[Jim-Bob]

Originally Posted by Daox

Sounds like an interesting build. Looking forward to the progress.

I think you are a bit mistaken (or I read your post wrong) on how gearing and throttle works. As an engine gets loaded more it operates more efficiently. Having taller gearing tends to load the engine more thereby increasing efficiency. So, you want to have to use a lot of throttle. I believe the manual trans from the 4 door is the one you want to use because of this, though I am no Metro expert.

Anyway, I don't think you'll have much problem hitting 50 mpg if you combine your modifications with some good driving techniques.

Everything in moderation though. I have a 1985 Cutlass with a 355 Chevy that picked up 2-3 city mpg by going from a 2.41 gear to a 3.23. In a car that was getting 12 mpg, that is a very significant change. Also, while pumping efficiency may be compromised by a throttle being closed the fact remains that the engine is still ingesting less air and fuel than it would need to sustain higher RPMs with a throttle more open. Ideally then, you would like to eliminate the throttle like Fiat did in the Multiair engine, but in a throttled engine you will still generally use less fuel with less throttle and less RPM. Are there mathematical exceptions to the rule? Yes. A car is a complex system and thus has many more variables than any one simple axiomatic answer can provide. All in all though it is an experimental process to optimize the car for a variety of situations.