SkiFreak
Crazy Person
I am guessing that the image is that of a 3D model, not of an actual truck.
Isuzu NRR / Acela Straya High-mobility 4×4 Cab-over Truck
- Thread starter carterd
- Start date
charlieaarons
Explorer
Re 2 piece wheels, somehow Iain, living is Brisbane, managed to obtain them and now has them on his U1250 camper.
FWIW my 2 piece wheels, which I obtained from a surplus dealer in near new condition, for ~93% discount in virtually new condition as US Army “surplus”, have DOT ratings stamped into them. Don’t know if that’s sufficient for an Australian roadworthy inspection or not.
FWIW my 2 piece wheels, which I obtained from a surplus dealer in near new condition, for ~93% discount in virtually new condition as US Army “surplus”, have DOT ratings stamped into them. Don’t know if that’s sufficient for an Australian roadworthy inspection or not.
The Isuzu NRR is also available in the U.S. with the Isuzu 5.2L I4 turbodiesel. 215 HP @ 2,500 RPM and 452 LB-FT @ 1,850 RPM. This comes with an Aisin 6 speed with PTO. I can't tell from the photos if they are using a divorced transfer case or not. They could have modified the output shaft of the Allison to mate to the NV273 transfer case, which may not have been possible with the Aisin. If they are using a divorced transfer case it wouldn't matter.
yabanja
Explorer
I reached out to them about getting a diesel model. Their response was:
"Thanks for reaching out. Until Isuzu puts a diesel with adequate hp we will stick with the gas engine."
Strange. I don't really care about hp in a big truck. What I do care about is Torque, and Fuel Economy both of which I am sure the diesel option has in spades.
My take on these vehicles:
1. From a business standpoint It is a stroke of brilliance to use the military axles and tires for the potential of industrial/military contracts.
2. For the private individual with a fairly light camper they are way overkill and the tires are prohibitively expensive to replace as well as comparatively difficult to source. I am sure the significant additional rolling mass has a fairly detrimental effect on acceleration, braking, and economy.
3. It is pretty exciting to see a 109" wheelbase option as we love our short wheelbase truck (112") for many reasons and I have considered going shorter on a future build.
Allan
"Thanks for reaching out. Until Isuzu puts a diesel with adequate hp we will stick with the gas engine."
Strange. I don't really care about hp in a big truck. What I do care about is Torque, and Fuel Economy both of which I am sure the diesel option has in spades.
My take on these vehicles:
1. From a business standpoint It is a stroke of brilliance to use the military axles and tires for the potential of industrial/military contracts.
2. For the private individual with a fairly light camper they are way overkill and the tires are prohibitively expensive to replace as well as comparatively difficult to source. I am sure the significant additional rolling mass has a fairly detrimental effect on acceleration, braking, and economy.
3. It is pretty exciting to see a 109" wheelbase option as we love our short wheelbase truck (112") for many reasons and I have considered going shorter on a future build.
Allan
If they are doing a 109" wheelbase option then I bet they are mating the transfer case to the Allison transmission versus being divorced. Below is a picture of the CORE chassis on the 132.5" wheelbase I took at Overland Expo West last year. With the divorced transfer case the rear driveshaft was short and at a fairly steep angle. A 109" wheelbase would be 2 feet shorter, so I don't think there would be room for a divorced case.
I also wonder if all this discussion is theoretical for a DIYer. With the supply chain challenges, labor shortages, and high demand, these trucks might be unobtanium. CORE is under contract to provide their chassis to six fire districts across Oregon under the State Preparedness and Incident Response Equipment (SPIRE) grant. There is another $10 million of SPIRE grant money available in 2022-2023, with the next round opening in March. The DIYer isn't going to compete with this. Acela could be competing with similar state or federal contracts. It's okay to dream.
I also wonder if all this discussion is theoretical for a DIYer. With the supply chain challenges, labor shortages, and high demand, these trucks might be unobtanium. CORE is under contract to provide their chassis to six fire districts across Oregon under the State Preparedness and Incident Response Equipment (SPIRE) grant. There is another $10 million of SPIRE grant money available in 2022-2023, with the next round opening in March. The DIYer isn't going to compete with this. Acela could be competing with similar state or federal contracts. It's okay to dream.
tkj23qe1387
New member
Great points. Consumer supply could be a huge problem. Gov contracts are much more stable and lucrative.
