Hi,
Sorry I have to write this in english. I can read german but not write.
I want to simulate two different engines. One 6 cylinder inline 3 liter engine and one 12 cylinder 6 liter engine. Both engines have exactly the same level of technology. Thay also have the same cylinder shape and pistons an so on.
Everyone will understand that the V12 engine will consume more fuel. Why is that?
The main difference between the two engines is that the V12 engine have far more internal friction because is has more pistons that moves. At high revs the internal friction is one of the biggest area that affects the fuel consumption. Of course, the V12 will be able to consume a lot more if you use ALL horsepowers, but that is a completly another issue.
OK. What will happen if we enlarge the volume to 4 liter 6 cylinder and 7,5 liter V12? I would say that the fuel consumption will be about the same for the two 6 cylinder engines (and the two V12
) because the internal friction will be about the same! Please study the consumption figures for BMW 5 series when there were no turbo charging. All 6-cyliners had about the same fuel consumption and all the 8 cylinders about the same (when i EU-cycle, not using all horsepowers).
My point is that the general view is that, bigger engine volume will make the engine less fuel efficient (EU-cylce, not using all horsepowers). I mean that is wrong. It has more to do with number of cylinders and internal friction. (Of course if you use ALL horsepowers the bigger engine always will consume more).
OK. What will happen if we put on turbo charging on my engines. Well, there is some physics that always rules. When turbo charging is added (for otto-cycle) the compression ratio MUST be lowered. Please study compression ratios between SAME engines with or without turbo charging. You will find that the turbo engine always has lower compression ratio. I will not explain why but you can google it if you like. Now it will be intresting. What will happen if you lower the compession ratio for the otto-cycle? Answer: The engine will be LESS efficient.
OK. With this information I would say that my engines with turbo charging will consume more than that same engine without turbo, because the compression ratio must be lower on the turbo engine. My opinion is that it is IMPOSSIBLE to make the same engine more efficient if you add turbo.
You are all right, the E32,E38,E65 all had 4,X liter V8 with about the same consumpiton but something happened with F01 V8? Answer: Turbo always makes the same engine less efficient.
What can happen, and will happen, is that if you compare the E38 V12 to the F01 turbo 6 cylinder (same horsepower) the F01 might/will consume less because the 6 cylinder har far less internal friction compared to the v12. The irony is that the reason why The F01 consumes less is NOT the turbo. The reason is that the F01 has fewer cylinders and less internal friction!
So this is why the F01 V8 consumes more that the the S500 V8. It is very simple. First you decide how many cylinders you like to have. You now know that all V8 without turbo probably will consume about the same. You also know that if you add turbo the same V8 will consume more!
Now I will make it even more intresting:
For the diesel cycle it is the opposite! The turbo will make the diesel-cycle MORE efficent. Why? Answer: For the diesel cycle you do not have to lower the compression ratio when you add turbo.
My conclusion:
Diesel should have turbo.
Petrol shold not have turbo.
I would say that BMW efficient dynamics/turbo makes 326 horsepowers more efficent but it does not make my beloved V12 more efficient. So for me myself, I am a complete loser because I like the feeling and sound of many cylinders, and efficent dynamics has probably made my beloved V12 to be less efficient...
Esau: Yes, e38 V12 is a true masterpiece...
