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I was thinking of getting a new high flow / least restrictive muffler. I was wondering if this would help with MPG and if so how much. Then I was concerned about emissions problems or meeting code. The last and final questions is : what would be the best muffler that isn't too LOUD.


Thanks in advance for info or comments:)


http://http://www.cleanmpg.com/garage/images/294.png

Remember, you need more inflow to produce more outflow. That means a better intake. Also, having just a high-flow muffler/exhaust will decrease your backpressure, effectively lower your MPG.

By no means am I an expert on the subject, and would like to hear from others.

Try these (http://www.bulletperformance.com/) . All T304 S/S and reasonably priced . I had them(the turbo style) on my SHO and really liked them .
The catback on my Focus is a full 2.5" catback from Ford Racing/Borla and really doesn't seem to have hurt FE . One of the nicest sounding exhausts I've heard - Not loud , but noticeable in the normal rpm range & quite a song when you get on it .

The only issue I can see with it is that small engines need a little back pressure to help deliver torque at low RPMs. If you open it up too much you will get plenty of flow and power at higher revs but you may notice less punch off the line, and that's where the FE is made. Emissions won't be a problem as long as you leave the catalytic convertors alone.

Whatever floats your boat, I guess.

Is there anybody here with a small car like mine who has done this / and has good results?

Is there anybody here with a small car like mine who has done this / and has good results?

No first hand experience but here's a site that doesn't think to highly of the intake/exhaust mods from a FE standpoint.

I've always assumed if it was worth additional mpg Honda and Toyota would have optimized the intake/exhaust already.

http://www.fuelsaving.info/power_economy.htm

actually, its not "back-pressure" per se that gives you more torque at low engine speeds. its the fact that a smaller diameter set of pipes leading away from the combustion chambers forces the exhaust gas to leave the engine at a higher rate of speed than a larger set of pipes. the faster-flowing gas will draw more exhaust from the cylinders in a given length of time, thereby leaving behind less un-burnable exhaust gas in the cylinders to dilute the incoming fuel-air mixture.

ideally you want small pipes for low rpm (makes torque) , and large pipes at the top of the rpm range so as not to restrict the flow (makes horsepower).

the camaro saw better FE after I went to a 3" catback from the stock 2.25" pipes, but that was a much larger motor, the headers helped more though (the stock manifolds were rather restrictive)