However, on the specs sheet, Acela explicitly mentions how their brake system complied with FMVSS 105. I suspect that they might be trying to match EC/CORE’s marketing of how much testing they had done on the Isuzu modification. Gov procurement people obviously have their own due diligence questions, so was this point directed more at consumers?
Acela also claims that their offering is developed with some form of involvement from Isuzu. According to Instagram, truck will also be shown at a March trade show in the Isuzu booth. OEM involvement might explain why they are able to offer a three year base warranty with five year extended warranty options. EC/CORE’s warranty is two years, I recall? Before EC/CORE switched to Isuzu, I think they had a much closer working relationship with Fuso as a final-stage manufacturer. I haven’t seen a similar claim regarding Isuzu.
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tkj23qe1387
New member
Does anyone have a sense of the remaining surplus LMTV supply as of now? Acela's class 6-8 options rely on those surplus trucks as the basis of refab. The supply of LMTVs' Austrian ancestor (12M18) kind of dried out as of now I think.
Interesting that Acela mentions the lack of a high-powered Diesel in the NRR line. Why hadn't they opted for an FTR as basis instead? Perhaps it is due to business concerns of not cannibalizing their Monterra lines?
So far, it seems that most commercial clients are using the Monterra for heavy duty field work, e.g., in oil fields, while most government clients are using the Monterra for fire-fighting or high water rescue. With the high fording option, the Straya has even better fording capabilities than the Monterra. Is cannibalization really avoidable?
As such, as long as the LMTV supply will eventually dry out, Acela will have to turn their attention to the F series sooner or later. And we will finally get a suitable cab-over truck here in the US.
This is a common sentiment but is a misunderstanding of what torque and power are. Torque is a force and in and of itself cannot be used to determine anything of value. Torque became a sales tool when turbo diesel engines became available in light trucks and the jump higher pee further crowd wanted to one up the guy beside him. Go ask a truck driver what engine they have in their truck. They will say a Cat 450, Cat 500, Cat 600. That number is the Hp, not torque. They dont care about torque, its all Hp.
I can give my 105 lbs daughter a 10'pipe stuck on the end of a wrench and she can make 1000lbft of torque but only about 1/2 horse power regardless of how long or short the pipe is. Torque can be increased or decreased through gearing. 300lbft of torque produced by the old vortec 5.7 in my truck, through a torque converter resulting in up to a 2.5:1 torque multiplication, 2.482:1 first gear in the 4L80e, ~2.5:1 in the black box underdrive, 2:1 in the np205 and finally 5.38:1 in the rear end means that the axles see around 50,000 lbft of peak torque. Lock out the under drive unit and im down to less than 25,000. Its just gearing. No matter what the torque is, the engine is only capable of doing X amount of work.
Horse power on the other hand is the rate at which work can be done. It is calculated by how much torque an engine is producing, multiplied by the engine speed at which it is being produced divided by 5252.
An engine that produces 215hp can only work half as fast as an engine that produces 430hp, regardless of how much torque it makes. That truck probably requires 100-140 Hp to push it down a highway, never mind up a hill at highway speeds or god forbid up a hill into a headwind. 215Hp is simply not enough power to meet its peak demands.
charlieaarons
Explorer
215 hp at 2500 = 75mph is a lot more than (6.0L Vortec) 160hp at 2500 = 75mph. The 311 hp at 4900 rpm in 6th gear for the 6.0L Vortec at 150mph is obviously irrelevant.
Ultimark
Active member
My nephew worked in the Pilbara region of Australia as a road train driver for close to 10 years, made his dough and is back in the eastern states with one of the trucks that originally was a road train prime mover, bought it from his boss and rebuilt it and reconfigured the unit for his purposes. He did though keep the 2000 litre fuel tanks, perfect for refuelling his big earth moving equipment.
