Towing with a 3.0 L Touareg TDI diesel

rjstractor wrote:

NinerBikes wrote:
Think about the load bearing surfaces for making that torque and HP from a 444 Ci 7.3 L diesel, how much piston surface, block bore surface, bearing surface, the size of the wrist pins and connecting rods, etc, to get the same horsepower... that's a mere 181 cubic inch, 3.0 liter motor. Ask a mechanical engineer to do the stress loads on all the parts for the amount of work done. You have to run 2.5x the amount of fuel and air or more, due to VW using the turbochargers boost to air cool the motor also, volume wise to a 3.0L to a 7.3 motor.

The little motor, is working much, much harder, with much less material, for the same amount of work being done. Guess which motor will wear out quicker and fail sooner?

Good points, but playing devil's advocate, look at the history of automotive engines. Displacement continues to shrink while output continues to rise, yet engine longevity also continues to rise. 40 years ago most engines wouldn't make it 100,000 miles without a rebuild. The excellent TDI motor in your Passat when compared with VW's first car diesel has over twice the power output, better fuel efficiency, and will last probably twice as long, all while moving a much heavier car.

The passat makes 10 to 12 HP all day long on a 2 liter motor traveling at 60-65 mph, based on fuel consumption. Burning 8+ gallons of diesel towing per hour at 9 to 10 MPG is having a 3.0 liter motor running a lot of boost on the turbo charger at all times, and using 85 to 100 HP to tow down the road. That's about a 40-55% load, on flat ground. Add in hills or mountains, and that percentage climbs fast, leaving not much margin when towing, on the whole drive train.

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.