Exhaust Inquiry - Performance vs. Stock

Pote · **Posted:** Thu Oct 11, 2007 11:02 am

Hi guys and gals...have a simple question:

I have been looking up muffler posts and came across a couple that has made me wonder something. I have seen where people are having mufflers like Flowmasters and such put on to replace our stock mufflers. What is it about these "performance" mufflers that equates with better engine and MPG performance? I ask because I know the theory that having the air and exhaust exit in a more streamlined fashion opens up the engine for better performance but these add-on mufflers use things like baffles (right word?) and are double and triple chambered. Our existing stock mufflers are a straight through exhaust as they stand now. One poster stated that when he took off his stock muffler, he could see straight through it with no chambering or baffle. This being the case, why would a muffler like a Flowmaster improve anything when it has multiple chambers and flanges in it that bounce the exhaust gases back and forth before exiting the rear of the muffler? Doesn't this contradict the theory that unimpeded air shooting straight through the muffler is optimal? I know the aftermarket mufflers like these use those chambers and baffles to produce a desired sound, but how does that also make for improved emission for power gains. I hope I expressed this correctly, but it would seem that our stock mufflers with a straight flow through would be better than a "performance" muffler that utilizes the things above to produce a better sound and such. Does my question make sense?

Can anyone clear this up for me? thanks in advance.
Dave

hyedipin · **Joined:** Thu May 11, 2006 10:20 am **Posts:** 1667

Hey Pote.
We got jeeps, not Hondas. So "performance increase" from simply swapping a muffler is a gimmick. We just have to be honest and say all we want is louder muffler that sounds better and spits out whatever our tiny v6 has gotten under the hood. Otherwise, how much can you expect from swapping a muffler? Maybe half mpg or 1 mpg on highway at best, and that's not performance increase, that just saves mpg (or, otherwise, more performance at same mpg)

However, I do believe that when other components like intake, plugs, battery, cleaner fuel, regular maintenance along with a new muffler will increase performance, and might give better torque.

Someone with technical background and research results with facts and comparison of stock vs aftermarket may give you more information.

Pote · **Posted:** Thu Oct 11, 2007 2:42 pm

hyedipin wrote:

Hey Pote.
We got jeeps, not Hondas. So "performance increase" from simply swapping a muffler is a gimmick. We just have to be honest and say all we want is louder muffler that sounds better and spits out whatever our tiny v6 has gotten under the hood. Otherwise, how much can you expect from swapping a muffler? Maybe half mpg or 1 mpg on highway at best, and that's not performance increase, that just saves mpg (or, otherwise, more performance at same mpg)

However, I do believe that when other components like intake, plugs, battery, cleaner fuel, regular maintenance along with a new muffler will increase performance, and might give better torque.

Someone with technical background and research results with facts and comparison of stock vs aftermarket may give you more information.

That's what I figured about the sound...and I admit, KJs sound pretty good with a FM 50 on them. I was just wondering about the "claims" some make about better performance with these mufflers when our stocker muffler is a straight through exhaust also. thanks for the clarification about something I already suspected. :wink:

LibertyGuy · **Posted:** Fri Oct 12, 2007 4:00 pm

It will take a lot more than just a muffler to get better performance. I noticed the JET chip gave my jeep better performance than the intake & exhaust combined. Putting everything together in the end equates to a bit more performance than one single item. And of course the exhaust makes the jeep sound better than stock.

KY Liberty · **Joined:** Sat Jul 09, 2005 1:46 pm **Posts:** 1195

LibertyGuy wrote:

It will take a lot more than just a muffler to get better performance. I noticed the JET chip gave my jeep better performance than the intake & exhaust combined. Putting everything together in the end equates to a bit more performance than one single item. And of course the exhaust makes the jeep sound better than stock.

The Jet chip must work a lot better with the newer ECU. The stage 1 lost 5 hp compared to stock when we dyno'd it. Still would much rather have my B&G. They delete the torque management. Really wakes up your other modifications.

Bodz123 · **Posted:** Thu Oct 18, 2007 6:32 pm

The stock exhaust is not a straight through design. Just to Let everyone know. It has at least 1 baffle and restricts down at the begining of the first baffle. The inlet side (center of muffler) travels all the way down to the back but the exit side is offset of center, therfore it cant be a straight through.

FastTRX · **Posted:** Sun Oct 21, 2007 11:34 pm

KY Liberty wrote:

LibertyGuy wrote:

It will take a lot more than just a muffler to get better performance. I noticed the JET chip gave my jeep better performance than the intake & exhaust combined. Putting everything together in the end equates to a bit more performance than one single item. And of course the exhaust makes the jeep sound better than stock.

The Jet chip must work a lot better with the newer ECU. The stage 1 lost 5 hp compared to stock when we dyno'd it. Still would much rather have my B&G. They delete the torque management. Really wakes up your other modifications.

How big of a difference does the B&G programmer make on the 02 KJs'? Would it make a considerable difference without a shift kit? I have the 45rfe and a flowmaster 40....looking to possibly get an intake and this programmer. Is it worth the extra money? I want a little more power over what I have now...get rid of the V6 pudgyness...

Exhaust Inquiry - Performance vs. Stock

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