HYBRID-ENGINE WARM-UP?

After reading the article about the C350e in the November 2016 issue of CAR, I realised that Mercedes-benz says there’s no engine sound on startup. It was also mentioned that the vehicle can drive up to 130 km/h on electric power alone. I’d like to know what happens after that speed? Does the petrol engine take over from 131 km/h onwards while still cold, without having reached its optimal operating temperature? If so, wouldn’t that ultimately damage the engine? JAYE HADEBE Ekangala Having driven the C350e ourselves, we can confirm that it is actually very difficult to reach 130 km/h in electric mode, as very gradual acceleration is needed. We found that, in most cases, the petrol engine kicks in before then if the driver applies too much pressure on the accelerator pedal. Your argument stands, however, as the engine is cold after initial start and, when it is tasked to provide additional power, it does so from cold. The advantage of the electric-motor assistance in this case is that, hopefully, the additional power requirement is not the full potential of the turbopetrol engine (as the electric power is provided in parallel), except when the driver absolutely floors the accelerator. This would be the same as thrashing a cold engine in a normal (internal-combustion-engine only) vehicle, and is not recommended.

The best method of getting an engine to operating temperature is to drive it at moderate loads and speeds, which would be mostly the case in hybrid vehicles. To let an internal-combustion engine idle for extended periods for warm-up purposes can do more harm than good. The air-fuel mixture after cold start is rich to improve smoothness, and the seal between the piston rings and cylinder walls not perfect before heat expansion. This leads to the boundary layer of oil on the cylinder walls being washed away, increasing wear, and some of the fuel may reach the oil, leading to oil dilution.