Has your modifications helped with your MPG at all? I'm also looking for some easy methods to perk my mileage up as well.

 

All I have done so far is to change to a K&N air filter. Still looking to get rid of the stock muffler and that little bitty 1 1/2" pipe - just haven't done it yet. The gearhead in me just cannot fathom that an exhaust would get smaller in size toward the exit and be efficient. I did get 31.3 with my last tank after switching out the af tho - and that is with near 100 degree temps and a/c blasting all the time. I run K&N drop-in air filters on everything I have, and I would suggest that at least. I got one for $33 from Amazon..."K&N 33-2104 Replacement Air Filter"

 

Civic engines gain low end torque from back pressure. Pull off the muffler and you'll lose a lot of power and see a big drop in fuel economy. it would be neat to figure out optimal back pressure at all rpm and build a dumper port that responded to your tach... anyone ever try that?

edit: btw, I know someone is going to disagree about back pressure, all I ask is that you explain away my huge loss of power and mpg when I had a missing muffler

 

I think that if the exhaust starts at 2", if it necked down to 1.5" that would cause some major restriction? The exhaust gases would move slower in the 2" part then they would have to speed up through the smaller pipe, creating more pressure. I think as long as the pipe is one size it would be okay

 

Yeah - it had a 1.5" muffler/tip on it. I got it changed out when it came apart a few months ago - just had the shop weld on a 2" pipe and a turbo muffler from the last bolt on joint by the axle. Cost me $100. Runs better, has a little sound to it, and mileage went up like 2mpg....