Porsche has temporarily closed order books for its entire range as it updates and retests each model to the new Worldwide Harmonised Light Vehicle Test Procedure (WLTP) standards, which come into force in September.

A spokesman told Autocar UK that Porsche has increased its existing stock of cars to reduce the order bottleneck this causes, but buyers wanting to spec a completely custom model will have to wait until the WLTP-approved models reach the market.

“Due to the time this test procedure takes, some models might not be ready for 1 September,” the spokesman said. “But we have grown the stocks of each car in the same way we would if a new model year were to be introduced so as to minimise the impact.”

Such a technique is often employed by manufacturers to fill the space between one generation of car and its successor, but this is the first time Porsche has grown stock for its entire range to minimise disruption for a new regulation. Other major brands are thought to be employing the same tactic.

The carmaker has increased its stock to minimise order bottlenecks

Porsche axes all diesel models from the current line-up

The WLTP test, which is tougher than the outgoing New European Driving Cycle process because it moves emissions testing from the lab to the real world, is forcing manufacturers to add more emissions-fighting hardware to their cars. The vehicles now have to be retested and given new official emissions and fuel economy figures.

The complicated changes required have already forced several manufacturers to slim down their ranges. BMW confirmed that the F80 M3 is being axed early because of WLTP, while several others have ditched low-volume diesel models as the deadline for the new regulation nears.

Manufacturers are employing these drastic measures to prevent a large volume of unsold pre-WLTP cars from existing after 1 September. While the UK Government is expected to allow a small percentage of pre-WLTP cars, estimated to be 5-10% of a car maker’s overall sales, to be sold after the new regulation comes into effect, any cars over that percentage might have to be scrapped.

Also read: New WLTP emissions test: when it's in force and how it could affect your car