From owner-diy_efi Sat Jul 2 04:37:33 1994 Received: by coulomb.eng.ohio-state.edu (920330.SGI/920502.SGI) id AA11675; Sat, 2 Jul 94 04:37:33 GMT Received: from doc.cc.utexas.edu by coulomb.eng.ohio-state.edu via SMTP (920330.SGI/920502.SGI) for /usr/local/mail/majordomo-1.92/wrapper resend -p bulk -M 10000 -l Diy_Efi -f Diy_Efi-Owner -h coulomb.eng.ohio-state.edu -s -r DIY_EFI diy_efi-outgoing id AA11670; Sat, 2 Jul 94 00:37:31 -0400 Received: (from efrank@localhost) by doc.cc.utexas.edu (8.6.8.1/8.6.6/cc-wf-sunos.mc-1.1) id XAA08850; Fri, 1 Jul 1994 23:35:33 -0500 Date: Fri, 1 Jul 1994 23:35:32 -0500 (CDT) From: The_Mechanic Subject: Re: your mail To: DIY_EFI In-Reply-To: Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-diy_efi Precedence: bulk Reply-To: DIY_EFI From owner-diy_efi Sun Jul 3 22:46:39 1994 Received: by coulomb.eng.ohio-state.edu (920330.SGI/920502.SGI) id AA14013; Sun, 3 Jul 94 22:46:39 GMT Received: from Jane.UH.EDU by coulomb.eng.ohio-state.edu via SMTP (920330.SGI/920502.SGI) for /usr/local/mail/majordomo-1.92/wrapper resend -p bulk -M 10000 -l Diy_Efi -f Diy_Efi-Owner -h coulomb.eng.ohio-state.edu -s -r DIY_EFI diy_efi-outgoing id AA14008; Sun, 3 Jul 94 18:46:36 -0400 Received: from Jetson.UH.EDU by Jetson.UH.EDU (PMDF V4.3-8 #5185) id <01HEA0P4E51C8YO42D@Jetson.UH.EDU>; Sun, 03 Jul 1994 17:46:26 -0500 (CDT) Date: Sun, 03 Jul 1994 17:46:26 -0500 (CDT) From: ST3XD@Jetson.UH.EDU Subject: Accessing WWW page... how? To: DIY_EFI Message-Id: <01HEA0P4F7MA8YO42D@Jetson.UH.EDU> X-Vms-To: IN%"DIY_EFI@coulomb.eng.ohio-state.edu" Mime-Version: 1.0 Content-Type: TEXT/PLAIN; CHARSET=US-ASCII Content-Transfer-Encoding: 7BIT Sender: owner-diy_efi Precedence: bulk Reply-To: DIY_EFI I've been away from internet for some time and need to backtrack on the DYI_EFI discussions. How can you access the WWW page? Also, I remember last time I was current on the EFI project, the processor was still a big question. Has the 68332 been considered? I read in the SAE inovations for 1993 book about a EFI control box using the 68332. It said the 68332 was designed SPECIFICALLY for EFI applications. I even think it had some built in EFI algorithyms. I'm very busy this summer (taking 10 hours in 3 months!) but sure wish I could complete a schematic and PCB board for our truly custom EFI box. I'm sure some of you have access to auto-routing PCB software, but if not I can make foil patterns of just about anything. Later, Jeff From owner-diy_efi Sun Jul 3 23:42:55 1994 Received: by coulomb.eng.ohio-state.edu (920330.SGI/920502.SGI) id AA14093; Sun, 3 Jul 94 23:42:55 GMT Received: from knuth.mtsu.edu by coulomb.eng.ohio-state.edu via SMTP (920330.SGI/920502.SGI) for /usr/local/mail/majordomo-1.92/wrapper resend -p bulk -M 10000 -l Diy_Efi -f Diy_Efi-Owner -h coulomb.eng.ohio-state.edu -s -r DIY_EFI diy_efi-outgoing id AA14087; Sun, 3 Jul 94 19:42:53 -0400 Received: by knuth.mtsu.edu (Smail3.1.28.1 #17) id m0qKbFH-000AVTC; Sun, 3 Jul 94 18:46 CDT Message-Id: From: lusky@knuth.mtsu.edu (Jonathan R. Lusky) Subject: Re: Accessing WWW page... how? To: DIY_EFI Date: Sun, 3 Jul 1994 18:46:47 -0500 (CDT) In-Reply-To: <01HEA0P4F7MA8YO42D@Jetson.UH.EDU> from "ST3XD@Jetson.UH.EDU" at Jul 3, 94 05:46:26 pm X-Mailer: ELM [version 2.4 PL23] Content-Type: text Content-Length: 544 Sender: owner-diy_efi Precedence: bulk Reply-To: DIY_EFI ST3XD@Jetson.UH.EDU writes: > > I've been away from internet for some time and need to > backtrack on the DYI_EFI discussions. How can you access > the WWW page? For graphical access, use a program called Mosaic. For text only, use lynx. Mosaic is available for a variety of platforms from ftp.ncsa.uiuc.edu. lynx source is available from ftp.cc.ukans.edu (i think). -- Jonathan R. Lusky -- lusky@knuth.mtsu.edu "Turbos are nice but I'd rather be blown!" 