| First Drive | Millbrook, England | Volvo S40 with CPT SpeedStart |

In recent years several engine stop-start systems and "mild hybrid" solutions have been introduced by manufacturers to improve fuel economy and cut emissions. British company, Controlled Power Technologies (CPT), has developed a belt-driven integrated starter and generator, known as SpeedStart, capable of supporting both stop-start and mild hybrid operation for petrol and diesel engines. CPT claims its solution provides a faster start-up than existing stop-start systems. We took the opportunity to drive a Volvo S40 diesel equipped with the integrated starter and generator.

How it works

CPT's goal was to build a device capable of starting a diesel engine in about half the time it takes a conventional starter. Other objectives included high current output and compatibility with existing 12-volt electrics.

The principle is simple: when the engine is running the SpeedStart unit functions as a "high output" generator. Apply electrical current from the battery and it works as a motor powerful enough - it is claimed - to start a 2.5-litre diesel engine.

The most unusual feature of the SpeedStart unit is the water jacket that connects to the vehicle's cooling system. Water cooling allows the motor and electrical components a stable operating temperature while the components inside the unit are protected from the ingress of dirt and moisture. As a result the unit is claimed to have an operational life of around 150,000 miles.

CPT claims that a five percent reduction in carbon dioxide emissions is possible on the New European Driving Cycle test. That's in part due to the reduced start-up time allowing the engine to spend more time switched off. Further savings are possible by using the alternator to charge the battery only when the car is decelerating. By effectively managing the time when the alternator is generating electricity an additional 3-5% CO₂ reduction can be achieved.

In practise

To see how the CPT unit worked we drove the Volvo S40 demonstrator around the urban circuit at the Millbrook proving ground in Bedfordshire. Usually there is nothing more frustrating than stop-start traffic when testing a new car but this time every opportunity to stop was welcome. When you first start the car the conventional starter operates. Once on the move the integrated starter generator is used to re-start the engine. The big difference between the two starting systems is the time it takes for the engine to fire up. The Volvo's existing starter was far from sluggish but the CPT system was noticeably faster.

Because the engine starts so quickly it is practical to shut the engine off whenever the car is stationary with the clutch disengaged and the brake applied. Other stop/start vehicles generally require the driver to put the transmission in neutral. To remind the driver that the system is working a warning light in the instrument cluster flashes when the engine is automatically shut off.

In town driving and stop-start traffic the system comes into its own. It is easy to adjust to the repeated cutting in and out of the engine though there was a slight rattle as the engine switched off. The time delay built into the stop-start system allows enough time to snatch reverse and quickly back into a parking space or pull away without the engine cutting out. There little adaption of your driving style to the needs of the system.

Future plans

Don't read anything into the fact that the test vehicle we drove was a Volvo. Control Power Technologies is working with a number of vehicle and engine manufacturers to get the Integrated Starter Generator fitted to production vehicles. Although it will be down to the manufacturers as to exactly when the system is put into production, the first cars to use the technology should be on sale within a year or two.

Summary

Stop-start systems make sense if you spend a lot of time stuck in traffic, and these days who doesn't? We weren't able to check fuel consumption to verify CPT's claims but based on our experience with other stop-start systems the SpeedStart does seem to start more quickly and shut down more frequently. Even though it might not revolutionise transport the SpeedStart does feel like a logical development of existing technology. We look forward to seeing it in production soon.