i'm exhausted

Jan 9 02:30 UTC 1992

let's say, hypothetically speaking, i removed my entire exhaust system.  what
affect would this have on my car?

response 2 of 19:

Jan 9 12:24 UTC 1992

Back in the early '80's I had a friend who owned an old Firebird that
had been set up as a "quarter mile car" in a previous life.  The car
was in good shape, but the bottom of the trunk was totaly rusted out!
He claimed that it was from the exhaust being terminated just shy of 
the rear axle in its previous life.  He had put in exhaust that went
about 6 in. beyond the rear bumper, but fumes were still sucked up
through the rear deck and seat due to the back-draft when the car was
moving.  I got one of the worse headaches of my life after going to 
Detroit and back in that car!
Did the exhaust really cause the trunk to rust out?  I don't know but
considering how fast the exhaust system in my car goes, I would  not 
be surprised.

response 4 of 19:

Jan 14 13:22 UTC 1992

The loss of backpressure due to a minimal exhaust system only in-
creases fuel consumption as far as I know.  I don't think you can
hurt the engine by reducing the back pressure.  Go to the auto parts
store and get one of those "turbo muflers" and fit it to the end of
whatever solid pipe remains.  It will be loud in the car, but not
too bad for others who have to listen to your heap go by.

response 6 of 19:

Jan 15 13:26 UTC 1992

I've fiddled with engines since the mid 60's.  #5 makes no sense.
The exhaust system has an effect on tuning.  If you change it, you
change the tuning of the system which effects back pressure, which may
well be a vacuum at some RPMs.  You will effect fuel economy because
valve timing may be adjusted for optimal economy.  Changing the exhaust
system may cause more or less exhaust to exit the cylinder during the
exhaust cycle because the pressure in the exhaust manifold may now be
different.  Does the engine no harm.

response 8 of 19:

Jan 16 14:16 UTC 1992

Answers without reasons = nonsense.

response 10 of 19:

Jan 18 20:49 UTC 1992

On most older cars, say, before 1970, removing the exhaust system is
certainly not going to be a major inconvenience to anything except
people's hearing.  Except perhaps for race cars, there really wasn't
anyting that finely adjusted, nor much need; a slight tune-up might be
all that's needed, the engine itself would end up with significantly
more power without the back pressure, but probably slightly worse fuel
economy (in fact, one of the early economy measures was to deliberately
introduce some exhaust into the input air stream at low speeds -- saves
energy that way.  Many high performance aircraft engines feature
extremely short individual exhaust pipes leading to the outside world.
Fuel economy isn't nearly as important as power-to-weight ratios there.

Certainly, the theory of #5 makes no sense.  The most important forces,
by far, on the valve, include the pressure from the power stroke, the
impulse imparted by the valve train including that of the cam shaft &
the spring, & stress caused by heating & cooling including that of the
exhaust gas and the valve seat.  The exceedingly small amount of force
caused by air resistance is going to be exceedingly minute compared to
these other stresses.

An interesting factor for the exhaust system & back pressure might well
be the harmonics -- the length of the exhaust pipe is going to be as
significant as anything in determining how loud it's going to be, and
how much back pressure will exist.  Sometimes, on high performance
engines, you'll see that the exhaust manifold will have strange kinks in
it for various cylinders -- this is in an effort to equalize the whole
system and get the best performance (this is even more important for the
intake manifold, as you might well imagine.)

'Course, in modern cars, there's another factor -- the oxygen sensor.
You still need enough exhaust pipe to collect the exhaust together, and
it should probably have a configuration roughly similar to what it was
designed with, so that the engine's electronics will be able to
determine the optimal fuel/air mixture for the engine.  At the same
time, that means there's a fairly good chance you could just cut the
exhaust off past the sensor with no problems -- it'll adjust its timing
& fuel mixture automatically.  If you don't mind risking the wrath of
the neighbors, the noise, & all, shouldn't be a problem.

Corrosion does sound a very likely problem.  The problem is that any car
is going to emit a very acidic exhaust.  There are going to be major
amounts of water vapour -- so any cool metal surface it comes in contact
with is going to get nice warm water deposited on it.  Add to that the
large amounts of co2 & small amounts of so3,so4,nox, &etc., and you have
instant acid with no doubt trace quantities of various unstable reactive
chemicals and you indeed have a very nasty threat to your car's
underbody.  The only reasion your car's exhaust doesn't fall sooner is
that it gets hot enough in operation that the water doesn't condense
out.  That's why, if you only drive your car short distances, the
exhaust rusts out a lot faster.

The volvo 240 has an incredible exhaust system with not 1, but TWO
mufflers, and on the more recent cars, it's aluminum plated.  My volvo
is now 3 years old, and still rather quiet.  The exhaust is rusting out.
From the end in -- it's now reached back about 2 inches from the end of
the tale pipe.  It's a shame they don't plate the cut edges but I still
can't complain.  I've never had an exhaust system last this long before.

response 12 of 19:

Jan 20 22:13 UTC 1992

Muffler Man will bend pipe... in fact, they dont even stock anything
other than straight pipe...  low (no) inventory on special bent pipes.

response 14 of 19:

Feb 9 19:34 UTC 1992

I never considered the possible corrosive effects of exhaust until reading this
.  Glad I had my car fixed now.  The aspirator tube to the front catalytic
convertor (yup, there are two for California emmissions Omni's) had broken
free (when the mech at the dealer was 'inspecting' the system) and there
was a 3/4" hole.  Dealer wanted to relpace the convertor since the mounting
which comes built into the convertor was useless.  Meineke's guy just
welded the tube back in place for a $10 tip.  Jodi's car has the same 
problem and will go in this week.

response 16 of 19:

Feb 10 13:39 UTC 1992

I dont think that exhaust gasses are very corrosive.  They can get
very hot though and burn paint/undrercoating off, exposing bare metal
underneath to where road salt can get to it.  Elevated tempratures also
increase chemical activity, including the process of rusting.  Most of
my exhaust systems have rusted from the outside in.

response 18 of 19:

Feb 12 02:36 UTC 1992

Re 15- I've actually had wonderful service from the dealership side of Arbor
Dodge, it's the actual serviec department that has given me and several others
I've talked to problems.