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Date: Tue, 10 Jul 2012 09:02:13 -0400 (EDT)
Subject: Re: [FlyRotary] Re: On the step
To: flyrotary@lancaironline.net
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This falls under the phrase "everything affects everything" On the dyno you 
 may find that a particular combination of cams and exhaust headers has one 
or  more dips in the HP curve. So, it is not possible to hold a steady load 
on the  way up. So the engine gets to lump (A) and will not pull higher, so 
you back off  the load just a bit and let the engine through the trouble 
RPM and then pile on  the load again until you get to lump (B). Then repeat. 
This is of no matter, so  long as the problem RPM are not where you use the 
engine. Typical RPM for us  with only stock rods being legal, was 6,800 to 
8,000 RPM. So the driver had to  be in a gear that would give him above 6,800 
on the start as lump (B) was at  5800 RPM. Many cars have such problems and 
they do not show up until the aero  load is high enough to make a dip in HP 
obvious at a particular RPM. A carb  getting standoff and going over rich, 
or shaking so hard it foams the fuel  and goes over rich then over lean right 
after that when the carb calms  down. 
 
Advantage fuel injection.
 
So it is not only possible it is common if you dyno down low in the RPM  
range. It is less common in higher RPM ranges, and is more likely a result of 
a  more subtle cause. Exhaust back pressure spike. Unhappy distance between 
intake  horn and flat air cleaner cover. Harmonics in any system changing an 
output.  Boundary layer separation in front of an intake. A standing wave 
fooling a  sensor. And about 500 more major possible faults, including your 
hat is too  tight, or your sectional is improperly folded..
 
If you can dive a bit from your best speed to a bit higher speed and then  
hold the new speed for some time, you may have such a problem.
 
If you just slow to the original speed then you probably do not. Drag  
increases at the cube of velocity, so steps up from best speed require more  
effort on clean up, and, or more power.
 
Lynn E. Hanover
 
In a message dated 7/9/2012 2:23:24 P.M. Eastern Daylight Time,  
rwstracy@gmail.com writes:
 
The effect you mentioned is true but whether it is significant or not  will 
depend on the shape of your HP curve which depends in turn on the design  
of intake, exhaust, etc.  Torque curve is probably pretty flat around  6200 
so not too likely to be a big factor.


But more significantly, was that 150 IAS, TAS, or GPS?   Were you at  WOT?  
I've forgotten what the AC type was so don't know how to judge the  results 
from just this figure.


Tracy


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<DIV>This falls under the phrase "everything affects everything" On the dyn=
o you=20
may find that a particular combination of cams and exhaust headers has one =
or=20
more dips in the HP curve. So, it is not possible to hold a steady load on =
the=20
way up. So the engine gets to lump (A) and will not pull higher, so you bac=
k off=20
the load just a bit and let the engine through the trouble RPM and then pil=
e on=20
the load again until you get to lump (B). Then repeat. This is of no matter=
, so=20
long as the problem RPM are not where you use the engine. Typical RPM for u=
s=20
with only stock rods being legal, was 6,800 to 8,000 RPM. So the driver had=
 to=20
be in a gear that would give him above 6,800 on the start as lump (B) was a=
t=20
5800 RPM. Many cars have such problems and they do not show up until the ae=
ro=20
load is high enough to make a dip in HP obvious at a particular RPM. A carb=
=20
getting standoff and going over rich, or shaking so hard it foams the fuel=
=20
and&nbsp;goes over rich then over lean right after that when the carb calms=
=20
down. </DIV>
<DIV>&nbsp;</DIV>
<DIV>Advantage fuel injection.</DIV>
<DIV>&nbsp;</DIV>
<DIV>So it is not only possible it is common if you dyno down low in the RP=
M=20
range. It is less common in higher RPM ranges, and is more likely a result =
of a=20
more subtle cause. Exhaust back pressure spike. Unhappy distance between in=
take=20
horn and flat air cleaner cover. Harmonics in any system changing an output=
.=20
Boundary layer separation in front of an intake. A standing wave fooling a=
=20
sensor. And about 500 more major possible faults, including your hat is too=
=20
tight, or your sectional is improperly folded..</DIV>
<DIV>&nbsp;</DIV>
<DIV>If you can dive a bit from your best speed to a bit higher speed and t=
hen=20
hold the new speed for some time, you may have such a problem.</DIV>
<DIV>&nbsp;</DIV>
<DIV>If you just slow to the original speed then you probably do not. Drag=
=20
increases at the cube of velocity, so steps up from best speed require more=
=20
effort on clean up, and, or more power.</DIV>
<DIV>&nbsp;</DIV>
<DIV>Lynn E. Hanover</DIV>
<DIV>&nbsp;</DIV>
<DIV>In a message dated 7/9/2012 2:23:24 P.M. Eastern Daylight Time,=20
rwstracy@gmail.com 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>
  <DIV>The effect you mentioned is true but whether it is significant or no=
t=20
  will depend on the shape of your HP curve which depends in turn on the de=
sign=20
  of intake, exhaust, etc. &nbsp;Torque curve is probably pretty flat aroun=
d=20
  6200 so not too likely to be a big factor.</DIV>
  <DIV><BR></DIV>
  <DIV>But more significantly, was that 150 IAS, TAS, or GPS? &nbsp; Were y=
ou at=20
  WOT? &nbsp;I've forgotten what the AC type was so don't know how to judge=
 the=20
  results from just this figure.</DIV>
  <DIV><BR></DIV>
  <DIV>Tracy<BR></DIV></FONT></BLOCKQUOTE></DIV></FONT></BODY></HTML>
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