Hello, my name is John Kelly
and this is the WeberAuto YouTube Channel. Today I am going to
show you something that I discovered accidentally
the thermal expansion of an exhaust system
I have always read about the thermal expansion of an exhaust system and
heard that it could grow in length
several inches depending on how long the exhaust system is to begin with, but the
other day I was shooting a transmission video and when I was editing the video I
noticed the exhaust system had changed position from the time I started
shooting the video, and then several minutes into it, it was in a
different position. so I thought wow, I wonder how quickly and how far it
actually moves, and so I have got four cameras set up, and i also have for dial
indicators set up on the exhaust system
I have got one on the cross member or on the crossover pipe right in front of
the crossmember
we will see how far it goes down, I have got another one right after the
second catalytic converter, right before the expansion joint in the exhaust pipe
and then another one right after the expansion joint in the exhaust pipe and
then one clear back on the tailpipe bracket. So we are going to start the the
engine here and watch how far these grow over time. In the video I shot the other
day it took about three minutes to see some major change in the exhaust system
length
let's see what happens on this truck here, Okay go ahead and start it.
Allright le us watch and see what happens
Alright, things should be
starting to cool down now.
Wow, look at this dial indicator just rolling backwards as the exhaust system
cools down. The one behind the flex coupling is not moving nearly is rapidly but
it is obviously still moving, and back here at the tailpipe, let us see how
quickly it is moving, it should be moving.
Oh yeah, it is moving about a half thousanth of an inch every second or two
that is just absolutely amazing!
Like I said, I have never seen that before but I always heard about it and read
about it.
The reason that this is important is that you can have an
exhaust system that can be the transfer path of normal engine vibrations and
maybe it doesn't transfer the vibration when the engine is cold and the exhaust
system is cool,
maybe it only does it after heats up and the exhaust system grows and it starts
to groundout or rub on something that it it should not be, and it it could be just
the opposite also, maybe when it is cold it rubs on something and as it heats up
it expands and get away from whatever it was rubbing on.
So factory exhaust systems are designed to avoid all of that but they still have
problems occasionally with rattles and so on.
But aftermarket exhaust systems, if you put an aftermarket exhaust system on
your your truck or your car,
it may, or may not, end up having problems like this depending on what type of
flexible mounting, obviously we have to have a flexible mount there,
I have seen exhaust systems put on where they just welded a solid strap to the
exhaust pipe and ran a screw into the into the frame of the vehicle or the
exhaust bracket and bypassed the rubber mounting and that certainly could cause
unwanted
normal vibrations from the engine to transfer through the exhaust system into
the frame up through the vehicle body into the passenger compartment and, of
cours,e the end result is a is a vibration.
Thank you for watching.