thegoat86

I just installed an MBRP aluminized exhaust system. four inch, with a nice tip. Single, exits behind tire. Has a turbo style muffler. As soon as I fired up the truck, it sounds like a badly running ford van or something at idle, I love the sound when I crank on the fuel, And the turbo spool sounds great. But it literally sounds like EDIT at idle. The only thing I can think of is a turbulance issue. I followed the directions they gave me. They werent that detailed and were pretty generalized for my truck. The only other thing I can think of is the muffler. It didnt have a marking for in and out. So I installed it as it looked with the letters going towards the back of the truck in the picture. There are little half cirle cups inside the muffler, they are facing towards the back. I am wondering if the open sides of these little cups should be facing towards the front. Any help would be appreciated. Also just installed a billet torque conv. and updated valve body. Hoping to do more mods......

JFlory

You better double check that muffler. I bet you installed it the opposite of what you described. The little cups inside should be open to the back. When you look in from the front of the truck, all you see is little bumps. I've heard them put on backwards and they sound horrible, kinda like your describing.

progrower

I just installed the same system on my truck. I called MBRP about the muffler and they said the same thing as JFLORY said. He also told me that it will work both ways but if the cups are pointing forward there will be more noise in the cab.

thegoat86

I installed it correctly. the problem was my idle was set too low. I checked it on a scan tool, 587 in gear with a/c. I set it to 800. Now in park it idles just shy of 900 and sounds great. plus it doesnt stall anymore. response and spool up are better too. Problem fixed. I do wish they would explain better the direction of install for the muffler. I guessed and just happened to be right. I bet other guys out there are running them backwards and dont know it.

Joe Diesel

its a flow through muffler so it doesnt matter which way it faces.

ldornak

The direction of the muffler does matter. If installed incorrectly, you'll get a good drone in the cab.

I too just installed a 4" MBRP and did not find the muffler direction anywhere in the instructions. I found the correct direction on MBRP's web site - I think under the FAQ link.

wood_n_soldier

I have this exhaust and it turns out it is installed backwards.... Who knew... I'll see about turning it around next weekend.

From: http://www.mbrp.com/index.php?faq=faqdiesel&page=faq

21. WHICH WAY SHOULD I INSTALL THE MUFFLER?
The muffler on the single diesel exhaust systems should be installed to allow the exhaust gasses to flow smoothly over the louvers on the muffler core. If the muffler is installed so that the louvers catch the exhaust gases it will increase resonance levels inside the vehicle.

thegoat86

Yeah, they are pretty great with the instructions they ship. Gee wouldnt it be great to waste somebodys time not giving them the right instructions, as we know they will probably be doing this on the weekend, and maybe wont have access to a computer.