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My new muffler has a cost

Posted by Bob in Everett 
June 29, 2013 11:37PM
After getting the engine back together I put a new muffler on it because of a inch diameter rusted hole in the middle of the bottom it. Took a leisurely drive for a scenic tour of back roads today. I nolticed that my gas mileage seemed to be unusually low. Got to thinking about the last road trip at the end of May where I noticed that my mileage was better than it had been in a while. There seems to be a correlation to having a hole in the muffler and getting about 10-15% better mileage. I wish I had thought of that before I chose the muffler. Might have just tried a glass pack type straight through type. Is there a better "stock" muffler that does not restrict so much that mileage suffers?

Bob in Everett
July 01, 2013 02:49PM
Is it really the muffler that did this, didn't you change anything else before noticing the mileage going bad? If it should be the muffler, do you have the right type?
July 01, 2013 06:17PM
Quote
Michiel 318iS
Is it really the muffler that did this, didn't you change anything else before noticing the mileage going bad? If it should be the muffler, do you have the right type?

I had the oposite idea, bad exhaust or mufler causes worse mileage, but never had that explained "as if I was very dumb"....
:boohoo:
July 04, 2013 01:40PM
Make sure you're getting accurate mileage readings. A couple of years ago I though I had suddenly started getting really bad mileage and it turned out the real problem was that my odometer gears were falling apart. As I lost teeth off the gears, I got less mileage recorded for each tank purchased which made it look like the mileage was dropping off. I think the OBC mileage was still accurate, but I keep a log and that was what was looking bad. I put in new odometer gears and everything went back to normal.

John
rkj
July 09, 2013 10:48PM
Quote
Bob in Everett
After getting the engine back together I put a new muffler on it because of a inch diameter rusted hole in the middle of the bottom it. Took a leisurely drive for a scenic tour of back roads today. I nolticed that my gas mileage seemed to be unusually low. Got to thinking about the last road trip at the end of May where I noticed that my mileage was better than it had been in a while. There seems to be a correlation to having a hole in the muffler and getting about 10-15% better mileage. I wish I had thought of that before I chose the muffler. Might have just tried a glass pack type straight through type. Is there a better "stock" muffler that does not restrict so much that mileage suffers?

This seems odd to me also. Too bad Primaflow went out of bussiness, I liked their pipes, gave great sound and good power at a reasonable price. They also lasted more than a few years!

Lets have more feedback on this thread :wavey: I'm wondering how a leaky exhaust causes worse mileage....

Rick
July 27, 2013 07:05PM
Quote
Bob in Everett
There seems to be a correlation to having a hole in the muffler and getting about 10-15% better mileage.

Hmmm... something's not right. Maybe the muffler is super-restrictive (it would have to be really bad to affect cruising MPG that much). But I think more likely the O2 sensor is dead, and by coincidence it worked better with a holey muffler.
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