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1500 vs 2500 Diesel or Gas
#31
(12-17-2017, 08:04 PM)BadSaver Wrote: The next question is, what is considered high mileage for a diesel engine? I've looked around the web for examples of trucks with more than 200,000 miles. There are not many to be found. I would consider 200,000 miles on a diesel high mileage. Sure, there are examples of engines with a million miles plus on them, but then there's the chassis, etc. Not sure I'd pay a premium for a high mileage diesel. Rebuilding a diesel can be expensive.

7.3 400,000
6.0 150,000
cummins 400,000
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#32
So rule of thumb. If you can get a rebuilt truck with rebuilt classic Diesel engine, you might be at a significant advantage. Rebuilt would include all the suspension parts. Plus rebuilt engine transmission and drive train.

Maybe that will get you an ideal solution.


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#33
(12-17-2017, 06:14 PM)BadSaver Wrote: Torque is twisting force. Horsepower is the measurement of the ability to do work.

With vehicle engine ratings, they both measure power output.

The main difference is that horsepower has time factored in...ie, how much and how fast (or the rate at which) the work gets done.

Torque is a similar measurement but with no time in the equation. Not, how fast it can get done, just that it CAN get done.
Never trust a camp cook with lots of shiny new pans...
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#34
Horsepower is a measure of power. Torque is not a measure of power. It is a measurement of twisting force.

Per Britannica, “Horsepower, the common unit of power; i.e., the rate at which work is done. In the British Imperial System, one horsepower equals 33,000 foot-pounds of work per minute—that is, the power necessary to lift a total mass of 33,000 pounds one foot in one minute.”

Torque is twisting force, as you mentioned, not related to time. Therefore, it’s not directly related to a measurement of work (like horsepower above).

A. A engine with 200 lbs of torque at 6,000 rpm = 228 Horsepower
B. A engine with 500 lbs of torque at 1,000 rpm = 95 Horsepower
The engine with the most torque (B.) isn’t the engine with the greatest ability to do work.

(Torque x RPM) / 5252 = Horsepower

In a gas engine, peak torque in rpm terms, is often about 75% of the way to peak horsepower.

Power as I define it: The rate of doing work, measured in watts or less frequently horsepower.
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#35
(12-18-2017, 04:22 AM)thatdarncat Wrote: 7.3 400,000
6.0 150,000
cummins 400,000

So, what I did was go to Auto Trader and search all vehicles for sale over 200,000 miles. Lots of diesels above that range. Not many way above. Information there would make a great statistical analysis. Going down that path (adding production numbers), it might be possible to determine which engines were better over time. 

I was a Chevy guy and my Dad was a Chevy guy. My F250 is the first Ford in the family. Similar research indicated that there were more F250s for sale above 200,000 than any other vehicle. At the time, they appeared to make up 12% of the over 200,000 miles population of vehicles for sale.

If I sound anti-diesel, I'm not. I don't want to afford one. And, I work on my stuff myself. Gas is what I know. Congrats on your miles.
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#36
(12-18-2017, 03:07 PM)BadSaver Wrote: Horsepower is a measure of power. Torque is not a measure of power. It is a measurement of twisting force.

Per Britannica,  “Horsepower, the common unit of power; i.e., the rate at which work is done. In the British Imperial System, one horsepower equals 33,000 foot-pounds of work per minute—that is, the power necessary to lift a total mass of 33,000 pounds one foot in one minute.”

Torque is twisting force, as you mentioned, not related to time. Therefore, it’s not directly related to a measurement of work (like horsepower above).

A. A engine with 200 lbs of torque at 6,000 rpm = 228 Horsepower
B. A engine with 500 lbs of torque at 1,000 rpm = 95 Horsepower

The engine with the most torque (B.) isn’t the engine with the greatest ability to do work.

(Torque  x RPM) / 5252 = Horsepower

In a gas engine, peak torque in rpm terms, is often about 75% of the way to peak horsepower.

Power as I define it: The rate of doing work, measured in watts or less frequently horsepower.
An engine with 500 lbs of torque at 1000 RPM is going to tow a trailer much better than one with 200 lbs of torque at 6000 rpm (which would in fact really suck at towing), and also get much better gas mileage and much longer longevity.  Diesels have the characteristic of having a lot of torque at very low RPMs, that's why they tow so beautifully.

