Detuned 6.7 diesel in Ford Super C RV

patperry2766 wrote:
Hypothetically speaking, wouldn't it be more beneficial to give this medium duty chassis all the power available so it wasn't necessary to run at near max/max capacity for extended lengths of time?

Basically what they are doing is artificially limit it so it is never running near max output.

These rigs also have much lower gearing then light-duty trucks, to put more torque to the rear wheels. This improves acceleration and gradability, however HP is what matters for top speed up grades. These sacrifice some speed in order to gain longevity.

more power needs bigger rad, might not be the room . imagine worst case
-full load
-climbing
-desert (air on full)
-summer
-head wind
all must be considered when designed and warranty costed in.

Hypothetically speaking, wouldn't it be more beneficial to give this medium duty chassis all the power available so it wasn't necessary to run at near max/max capacity for extended lengths of time?

With having to put more throttle into it to get the mass moving and to keep it moving vs the un-tuned diesel, it seems that would put extra stress on the engine and lead to excessive wear and tear.

Do they get around this by presumably putting taller rear-end gears to compensate for reduced engine output?

CumminsDriver wrote:
Detuned engine output also because of duty cycle requirements that the chassis cabs have that the pickups don't.

Hit the nail on the head !

"Medium duty" truck engines are run at/near max capacity for long periods of time. Cooling is key to pass this test. Less power, less heat.

Yes, you could easily change the tuning for more power, however keep in mind that will most definitely affect the powertrain warranty. I would not want to own a 6.7L without a warranty.

The chassis cabs are designed to run longer duty cycles at full output than the pickups. I have not seen those differences in the engine or transmission and all the tuning is done in software. You will find the chassis cab has different axles and RP ratios than the pickup to better use the detuned engine.

I've been driving a 2011 F350 6.7 PSD chassis cab at work since Dec of 2011, and now have approximately 115,000 miles on it. The F350 thru F550 chassis cabs have a different turbo, air intake, and different exhaust system than the pickups have. Detuned engine output also because of duty cycle requirements that the chassis cabs have that the pickups don't.

Rich

All the manufacturers do this with their commercial diesel engines. A lot of it has to do with reliability over many duty cycles hauling or towing near max capacity all the time. Different emissions requirements also play a part I'm sure.

I'm sure they could be reflashed with a different tune as I doubt there are any physical differences in the engine itself.

It is good to see a diesel in a class C though as an option.

No, they simply don't give the engine as much fuel.

The more fuel you give a diesel engine the more power you will make up to the point you burn it up, break it, or hydro lock it.

Many engine makers have the same engine make different power outputs. I think Cat's 3208 makes from low 200's to over 500 HP. Same engine, just different fuel settings.

My friend has a class 8 Volvo that he detuned to 400 HP to get better mileage. A lot of trucking company owners do this also.