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From: Lehanover@aol.com
Full-name: Lehanover
Message-ID: <d220e.3b6ced1b.3f615dce@aol.com>
Date: Wed, 11 Sep 2013 01:46:54 -0400 (EDT)
Subject: Re: [FlyRotary] Re: First Flight jitters
To: flyrotary@lancaironline.net
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I must admit I have never understood manifold pressure. I have been working 
 on that. The lack of power at lower RPM is understood.
 
RPM X torque = HP. So, the engine has poor torque due to short stroke.  
There goes half of your multiplier. Tuning needs to be a bit closer to ideal.  
The best way to remove HP is a poor exhaust system. 
Look at the care in the designs of dirt bike exhaust systems. A typical  
turbo exhaust manifold is a poor design for a normally aspirated engine.
And until the boost is up to overcome that poor design and add the  
recovered power to the intake, you just have a NA engine with a bad exhaust  
design.  
 
So the first engine saw 44" HG when it failed. That would be 21.5 pounds of 
 boost. Over 20 pounds you need to be right on the tune. 
Well rich of peak EGT to fuel cool and lower charge temperature. 
Timing 2 degrees below best power. Good size intercooler and a quick waste  
gate. That was on the way to being a drag racing engine before adding the 
known  problems. 
 
When the boost is low or there is none, then you can use more ignition  
advance.  Once you can limit boost to say 4 to 6 pounds or 8" to 16"HG with  a 
waste gate you can be close to 18 degrees. Same as a NA engine. When the  
boost is up to maximum then you need to retard a bit. On long closed throttle  
runs you can be up to 35 degrees.
This because you have few pounds of air, and nearly no fuel flow. So, very  
low compression. All this takes a long time to burn the idle mix. 
The RX-8s do this. 
 
How is this? One pound of boost is the same as 2.04" HG. Or, 14.7 pounds at 
 sea level times 2.04 =29.98" HG. At any throttle setting,
local barometer showing on the manifold pressure gage suggests a well  
designed intake system and a free flowing air filter. The Manifold pressure gage 
 is measuring vacuum in the intake system. The gage is connected between  
the butterfly and the engine or turbo inlet. 
 
The boost gage measures pressures above local barometric in either pounds  
of boost or inches of Mercury or both and is connected between the turbo  
and the engine. It is measuring pressure in the inlet runner. 
 
Is that correct? 
 
Add timing marks to your starter ring gear. Divide the number of teeth by  
360 to get degrees per tooth. Clean and paint a green tooth at TDC.
Turn the engine backwards and paint a tooth or valley between teeth another 
 color for 15 degrees. Paint a red tooth at 20 degrees, and so-on. Write 
the code  on the engine beside the pointer you have constructed. OK for 
tractor aircraft.  Not so much fun for pushers where the prop is pulling at your 
loose clothing. 
 
Lynn E. Hanover
 
 
In a message dated 9/9/2013 9:36:25 P.M. Eastern Daylight Time,  
rwstracy@gmail.com writes:

If your ignition timing measurement was accurate at 3000 rpm and 16" mp,  
it's way too retarded.  What did you set the static timing to?  Remember that 
that has nothing to do with actual ignition timing.  It's just a reference 
point for the computer.


Tracy


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<DIV>I must admit I have never understood manifold pressure. I have been wo=
rking=20
on that. The lack of power at lower RPM is understood.</DIV>
<DIV>&nbsp;</DIV>
<DIV>RPM X torque =3D HP. So, the engine has poor&nbsp;torque due to short =
stroke.=20
There goes half of your multiplier. Tuning needs to be a bit closer to idea=
l.=20
The best way to remove HP is a poor exhaust system. </DIV>
<DIV>Look at the care in the designs of dirt bike exhaust systems. A typica=
l=20
turbo exhaust manifold is a poor design for a normally aspirated engine.</D=
IV>
<DIV>And until the boost is up to overcome that poor design and add the=20
recovered power to the intake, you just have a NA engine with a bad exhaust=
=20
design.&nbsp; </DIV>
<DIV>&nbsp;</DIV>
<DIV>So the first engine saw 44" HG when it failed. That would be 21.5 poun=
ds of=20
boost. Over 20 pounds you need to be right on the tune. </DIV>
<DIV>Well rich of peak EGT to fuel cool and lower charge temperature. </DIV=
>
<DIV>Timing 2 degrees below best power. Good size intercooler and a quick w=
aste=20
gate. That was on the way to being a drag racing engine before adding the k=
nown=20
problems. </DIV>
<DIV>&nbsp;</DIV>
<DIV>When the boost is low or there is none, then you can use more ignition=
=20
advance.&nbsp; Once you can limit boost to say 4 to 6 pounds or 8" to 16"HG=
 with=20
a waste gate you can be close to 18&nbsp;degrees. Same as a NA engine. When=
 the=20
boost is up to maximum then you need to retard a bit. On long closed thrott=
le=20
runs you can be up to 35 degrees.</DIV>
<DIV>This because you have few pounds of air, and nearly no fuel flow. So, =
very=20
low compression. All this takes a long time to burn the idle mix. </DIV>
<DIV>The RX-8s do this. </DIV>
<DIV>&nbsp;</DIV>
<DIV>How is this? One pound of boost is the same as 2.04" HG. Or, 14.7 poun=
ds at=20
sea level times 2.04 =3D29.98" HG. At any throttle setting,</DIV>
<DIV>local barometer showing on the manifold pressure gage suggests a well=
=20
designed intake system and a free flowing air filter. The Manifold pressure=
 gage=20
is measuring vacuum in the intake system.&nbsp;The gage is connected betwee=
n=20
the&nbsp;butterfly and the engine or turbo inlet. </DIV>
<DIV>&nbsp;</DIV>
<DIV>The boost gage measures pressures above local barometric in either pou=
nds=20
of boost or inches of Mercury&nbsp;or both and is connected between the tur=
bo=20
and the engine. It is measuring pressure in the inlet runner.&nbsp;</DIV>
<DIV>&nbsp;</DIV>
<DIV>Is that correct? </DIV>
<DIV>&nbsp;</DIV>
<DIV>Add timing marks to your starter ring gear. Divide the number of teeth=
 by=20
360 to get degrees per tooth. Clean and paint a green tooth at TDC.</DIV>
<DIV>Turn the engine backwards and paint a tooth or valley between teeth an=
other=20
color for 15 degrees. Paint a red tooth at 20 degrees, and so-on. Write the=
 code=20
on the engine beside the pointer you have constructed. OK for tractor aircr=
aft.=20
Not so much fun for pushers where the prop is pulling at your loose clothin=
g.=20
</DIV>
<DIV>&nbsp;</DIV>
<DIV>Lynn E. Hanover</DIV>
<DIV>&nbsp;</DIV>
<DIV>&nbsp;</DIV>
<DIV>
<DIV>In a message dated 9/9/2013 9:36:25 P.M. Eastern Daylight Time,=20
rwstracy@gmail.com writes:</DIV>
<BLOCKQUOTE=20
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  <DIV>If your ignition timing measurement was accurate at 3000 rpm and 16"=
 mp,=20
  &nbsp;it's way too retarded. &nbsp;What did you set the static timing to?=
=20
  &nbsp; Remember that that has nothing to do with actual ignition timing.=
=20
  &nbsp;It's just a reference point for the computer.</DIV>
  <DIV><BR></DIV>
  <DIV>Tracy<BR></DIV></FONT></BLOCKQUOTE></DIV></FONT></BODY></HTML>
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