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The flood of M939 series trucks has started, and we have a new toy to play with. After having read ~all of the related threads on M939 series trucks, motors, transmissions, there seems to be some room for a separate discussion of how to get more power out of the NHC 250 when it is installed in front of the Allison Automatic.
The M923 I have has the Allison MT 654 transmission, rated for 300 HP and 950 ft lbs torque. The Allison dealer did not want to up the HP on my motor in front of that transmission beyond what the transmission is rated for. I understand why.
From what i have been able to glean, the NHC 250 is 855 cubic inches, and is the same motor as the Cummins 350 and 400 but with smaller injectors and less fuel to them.
The driveability of the truck would be greatly enhanced with another 100 HP or so, and I think that as an owner operator I am grown up enough to be able to safely operate it with increased HP without tearing up the transmission. Especially considering how difficult it is to even get a full weight load on the truck.
Here is what I would like to hear from you about:
1. What are your thoughts on the ability of this transmission to handle the increased HP?
2. I have been told that all one needs to do to get more power is to install, say 350 HP injectors and turn up the pump, that a turbo is not needed. Maybe just a pyrometer. Is this true?
3. What models of Allison transmissions have you encountered that were installed in M939 series trucks?
This has already been thoroughly discussed, but seems pretty specific to the M800 series trucks, so here we go!
The M923 I have has the Allison MT 654 transmission, rated for 300 HP and 950 ft lbs torque. The Allison dealer did not want to up the HP on my motor in front of that transmission beyond what the transmission is rated for. I understand why.
From what i have been able to glean, the NHC 250 is 855 cubic inches, and is the same motor as the Cummins 350 and 400 but with smaller injectors and less fuel to them.
The driveability of the truck would be greatly enhanced with another 100 HP or so, and I think that as an owner operator I am grown up enough to be able to safely operate it with increased HP without tearing up the transmission. Especially considering how difficult it is to even get a full weight load on the truck.
Here is what I would like to hear from you about:
1. What are your thoughts on the ability of this transmission to handle the increased HP?
2. I have been told that all one needs to do to get more power is to install, say 350 HP injectors and turn up the pump, that a turbo is not needed. Maybe just a pyrometer. Is this true?
3. What models of Allison transmissions have you encountered that were installed in M939 series trucks?
This has already been thoroughly discussed, but seems pretty specific to the M800 series trucks, so here we go!