|
Surely if they need to change gears that often a CVT would be better? Or would this be an issue due to the fact some drivers don't like steady RPM while accelerating...
I'd imagine there are a lot of factors to consider. Efficiect engines should automatically adjust timing to maximum possible advancement by use of a knock sensor... use EGR correctly to reduce manifold vacuum... use different measures to ensure the engine heats up faster during cold starts etc. Also such things as higher compression, gearing for low RPM while cruising as said above, variable valve timing, smarter turbo control on turbo models (e.g. variable vane turbos that can adjust for power or economy on demand).
What else can I think of... cylinder deactivation as VW is now implementing, injector shutoff during engine overrun, automatic stop/start, regenerative braking, smart alternators that adjust their output, lean burn modes, heat recovery systems to make use of wasted exhaust heat.
There are so many factors really, but when it comes to the manufacturers the problem is they must consider multiple types of drivers when making a car. They don't tend to design cars just for people who drive slowly, smoothly and with greatest efficiency (with the exception of some hybrids maybe) but they need to cater for anybody who might drive, including those who want to get some power out of it.
Also it depends on the car it has to go in. If you have a light car with great aerodynamics then you can use smaller displacements. If it's going in a sporty car or a boxy/heavy car, then it needs more torque. Basically, if you design a car JUST for efficiency, it would be very different than a lot of them you see today. It's always a compromise between power, efficiency, aesthetics, and cost.
|