68 Camaro Convertible - 350 / TH350 80 Toyota Celica - 20R / 5spd From owner-diy_efi Thu Jul 7 21:28:58 1994 Received: by coulomb.eng.ohio-state.edu (920330.SGI/920502.SGI) id AA29464; Thu, 7 Jul 94 21:28:58 GMT Received: from aztec.al.bldrdoc.gov by coulomb.eng.ohio-state.edu via SMTP (920330.SGI/920502.SGI) for /usr/local/mail/majordomo-1.92/wrapper resend -p bulk -M 10000 -l Diy_Efi -f Diy_Efi-Owner -h coulomb.eng.ohio-state.edu -s -r DIY_EFI diy_efi-outgoing id AA29459; Thu, 7 Jul 94 17:28:54 -0400 Message-Id: <9407072128.AA29459@coulomb.eng.ohio-state.edu> Date: 7 Jul 1994 15:31:08 -0700 From: "Ciciora Steve" Subject: fuel map discussion To: DIY_EFI Sender: owner-diy_efi Precedence: bulk Reply-To: DIY_EFI Below is my first draft of a discussion of how I think fuel injection systems work. I faithfully submit it for peer review... _______________________________________________________________________________ To: Ciciora Steve From: CICIORA STEVEN JOSEP on Thu, 7 Jul 1994 3:26 PM Subject: fuel map Lets start off by assuming a few things before we get started. For this example, let's assume we have a 4 cyl 4 liter engine and we want an air/fuel ratio of 14.7/1. This means 14.7 grams of air for each gram of fuel. Also for now, lets assume this engine is operating at an RPM that gives us 100% volumetric effency. Since our engine is 1 liter per cylinder, in order to determine how much fuel to deliver to each cylinder, we need to know the mass of the air in each cylinder. Remember back in high school physics, PV=nRT? P is the pressure in atmosphers, V is the volume in Liters, n is the number of mols of air, R is the universal gas constant (8.206x10E-2 Liters * atmosphers/mols*K), and T is the temperature in degrees Kelvin. A little bit of manipulation will give us P/(R*T)=n/V, where n/V is the density of air in mols per liter. This isn't very useful, so to convert mols to grams, we multiply bolth sides of the equation by the molecular weight of air. I know that somewhere there must be a 'standard' average value for air, but I couldn't find it. I calculated the molecular weight of dry air to be 28.96475143. This should be close. So anyway, the result is: density of air in grams per liter = (mw * P)/(R*T) where mw is the Molecular Weight of air, P is the pressure of air in Atmospheres, R is the gas constant and T is the Temperature in degrees Kelvin. For example, let's plug in 1 atmosphere and 300 degrees Kelvin (24 degrees C, about room temperature). At this temperature and pressure, the density of air is 1.1765 grams per liter. Dividing by the desired air/fuel ratio (14.7) tells us that we want 0.08019 grams of fuel for each liter of engine per cycle. Using a lookup table (generated using a fuel injector flow bench like the one described in Performance Engineering Magazine) we would determine the desired amount of time to hold the fuel injector open. So by measuring the intake manifold pressure and the intake air temperature (hopefully at the same spot that the pressure was measured) we can calculate the amount of fuel needed for a given a/f ratio. But wait! This assumes a constant 100% volumetric effency. We all know that most of the time it is less than 100%, and some times greater. A good estimate is to assume volumetric effency changes with engine RPM and to correct the mass of air calculation with an RPM factor. This is usually done with a 3D Fuel Map. On the X axis we would have the mass of air, the Y axis we would have the engine RPM, and