation can say 335HP while another one for the exact same vehicle, down to the VIN, can say 35HP - and have both be correct.

BTW, this isn't a Bobcat with a micro-diesel. It's a Case 580SK with a full-sized Cummins in it, like this one but without the brand new paint:

[trent]

WABoating,

Curious what is the Max RPM of a tractor vs a diesel truck?

[JohnnieMo]

What is the torque rating on that engine?

If you hook the crank of that engine up to a dyno you would likely only get 35HP. However the torque is probably more like 500.

[Ewok]

Most of the power to pick stuff up from that tractor comes from the Diesel engine turning a hydraulic pump to supply pressure to the lines. Don't need a huge HP engine for that.

[chpthril]

Same principal behind a locomotive. Electric motors do the pulling as they are 100% torque at all RPMs and the diesel engine is just a big generator.

[IDBoating]

Most of the power to pick stuff up from that tractor comes from the Diesel engine turning a hydraulic pump to supply pressure to the lines. Don't need a huge HP engine for that.

But work is work. Doesn't matter if it's straight off the PTO or after a hydraulic pump, some control valves, some hydraulic lines, and a hydraulic cylinder (other than those extra components introduce losses). Ultimately the energy required to get the work done comes from that engine.

[IDBoating]

Curious what is the Max RPM of a tractor vs a diesel truck?

Max RPM on the loader is around 2100. Max RPM on the truck is 3200.

[chpthril]

But work is work. Doesn't matter if it's straight off the PTO or after a hydraulic pump, some control valves, some hydraulic lines, and a hydraulic cylinder (other than those extra components introduce losses). Ultimately the energy required to get the work done comes from that engine.

Work is work, but the hydraulic pump is a multiplier.

[IDBoating]

Same principal behind a locomotive. Electric motors do the pulling as they are 100% torque at all RPMs and the diesel engine is just a big generator.

The diesel-electric system is used because:

1) The electric drive motors can develop torque when stalled

2) Using an intermediate electric drive system permits convenient energy storage in batteries

3) The electric drive motors can be run as generators to recover kinetic energy when braking the train (due to back-EMF from the motors)

4) The stored battery energy can be used to supplement the diesel output during peak loads, such as starting from a dead stop

...but still, with all of that, ultimately all of the energy to move the train comes from the diesel engines. Which brings us full circle back to "work is work". Whatever work is accomplished by moving that train ultimately came out of the engines.

BTW: A research paper I read several years ago showed that the diesel-electric hybrid system, such as that used on modern locomotives, is by far the most efficient transportation powertrain currently available. They compared it against pure electrics, hydrogen engines, fuel cells, turbines, and all manner of other production and laboratory designs and the D-E beat them all, primarily because of its efficiency in recapturing braking energy. Particularly for in-city driving, braking energy is the big loss: Fully 50% of the energy generated by a city bus engine is dissipated as waste heat in the brakes! The ideal commuter car would be one with a D-E powertrain, which is one reason I'm anxious to see more diesels in US autos. Once folks get comfortable with small diesels, it will be easier to move to the D-E and its efficiencies.

OK, stepping off the soapbox, sorry to ramble....

[Wickedcummins]

So is torque and Hp measured differently in gas as it is in diesel? Is gas Hp and torque like .75 of a diesel Hp and torque value? Having a standard unit of measurement like Hp and torque, allow for a fair comparison, right? Now, I will say that a diesel does hit its power range at a lower RPM, and that can be an advantage when towing a load.

Can you please show me a light duty gas truck and that produces 850ft lbs from the factory?

[IDBoating]

Work is work, but the hydraulic pump is a multiplier.

Yes, but the laws of thermodynamics say you don't get something for nothing. What are you gaining and losing by this "multiplying"?

By the way, here's a fun layman's explanation of the laws of thermodynamics:

First Law: You can't win.

Second Law: You can't break even.

Third Law: You can't stop playing.