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From: Lehanover@aol.com
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Date: Wed, 18 Jul 2012 01:21:26 -0400 (EDT)
Subject: Re: [FlyRotary] Re: Tuning advance timing
To: flyrotary@lancaironline.net
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If you go to full throttle for tuning data observe the peak EGT rule. Stay  
well rich of peak EGT and not above 1650 degrees. Best power is about 50 
degrees  rich of peak. So the method for idle and off idle is not used.
Peak EGT is a function of cylinder filling, mixture strength, lubrication  
availability, intake air temps and timing. The reasoning is that peak EGT 
can be  well over 1900 degrees, and you may get into overheated apex seals. 
Best power  is just rich of peak, but we must NOT go there unless you have  
ceramic seals.
.
 
So make any changes you like with each pass but stop at 1600 EGT.
Adding advance past about 26 degrees usually does not add much power unless 
 you are using very high octane fuel. You can get up to 30 degrees, but you 
are  making more heat rather than power.
The engines produce more power on lower octane faster burning fuel,
so less advance can be used, thus less cylinder pressure before TDC which  
subtracts from torque. Mistral had it working on Jet A.
 
All of this is for normally aspirated engines. Boosted engines are  very
much different. Because you are screwing with over 100% cylinder filling.  
So you are increasing the swept volume ingested while keeping the same  
headspace. So, the effective compression ratio is going up with boost. So,  
timing is pulled out at the boost comes up. A more complex tuning issue. You  
still want peak cylinder pressure at about 50 degrees, but the mixture is now  
tightly packed and very fast burning.
So you roll back the timing and at best power may see near zero degrees of  
advance. No split timing on boosted engines. It looks like 
detonation. Rewind detonation definition.
 
This will all seem obvious after a while.
 
Lynn E. Hanover 
 
 
In a message dated 7/18/2012 12:02:46 A.M. Eastern Daylight Time,  
echristley@att.net writes:
 
I  discovered the log viewer's scatter plots this evening.  It's a way to  
visualize how various parameters affect each other.  It is fairly obvious  
that I can add in a lot more advance.

The task for the next session is  to set the whole table to 20*.  Run the 
throttle up and down a couple  times, increase 2* and repeat.  The end of the 
day should find me with a  graph showing RPM against advance for a range of 
throttle  positions.


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<DIV>If you go to full throttle for tuning data observe the peak EGT rule. =
Stay=20
well rich of peak EGT and not above 1650 degrees. Best power is about 50 de=
grees=20
rich of peak. So the method for idle and off idle is not used.</DIV>
<DIV>Peak EGT is a function of cylinder filling, mixture strength, lubricat=
ion=20
availability, intake air temps and timing. The reasoning is that peak EGT c=
an be=20
well over 1900 degrees, and you may get into overheated apex seals. Best po=
wer=20
is just rich of peak, but we must <STRONG>NOT</STRONG> go there unless you =
have=20
ceramic seals.</DIV>
<DIV>.</DIV>
<DIV>&nbsp;</DIV>
<DIV>So make any changes you like with each pass but stop at 1600 EGT.</DIV=
>
<DIV>Adding advance past about 26 degrees usually does not add much power u=
nless=20
you are using very high octane fuel. You can get up to 30 degrees, but you =
are=20
making more heat rather than power.</DIV>
<DIV>The engines produce more power on lower octane faster burning fuel,</D=
IV>
<DIV>so less advance can be used, thus less cylinder pressure before TDC wh=
ich=20
subtracts from torque. Mistral had it working on Jet A.</DIV>
<DIV>&nbsp;</DIV>
<DIV>All of this is for normally aspirated engines. Boosted engines are=20
very</DIV>
<DIV>much different. Because you are screwing with over 100% cylinder filli=
ng.=20
So you are increasing the swept volume ingested while keeping the same=20
headspace. So, the effective compression ratio is going up with boost. So,=
=20
timing is pulled out at the boost comes up. A more complex tuning issue. Yo=
u=20
still want peak cylinder pressure at about 50 degrees, but the mixture is n=
ow=20
tightly packed and very fast burning.</DIV>
<DIV>So you roll back the timing and at best power may see near zero degree=
s of=20
advance. No split timing on boosted engines. It looks like </DIV>
<DIV>detonation. Rewind detonation definition.</DIV>
<DIV>&nbsp;</DIV>
<DIV>This will all seem obvious after a while.</DIV>
<DIV>&nbsp;</DIV>
<DIV>Lynn E. Hanover&nbsp;</DIV>
<DIV>&nbsp;</DIV>
<DIV>&nbsp;</DIV>
<DIV>&nbsp;</DIV>
<DIV>In a message dated 7/18/2012 12:02:46 A.M. Eastern Daylight Time,=20
echristley@att.net writes:</DIV>
<DIV>
<BLOCKQUOTE=20
style=3D"BORDER-LEFT: blue 2px solid; PADDING-LEFT: 5px; MARGIN-LEFT: 5px">=
<FONT=20
  style=3D"BACKGROUND-COLOR: transparent" color=3D#000000 size=3D2 face=3DA=
rial>I=20
  discovered the log viewer's scatter plots this evening.&nbsp; It's a way =
to=20
  visualize how various parameters affect each other.&nbsp; It is fairly ob=
vious=20
  that I can add in a lot more advance.<BR><BR>The task for the next sessio=
n is=20
  to set the whole table to 20*.&nbsp; Run the throttle up and down a coupl=
e=20
  times, increase 2* and repeat.&nbsp; The end of the day should find me wi=
th a=20
  graph showing RPM against advance for a range of throttle=20
positions.<BR></FONT></BLOCKQUOTE></DIV></FONT></BODY></HTML>
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