The Big Three's New Diesels put on a Dyno

demiles wrote:
The maximum torque limit on today's emissions controlled diesels is dynamic depending on many variables. The two different tests by TFL with the Ford proves this.
These are general limitations and each manufacture may use variations and set points to suit they're needs.

1)Maximum engine torque is limited by DPF soot load,atmospheric pressure, and intake pressure / temperature.
2)Transmission torque limit
3)Torque reduction for heating protection
4)Torque reduction for smoke limitation
5)Fail safe mode ECU failure

So these tests are really only valid under the very specific conditions they were performed. Change the weather conditions, temps ect and the results will probably change as well. The rated peak torque figures will only occur under proper conditions and obviously Ford is reducing it's max torque number under the TFL test conditions that day. So what is learned from this test? Ford guys don't challenge a LP5 or a RAM 6.7 during the heat of the day,wait till night time.

Exactly! With computer controlled injection and turbocharging, the manufacturers can program an array of fuel maps for many different variables. They can set the engine to reduce power if certain temps are getting to high or even program the engine to not get all the fuel(power) available in the first few gears like the Cummins has had for a while and now the new Ford from what I have read. I know from my time at Cummins that the 6.7L is definitely programmed to de-fuel if EGT's get to high.

I also know from my experience in the diesel aftermarket world, that if a 450 whp(@ 520 hp crank) tuned diesel with an intake and a free flowing deleted exhaust can get it's EGT's high enough when towing heavy to need to be turned down(de-fuel) to it's 400 whp (@ 460 hp crank) tune to keep then in check. Then there is no way a 450 hp truck with a stock intake and all of its emissions equipment will not have high EGTs pulling heavy loads. There is a reason why the aftermarket diesel tuners recommend their customers to tow heavy with their lowest power(fuel and timing) setting and high EGTs with the higher power tunes under sustained load is the main reason.

So it is not a shocker that while these new trucks will put out the advertised power numbers if all the temps are good like in normal driving or towing light to medium loads, but will reduce power output(de-fuel) to lower power numbers if the temps get too high. Although, if the Ford would have downshifted to a lower gear then it would have lowered the EGTs a little or at least kept them in check for the whole run. The Cummins was probably fine in fourth due to the 6.7L "play it safe" lower power numbers along with the Ram Active Air intake it probably had enough air to burn the fuel to keep the EGT's from getting to high. Just to be clear, these are just my theories.