Detonation Monitor
David Hunt
bamainc at home.com
Sat May 26 23:18:11 GMT 2001
This is a multi-part message in MIME format.
------=_NextPart_000_003F_01C0E610.3281B380
Content-Type: text/plain;
charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
I have been thinking about the detonation situation and you have ignited =
some further thoughts on that subject. You have mentioned that the =
detonation frequency would be at about the combustion chamber Helmholtz =
frequency. I think you're probably right but it just occurred to me =
that the speed of sound should be quite high due to the compression =
ratio.
So, if the volume is (for a 350 small block Chevy)=20
350/8 * sine(degrees BTDC) + .125(350/8)
where:
The .125 is clearance volume for an 8:1 engine.)
350/8 is the volume of one cylinder.
sine(degrees BTDC) is the ratio of volume of the cylinder at that =
position
And the pressure is:
14.7PSI * .8 * 8
Where:
14.7 is the initial pressure
.8 is the volumetric efficiency
8 is the compression ratio
Then we should have the 'ping' frequency. That's as far as I can go =
right now, I'll work more on it later. I don't know the Helmholtz =
theorem right now. But it seems that the ping frequency will increase =
depending on where the ping is started in relationship to the cycle
dh
----- Original Message -----=20
From: Hugh=20
To: diy_efi at diy-efi.org=20
Sent: Saturday, May 26, 2001 2:47 PM
Subject: Detonation Monitor
Hello=20
My Nissan runs two detonation microphones that are linked into the =
ECU.
I would like to monitor the microphones to see if they are receiving =
signals that are at the detonation frequency.
I believe that the frequency of most of the noise can be calculated =
from the bore diameter and should therefore be avoided.
Is there an aftermarket device that can be built / purchased that will =
allow you to select the right frequency to pick up detonation?
Thanks=20
Hugh
------=_NextPart_000_003F_01C0E610.3281B380
Content-Type: text/html;
charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META http-equiv=3DContent-Type content=3D"text/html; =
charset=3Diso-8859-1">
<META content=3D"MSHTML 5.50.4522.1800" name=3DGENERATOR>
<STYLE></STYLE>
</HEAD>
<BODY bgColor=3D#ffffff>
<DIV><FONT color=3D#008080 size=3D2>I have been thinking about the =
detonation=20
situation and you have ignited some further thoughts on that =
subject. You=20
have mentioned that the detonation frequency would be at about the =
combustion=20
chamber Helmholtz frequency. I think you're probably right but it =
just=20
occurred to me that the speed of sound should be quite high due to the=20
compression ratio.</FONT></DIV>
<DIV><FONT color=3D#008080 size=3D2></FONT> </DIV>
<DIV><FONT color=3D#008080 size=3D2>So, if the volume is (for a 350 =
small block=20
Chevy) </FONT></DIV>
<DIV><FONT color=3D#008080 size=3D2></FONT> </DIV>
<DIV><FONT color=3D#008080 size=3D2>350/8 * sine(degrees BTDC) +=20
.125(350/8)</FONT></DIV>
<DIV><FONT color=3D#008080 size=3D2></FONT> </DIV>
<DIV><FONT color=3D#008080 size=3D2>where:</FONT></DIV>
<DIV><FONT color=3D#008080 size=3D2> The .125 is =
clearance volume=20
for an 8:1 engine.)</FONT></DIV>
<DIV><FONT color=3D#008080 size=3D2> 350/8 is the =
volume of one=20
cylinder.</FONT></DIV>
<DIV><FONT color=3D#008080 size=3D2> sine(degrees =
BTDC) is the=20
ratio of volume of the cylinder at that position</FONT></DIV>
