From: "Tracy Crook" <lors01@msn.com>
Date: 2005/06/11 Sat AM 10:47:10 EDT
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Subject: [FlyRotary] Re: EC2 turbo updates

Good discussion on turbo considerations.  I have made a number of significant improvements in the turbo version of the EC2 code in the last few months, many of them related to the matters being discussed here.  They are significant enough that I would like to see everyone running turbos to have these updates.  I will furnish the new chips at cost ($20 a pair) but there is a snag.  I have migrated the EC2 to a new chip family that requires 5 on-board jumpers to be compatible with the new chip.  If your unit already has chips with the number PIC18F6680, it already has the jumpers installed.  If you are adept at soldering I will furnish the instructions.  If not, send the unit back and I'll do it.  Include enough postage to ship the unit back to you.

Tracy (making work for myself )




  On 6/10/05, Ian Dewhirst <ianddsl@magma.ca<mailto:ianddsl@magma.ca>> wrote:     Hello, Dave & Dave

    Disclaimer:  No turbo rotary experience - plenty of turbo piston engine
    experience - I figure the concepts are the same, the implementation seems a     bit different however.

  Kpa's?  they make gauges in those units?
  to make it easy for this discussion:
  90Kpa= 26.6" Hg
  120Kpa=35.5"
  200kpa=59"

  Also, assuming I remember correctly and:
  0 clicks advance = 24 deg advance, then
  2 clicks = 27.6 deg
  3 = 29 deg
  5= 32.5


    Clearly retarding the timing solved the detonation problem. I emailed a
    friend of mine that campaigns a turbo 13B drag boat. His recomendations at     5500 rpm: 30 to 35 deg advance to 90kpa, dropping quickly to 24 at 120kpa
    dropping slowly to 10 to 17 total advance at 200kpa.

  I assume that is MAP not boost.
  so to paraphrase, he runs:
  30-35 deg to 26 "MAP,  24 deg to 35" MAP, and down to 10-17 by 59" MAP

  and I was running
  32.5 deg to 29" MAP while n.a. and got detonation between 31" and 35" MAP
  now at 27 deg. and get detonation at about 38"
  and previously ran 24 deg advance up to 45" MAP without noted detonation.

  So I ended up pretty close.  Mine is a little more aggressive than his, but he almost surely has a ported engine while mine is currently not ported.  I think that would more than make up for the difference.



    I am surprised that at 3 lbs of boost one needs to retard the timing so much
    from the N/A setting, logically with only a three pounds of boost the     combustion pressure should be not much more then a rotary with 9.7:1 CR.
    (assuming that you have 8.5:1 rotors).  Hmmm...

  I believe mine are 9.0:1 rotors.  ('91 turbo rotors)



    So You can reduce detonation several ways:

    - Retard the timing, that way the peak combustion pressure occurs later in     the cycle.
    - Richen the fuel mixture so that the charge is cooler and the flame front
    travels more slowly which helps to ensure that peak combustion pressure
    occurs later.
    - Higher octane fuel, burns slower, same solution as above. You are probably     running 100LL

  91 MOGAS now with the the turbo (previously 87).  Don't want to foul the plugs or pay the cost for 100LL.  I only run 100LL on cross countrys.


    - Lower air charge temperature, technically your new turbo should generate a
    lower charge temperature rise then the stock turbo. Your intercooler looks     pretty decent.

    Do you monitor your intake charge temperature?

  Yes, it was 120-140 after the intercooler with the old stock turbo.


    Can you program your EC2 to increase the AFR exponentially above 30"
    mercury?

  Yes, and it is currently mapped a little lean up there... Can't get my O2 sensor back in because the cap rusted into place...  have to weld in a new bung.


    What retard options do you have under boost?

  The EC2 only allows a single transition point worth 4 deg.  right now it is set at 31"  so below 31"MAP  I have 31 deg advance and above that I have 27 deg advance.  (nudging Tracy for an upgrade  :-)

  Thanks for all the input Ian.
  --   Dave Leonard
  Turbo Rotary RV-6 N4VY
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