In an earlier video from TFLCar, they asked five significant questions about the Dieselgate scandal. These questions circled around various aspects of “Why did VW decide to cheat the emissions tests?” VW’s management aren’t idiots, they had to have a reason for committing this fraud.
One question was how much power is lost when emissions controls were engaged during emissions testing? The VW TDI Diesel’s are fun zippy cars, and VW would want to preserve that behavior to keep sales going. Obviously when the emissions control is engaged the car passes its emissions, so in theory VW could leave that system engaged all the time to avoid committing fraud. But they chose to commit fraud, and maybe the justification had to do with engine power (torque, horsepower).
To test that idea, TFLCar found a tuning shop with a dyno that could run in four wheel drive mode. The theory was that if all four wheels were spinning the car might think its on the highway. They first dyno’d the car with the four wheels spinning, and the torque produced matched VW’s specifications for the car. They then dyno’d the car in two wheel drive mode, meaning the rear wheels were not spinning, and suddenly the car changed its behavior quite a bit and produced significantly less torque.
Going by the torque curve, it would be much slower off the line but still produce about the same power once it gets up to speed.
In other words, if this car were to drive that way on the streets that zippy fast fun feel would be gone.