The truck he brought back is an old Scania R730, I have no idea how many kilometres it has done, but on average they were doing around 500,000 to 540,000 kilometres annually running 24/7 on a double 12 hour shift with two drivers. That old truck is now his work truck, he has an earth moving business in rural Australia.
The first thing anyone who is going to haul weight does, is to check out the torque output, very closely followed by the power output. then they look as to where the torque comes in and how far the torque curve is flat, in other words, where the real power is. Power basically determines what your top speed is, torque determines how fast you can get there with whatever weight and wind resistance you need to overcome.
The Scania R730 is 730 HP, or in metric land 537 kW, the torque available is 3,500 Nm (2581 lb ft). That maximum torque is available from 1000rpm and in its former life it was carrying and pulling around 170 tonne of load, the combined prime mover with a quad trailer system on the rear, was 53 metres long (174 feet) and around 195 tonne travelling at 90 km/h day in day out. When you have a truck moving that amount of weight, a question he was often asked was, "how much torque is that thing making?"
Now for our purposes, and I would suggest this is really what yabjana is on about, is the ease of driving with oodles of torque in a touring truck with a house on the back as you idle through interesting and sometimes difficult terrain. I have an Isuzu NPS it has a very modest power output, 114kW (155PS) combined with 419Nm of torque. My torque availability at 1000 rpm, is 90% of torque, maximum torque is available from 1600 rpm to 2600 rpm. Idle is 750 rpm and at idle and sometimes slightly lower than idle on a decent incline, a slight application of throttle and the engine just pulls as clean as a whistle and no touching of the clutch pedal is required. This is mainly due to having a large 5.2 litre engine with a modest power output and reasonable torque figures. The ease and tractability of something like this is what I myself love about diesel powered stuff; effortless driving.
As for performance, high power output, yep, that can be arranged. As you extract more power from the engine, both torque and power outputs move up the rev range and the vehicle certainly loses some low down tractability and eventually has none to little low down tractability. Basically one needs to figure out where you need/wish your power and torque to be, then pick the vehicle that suits your needs.
The truck he brought back is an old Scania R730, I have no idea how many kilometres it has done, but on average they were doing around 500,000 to 540,000 kilometres annually running 24/7 on a double 12 hour shift with two drivers. That old truck is now his work truck, he has an earth moving business in rural Australia.
The first thing anyone who is going to haul weight does, is to check out the torque output, very closely followed by the power output. then they look as to where the torque comes in and how far the torque curve is flat, in other words, where the real power is. Power basically determines what your top speed is, torque determines how fast you can get there with whatever weight and wind resistance you need to overcome.
The Scania R730 is 730 HP, or in metric land 537 kW, the torque available is 3,500 Nm (2581 lb ft). That maximum torque is available from 1000rpm and in its former life it was carrying and pulling around 170 tonne of load, the combined prime mover with a quad trailer system on the rear, was 53 metres long (174 feet) and around 195 tonne travelling at 90 km/h day in day out. When you have a truck moving that amount of weight, a question he was often asked was, "how much torque is that thing making?"
Now for our purposes, and I would suggest this is really what yabjana is on about, is the ease of driving with oodles of torque in a touring truck with a house on the back as you idle through interesting and sometimes difficult terrain. I have an Isuzu NPS it has a very modest power output, 114kW (155PS) combined with 419Nm of torque. My torque availability at 1000 rpm, is 90% of torque, maximum torque is available from 1600 rpm to 2600 rpm. Idle is 750 rpm and at idle and sometimes slightly lower than idle on a decent incline, a slight application of throttle and the engine just pulls as clean as a whistle and no touching of the clutch pedal is required. This is mainly due to having a large 5.2 litre engine with a modest power output and reasonable torque figures. The ease and tractability of something like this is what I myself love about diesel powered stuff; effortless driving.
As for performance, high power output, yep, that can be arranged. As you extract more power from the engine, both torque and power outputs move up the rev range and the vehicle certainly loses some low down tractability and eventually has none to little low down tractability. Basically one needs to figure out where you need/wish your power and torque to be, then pick the vehicle that suits your needs.
