HumberMart
Active Member
I do agree that this is more complex than that (almost irrespectively what "that" is ).
But I did not follow certain points above. Like the power to weight ratio is improved for max power and the engine would not be used at anything close to max power or even max torque at those minor speed corrections.
The key has to be more efficient combustion. I cannot see fuel efficiency increase if combustion efficiency is not improved. But the question is how combustion efficiency can be improved from the factory settings.
I'm not engine expert but I believe the key is to optimise the combustion process towards efficiency and compromise emissions. The free parameters are fuel injection timing (assuming no variable valve timing) and the amount of air (on a diesel more air than needed to burn the fuel can be used). What ever the details are, the only option is to compromise emissions (or perhaps engine longevity too), otherwise the factory would have used the same settings to reach better figures.
The maximum power and torque are a bit different thing but emissions are a key there too, engine longevity compromise starts to be another key.
I'm afraid that car engines these days are designed like most consumer products, being marketing led, and the optimum process settings are not the prime objective. Just look at the fact that MB market the CD220 and 250 BE engines, that are just mapped differently. Same with Audi/VW etc.
They also have to consider longevity and emissions, but they are after getting the best results from the standard EU tests, not producing a car that has optimum efficiency throughout the rev range, or in real world conditions.
This keeps all the tuning and chip companies very busy, and the results are very worthwhile.
A better power to weight ratio does have an impact, again only in real world conditions, increasing the power in the same car can be compared against lowering the weight in the car with the same power.