2014 Ultimate 1 Ton Challenge results

4x4ord wrote:
You are thinking about it in too much depth, it's much simpler. The longer the engine has to load the more power it will make.

There is also a big difference in torque, and sometime hp, based on how the run is started. 1400 rpms with no boost will make a lot less torque and possibly hp than 1400 rpm with 10 psi at the start of the run.

A 5th gear run from 1400-3200 has 46 mph to complete the run in, but 6th has 64. That extra speed of the roller means the engine gets closer to full load.

Correct, conditions on a hill are very difficult to duplicate on a chassis dyno. I make 30-32psi on no grade, and only 28ish on the dyno. That's load.

And it's for this reason that IMHO, all turbo diesel trucks should be done on a pull-down dyno, like big rigs.

A big diesel's inertia is too high for inertial dynos to measure accurately, and modern transmissions do not always allow full loading in a high gear.

Every heavy truck, school bus, tour coach, that I've seen is measure on a reverse pull-down dyno, which you start at max rpm and load it till below peak torque. But few light diesel shops are equipped with such expensive hardware.