DIY_EFI Digest Monday, 28 July 1997 Volume 02 : Number 252 In this issue: RE: Ignition Controllers Re: Ignition Controllers - knock detection RE: Ignition Controllers See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- From: "Stuart Baly" Date: Mon, 28 Jul 1997 11:14:39 +0000 Subject: RE: Ignition Controllers Tim wrote: >At what frequencies? It depends on the engine, which is why I didn't >include this feature in my system. Engines knock and resonate at >different frequencies. You can look at all the technical papers you >want (and this is a good idea to learn how knock detection works) but >unless you see one for your application, the frequencies may be a >little off. I remember reading a formula somewhere that relates the knock frequency to the engine bore. It was a simple thing like Knock Freq=Constant/Bore. I'd guess that the frequency would change with a turbo engine as the speed of sound would change with gas pressure. Anyway, this is of no use at all to a rotary engine. I might just take a large step outside my area of knowledge for a second. Perhaps the resonant frequency of a rotary's combustion chamber is determined by the distance between the sideplates, as these are the only two parallel surfaces in it. If you can find the above equation, and substitute that distance into the Bore variable, it'd be a starting point. 0.02c is way overpriced for this. Stuart Baly. ======================================================== Stuart Baly (s.baly@xxx.au) Technical Officer Cape Grim Baseline Air Pollution Station '71 Datsun 510, '81 Yamaha RD350LC, '89 Kawasaki GPz900R ======================================================== ------------------------------ From: Steven Arnold Date: Mon, 28 Jul 1997 12:51:25 -0700 Subject: Re: Ignition Controllers - knock detection > I remember reading a formula somewhere that relates the knock > frequency to the engine bore. It was a simple thing like Knock > Freq=Constant/Bore. I'd guess that the frequency would change with a > turbo engine as the speed of sound would change with gas pressure. In the sillicon chip engine knock indicator article, they quote the formula - F=900/(pi*r) r=cylinder radius in metres However, I think they proceed to do some calculations that seem to be based bore diameter, rather than radius - which seen to be incorrect. I have also read that the knock frequency reduces the later the knock occurs or is measured - due to the increasing volume of the cylinder. So positioning of the knock detection window will have some effect on the freq - however this probably wouldn't matter, as the bandwidth of your bandpass filter would be wider than this freq variation. - -- sarnold@xxx.com http://www.geocities.com/MotorCity/1309 RE - That is all, there is no more. ------------------------------ From: "Graham, Peter" Date: Mon, 28 Jul 1997 18:03 +0930 Subject: RE: Ignition Controllers - --====S1ZzxGxasItfaKC2jsgrWKfqrLs_l==NG100000119== Content-Type: text/plain;charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable >Have any one seen the instrument that Link is offering ? Its called >Knocklink. >Its made so You can tune it to hear pinging from different engines and =20 its >cheap to ($100,) >Stefan Stefan =20 Silicon Chip published an article where they designed a basic knock =20 indicator. It is basically a bandpass filter that is gated from the =20 ignition coil, which is then rectified and filtered and then displayed on =20= a 10 led bar graph . If the knocking got to bad they also had a buzzer =20 that sounded. It could be set to 'tune' out the background noise by the =20 use of a gain controlled amplifier. The kit is available from Jaycar Electronics for those in Australia for =20 A$35. They have a mail order section for those people overseas. Ph +61-2-9743-6144 fax +61-2-9743-2066 =20 The kit includes a crystal earpiece and a TO3 transistor for those that =20 want to make their own knock sensor. Peter Graham =20 =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D _--_|\ Peter Graham [Peter.Graham@xxx.au] / DSTO \ Maritime Operations Division \_.--._/ Defence Science & Technology Organisation v Fax : 61-3-9626 8999 Voice: 61-3-9626 8658 =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D - --====S1ZzxGxasItfaKC2jsgrWKfqrLs_l==NG100000119==-- ------------------------------ End of DIY_EFI Digest V2 #252 ***************************** To subscribe to DIY_EFI-Digest, send the command: subscribe diy_efi-digest in the body of a message to "Majordomo@xxx. A non-digest (direct mail) version of this list is also available; to subscribe to that instead, replace "diy_efi-digest" in the command above with "diy_efi".