Towing with a 3.0 L Touareg TDI diesel

NinerBikes wrote:

rjstractor wrote:

NinerBikes wrote:
The chassis may handle 7700 pounds for towing, day in and day out, but the motor and drive train is light duty diesel. VW Audi runs these motors in a lot of sedans in their line up, VW is not really in the heavy duty SUV or truck business. It's my belief they engineer their motors accordingly.

That is likely very true. Isuzu builds a 3 liter diesel that they deem to be heavy duty in their Ecomax commercial trucks. Granted it's only rated at 150 hp/282 torque but at 18000 GCWR it's going to be at full power a lot of the time. Isuzu gives it a 310,000 mile B10 rating. It would seem that this is a 3 liter diesel that can handle heavy use over a long period of time.

Lowering the maximum HP and maximum torque, per engine displacement size, in this case 3.0 liters, is how they increase the longevity, along with beefing up the parts. You start making big HP and big torque numbers out of a 3.0 Liter diesel to start towing, with a sedan based motor, you are going to markedly shorten the longevity of the whole engine and drive train, when you stick the same motor in a SUV that weighs 5000 pounds and people trailer with it at or near the limits at high speeds. I'd rather get 9.5 MPG out of an engine with 6.7 L of turbo diesel displacement than 3 L of turbo diesel displacement. I am of the opinion that at that fuel consumption rate, the little motor when not on the flats, is doing too much work at too hard a rate, sending a boy out to do a man's job.

Not an expert in this field, but you are talking about duty rating as I understand it. And I think your theory re: the little engine not being designed to run at 80% output continuously is probably spot on.

Most motors will be designed with a duty rating, ie, how long they are intended to run at a certain percentage of output. The engine in a Corvette might put out a lot of power, but in reality, it will only put out max power for 10 seconds at a time. Going down the road 90% of its life, it will be at 10% output. Conversely, a medium duty engine in a commercial truck might be running at 50% of its output going down the road all the time, and subjected to 100% output for extended periods of time. So the engine, cooling, and drivetrain parts need to be designed for this purpose.

A non-automotive example is a blender. Try running your blender for a minute -- you'll smell hot electronics. 5 minutes and the motor will be toast. It just isn't designed to operate at full output for more than short bursts.