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[MIKE MOG]

Where would I find some info on exhaust systems. Need to know if a 4 inch or 5 inch would be better and what exhaust system would not have to much in cabin noise.
Mike

[DmaxMaverick]

If you find what you are looking for, it will be wrong. Exhaust sound (noise) is much too subjective for a "one size fits all" description. Power can be measured and dosed, but tolerance can't.

As a general rule, bigger is louder, all else being equal. The Db's aren't really the discouraging factor, as much as the drone at certain speeds or RPMs. If you are wanting a non-loud system, 5" will not be for you. Most of them are tame at idle and low power levels, but really wake up in the mid range, even when empty. Loaded acceleration can be very loud.

Other things to consider:

Larger pipe costs more, exponentially.

What power levels are you wanting to achieve? Very few folks will make enough power to ever reach the potential of a 5" system, and you will probably never see this on a 6.5L DD. For most applications, even a 3.5" system is overkill. Competition is different, and you expect to break things from time to time. If you are getting near the potential of a 5" (or even a 4") system with a 6.5L, it gonna break, sooner or later.

Fitment. They are not easy to shoehorn in there. I don't care what they say. You're gonna have to tweak something, and the 5" kits I've seen are not "custom fit".

What is your understanding of 5"? The vast majority are only 5" from the muffler (if it has one) back. What is the size up front? The downpipe will have to transition to your pipe size, too. Some of these can be as ugly as the OEM downpipe.

If you are an accomplished mechanic and can cut and weld, build your own system for half the cost of an aftermarket "bolt on". Straight pipe and elbows is all you need. Hangers are easy, and you can use the standard muffler shop clamp/hanger types for the pipe size.

[MIKE MOG]

Thanks dmax. I have a 6.6 duramax not a 6.5. is there a difference in exhaust. I tow about 10k and just want to lower egts and pick up a little extra hp's. I called summit on a cold air kit and they have one in stock. I was going to try to get a quicker spool up and figured with a less restrictive exhaust system and a less restrictive induction system I could do this. I have a bully dog box but had some problem with no power and a misfire so I was going to send it back. what do you think?
Thank You,
Mike

[DmaxMaverick]

Oops! Musta' had the 6.5L on the brain. Not enough sleep lately.....

For your application, a 4" is ideal. The sound can be quite tame to annoyingly loud, and some with unbearable drone, depending on the mfg and muffler type/install. Although some gains are there, an exhaust system will not provide power levels claimed by most mfg's. A larger system will decrease EGT's under load, sometimes as much as 200

[MIKE MOG]

Thank you so much for the info, like I said before. my 10 yr old has hearing aids and the noise is the big issue thats why I went to a duramax, I pulled with a 5.3 but the trans was to busy. What do you think about the bullydog box. I really did like the power but I dont know about the misfire or the low power. I think it went into a defuel mode but Im not sure.
Can this box blow my engine or trans? its a bullydog rapid power for towing.
Thank you DmaxMaverick!
Mike