Home
Articles
Miscellaneous
Links
Toyota Parts
MR2 Parts
MR2 Body Kits
          

Dissection of a Stock Muffler
By: Blitzo 

Introduction

It's no secret that I'm obsessed with exhausts for the Spyder.  I just had to know what makes the stock exhaust tick (or make that awful restriction noise at full throttle).  I took a stock exhaust and introduced it to Mister Oxy-Acetylene one afternoon in a quest for stock brackets and exhaust pipe.  I know there are others who are just as interested as I am to see inside one of these things.  Here's the autopsy photos.

The short perforated pipe on the bottom is the inlet.  Strike 1 - the end of the pipe is solid plate, so all exhaust goes through these holes.  This is a serious restriction right at the inlet.
The next line of defense is three baffle plates that the exhaust must travel through.  More muffling and more restriction.  Notice the chambers are different widths - to cancel different frequencies of sound.
 
After all the plates, the flow reverses in the end chamber and gets to finally flow through a pipe.  Notice the pseudo-venturi radiused opening of the inlet - at least they tried to make that part flow well.
Before exiting the muffler again, there is a resonator around the exit pipe.  I did not cut this piece apart, but expect that there is the same perforated pipe and possible glass packing material, but it could be hollow.
 

The outer casing you are looking at is actually two layers of stainless steel.  Around these layers is a layer of glass matt and then the final sheet of polished stainless that gives the stock exhaust it's nice shiny appearance that is apt to stay shiny for quite some time.  All the hanger hardware and welds are all 100% stainless.  This exhaust should last in excess of ten years - unless you cut it open with a torch.