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power limitations of a 250 Cummins?
- Thread starter Machinist22
- Start date
- 1,046
- 45
- 48
- Location
- Syracuse, New York
Big rigs run at a relatively low RPM. They get good fuel economy because they are geared for continuous duty near, or slightly beyond, the torque peak. 1200-1400RPM at highway speed is typical. The low piston speed allows for a very long TBO. They also use big boost, 36-40psi is common, so they are all intercooled. Some have steel crown pistons.
A M35A2 in standard tune makes less than 1/3 the torque as the 'weak' work truck I used to drive (contemporary Mack single axle tractor w/EM7~250 - rated at 250HP @ 2100 and 1040 lb-ft @1200rpm ~9mpg) . Interestingly the deuce uses almost 50% more fuel to make less than 1/3 the power.
A hopped up M35A2 w/LDT-465 makes about 1/3 the torque and will use a bit less than twice the fuel (as the Mack)*.
The 5 ton w/LDS465-1 is rated at 170-185HP @2600rpm**. It makes 440 lb-ft torque @ 1800rpm** so it too has less than half the torque and uses about twice the fuel (as the Mack).
The 5 ton NHC250 is rated at 240HP @ 2100rpm*** and 658 lb-ft @ 1500rpm*** (that's 600 lb-ft @2100) and gets 4.4mpg***... so it puts out about 35% less power and uses twice as much fuel (as the Mack).
IMO you'd have to make too many changes to get a NHC250 to match the performance/efficiency big rigs enjoy.
* My LD 465 w/turbo set at 13psi @2600rpm (5-6mpg)
** LDS-465-1 Troubleshooting Manual
*** TM9-2320-260-20
A M35A2 in standard tune makes less than 1/3 the torque as the 'weak' work truck I used to drive (contemporary Mack single axle tractor w/EM7~250 - rated at 250HP @ 2100 and 1040 lb-ft @1200rpm ~9mpg) . Interestingly the deuce uses almost 50% more fuel to make less than 1/3 the power.
A hopped up M35A2 w/LDT-465 makes about 1/3 the torque and will use a bit less than twice the fuel (as the Mack)*.
The 5 ton w/LDS465-1 is rated at 170-185HP @2600rpm**. It makes 440 lb-ft torque @ 1800rpm** so it too has less than half the torque and uses about twice the fuel (as the Mack).
The 5 ton NHC250 is rated at 240HP @ 2100rpm*** and 658 lb-ft @ 1500rpm*** (that's 600 lb-ft @2100) and gets 4.4mpg***... so it puts out about 35% less power and uses twice as much fuel (as the Mack).
IMO you'd have to make too many changes to get a NHC250 to match the performance/efficiency big rigs enjoy.
* My LD 465 w/turbo set at 13psi @2600rpm (5-6mpg)
** LDS-465-1 Troubleshooting Manual
*** TM9-2320-260-20
Machinist22
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- Location
- Colville, WA
Yeah, the more I think about it, the more I like the idea of dropping in a 5.9 common rail engine from '03 or newer. These things are great for power and there are a ton of aftermarket parts for upgrading. Also, the 6-speed manual is more attractive to me than the older 5-speed. The disk brake conversion is also a must.
This engine is also very quiet and efficient.
However, instead of bobbing it, I think I'll pull the front of the rear axles and do an extended cab with the trailer bed. It's a longer wheel base but it'll fit the whole family when we go to rally's and stuff. The other option I have is bobbing and doing an extended cab but that leaves me with very little bed. All that "heavy duty" going to waste then.
At this point it's all still conjecture, but if you can't dream, what's the point.
When I finally do get an M35 I'll have so many ideas floating around in my head I won't know which direction to go and will probably end up leaving it stock.
Still looking and dreaming (and researching),
Jim
This engine is also very quiet and efficient.However, instead of bobbing it, I think I'll pull the front of the rear axles and do an extended cab with the trailer bed. It's a longer wheel base but it'll fit the whole family when we go to rally's and stuff. The other option I have is bobbing and doing an extended cab but that leaves me with very little bed. All that "heavy duty" going to waste then.
At this point it's all still conjecture, but if you can't dream, what's the point.
When I finally do get an M35 I'll have so many ideas floating around in my head I won't know which direction to go and will probably end up leaving it stock.
Still looking and dreaming (and researching),
Jim