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From: Lehanover@aol.com
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Date: Mon, 22 Nov 2010 01:41:57 EST
Subject: Re: [FlyRotary] Trailing Coil Disable to Turbo too? Was: N20
To: flyrotary@lancaironline.net
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In a message dated 11/21/2010 4:13:32 P.M. Eastern Standard Time,  
wdleonard@gmail.com writes:

This is the first I am hearing about disabling the trailing coils for  
prevention of detonation.  Should I be doing this when I am at high boost  as 
well.  Right now I seem to be able to run 45" without issue but may  start 
pushing that a little.  Can you guide me to the  background?

-- 
David Leonard


Detonation is an auto ignition of compressed gasses after the planned  
ignition event. If you have two plugs and one plug fires later than the leading  
(ignition split) the second plug starts looking like detonation. 
 
Worse for higher boost. Worse for wider split.
 
Since the second event (auto ignition) occurs in an area away from the  
leading plug it is in a higher pressure and with fuel and air molecules  closer 
together and at a higher temperature. So combustion is more energetic  with 
higher than normal flame front speeds. The pressure spikes generated may  
overcome the oil film on bearings, or break apex seals, or, rings and ring 
lands  in piston engines. Very bad mojo.
 
Detonation is charge temperature dependant. So cooler intake air, richer  
mixture (well rich of peak EGT) as in take off and climb. (Fuel cooling) 
Cooler  oil (rotor face temps) and cooler housing walls (bigger radiator). 
Higher octane  fuel. Octane is a measurement of detonation resistance. Higher 
number is better.  Very lean mixtures with their low flame speeds can mimic 
higher octane fuel. 
 
The rotary with its huge combustion chamber and cool charge temps is more  
resistant to detonation than is a piston engine. Until you pour on the 
boost.  Modest boost and almost nothing changes. Weekend killer....hold my beer 
and  watch this kind of boost.... You can get 800 HP from a 13B but engine 
life may  be in seconds. The added fuel and air produces a bigger engine. Let 
us say that  you double the fuel and air processed per revolution. That 
would be the same as  an engine of twice the swept volume, correct?
 
But, the combustion chamber remains the same size, so the effective  
compression ratio has gone way up. Flame speed may more than double. Since we  
want best chamber pressure at about 45-50 degrees after TDC, the ignition 
timing  must be reduced a bunch. 
 
Racing Beat says no split timing at high boost. Engine development is at 10 
 degrees of total advance. Racing at high boost is at 12 degrees of total  
advance.  Crazed drag racers may be running all of the timing after TDC.  
The lure of 800 HP you know.
 
I have no knowledge of boosted rotary engines. It is a fad. It will go  
away.
 
Lynn E. Hanover  

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<DIV>
<DIV>In a message dated 11/21/2010 4:13:32 P.M. Eastern Standard Time,=20
wdleonard@gmail.com writes:</DIV>
<BLOCKQUOTE  style=3D"BORDER-LEFT: blue 2px solid; PADDING-LEFT: 5px; MARG=
IN-LEFT: 5px"><FONT    style=3D"BACKGROUND-COLOR: transparent" color=3D#00=
0000 size=3D2 face=3DArial>
  <DIV>This is the first I am hearing about disabling the trailing coils=
 for=20
  prevention of detonation.&nbsp; Should I be doing this when I am at high=
 boost=20
  as well.&nbsp; Right now I seem to be able to run 45" without issue but=
 may=20
  start pushing that a little.&nbsp; Can you guide me to the=20
  background?<BR></DIV>
  <DIV>-- <BR>David Leonard<BR><BR></DIV></FONT></BLOCKQUOTE></DIV>
<DIV></DIV>
<DIV>&nbsp;</DIV>
<DIV>Detonation is an auto ignition of compressed gasses after the planned=
=20
ignition event. If you have two plugs and one plug fires later than the le=
ading=20
(ignition split) the second plug starts looking like detonation. </DIV>
<DIV>&nbsp;</DIV>
<DIV>Worse for higher boost. Worse for wider split.</DIV>
<DIV>&nbsp;</DIV>
<DIV>Since the second event (auto ignition) occurs in an area away from th=
e=20
leading plug&nbsp;it is in a higher pressure and with fuel and air molecul=
es=20
closer together and at a higher temperature. So combustion is more energet=
ic=20
with higher than normal flame front speeds. The pressure spikes generated=
 may=20
overcome the oil film on bearings, or break apex seals, or, rings and ring=
 lands=20
in piston engines. Very bad mojo.</DIV>
<DIV>&nbsp;</DIV>
<DIV>Detonation is charge temperature dependant. So cooler intake air, ric=
her=20
mixture (well rich of peak EGT) as in take off and climb. (Fuel cooling)=
 Cooler=20
oil (rotor face temps) and cooler housing walls (bigger radiator). Higher=
 octane=20
fuel. Octane is a measurement of detonation resistance. Higher number is=
 better.=20
Very lean mixtures with their low flame speeds can mimic higher octane fue=
l.=20
</DIV>
<DIV>&nbsp;</DIV>
<DIV>The rotary with its huge combustion chamber and cool charge temps is=
 more=20
resistant to detonation than is a piston engine. Until you pour on the boo=
st.=20
Modest boost and almost nothing changes. Weekend killer....hold my beer an=
d=20
watch this kind of boost.... You can get 800 HP from a 13B but engine life=
 may=20
be in seconds. The added fuel and air produces a bigger engine. Let us say=
 that=20
you double the fuel and air processed per revolution. That would be the sa=
me as=20
an engine of twice the swept volume, correct?</DIV>
<DIV>&nbsp;</DIV>
<DIV>But, the combustion chamber remains the same size, so the effective=
=20
compression ratio has gone way up. Flame speed may more than double. Since=
 we=20
want best chamber pressure at about 45-50 degrees after TDC, the ignition=
 timing=20
must be reduced&nbsp;a bunch. </DIV>
<DIV>&nbsp;</DIV>
<DIV>Racing Beat says no split timing at high boost. Engine development is=
 at 10=20
degrees of total advance. Racing at high boost is at 12 degrees of total=
=20
advance. &nbsp;Crazed drag racers may be running all of the timing after=
 TDC.=20
The lure of 800 HP you know.</DIV>
<DIV>&nbsp;</DIV>
<DIV>I have no knowledge of boosted rotary engines. It is a fad. It will=
 go=20
away.</DIV>
<DIV>&nbsp;</DIV>
<DIV>Lynn E. Hanover&nbsp;&nbsp;</DIV></FONT></BODY></HTML>

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