From: "Marvin Kaye" <marv@lancaironline.net>
Subject: Re: Compression, boost, and detonation
To: lml
Date: Tue, 25 Apr 2006 00:42:39 -0400
Message-ID: <web-1079911@logan.com>
In-Reply-To: <E1FYCSh-00070R-Qd@smtpauth08.mail.atl.earthlink.net>
References: <E1FYCSh-00070R-Qd@smtpauth08.mail.atl.earthlink.net>
MIME-Version: 1.0
Content-Type: text/plain; charset="ISO-8859-1"; format="flowed"
Content-Transfer-Encoding: 8bit

Posted for "richard  titsworth" <rtitsworth@mindspring.com>:

  
  
  George,
  
  
  
  I was at your Jan 06 APS course (well worth it - I'd recommend it anyone)!
  
  I know/realize "tuning" is all very inter-related (and often secret), but a
  few questions.
  
  
  
  Was it a TSIO-550 w/ 8.5:1 or a normalized IO-550?   Any other mods -
  ceramic piston domes, etc?
  
  Any "landmarks" (MP, RPM, FF, CHT) that seem to consistently represent the
  "detonation edge"?
  
  Any info you can share/suggest for spark advance, and/or target manifold
  temperatures, to minimize/optimize detonation with the TSIO-550 - 8.5:1?
  
  
  
  I fully respect your testing.  I love airplane engines and I know you hate
  to hear about autos..
  
  But, our detonation challenges (at reasonable mid 30"s MP boost levels, with
  reasonable 8.5:1, and with good 100LL fuel) occur where high perf autos
  operate successfully.
  
  (I'm not going there with the comparisons - just focusing on detonation
  phenomenon)
  
  
  
  I understand the effects of timing, RPM, and mixture, but those are
  "patches" not "fixes".  (Perhaps variable timing is the fix?)
  
  
  
  Seems like I keep coming back to scavenging/eliminating heat as the key to
  delaying the onset of detonation, HP, economy, etc.
  
  
  
  Any sense/confirmation on this?  Any detailed insight on what heat source is
  the prime cause (internal head face, piston crown, walls, value face, etc)?
  
  
  
  How does the air (in the cylinder) get over-heated?
  
  Is the air too hot before it enters the cylinder? (that seems controllable
  if we're willing to accept additional cooling drag)
  
  Does heat built too much during compression (adiabatically)? (@ 8.5:1
  compression is not un-reasonably high)
  
  Is it absorbed from the piston, head face, walls?  (The air isn't in there
  very long to be heated by radiation/convection - I think I'll try some heat
  transfer modeling - any insights on coatings?
  
  Is it heated in the port while waiting for the intake value to open (sitting
  there for 3 strokes)
  
  
  
  Have you done much testing with value overlap, intake vs exhaust pressure
  ratio, etc - perhaps residual air/exhaust from the prior cycle (hot) is
  helping to heat the incoming air?  Seems higher compression would help
  reduce this effect (less residual air)?
  
  
  
  Have you ever had the opportunity to test a TCM LTSIO-550 (liquid)?  I know
  it's not the same cross-flow arrangement (and too much trouble for me to
  consider for my plane), but I'm curious if it offers any detonation/heat
  insights?
  
  
  
  Have you ever tested the "Cool Jugs"?
  http://www.liquidcooledairpower.com/products.shtml   I know these are for
  smaller engines, but perhaps any heat/detonation insights?
  
  
  
  I don't recall if you can simulate altitude with your dyno (i.e. throttle
  the compressor input)?
  
  Any sense of altitude's effect on detonation margins (say above 18,000)?
  
  Presumed effects (ceteris peribus):
  
  Hotter upper deck temps due to compressor pressurization (thus exercising
  the intercoolers)
  
  Higher exhaust back pressure due to waste gate being "more closed" to drive
  compressor to create upper deck pressure
  
  Lower exhaust back pressure due to lower turbine exit pressure (ambient) -
  negligible?
  
  
  
  
  
  Rick Titsworth
  
  APS Jan, 06
  
  Lancair ES - TSIO-550E-8.5
  
  rtitsworth@mindspring.com
  
  cell: 313-506-5064