Gary Wolf wrote:

Paul,
   The other day one of our club members told me the old chestnut about
exhaust wrapping creating more horsepower by holding the heat in the

pipe. I

explained that the origin of that myth was in Nascar, where the carb air

had

to come from under the hood and the hp was increased by lowering the
under-hood temperature.
   Since the use of this tape began, I have been seeing lots of exhausts
(mild steel) that have a zillion spider-web cracks from the absorption of
carbon into the 1010 steel until it becomes brittle. There is little

point

in welding them up as they continue to propagate.
   My question is: does this happen with the common stainless steels as

well?

                                                        Gary Wolf

tommayer wrote:

Two of us in this area have done a good deal of experimenting with this on
turboed engines--a Lyc IO-320 in an RV-6, and an IO-360 in a Mustang II.
    I had wrapped mild steel exhausts on the Mustang before it was blown,
with VERY bad results.  Beaucoup cracks.
    On the blown version with stainless exhaust I have covered most of the
stacks with aluminized insulation sheets.    You can get it at performance
stores.  Best prices I've found are from CFI in Stocton, Cal. 800-624-2641.
The guys there--Dave and Rick--seem to know a lot about insulating turbo
exhaust systems, and they don't hang up on you when you tell them you're
dealing with airplanes.
    I have had absolutely no exhaust cracking problems in over 500 hours of
use.
    The only problem with the sheets is holding them in place.  I have yet
to find anything but hose clamps that both stay in place and do not eat up
the material.  I bet I have 5 pounds of hose clamps holding insulation on.
    The places that I cannot cover with the sheet I have wrapped with the
tape you talk about.  I unwind the stuff every 25 hours to check for
problems.  So far, so good.
    Insulating the exhausts is very helpful on my installation.  EGTs with
about a 30 degree split,  CHTs about 25 degree split in cruise.  Without the
insulation there were CHT cooling problems in hot weather climbs.
    Jeff Nielson, who is braver than I am, wrapped with tape his entire
system in his blown RV-6.  He has not had any problems, and I think is up to
around 200 hours with the turbo system.  I am still very leery of the tape
because of my earlier bad experiences with the mild steel exhaust.
    Tom Mayer

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