Exhaust and Performance

crewleader22 · November 9, 2004

OK, this has probably been posted before, and if it has, please direct me to the thread as I know things get beat to death in here sometimes. I know a little about performance and modifications, but I am not a hi-tech mechanic by no means. I can do bolt-ons and your basic maintenance, but technical and indepth I am not.

The question I have is about exhaust exit dimensions and increased performance or MPG. I know that having too much exit flow will screw up the back pressure and, from what I understand, has an affect on bottom end. I have participated in some posted threads here and there and have seen what other people have done, now I would like some technical advise from those with 2¢ to spare.

I have seen threads where duals were ran into a Y then into a single in/out muffler. I have questioned why one muffler had 3" dual in/out and another had 3" dual in and 2.5" dual out and the guy told me "no difference, just that some people want/have 2.5" exhaust". I really don't necessarily believe this statement. I just think that combination was for a reason and he didn't know the answer. Just the feeling I got talking to him. I have leaned toward MagnaFlow because of the tone and the things others have posted about them. All three of the afore mentioned were MagnaFlow mufflers, the latter two with built in X pipes. I would really rather have dual exhaust on my truck, just a personal preference, and I would like some help in making my decision from those that know and have experience on this subject.

So, having said all that, my question is this: What is the best exhaust combination for the best performance from my truck and how does the size of the exit exhaust affect overall performance?

Thanks in advance for all your time, patience and information!

gixxer · November 9, 2004

I personally have a Borla Catback thats 2- in and 1 out to a 3 in with a 4 inch tip. Everyone is always asking me what exhuast I have it cause they love the way it sounds. Granted I do have headers and high flow cats. My tailpipe exits in the factory location.

My buddy had the 2 in and 2 out which exited on each side of the hitch and his truck was much louder even with out the headers/cat upgrade.

Now there are my 2 cents

dannyukonxl · November 9, 2004

im not an exhaust enginner or anything but i think it all has to do with the core of the muffler, the bigger the core then the more low end power you will loose, for the 5.3 i would think a 3 inch or 2.5 inch single in and single out with keep good bottom end, for the bigger engines probably a dual 2.5 in and a single 3 inch out or 2 separate mufflers, i am going to do 2 seperate single 2.5 inch in and out, on my 8.1 with a connector pipe with 2.5 inchers out the back to keep resonance low, but im not too sure if im going to loose low rpm power. An even better bang for the buck is small diameter long tube headers, thats power you can feel and use too

edit: the smaller the tail pipes the less resonation

99Silver6.0 · November 10, 2004

Im running a Borla cat-back with a single 12" Borla XR1. Love the way it sounds. If I hadnt gone Borla I would have run Magnaflow. Or maybe a Dynomax bullet. I had Flowmasters before and took them off because they made my truck run like ass!! Down with the 40 series!

crewleader22 · November 10, 2004

Thanks for all the input!

I ran into an engineer here at work whose dad used to build engines for NASCAR way back when, so I thought he would be a good source. After looking into a book on internal combustion engines, we came to the conclusion that there is no exact science for exhaust. I figured this anyway, but didn't know for sure. So I figured out the area of volume for the exhaust. It's kind of interesting the a single 3.5" diameter pipe only has .2 in² less volume than dual 2.5" exhaust. I wonder if keeping around the same volume will keep close to the same back-pressure therefore not loosing any low end?

Just a FYI.....thinking on monitor .

gixxer · November 10, 2004

Unless you are building an all out race car, no matter what exhaust you choose will have some pros and cons depending on its rpm range. Find a sound you like and a resonance you can live with and enjoy

fluxu8 · November 11, 2004

Unless you are building an all out race car, no matter what exhaust you choose will have some pros and cons depending on its rpm range. Find a sound you like and a resonance you can live with and enjoy

<{POST_SNAPBACK}>

I smell Magnaflow!

catiaeng · November 11, 2004

MAGNAFLOW!!!!!!!! I love mine and only had for one week

It's a 3" in/out because I wanted to keep some back pressure for torque when pulling my trailer.

Great sound, better MPG, gets drool on it every where I go .

BJ

chevhot · November 12, 2004

does that muffler fit in place of the stock one? do you know the part# of it ?

or do you have the measent of it

catiaeng · November 12, 2004

does that muffler fit in place of the stock one? do you know the part# of it ?
or do you have the measent of it

<{POST_SNAPBACK}>

Mine is P/N 14614 (3" In/Out, 6" Dia 34" total length) and it is NOT the direct replacement. I had the factory cut off behind the cats. I had new mandrel bent pipes placed from the muffler to the tail pipe, and from the cats a y-pipe to the muffler. An engine tuner that works with the owner of the muffler shop said this would be best for my HD. How does he know that? I have no clue but I LOVE it!

BJ

c502cid · November 13, 2004

If you have stock exhaust manifolds and a stock motor (internals) you can't go too big on the exhaust. Your stock motor, exhaust manifolds, and cats will do plenty to keep "backpressure". The factory set ups are designed for noise limits not performance.