Isuzu NPR Diesel Towing and Hauling thoughts

[Snobdds]

Diesel pickup trucks have Class 8 power, but they dont have the torque at cruising speed and neither the longevity.

The NPR has an industrial duty diesel engine. Look at its CONSTANT POWER rating of 173hp at 1800rpm, despite its modest peak power of 190hp. This engine isnt made to drag race, but it will lug the long run.

https://www.isuzuengines.com/products-h-series/

Duty cycle is largely a function of a motor's ability to cool. Diesels need heat to efficiently burn in a compression ignition design. These are at odds with each other. So the physics says to make larger displacement motors and run them at less rpm to get the torque needed without generating so much heat the cooling can not keep up.

I understand the physics involved here, but it's still a bit underpowered for towing. It does have adaquate power to haul the contents of a box truck design.

One side note on cooling and duty cycle. My 6.7 powerstoke has two radiators in it. They solved the age old duty cycle problem in high HP and torque trucks.

 

[Renze]

Duty cycle is largely a function of a motor's ability to cool. Diesels need heat to efficiently burn in a compression ignition design. These are at odds with each other.

With electric motors and welders its about the ability to cool. With diesels, you can add radiators all you want but you will still wear piston rings and valves if you exceed the duty cycle too much.

So the physics says to make larger displacement motors and run them at less rpm to get the torque needed without generating so much heat the cooling can not keep up.

Thats exactly what Isuzu does: use a 5.1 liter long stroke engine at relatively low redline instead of a 3 liter V6 oversquare high speed engine that can create a lot of hp if you make it work at the rpms where it wears fast. And dont give it the horsepower that it cant deliver day in, day out anyway.

One side note on cooling and duty cycle. My 6.7 powerstoke has two radiators in it. They solved the age old duty cycle problem in high HP and torque trucks.

If you can solve the age old duty cycle problem with radiators, let us swap the C13 Cat engine of a Cat 352 excavator for your 6.7 powerstroke and see how many operating hours before it blows its sump empty through the crankcase breather... i'll give it 3000hrs.

 

[Snobdds]

With electric motors and welders its about the ability to cool. With diesels, you can add radiators all you want but you will still wear piston rings and valves if you exceed the duty cycle too much.


Thats exactly what Isuzu does: use a 5.1 liter long stroke engine at relatively low redline instead of a 3 liter V6 oversquare high speed engine that can create a lot of hp if you make it work at the rpms where it wears fast. And dont give it the horsepower that it cant deliver day in, day out anyway.



If you can solve the age old duty cycle problem with radiators, let us swap the C13 Cat engine of a Cat 352 excavator for your 6.7 powerstroke and see how many operating hours before it blows its sump empty through the crankcase breather... i'll give it 3000hrs.

Still underpowered for towing applications...

 

[ptsg]

Why tow with it if you can simply put the load on the bed of the truck? Not quite getting the fixation with towing.

 

[MTGreen]

I have a 2007 NQR with a 5.2L diesel and an 18.5' flatbed with trailer hitch. The NQR in the US is the 5 ton version with a 19k gvwr (2 steps up from the US NPR model and 1 step down from the NRR 6 ton model). Upsides are it will haul/tow 26k+ lbs up any grade I have pointed it at, gets 9mpg loaded and 13-14mpg unloaded, doesn't require a CDL, no DPF/DEF garbage, and has a B10 (90% still on the road) rating of 310k miles with current versions at 375k. Downside is it doesn't like going over about 60-65mph and goes 28mph up the steepest grades fully loaded. But it gets there. The 8x18.5' bed is really useful for building supplies, fencing, hay, etc. I love it

 

[Hay Dude]

I have a 2007 NQR with a 5.2L diesel and an 18.5' flatbed with trailer hitch. The NQR in the US is the 5 ton version with a 19k gvwr (2 steps up from the US NPR model and 1 step down from the NRR 6 ton model). Upsides are it will haul/tow 26k+ lbs up any grade I have pointed it at, gets 9mpg loaded and 13-14mpg unloaded, doesn't require a CDL, no DPF/DEF garbage, and has a B10 (90% still on the road) rating of 310k miles with current versions at 375k. Downside is it doesn't like going over about 60-65mph and goes 28mph up the steepest grades fully loaded. But it gets there. The 8x18.5' bed is really useful for building supplies, fencing, hay, etc. I love it

Low to the ground-easy to work out of-great in tight spots.

 

[Hay Dude]

Why tow with it if you can simply put the load on the bed of the truck? Not quite getting the fixation with towing.

Probably because of the bed length limitation and loading the bed. High cargo, like a tractor, may exceed height limitations.
Trailers are much lower

 

[Renze]

Why tow with it if you can simply put the load on the bed of the truck? Not quite getting the fixation with towing.

When your only tool is a hammer, you go to see every problem as a nail.

When your only vehicle is a pickup with a fragile and impractical tin foil bed, you want to put everything on a trailer. When you drive a commercial Isuzu with a real bed, you dont use a trailer often...
(Or like me, when you dont want dirt in the back of your wagon Diesel and fuel is expensive, you only hook on the bed on wheels, when required)

 

[Renze]

Downside is it doesn't like going over about 60-65mph and goes 28mph up the steepest grades fully loaded. But it gets there.

I assume those hills are only so steep on backroads where the speed limit is 30 anyways ?

 

[ptsg]

When your only tool is a hammer, you go to see every problem as a nail.

When your only vehicle is a pickup with a fragile and impractical tin foil bed, you want to put everything on a trailer. When you drive a commercial Isuzu with a real bed, you dont use a trailer often...

I've been on the two sides of the spectrum.

Heck, the only reason I got rid of my dual cab Mitsubishi Canter was because of weight restrictions. Even though it was technically built to have 5500 kgs gross weight, it was registered as 3500kgs and therefore could only legally carry 1000kgs or not even that. Kinda silly.

Ended up going with a Mitusbishi L200 with a trailer and can now haul 2200-ish kgs. I didn't really wanted to get into a "bigger" truck with higher payload capacity and having to deal with the tachograph, more expensive inspections, Category C driving license, and so on. Even though I would like to have C+E driving license eventually.

I would much prefer haul the load on a bed of a truck than having to pull the load on a trailer but it is what it is. About the only advantage of the L200 is that I can use it as a daily, while before I had a small Ford Fiesta as daily and the Canter to haul stuff, so basically double the expense.