[t vago]

Originally Posted by Ecky

There seems to be some confusion here. Usable power gains and improved economy can be seen from:

-Reducing parasitic loads
-Increasing compression
-Fundamental combustion chamber redesign, for higher efficiency (e.g. longer stroke*)
-Weight reduction
-Aerodynamic drag reduction
-LRR tires

*Longer stroke may actually reduce peak power if you need to reduce redline RPM

However, many methods of adding usable horsepower have the opposite effect and will reduce economy, all else being equal, such as:

-Running rich
-Adding more displacement
-Higher RPM / shorter gearing
-Forced induction (on non-diesel)
-Cold air intake

Many modifications that improve economy, do so at the expense of power, such as:

-Smaller displacement (cylinder deactivation, smaller block, etc.)
-Cam regrind
-Warm air intake
-Running lean
-Taller gearing


So, it really depends on which approach you're going to take.

This post really ought to be a sticky, all by itself.