on the Z axis we output the amount of fuel needed. This can be in grams per cycle or if we include the fuel injector correction factor in the fuel map, it can output pulse width. (ranges of values for map/temp) (corrections for cold start, acc, power mode, emmissions mode, fuel econ, etc) (what do you think?) From owner-diy_efi Thu Jul 7 22:38:19 1994 Received: by coulomb.eng.ohio-state.edu (920330.SGI/920502.SGI) id AA29588; Thu, 7 Jul 94 22:38:19 GMT Received: from knuth.mtsu.edu by coulomb.eng.ohio-state.edu via SMTP (920330.SGI/920502.SGI) for /usr/local/mail/majordomo-1.92/wrapper resend -p bulk -M 10000 -l Diy_Efi -f Diy_Efi-Owner -h coulomb.eng.ohio-state.edu -s -r DIY_EFI diy_efi-outgoing id AA29583; Thu, 7 Jul 94 18:38:11 -0400 Received: by knuth.mtsu.edu (Smail3.1.28.1 #17) id m0qM28g-000AdiC; Thu, 7 Jul 94 17:41 CDT Message-Id: From: lusky@knuth.mtsu.edu (Jonathan R. Lusky) Subject: Re: fuel map discussion To: DIY_EFI Date: Thu, 7 Jul 1994 17:41:54 -0500 (CDT) In-Reply-To: <9407072128.AA29459@coulomb.eng.ohio-state.edu> from "Ciciora Steve" at Jul 7, 94 03:31:08 pm X-Mailer: ELM [version 2.4 PL23] Content-Type: text Content-Length: 2455 Sender: owner-diy_efi Precedence: bulk Reply-To: DIY_EFI Ciciora Steve writes: > > Below is my first draft of a discussion of how I think fuel injection systems > work. I faithfully submit it for peer review... > Subject: fuel map [ math/chem stuff deleted ] > So by measuring the intake manifold pressure and the intake air temperature > (hopefully at the same spot that the pressure was measured) we can calculate > the amount of fuel needed for a given a/f ratio. But wait! This assumes a > constant 100% volumetric effency. We all know that most of the time it is > less than 100%, and some times greater. A good estimate is to assume > volumetric effency changes with engine RPM and to correct the mass of air > calculation with an RPM factor. This is usually done with a 3D Fuel Map. On > the X axis we would have the mass of air, the Y axis we would have the engine > RPM, and on the Z axis we output the amount of fuel needed. This can be in > grams per cycle or if we include the fuel injector correction factor in the > fuel map, it can output pulse width. I believe if you play with the math a little more, you will find that you can eliminate a bit of it. I don't think you actually need to know or calculate the exact airflow, since all of its factors will be present in the lookup tables. The basic equation I'd use would be OT = BPC * 1/AF * VE * ATC, where OT = injector on time, AF = desired air/fuel ratio, VE = volumetric efficiency, ATC = air temp correction (note to John: I made that acronym up off the top of my head), BPC = a constant that makes all of this work. VE is a function of MAP,RPM and comes from a lookup table. BPC is a constant or could come from a lookup table. AF would probably come from one of several lookup tables. ATC I guess would be the temp in K? > (ranges of values for map/temp) Depends on the application... forced induction will require a much wider range on both of those. > (corrections for cold start, acc, power mode, emmissions mode, fuel econ, etc) > (what do you think?) Power Enrichment is accomplished by changing the value for AF. Cold start is accomplished by changing the value for AF (f[Temp]). Emissions "mode" is closed loop around stoich. Economy mode is probably also closed loop around stoich, with maybe a higher threshold for power enrichment. -- Jonathan R. Lusky -- lusky@knuth.mtsu.edu "Turbos are nice but I'd rather be blown!" 