Interview: Phil Stones, Chief Engineer – Powertrain at Millbrook Proving Ground

25 September 2018

Autovista Group caught up with Phil Stones, chief engineer – powertrain at the UK’s Millbrook Proving Ground, to discuss how the facility is working through the worldwide harmonised light-vehicle test procedure (WLTP).

What is your role – and Millbrook’s role, in WLTP? 

Millbrook is a testing organisation, and we can test customer’s vehicles to the requirements of WLTP to deliver test results that they can use for development or certification purposes.

How big a job is it to test vehicles, and what is the average timescale for a vehicle model to clear the RDE test?

It is a very complicated and involved process to test a vehicle to the regulations correctly, as the regulation is many hundreds of pages long. The timescale to develop a vehicle to RDE is dependent on many factors within an OEM’s control, and Millbrook is not based to judge this. A Regulatory RDE test process takes two days per run (one day soaking and one-day test, so in theory one test per day once setup). The OEM will then need to conduct multiple tests to satisfy the Type Approval Authority and themselves that the vehicle will be compliant under all RDE boundary conditions.

Are WLTP results hugely differing from NEDC (in general rather than manufacturer specific)? 

The CO2 values have been noted to being up to 13% (industry-sourced figures) higher on WLTP than NEDC due to a number of difference in the dynamics of the drive cycle and the differences in certain elements of the test procedure.

In your view, is WLTP needed in the automotive industry? 

Yes. All industries should look to progress and question if the current approach fits the modern world and if not adapt. The NEDC had met its needs but did not now meet the modern world of more dynamic driving speeds, and accelerations and the procedure needed tightening to meet was it able to be catered for with modern equipment and also to gain more consistent and representative results between different facilities and vehicles.

Could you give me a rough overview of the process for a vehicle going through WLTP from arrival at Millbrook? 

Vehicle inspection, fuel drain and refill with reference fuel, tyre pressure setting, exhaust leak check, instrumentation, vehicle warm up and coast-down match on the dyno, preconditioning drive, overnight soak to 23°C +/- 3°C, set up on the dyno for the WLTC emissions test, perform the emissions test and then analyse the results.

Now WLTP has been introduced, will the workload at Millbrook slow? 

No, this is only the start as now all vehicles have to be approved to this and all future vehicles developed to it which has much-increased workload over an equivalent NEDC development and certification programme. Additionally, there is RDE work to develop and validate the vehicles’ performance. Lastly, we have more hybrids in the mix, which have even longer tests to perform to account for various battery states of charge and to calculate the electric range of the vehicle.