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‘Muscle cars’ defy WLTP testing to produce lower CO2 emission figures

‘Muscle cars’ defy WLTP testing to produce lower CO2 emission figures

High-performance ‘muscle cars’ have lower carbon dioxide (CO2) emissions after going through Worldwide harmonised Light vehicles Test Procedure (WLTP) than their New European Driving Cycle (NEDC) correlated figures, according to an analysis by Autovista Group, which owns Glass’s Guide.

By contrast, many cars that are considered to be environmentally-friendly, have higher figures.

The Lotus Exige Cup 430, Ford Mustang 5.0 GT automatic and manual derivatives and the Subaru BRZ manual all had WLTP CO2 emission figures below their NEDC-correlated equivalent, although the automatic version of the Subaru BRZ was higher.

The UK government has said that it will introduce a motoring tax system based on WLTP CO2 values in April 2020. Until then the current system based on NEDC data remains in place.

During the current ‘transitional period’ vehicles tested to WLTP protocols then see the resulting figures ‘converted’ into a so-called NEDC-correlated value using a European Commission-produced mathematical tool.

It had been anticipated by the motor industry that NEDC-correlated figures would be tax neutral, but the reality has proved to be somewhat different. Autovista Group has previously reported that WLTP CO2 emissions figures were averaging 25% higher than NEDC-correlated values and the latest data reveal that the average discrepancy between the WLTP and NEDC-correlated figures now stands at 22%.

As Autovista Group highlights the new CO2 figures highlight a challenge for legislators in how high-performance cars will be taxed in light of WLTP testing. Simply adopting WLTP emissions figures would make the tax burden on such ‘muscle cars’ lower than with NEDC-correlated figures. By contrast, many cars considered to be environmentally-friendly would face significant tax hikes.

Autovista Group said: “This would appear to defeat the object of the more sophisticated WLTP test. The reality is that cars are more polluting in the real world than under NEDC test conditions and the new WLTP process is focusing attention on this.”

However, the cars still produce high CO2 emissions under WLTP testing, ranging from 191g/km CO2/km for the manual BRZ to 271g/km for the manual Mustang.

But, said Autovista Group: “It does present an interesting challenge for policy makers who will surely not be keen to reduce the tax burden on such vehicles.”

In its newsletter (7 June, 2018), it added: “Conversely, initial analysis reveals that many cars with comparatively low CO2 emissions are suffering from far higher WLTP: NEDC-correlated ratios. This is because the demands of the faster WLTP test cycle are greater than they were under NEDC testing and less powerful engines are having to work harder. This includes increasing the injection of fuel, which in turn increases fuel consumption and emissions. Paradoxically, these efficient models will all be rather heavily penalised compared to today if tax regimes adopt WLTP emissions figures.”