311 hp at 4900 rpm is very relevant in 2-4 gears.
If you only had one gear, and the gearing used for both power plants was the same, that would be correct. That is not the case. What I was trying to point out above is that engine torque is irrelevant. That is not to say how broad the torque curve is, is irrelevant, as the "area under the curve" is very relevant to how many gears you need between the engine and the axles.
The torque figure you need to concern yourself with is: How much torque do you need at the WHEELS and how fast do those wheels need to be spinning (this is precisely what dictates how much power you will require). That is what matters. The example above of my daughter on a 10' pipe producing 1000 lbft of torque. If you connect her to the drive line and gear it low enough, she will get the truck up the hill, there is no question about it, it will take a while though. You can gear to generate enough torque at the wheels to get the job done, it just wont be very quickly. The same holds true with the diesel vs gas argument. The diesel will get the job done with its 215 hp, but on the highway, loaded, up a hill with a head wind, 215 hp at 2500 rpm will not = 75mph. It will have to gear down to be able to produce the required wheel torque to keep moving but will result in the vehicle moving slower. Again, wheel torque is what is required to move
215 hp at 2500rpm may very well = 75mph, but that is ignoring load conditions. Truck drivers do not care what peak torque is. When under maximum load, the goal is to operate the engine at peak power by selecting the gear that will allow the engine to operate there. Just to be clear, it isnt just this simple but it isnt much more complicated than this. There are circumstances such as starting from a stand still, on a hill, with a maximal load with inadequate gearing where the location of peak torque is very important, but again, adequate gearing will fix that so lets not get into a circular argument on that.
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Buddha.
Finally in expo white.
I had a GM truck with this 6.0 engine, and a six speed trans.
Towing my big boxy travel trailer we were 17,000lbs combined weight(4,000 under what the truck was rated for).
The engine did it but at 3500-4500rpms to maintain 55mph with a headwind, that makes for a long day.
I don’t think this truck would be any better.
Towing my big boxy travel trailer we were 17,000lbs combined weight(4,000 under what the truck was rated for).
The engine did it but at 3500-4500rpms to maintain 55mph with a headwind, that makes for a long day.
I don’t think this truck would be any better.
It almost certainly wouldnt be, but your real world experience is perfect! Just to do 55mph your 6L had to spin at 3500-4500. From this website: https://www.dieselhub.com/gas/gm-6.0-vortec-l96.html here is a graph of a 6l torque/hp curve:
At 3500rpm your 6l was producing somewhere around 250-275 hp meaning it was taking around that to move the truck, trailer. It should be clear that an engine with 215 peak hp would not be traveling at 55mph in the same conditions.
Dont get me wrong, the small diesel engine will make some people happy. It would do a fantastic job off road and for the people who dont mind traffic piling up behind them on hills or in headwinds, they would be perfectly happy with 215 hp. But for a large number of customers this would be unacceptable and that is what the manufacturer cares about, not the fringe.
tkj23qe1387
New member
This is a super relevant comparison.
I think a diesel with 200-250 max hp would probably do great in anywhere but North America where trucks must remain under a strict speed limit. However, in North America, trucking speeds on highways are crazy by any other standard. Acela needs to appease the North American clientele so I totally understand what they mean by the lack of power from Isuzu. Their Gov customers need the vehicles to be able to RUSH from base to the work location ASAP.
Ignoring vector aspects, power = force x speed. For the same vehicle going up the same hill under same wind conditions, it must overcome the same air drag, rolling friction, and the road-oriented component of gravity. That combined effective force multiplied by the velocity is the rate of work, i.e., power, that the engine must meet. If 300hp of power is required to move at a certain velocity in set conditions, a 200hp engine simply cannot move that fast, or the load must be lightened, or the shape must be optimized, so as to reduce either force or speed.
If torque is insufficient, the auto gearbox will figure it out, most of the times. Starting from stall or a hill would certainly benefit from high torque at low ends, which I think is why engine manufacturers offer different tuning options for end users. There will be some type of trade off between power and torque.