REFLECTOR: Reflector Digest, Vol 98, Issue 35

Dave T Nelson dtnelson at us.ibm.com
Fri May 10 12:49:31 CDT 2013


Bill, With all due respect, no, my exhaust isn't tuned.  Neither is yours.
Or really anyone else's.  If you think I'm wrong, a great engine book to
read (my bible for engines) is the "Skyranch Engineering Manual"... the net
of it is, if you think your exhaust is tuned, I'll ask - for what RPM? ...
No exhaust can be tuned for all RPMs., and that's just one of the fallacies
with "tuned" exhausts.  The manual essentially makes the point that, from
the engine's perspective, the best exhaust is no exhaust, and anything else
is a compromise (from a pure efficiency standpoint).

BTW, there were no other engine changes.  The exhaust went from a straight
out the bottom setup to the "tail shooter" setup.   So... I don't think I'm
"forgetting the obvious".

Dave

Dave T. Nelson
T/L 553-4327, Voice 507-253-4327, Fax 507-253-3648
Program Director, ISC ECAT NPI & Test Engineering

      ----- Message from "Stockman, Bill" <bill.stockman at daytonaero.com> on
      Fri, 10 May 2013 11:09:01 -0500 -----
                                                           
      To: Velocity Aircraft Owners and Builders list       
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 Subject: Re: REFLECTOR: Reflector Digest, Vol 98, Issue   
          33                                               
                                                           

You are all forgetting the obvious.
Accepting the increase in performance as described by Dave, it may also be
coming from improved engine performance.
The four pipes out the back are somehow acting like a tuned exhaust which
will greatly improve engine output.
I have a four into one exhaust on my Velocity173 that also exists to the
rear and noticed an improvement over the standard
exhaust.    I didn’t get 15 kts improvement, but did gain 4-5 kts.
bill
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