68 Camaro Convertible - 350 / TH350 80 Toyota Celica - 20R / 5spd From owner-diy_efi Wed Jul 13 20:32:00 1994 Received: by coulomb.eng.ohio-state.edu (920330.SGI/920502.SGI) id AA28182; Wed, 13 Jul 94 20:32:00 GMT Received: from aztec.al.bldrdoc.gov by coulomb.eng.ohio-state.edu via SMTP (920330.SGI/920502.SGI) for /usr/local/mail/majordomo-1.92/wrapper resend -p bulk -M 10000 -l Diy_Efi -f Diy_Efi-Owner -h coulomb.eng.ohio-state.edu -s -r DIY_EFI diy_efi-outgoing id AA28177; Wed, 13 Jul 94 16:31:57 -0400 Message-Id: <9407132031.AA28177@coulomb.eng.ohio-state.edu> Date: 13 Jul 1994 14:36:08 -0700 From: "Ciciora Steve" Subject: FW: Re: fuel map discussion To: DIY_EFI Sender: owner-diy_efi Precedence: bulk Reply-To: DIY_EFI John Lusky writes: >I believe if you play with the math a little more, you will find >that you can eliminate a bit of it. I agree. I'm not shure where to draw the line between fast and less readable and slower and easer for someone else to understand. > The basic equation I'd use would be > OT = BPC * 1/AF * VE * ATC, where OT = injector on time, AF = > desired air/fuel ratio, VE = volumetric efficiency, ATC = air temp > correction (note to John: I made that acronym up off the top of my > head), BPC = a constant that makes all of this work. VE is a > function of MAP,RPM and comes from a lookup table. BPC is a > constant or could come from a lookup table. AF would probably > come from one of several lookup tables. I believe the above approach above will work, but it is not how I think I understand it. I'm not sure why VE would be in it's own 3D look up table. The VE of an engine is not something I have a good feel for, know how to calculate or know how to measure. Please correct me if I'm wrong, but besides some sensors (thermistors) VE and the fuel injectors are the only non-linear things in the equation. I envision a 3-D 'fuel map' (for steady state conditions) that would have RPM on one side, a combination of MAP and air temp on the other side, and would output the base pulse width. Other factors (cold start, power, etc) would modify this base pulse width. If it would help clear things up, mabe the fuel map would output the amount of fuel (in grams or something) which would go to another table that accounted for the non-linear fuel injectors (and output the pulse duration in ms). I doubt that this would help since the injector response time changes with age. Na, forget what I just said about a second table to linearize the injectors. Right now I don't think its a good idea anymore (tomorrow I'll change my mind... probably). It it were not for VE, the fuel map would be a flat slab with no nice looking shape. I think what I described is what you described with the VE map incorporated. I think for 'tuning' an engine, having one 3D fuel map would be easer for someone to play with and see the results. "Seems a bit lean between 4k and 4.5k rpm, I'll just push up these data points a little..." Correct me if I'm wrong, but wouldn't you want 14.7 A/F most of the time (all rpms and pressures) except under cold start, power, etc? Would my base 'fuel map' be to get you at 14.7 A/F and other modifiers pull you away from 14.7? These are just my opinions, and I make no claims as to their accuracy. I just made them up. - Steven Ciciora From owner-diy_efi Wed Jul 13 21:46:37 1994 Received: by coulomb.eng.ohio-state.edu (920330.SGI/920502.SGI) id AA28717; Wed, 13 Jul 94 21:46:37 GMT Received: from knuth.mtsu.edu by coulomb.eng.ohio-state.edu via SMTP (920330.SGI/920502.SGI) for /usr/local/mail/majordomo-1.92/wrapper resend -p bulk -M 10000 -l Diy_Efi -f Diy_Efi-Owner -h coulomb.eng.ohio-state.edu -s -r DIY_EFI diy_efi-outgoing id AA28712; Wed, 13 Jul 94 17:46:15 -0400 Received: by knuth.mtsu.edu (Smail3.1.28.1 #17) id m0qOCBI-000B1uC; Wed, 13 Jul 94 16:49 CDT Message-Id: From: lusky@knuth.mtsu.edu (Jonathan R. Lusky) Subject: Re: FW: Re: fuel map discussion To: DIY_EFI Date: Wed, 13 Jul 1994 16:49:32 -0500 (CDT) In-Reply-To: <9407132031.AA28177@coulomb.eng.ohio-state.edu> from "Ciciora Steve" at Jul 13, 94 02:36:08 pm X-Mailer: ELM [version 2.4 PL23] Content-Type: text Content-Length: 5182 Sender: owner-diy_efi Precedence: bulk Reply-To: DIY_EFI Ciciora Steve writes: > I agree. I'm not shure where to draw the line between fast and less readable > and slower and easer for someone else to understand. IMHO, draw the line all the way over to the fast side :). You can smooth things out in the calibration software (looking at raw hex gets OLD real quick :). > > OT = BPC * 1/AF * VE * ATC, where OT = injector on time, AF = > > I believe the above approach above will work, but it is not how I think I > understand it. I'm not sure why VE would be in it's own 3D look up table. The > VE of an engine is not something I have a good feel for, know how to calculate > or know how to measure. Please correct me if I'm wrong, but besides some > sensors (thermistors) VE and the fuel injectors are the only non-linear things > in the equation. I envision a 3-D 'fuel map' (for steady state conditions) > that wouldhave RPM on one side, a combination of MAP and air temp on the other > side, and would output the base pulse width. Take air temp out as a seperate fudge factor and you have basically what I put above. The VE table isn't really VE, its just close :). VE is really the ratio of the actual mass of the air drawn in to the ideal mass of the air that would have been drawn in if the cylinder were to be filled with air of the same density as the air as the inlet (of the throttle body, I think). In other words, the % full of air that cylinders are. Since you are firing the injectors once per intake stroke, you don't need to know actually mass flowrate of the air, you just need to know the mass of air in the cylinder after a given intake event. Anyway, the pulse width table you describe is basically a VE table if you multiply it by the appropriate constant. > Other factors (cold start, power, > etc) would modify this base pulse width. I agree. I just think it makes more sense to fudge the base pulse with air temp instead of fudging the MAP value with air temp. > If it would help clear things up, > mabe the fuelmap would output the amount of fuel (in grams or something) which > would go to anothertable that accounted for the non-linear fuel injectors (and > output the pulse duration in ms). As long as everything is being multiplied, don't worry about carrying through units. Scaling the factors to fit in 8? bits with the best resolution is whats important. You correct the units with a constant tagged on near the end (BPC in my equation). > I doubt that this would help since the > injector response time changes with age. Na, forget what I just said about a > second table to linearize the injectors. Right now I don't think its a good > idea anymore (tomorrow I'll change my mind... probably). Actually it'd be nice to have some sort of injector correction table. The way the EFI Technologies ECU does injector correction is just a multiplier for each injector (1 = no correction... thats a one on the user end, not sure what the ECU gets fed), and minimum and maximum RPM for the correction table to be used. This will let you correct for distribution problems (very useful in some applications with single plane manifolds that have adjacent cylinders firing back to back). > It it were not for VE, the fuel map would be