No Muffler= loss of low end/MPGs?

VoodooMann · **Posted:** Wed May 27, 2009 3:17 am

So I recently removed my muffler, just because I wanted to hear what the Libby had for me in the volume/power department with straight pipes.

I have been running it this way for the last two weeks to make sure I got an accurate idea of how it sounded and performed.

I have gotten some looks, and even some compliments on how it sounds wide open. But I seem to have noticed a problem.

I remember that when I had the muffler on, I could put the hammer down at idle-about 10mph, and spin off the tires. Now I seem to have problems replicating this. I have also noticed that I am getting slightly (2-3 mpg less) crappier gas mileage. And then I began thinking.

I know that with small displacement engines, especially things like dirtbikes etc. If the exhaust has no backpressure/scavenging, the low end torque suffers due to the leftover gas in the cylinder contaminating the fresh air charge.

Does anyone know if it is possible that this is happening to a lesser degree on my KJ? I'm going to put the muffler back on and see if it fixes it, but I was wondering if anyone had experienced anything similar or if anyone thinks this could be the case.

JeepinJarhead03 · **Posted:** Wed May 27, 2009 8:44 am

had the same thing with my bronco II, it's just loss of backpressure, i've been told the banks muffler for the libs sits right on the money if you don't plan to run headers

tommudd · **Posted:** Wed May 27, 2009 11:38 am

You need to have some back pressure for the gasser engine to run properly. For example I had an 85 GMC pickup with a mildly :roll:

warmed over 350 dual 2.5 inch exhaust, ran good, then a buddy who owns a muffler shop talked me in to true 3 inch dual from the headers back, sounded great , but LOST a bunch of low end and fuel mileage. Took it off with with true dual 2.50 inch and it ran wicked then.

TAHOE · **Posted:** Wed May 27, 2009 11:51 am

Free flow exhaust = horsepower, good top end.
some backpressure = torque, low end grunt.
Got to finding that balance, thats why many of us tell people not to go with true duals, not enough backpressure for hte 3.7 to run well.

VoodooMann · **Posted:** Wed May 27, 2009 5:11 pm

I might EVENTUALLY run headers, maybe a few years on. but for now I think I'm just gonna throw the purple horny back on till I have the money for a flowmaster.

No Muffler= loss of low end/MPGs?

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