Here's how much power VW's cheating engines could lose without trick software

VW is mired in a scandal. The company has admitted that it cheated on emissions tests, installing software that could detect when a vehicle was being checked out.

The 2.0-litre TDI diesel engine is at the center of the storm. Almost 500,000 vehicles in the US are affected, out of 11 million worldwide.

But just how poorly does the engine perform when the cheating algorithms are switched off?

The crew over at The Fast Lane Car recently conducted their own testing to find out how much power the TDI could lose when the emissions cheating software isn’t active.

To conduct their test, TFL put a stock 2011 VW Jetta TDI on a four-wheel dynamometer, which measures car’s horsepower and torque output.

The four-wheel dyno allowed the TFL team to test the car while simulating both real world driving and emissions testing condition.

To gauge power output in real world-driving conditions, TFL ran the dyno with all four of the car’s wheels turning — tricking the car into believing it was on the road. In this case, the Jetta’s cheat software would turn off most of the car’s emissions control features.

As a result, the Jetta produced peak output of 138.5 horsepower and 260 lb/ft of torque. That’s on par with the manufacturer’s announced performance figures of 140 horsepower and 240 lb/ft of torque.

VW Jetta TDI TFLYouTube/The Fast Lane CarWith the pollution controls off.

TFL then ran the test again. This time, the dyno only the turned the Jetta’s front wheels. This tricks the car into believing that it is being emissions tested — activating all of the car’s pollution controls. In this setting, the Jetta produced a peak output 136.5 hp and 228.4 lb/ft of torque. 

With the full emissions controls on, the Jetta lost 2 horsepower and 32 lb/ft of torque at full throttle. However, TFL observed that the biggest difference in power at the lower end of the power curve, where the engine operates during acceleration. There, the TDI engine with the full pollution controls was down as much as 15 horsepower. 

This means that the TDI engines with the emissions control programs turned on will likely offer less peppy acceleration. 

VW Jetta TDI TFLYouTube/The Fast Lane CarWith pollution controls on in emissions test mode.

If The Fast Lane Car’s test are accurate, then the power loss is bad news for TDI enthusiasts.

“They are extremely impressive,” Consumer Reports’ director of automotive testing, Jake Fisher, said of the VW’s with the small TDI diesels.

“The TDI cars have a lot of torque and feel more powerful then they are.”

Before news broke of VW’s falsified emissions test, Consumer Reports had two of the affected models   — the Passat TDI and Jetta TDI — pegged with a “recommend” rating. The publication has since pulled those ratings and announced that they will retest the vehicles. 

The VW crisis led to the ouster of CEO Martin Winterkorn and the installation of Porsche CEO Matthias Mueller as VW’s new chief executive. 

In a speech to VW workers on Tuesday, Mueller reiterated the seriousness of the scandal and announced the company’s intent to cut back spending on non-essential investments. 

Here’s the complete video from The Fast Lane Car:


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