a flat slab with no nice looking > shape. I think what I described is what you described with the VE map > incorporated. If VE was constant, your pusle width would be constant except for air temp correction and injector linearization. > I think for 'tuning' an engine, having one 3D fuel map would be easer for > someone to play with and see the results. "Seems a bit lean between 4k and > 4.5k rpm, I'll just push up these data points a little..." Yeah, same thing as I proposed. Except you also need to specify a MAP range in addition to RPM or you'll end up making a mess (been there, done that). > Correct me if I'm wrong, but wouldn't you want 14.7 A/F most of the time (all > rpms and pressures) except under cold start, power, etc? Would my base 'fuel > map' be to get you at 14.7 A/F and other modifiers pull you away from 14.7? Yeah, most of the time you'd run at stoich. Cold start, warm up, and power enrichment will all be richer, and you'll probably want them all in tables as F(water temp). Your fuel map has all of the values multiplied by 14.7 where my method multiplies by 14.7 (actually 1/14.7) after pulling a value from the table. > These are just my opinions, and I make no claims as to their accuracy. I > just made them up. Ditto :) Actually, I'm pulling a lot of this out of GM docs and the calibration software for EFI Technologies performance-series ECU, and I'm combining ideas from both (BTW, the EFI-Tech ECU has a table of pulse width as a function of RPM, MAP instead of a table actually called VE). Now I finally remember what irk'd me about the pulse width table.. it gives you a false sense of knowing whats going on--once the pulse width has gone through all of the corrections, its ALOT different from whats in the table. -- Jonathan R. Lusky -- lusky@knuth.mtsu.edu "Turbos are nice but I'd rather be blown!" 68 Camaro Convertible - 350 / TH350 80 Toyota Celica - 20R / 5spd From owner-diy_efi Wed Jul 20 18:19:54 1994 Received: by coulomb.eng.ohio-state.edu (920330.SGI/920502.SGI) id AA20563; Wed, 20 Jul 94 18:19:54 GMT Received: from hwking.cca.rockwell.com by coulomb.eng.ohio-state.edu via SMTP (920330.SGI/920502.SGI) for /usr/local/mail/majordomo-1.92/wrapper resend -p bulk -M 10000 -l Diy_Efi -f Diy_Efi-Owner -h coulomb.eng.ohio-state.edu -s -r DIY_EFI diy_efi-outgoing id AA20558; Wed, 20 Jul 94 14:19:50 -0400 Received: by hwking.cca.rockwell.com (5.65/DEC-Ultrix/4.3) id AA19490; Wed, 20 Jul 1994 13:19:43 -0500 Received: by ohura.cca.rockwell.com (5.65/DEC-Ultrix/4.3) id AA03566; Wed, 20 Jul 1994 13:19:41 -0500 Message-Id: <9407201819.AA03566@ohura.cca.rockwell.com> To: DIY_EFI Subject: Knock sensor Date: Wed, 20 Jul 94 13:19:40 -0500 From: sdbartho@cca.rockwell.com X-Mts: smtp Sender: owner-diy_efi Precedence: bulk Reply-To: DIY_EFI Anyone know what voltage levels I could expect out of a knock sensor on a GM V-6? Are we talking millivolts, microvolts, what range of values? I want to build a simple knock indcator light that lets the driver know when knock is past a reasonable level. The race PROM disables the factory boost/timing retard vs. knock mechanism. The plan right now is to use a low input current op-amp fed into a FET to drive a lamp. Am I missing something obvious? How can I "excite" a knock sensor? (Ball-peen hammer ain't gonna cut it) I was thinking along the lines of a 5 khz signal generator tied to a speaker, or is there a better way? Wild guesses and speculation appreciated, too. Dig sdbartho@hwking.cca.rockwell.com From owner-diy_efi Wed Jul 20 18:55:34 1994 Received: by coulomb.eng.ohio-state.edu (920330.SGI/920502.SGI) id AA20673; Wed, 20 Jul 94 18:55:34 GMT Received: from