Reading Christ's
thread about a turbo install, I realized I know next to nothing about compression ratios, turbo chargers, and how it affects fuel economy. In this thread, I want to consolodate all of my questions and hopefully begin to understand the physics behind it all.
I have read before that increasing the compression ratio increases fuel efficiency, but what is the reason behind this?
If increasing cylinder pressure increases fuel efficiency, why not direct-inject gasoline into the cylinder at just the right moment and not worry about detonation (like a diesel engine)?
This leads me to the question of why it's important to have a stoichiometric air/fuel ratio in a gasoline car when it doesn't matter with a diesel?
I imagine a turbo increases the effective compression ratio, and this explains the increase in fuel efficiency. Why not just engineer a higher ratio into the design of the engine?