Is the 2-liter TSI engine in the Polo WRC a gas guzzler?

Hello,

The Polo WRC (special edition) has a 220 hp TSI engine, just like the Golf GTI.
The torque data according to the catalogs are the same (350 Nm from 2500 - 4400 rpm).
However, the fuel consumption comparison on the Volkswagen website looks strange (city / highway / combined / CO2 emissions).
Golf GTI: 7.5 / 5.1 / 6 / 139
Polo WRC: 10.1 / 6 / 7.5 / 174

According to the CO2 emissions data, the Polo consumes 25% more fuel (in the standard cycle) than the Golf, with practically the same weight. In city driving, it even consumes 35% more fuel than the Golf!

Does anyone know the technical reasons behind these differences?

The Polo still has an old engine .

http://www.autozeitung.de/auto-vergleichstest/vw-golf-7-gti-polo-r-wrc-2013-vergleich-polarkreis

Here are some details I found about the evolution of the 2.0L TSI engine:
http://www.autohaus-kubik.de/?p=2816

After some searching, I believe I know how VAG achieves the fuel efficiency advantage of the Golf GTI compared to the Polo WRC (by the way, the Scirocco 2l TSI with 210 hp has a CO2 emission of almost 172 g, which is nearly as high as the WRC Polo's 174 g): simply by using the currently popular "BlueMotion" features.
The start-stop function primarily reduces fuel consumption in urban driving by automatically shutting off the engine during periods of inactivity.
In addition to that, there's also what's known as recuperation:
When braking, the alternator voltage is disconnected, which tends to overcharge the battery. During acceleration, the alternator is switched off, and the electrical load is solely supplied by the battery. This allows you to achieve the desired acceleration or speed with slightly less fuel consumption.
This requires expensive specialized batteries, and the electrical components may not necessarily last as long under the constantly fluctuating onboard voltage that is typically encountered.

See also http://www.volkswagen.de/de/Volkswagen/InnovationTechnik/technik-lexikon/rekuperation.html.

Overall, I believe these are more like "tricks" for optimizing fuel consumption, which can significantly reduce the "normal" consumption and save a few euros on CO2-based taxes. However, with anticipatory driving that involves minimal braking and limited stop-and-go situations, the actual fuel consumption probably won't be reduced as much as the catalog data suggests.

That certainly contributes its part, but the engine in the GTI is simply a generation and several development stages ahead. The Polo WRC still uses the older EA113 engine, while the GTI features the EA888 series. And that has been extensively revised. Just Google the engine series to find plenty of information. According to initial practical tests, it seems you can actually drive it quite fuel-efficiently (relative to its power output) if you want to.
But starting on Tuesday, I can test it. From then on, the GTI will be mine .

ulf wrote:

... und die elektrischen Verbraucher werden eine permanent deutlich schwankende Bordspannung auch nicht unbedingt mit der sonst üblichen Lebensdauer belohnen.

For vehicles with regenerative braking, separate voltage regulators are installed for sensitive electrical components, which are supplied by dedicated circuits.