wotan.compaq.com by coulomb.eng.ohio-state.edu via SMTP (920330.SGI/920502.SGI) for /usr/local/mail/majordomo-1.92/wrapper resend -p bulk -M 10000 -l Diy_Efi -f Diy_Efi-Owner -h coulomb.eng.ohio-state.edu -s -r DIY_EFI diy_efi-outgoing id AA20661; Wed, 20 Jul 94 14:55:28 -0400 Received: from twisto.eng.hou.compaq.com by wotan.compaq.com with smtp (Smail3.1.28.1 #6) id m0qQgkZ-0002cgC; Wed, 20 Jul 94 13:52 CDT Received: from bangate.compaq.com by twisto.eng.hou.compaq.com with smtp (Smail3.1.28.1 #8) id m0qQgkY-000pdCC; Wed, 20 Jul 94 13:52 CDT Message-Id: Received: by bangate.compaq.com with VINES ; Wed, 20 Jul 94 13:51:34 CDT Date: Wed, 20 Jul 94 13:39:35 CDT From: Steve=Ravet%Prj=Eng%PCPD=Hou@bangate.compaq.com Subject: re: Knock sensor To: twisto.eng.hou.compaq.com!wotan!coulomb.eng.ohio-state.edu!diy_efi Cc: Sender: owner-diy_efi Precedence: bulk Reply-To: DIY_EFI sdbartho@cca.rockwell.com Wrote: | Anyone know what voltage levels I could expect out of a knock | sensor | on a GM V-6? Are we talking millivolts, microvolts, what range of | values? errr, not sure. | | I want to build a simple knock indcator light that lets the driver | know when knock is past a reasonable level. The race PROM | disables the | factory boost/timing retard vs. knock mechanism. | | The plan right now is to use a low input current op-amp fed into a | FET to drive a lamp. Am I missing something obvious? How can I | "excite" a knock sensor? (Ball-peen hammer ain't gonna cut it) | I was thinking along the lines of a 5 khz signal generator tied | to a speaker, or is there a better way? Actually, a ball-peen hammer would work. An article in Performance Engineering describes using a knock sensor to detect the opening and closing of a fuel injector. They are pretty sensitive. You will have to filter the output to a specific frequency range to see "just" the knock noise. Don't know what range, but I've been told 5-8 Khz. Included is an early post to this list that discussed knock sensors. --snip-- Knock sensors are basically just cheap accelerometers. They respond to vibration by generating a voltage. There are three basic types - resonant , flat response, and broadband resonant - which differ in their frequency response characteristics. Resonant sensors have a sharp response at a given frequency - if the engine does not knock at that frequency then you'll never know it. Flat\ response knock sensors are just that - they have low output (typically a few mV/g accel.) over a broad frequency range. They usually require amplification of some sort and more extensive filtering. Broadband resonant sensors are an attempt to take the best of the flat response and resonant sensors and combine them into one package. Broader response than resonant (peak response is spread over 2-3 kHz) with higher output that flat response sensors. I believe AC-Delco makes these type of sensors. As far as a knock control system goes, knock occurs somewhere between 5 kHz and 8 kHz (from my experience) and the most important item to locate the sensor in a place that won't pick up stray vibration. A crude knock control algorithm listens for output from the sensor of sufficient amplitude and then alters the timing. There's not really any black magic in knock detection and control - just some signal processing and good engineering in locating the sensor. Jeff Armfield --snip-- I think you will need a low noise op-amp since the signal is low level. hang on, I've got that article here somewhere. The article shows a scope hooked to a knock sensor, the display indicates +-5mv straight from the sensor. sounds like a good idea, let us know if it works out.... --steve