<DIV><FONT color=3D#008080 size=3D2></FONT> </DIV>
<DIV><FONT color=3D#008080 size=3D2>And the pressure is:</FONT></DIV>
<DIV><FONT color=3D#008080 size=3D2></FONT> </DIV>
<DIV><FONT color=3D#008080 size=3D2>14.7PSI * .8 * 8</FONT></DIV>
<DIV><FONT color=3D#008080 size=3D2></FONT> </DIV>
<DIV><FONT color=3D#008080 size=3D2>Where:</FONT></DIV>
<DIV><FONT color=3D#008080 size=3D2> 14.7 is the =
initial=20
pressure</FONT></DIV>
<DIV><FONT color=3D#008080 size=3D2> .8 is the =
volumetric=20
efficiency</FONT></DIV>
<DIV><FONT color=3D#008080 size=3D2> 8 is the =
compression=20
ratio</FONT></DIV>
<DIV><FONT color=3D#008080 size=3D2></FONT> </DIV>
<DIV><FONT color=3D#008080 size=3D2>Then we should have the 'ping' =
frequency. =20
That's as far as I can go right now, I'll work more on it later. I =
don't=20
know the Helmholtz theorem right now. But it seems that the ping =
frequency=20
will increase depending on where the ping is started in relationship to =
the=20
cycle</FONT></DIV>
<DIV><FONT color=3D#008080 size=3D2></FONT> </DIV>
<DIV><FONT color=3D#008080 size=3D2>dh</FONT></DIV>
<DIV><FONT color=3D#008080 size=3D2></FONT> </DIV>
<DIV><FONT color=3D#008080 size=3D2></FONT> </DIV>
<DIV>----- Original Message ----- </DIV>
<BLOCKQUOTE dir=3Dltr=20
style=3D"PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #008080 2px solid; MARGIN-RIGHT: 0px">
<DIV=20
style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>=20
<A title=3Dhugh at sol.co.uk href=3D"mailto:hugh at sol.co.uk">Hugh</A> =
</DIV>
<DIV style=3D"FONT: 10pt arial"><B>To:</B> <A =
title=3Ddiy_efi at diy-efi.org=20
href=3D"mailto:diy_efi at diy-efi.org">diy_efi at diy-efi.org</A> </DIV>
<DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Saturday, May 26, 2001 =
2:47=20
PM</DIV>
<DIV style=3D"FONT: 10pt arial"><B>Subject:</B> Detonation =
Monitor</DIV>
<DIV><BR></DIV>
<DIV><FONT face=3DVerdana size=3D2>Hello </FONT></DIV>
<DIV><FONT face=3DVerdana size=3D2></FONT><FONT face=3DVerdana=20
size=3D2></FONT> </DIV>
<DIV><FONT face=3DVerdana size=3D2>My Nissan runs two detonation =
microphones that=20
are linked into the ECU.</FONT></DIV>
<DIV><FONT face=3DVerdana size=3D2></FONT> </DIV>
<DIV><FONT face=3DVerdana size=3D2>I would like to monitor the =
microphones to see=20
if they are receiving signals that are at the detonation=20
frequency.</FONT></DIV>
<DIV><FONT face=3DVerdana size=3D2></FONT> </DIV>
<DIV><FONT face=3DVerdana size=3D2>I believe that the frequency of =
most of the=20
noise can be calculated from the bore diameter and should therefore be =
avoided.</FONT></DIV>
<DIV><FONT face=3DVerdana size=3D2></FONT> </DIV>
<DIV><FONT face=3DVerdana size=3D2>Is there an aftermarket device that =
can be=20
built / purchased that will allow you to select the right frequency to =
pick up=20
detonation?</FONT></DIV>
<DIV><FONT face=3DVerdana size=3D2></FONT> </DIV>
<DIV><FONT face=3DVerdana size=3D2>Thanks </FONT></DIV>
<DIV><FONT face=3DVerdana size=3D2></FONT> </DIV>
<DIV><FONT face=3DVerdana =
size=3D2>Hugh</FONT></DIV></BLOCKQUOTE></BODY></HTML>
------=_NextPart_000_003F_01C0E610.3281B380--
----------------------------------------------------------------------------
To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes)
in the body of a message (not the subject) to majordomo at lists.diy-efi.org
More information about the Diy_efi
mailing list