Tail Pipe

[wa7hra]

By now, most of you accept the fact that the outlet of the tail pipe is sooty. Both sides probably appear the same.

Mine was this way for a long time, but for some time now, one side is sooty and the other side is clean.

Has anyone else experienced this?

Bob, wa7hra

[wa7hra]

By now, most of you accept the fact that the outlet of the tail pipe is sooty. Both sides probably appear the same.

Mine was this way for a long time, but for some time now, one side is sooty and the other side is clean.

Has anyone else experienced this?

Bob, wa7hra

[edgray]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">one side is sooty and the other side is clean. </div></BLOCKQUOTE>
BOB: that is not necessarily a good thing, and MAY represent a "tune" problem with the "clean" side having somehow become too lean. I'd have it checked.

Perhaps MB or Keith, can offer their opinions. ED

[John-D]

When you first start a gas engine it runs a tad rich, This can result in a bit of soot.

Now on most cars the pipe gets hot enough to burn it off, but on a motor home you have a lot longer tail pipe. so it does not get as hot.

And no, I don't know if this is the reason or not. The amount of soot would be significant in that a little is perhaps normal. A lot is not.

[oemtech]

I would be concerned about clean tail pipes. Be aware that there is an enrichment fuel function to cool the cats.

[AmtrakEngnr]

As explained in the "Workhorse Chassis Guide"

EXHAUST SYSTEMS
The exhaust manifolds used on the big block gas engines were redesigned with the
introduction of the 7.4L Vortec. The redesigned manifolds promote maximum airflow through
the engine for maximum horsepower and torque as well as reduce tail pipe emissions. The
manifolds are constructed from a nodular cast iron that has some of the same properties as
cast but are not as prone to cracking or warping. In 2001 on the 8.1L Vortec the design
remained very similar but the construction material changed to a stainless steel casting,
increasing the heat resistance and longer life. The manifolds are sealed to the engines cylinder
heads by multi-layer stainless steel exhaust manifold gaskets that provide a positive seal,
Workhorse part no. 12558275.
The exhaust system on all 7.4L Vortec engines came with enlarged dual pipes running through
two catalytic converters, for maximum airflow. Both exhaust pipes then enter into a single
muffler with one larger diameter pipe exiting to the driver's side of the vehicle behind the rear
tires.
The 8.1L exhaust was redesigned for even higher flow for additional horsepower and torque.
Large diameter pipes are utilized with two high flow catalytic converters and two low
restriction mufflers. The standard exhaust is routed down the inside of each frame rail and
exits on both sides of the chassis prior to the rear axle. The optional exhaust is identical to the
standard exhaust through the mufflers; the optional exhaust then connects into one enlarged
pipe exiting behind the driver's side tire. Adjacent are diagrams of both exhaust systems. Either
system provides minimal restriction and utilizes long life components.
The standard dual exhaust can be changed to the
single exiting style if desired. The change requires
a Y-Pipe, Workhorse part no. W0006196, exhaust
pipe assembly, Workhorse part no. W0003731,
and connecting clamp, Workhorse part no.
W0005673. Reuse of the two muffler clamps and
one frame exhaust hanger is also required.
The W16 (16,000 lb. GVWR) and W18 (18,000 lb.
GVWR) equipped with the 6.0L Vortec as well as P
Series chassis with the 5.7L Vortec or the 6.5L
Diesel engine come standard with a high flow single exhaust system exiting behind the rear tire
on the passenger side, no optional exhaust systems are available for these engines
P Series chassis are standard with a heat/splash shield on the right side for the engine attached
to the frame, Workhorse part no. 15983041. This provides airflow along the right side exhaust
manifold and spark plug wires, thereby cooling these components and extending service life.
The driver's island, on the left side, provides similar airflow down this side of the engine, also
acting as a splash shield. This cooling is necessary due to the extreme heat that is developed by
the exhaust manifolds during normal engine operation, especially under heavy loads such as
climbing hills. Due to the repositioning of the engine in the W Series chassis, these shields
were not required to provide adequate airflow around the engine exhaust manifolds providing
the front cap of the coach allows adequate air flow in the engine bay. If it is determined that
additional airflow is needed an airflow routing kit has been developed, Workhorse part no.
W8002069.
56
With these long high-flow exhaust systems the exiting exhaust cools rapidly as it travels
through that exhaust system and exits at a considerable lower temperature then at the exhaust
manifolds. With these lower temperatures normal exhaust vapors including carbon (soot)
condenses along the pipe giving it a black coloring. During high engine load conditions (such
as climbing long grades) exhaust pipe temperatures elevate to the point that this soot can
vaporize in heavy concentrations, in combination with moisture (which is a normal by
product of the catalytic converters) this can produce black smoke. This is normal operation
and should not be confused with the engine running rich, as that condition would be detected
by the oxygen sensors and set a check engine light.