Torque at low RPMS is the greatest indicator of towing ability.

Diesels are a pain in the azz to repair, I know I repair mine occasionally, but as has been mentioned before the older cummins (98 and older 12valve) are actually very easy to work on and inexpensive. You can find a beater 2wd Dodge Cummins cheap, beater meaning the body and interior is shot, usually engine is strong. Those old Fords are nice too, but the Cummins is easier.
[Image: attachment.php?aid=16152]My Freedom-24' 4,000lb 1993 Lance 5th wheel w/1235 Watt Solar/LiFePo & 2003 4x4 Chevy Duramax

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#37
(12-19-2017, 06:29 AM)Itripper Wrote: Torque at low RPMS is the greatest indicator of towing ability.

The point was, the measure of power (as in the study of physics - matter & motion) is horsepower.

Your truck for example, 235 horsepower (@ 2,700 rpm) and 500 Lbs torque. 
http://www.duramaxhub.com/duramax-timeline.html

Horsepower is the measure of your truck's ability to do work.

Interesting article on your engine:
http://www.trucktrend.com/how-to/engine/...7-duramax/
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#38
To the original question.

To Maximize my value I'd look at the vehicle's performance (how does it fix my needs), initial cost, life-cycle cost (fuel / oil), maintenance cost, resale value, and the cost of money that's tied up.

With a vehicle having 200,000 miles, selling at a premium price, I doubt that it would meet my math criteria / risk assessment.
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#39
(12-18-2017, 03:07 PM)BadSaver Wrote: Horsepower is a measure of power. Torque is not a measure of power. It is a measurement of twisting force.

Quote:The point was, the measure of power (as in the study of physics - matter & motion) is horsepower.


Trust me, I do understand the engineering and the physical difference. Quite often, I try to distill complex subjects so that they can be understood by people asking questions and reading these articles. In fact, that is one of the guidelines of this forum. I'm attempting to make it easier to understand, rather than quote physics principles and formulas, which I try to avoid, as well as electronics formulas...(long story there too).

The very fact that vehicle engine ratings are DIRECTLY mathematically related means they can BOTH be used almost interchangeably for power output specs, and are very often done so in the real world. If you have one, you can 'calculate' the other, based on an assumption about expected RPM, say, when pulling a mountain grade. 

As iTripper points out, its WHERE in the RPM curve that matters when it comes to towing with a truck, as opposed to a sports car that might have very high horsepower ratings at 6000 RPM, but much less torque at, say, 1200 RPM. 

BTW, ALL torque vs horsepower rating curve charts cross at 5252 RPM. This is no coincidence, its evidence of the mathematical and direct relationship between torque and horsepower. 

Engineers and scientists in the labs will separate them, but in the real world of driving vehicles with internal combustion engines, in many ways, more HP (at a given RPM) almost always means more torque, and vice versa.

In the world of large 15 liter diesel engines, if my truck's engine is rated at 1500 lb-ft of torque (at 1400 RPM) and I have the mechanic hook up the laptop and reprogram it for 1700 lb-ft, (at 1400 RPM) I just instantly got more power, as a result of the new injector settings. Coincidentally, the displayed horsepower on a chassis dyno will also go up, because the engine now produces more power, by raising the torque ratings. 

The two specs ARE directly related in the real world of internal combustion engines. 

Wanna talk electric motors?  Yep....very different now....You can have MAXIMUM torque at zero RPM with ZERO horsepower being produced. 

But with diesel and gas engines, they have a range of productive RPM, so if either rating is changed, the other one changes also.
Never trust a camp cook with lots of shiny new pans...
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#40
Also, (in the just-thought-of-this category):

In heavy duty OTR class 8 trucking, many of these large diesel engines have horsepower ratings somewhere around 450-500...very common rating.

Well, many Chevy Camaros and Corvettes and Ford Mustangs can have that much horsepower rating, or more.

Do you think that gas motor under the hood of that car can 'outpull' the large motor in the truck?

Nope. 

The large engine for class 8 trucks will have about the same maximum horsepower rating but 3 or 4 times the maximum torque rating!

More torque = more power. No way to get around that when it comes to real world gas and diesel engines.
Never trust a camp cook with lots of shiny new pans...
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