Hybrid drives need efficient architectures to keep overall system costs low. In transmissions, stronger electrification enables measures like reducing the number of gears – do combustion engines have similar potential? An interview with Professor Uwe Dieter Grebe, Executive Vice President, AVL List.
As electrification levels grow, e-motors are taking load off combustion engines. To what extent can that simplify engines?
The more dominant the e-motor is, the more you can shift the combustion engine’s job to covering base load. For dynamic loads you use the emotor; the combustion engine just follows. So you can simplify the variable valve control system, for example, or even leave it out for stationary operation. The same may apply for charging. But when you take other parameters into account, it might still allow to give a higher technology level for combustion engines. If you want a compact engine, for example, it still makes sense to have at least a simple charging device. With hybrid drives, other factors come into play. For example, variable valve timing can help reduce warm-up times. Let’s say your combustion engine cuts in on the highway and you need to warm up the exhaust line quickly. On serial and powersplit hybrids, where you can set engine speed and load, and thereby run a warm-up program. In the same way, variable turbochargers let you balance temperatures in close-coupled treatment systems – or reduce the system temperature under heavy load.