Muffler placement

[Mrturner1]

What changes and how when you have mufflers close to the header collector as opposed to near the rear axle? How does sound or performance change?

[truckster]

The closer you place them to the cab the louder it's going to be inside the cab. Under the cab tends to make for very annoying exhaust drone, unless you like that sort of thing.

[Mike C]

I'd be more concerned about fitment rather than location. And I would want those big heat sinks as far from the cab as possible. Near front of bed is probably best location.

[Mrturner1]

Does it make the exhaust note deeper or higher pitched if they're towards the front or near the back?

[Overdriven]

Originally Posted by Mrturner1

Does it make the exhaust note deeper or higher pitched if they're towards the front or near the back?

Pitch doesn't really change according to muffler position. What you need to remember about a muffler is that it's going to give off sound around it. The muffler shell flexes a little, there's pressure waves bouncing around inside of it that the muffler shell can't fully contain. So when it's close to the cab you're going to have increased sound levels. Because of the nature of these sound pressure waves inside the muffler and the metal of the cab, the increased sound level is more of a drone. The same is true when you have turn downs anywhere underneath the truck, having piping after the muffler that exits outside the body is the only cure for this.

If you're thinking of imports with the muffler at the back there's a few reasons they sound the way they do. It's mostly the style of muffler, partly because there's no significant amount of exhaust piping after the muffler and then the engine itself. Put a v8 style muffler on an import and they lose the fart can sound. Put the muffler further under the car with more exhaust piping after it and they lose the fart can sound. There's lots of variables in an exhaust that determine how it sounds.

What kind of sound and sound level are you looking for? What engine (specs, mods please) do you have? What kind of exhaust are you looking for? Rear exit, side exit, turn downs in front of the rear axle? I can tell you that just adding over the axle tailpipes to turbo mufflers with turn downs in front of the rear axle makes a big difference in sound level. Also takes away some of the agressiveness to the exhaust note. Taking the same turbo mufflers with turn downs in front of the rear axles and adding enough piping to exit the side in front of the rear tires decreased the sound level in the vehicle. The decrease wasn't as much as going out the back but the drone was significantly decreased and the exhaust note retained more of its aggressiveness than going all the way out the back. Hope that helps a little.

[Overdriven]

Btw, the last paragraph in my previous post is all first hand experience. Dad bought a 65 Nova with a basic 350, about 300hp, and the exhaust it came with was headers, h pipe and generic turbo mufflers just before the rear axle with turn downs. I liked the sound, nice and deep, sounded meaner than it was but it was loud inside the car and had an annoying drone at cruising rpms.

The first attempt at lowering the sound level was just buying some bends to get it to exit out the sides before the rear tires. This got rid of a lot of the drone, lowered sound levels inside and didn't really effect the exhaust note much. Personally I could've lived with it but dad wanted quieter so we got some over the axle tailpipes. The tailpipes lowered the total amount of sound and changed the exhaust note to something less aggressive sounding but barely made a dent in the drone. The car still had its generic, cheapo turbo mufflers and they were definitely the source of the drone. Not because they were leaking or anything, they just couldn't contain all the sound pressure and it radiated out around them into the cabin. Stock mufflers and (certain) more expensive performance mufflers will send more sound out the tailpipe than those cheap generic turbo mufflers but they still should be as far from your ears as possible to minimize drone.

[66clow]

I have turndowns under my cab and ready to either extend the pipes or move the mufflers back. Sounds Cool but over time it is getting annoying inside the cab. Sounds like I need to move them under the bed.