RickMM
Active Member
- Joined
- Feb 26, 2016
- Messages
- 204
- Car
- C63 Saloon
Firstly, this is not about complaining of the cost of running an AMG, whether diesels are the spawn of Satan, or whether the future of the planet is doomed without eco electric vehicles.
I’ve just swopped in an M156 6.2 C63 after 3 years and nearly 40k miles for the 4.0tt model. I do a weekly commute where the traffic/roads often restrict progress and I regularly got 25mpg on A-roads from the old normally aspirated 6.2. This was actually better than my previous 4.0 V8 BMW M3 (although that did have the manual gearbox). Now the official mpg figures for the new 4.0tt AMG lump are a lot better than for the old M156, presumably because it’s a smaller engine, less friction, better engine management, etc. etc. plus it’s also turbocharged. As we all know, in theory the turbos make use of the free energy flowing out of the exhaust pipes to ram more air mass (as it’s pressurised) down the inlets. (Of course it’s not actually completely “free” because you have to impede the exhaust gas flow to spin the impeller, but it should still be a more efficient system overall).
Anyway, doing the same routes and type of driving I’m finding the fuel consumption on the new car to be only marginally better than on the old 6.2L. I was a bit surprised at this (again, not complaining about the cost of running a high performance car). Now when I keep an eye on the turbo pressure indicator on the AMG screen (which I use most of the time) for the vast majority of normal road driving conditions there is hardly any boost pressure at all (because you can't plant the loud pedal without ramming the car in front). So effectively the engine is behaving like a normally aspirated lump, and a low-compression one at that. So it’s no wonder it’s no more efficient a lot of the time
Perhaps I just need to get out more...
I’ve just swopped in an M156 6.2 C63 after 3 years and nearly 40k miles for the 4.0tt model. I do a weekly commute where the traffic/roads often restrict progress and I regularly got 25mpg on A-roads from the old normally aspirated 6.2. This was actually better than my previous 4.0 V8 BMW M3 (although that did have the manual gearbox). Now the official mpg figures for the new 4.0tt AMG lump are a lot better than for the old M156, presumably because it’s a smaller engine, less friction, better engine management, etc. etc. plus it’s also turbocharged. As we all know, in theory the turbos make use of the free energy flowing out of the exhaust pipes to ram more air mass (as it’s pressurised) down the inlets. (Of course it’s not actually completely “free” because you have to impede the exhaust gas flow to spin the impeller, but it should still be a more efficient system overall).
Anyway, doing the same routes and type of driving I’m finding the fuel consumption on the new car to be only marginally better than on the old 6.2L. I was a bit surprised at this (again, not complaining about the cost of running a high performance car). Now when I keep an eye on the turbo pressure indicator on the AMG screen (which I use most of the time) for the vast majority of normal road driving conditions there is hardly any boost pressure at all (because you can't plant the loud pedal without ramming the car in front). So effectively the engine is behaving like a normally aspirated lump, and a low-compression one at that. So it’s no wonder it’s no more efficient a lot of the time
Perhaps I just need to get out more...