Quote:
Originally Posted by CuriousOne
Misc. Exhaust Modifications - Most exhaust components are made of cast iron (which is much heavier than steel, stainless steel, etc.), and some are crush bent and just overall very restrictive which creates backpressure. Backpressure in an exhaust system is never needed...
Any other ideas...?
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This a popular misconception!
Almost all motors have valve overlap (intake & exhaust valves open at the same time). Exhaust backpressure keeps unburned gases in check during valve overlap!
Actually, this is one of the best things about direct gasoline injection - valve overlap doesn't affect FE - but that's a different discussion...
Anyway, what you *need* is negative overlap, if anything, e.g. exhaust gas retention, if you want to get the best mileage, NOT a free flowing exhaust system that sucks unburned fuel out your tailpipe.
Many, many ppl don't believe I get 40+ MPG with a high-performance B16A2 engine - been called a liar several times!
One of the ways I do this is by using an OEM airbox, OEM cast iron header, OEM midpipe, OEM cat, OEM resonator. The only aftermarket stuff I use in my intake/exhaust system is a K&N air filter, and Tenzo R muff - that's it. And, that's the biggest reason I get great FE!
Anyway, that's my recommendation - don't free-up your exhaust if you're looking for better FE...
