DIY_EFI Digest Friday, 22 November 1996 Volume 01 : Number 356 In this issue: Re: MACHINE DESIGN magazine? Re: Injection timing, electro valves &c. Re: MACHINE DESIGN magazine? Re: Diff between theory and practice Re: Electromotive TEC-II? Re: New member Re: O2 Sensor Open/Close Loop Re: Air Flow Measurement RE: Air Flow Measurement Re: Air Flow Measurement Re: Air Flow Measurement re: Air Flow Measurement Distributed processing articles in EETimes Re: Air Flow Measurement Re: Air Flow Measurement Re: Air Flow Measurement Re: Air Flow Measurement Re: Spark signal generation Re: Spark signal generation Re: Spark signal generation Re: ATTN: Todd Knighton Re: Diff between theory and practice Re: Air Flow Measurement Fuel vs advance Some (late) breaking news re: Air Flow Measurement Re: DIY vacuum canister Re: Programmable ECU for 4A_GE See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- From: Phil Dorman Date: Tue, 19 Nov 1996 19:32:10 -0800 Subject: Re: MACHINE DESIGN magazine? Robert Van Zant wrote: > I suppose a diy_valve_train mail list would > be even quieter than this one though. No way ! I'll be in that. There is just such a disussion currently on in the FF Motorcyle list. Under the topis "BIGGGG Single" and "Big2/Twin" FF-l@xxx.uk or http://www.shockwav.demon.co.uk/ff.html - -- Phil (Mig Pilot) Convenor-Motorcycle Modifiers Register of Australia at http://users.hunterlink.net.au/~ddped/mcmodrau.htm Member-Russian Motorcycle Owner's Association at http://users.hunterlink.net.au/~ddped/rmoa/index.html ------------------------------ From: Kalle Pihlajasaari Date: Thu, 21 Nov 1996 13:07:06 +0200 (sat) Subject: Re: Injection timing, electro valves &c. Hi All, > > > As I understand it, it is best to inject the fuel after the intake valve > > > closes, so the fuel vaporizes on the somewhat hot cylinder head > > > surfaces. Is this true? Is there any advantage to injecting at other > > > times during the cycle? If so, explain the reasoning. > > > > Yes, please do. Grumpy Jenkins said in his book that 85% of the fuel > > vaporization occurs in the cylinder. 'Couse he's talking race > > engines versus whatever we're running (street / HiPo / semi-race / > > whatever). It would be nice to know what the current state-of the > > art is. > > > Maybe it is not important as the Fuel gets squirted in\ > but when i ran my 4 cvl 2litre race engine on 50mm throttle bodies the > air spedd was so low i lost 25kwatts of power compared to 45mm ones. has > to do with taper as well as venturi effect In a similar vein. Could one not somehow measure the air charge in a cylinder by measuring the conrod compression or someother thing like a genuine pressure sensor in the actual cylinder. Then it would no longer matter how the ait got in the cylinder the temp would be close to constant at near max compression (correct for fuel load) and then you wuold know one cycle later what to inject for the next air load. This would mean there would be no gadgets in the inlet except for the bytterfly. No temp, no pressure, no flow, no venturi, and such. Now onto the like-wow electro valve head, you would then need no butterfly as you just close the valve early if you want less air. I want one of these engines as it will be the first real major change in IC engines in a very long time. With direct (in the cylinder) fuel injection one can already get rid of the inlet cam by just using a set or reed valves and suck in the air and then only inject if you want to with power controlled by the ignition timing and the number of cylinders to fire. To be fair this is essentially what 2 stroke engines do at the moment but they still use the 'carb' and could eliminate this as well if they only metered the fuel and not the air. Cheers - -- Kalle Pihlajasaari kalle@xxx.za Interface Products P O Box 15775, DOORNFONTEIN, 2028, South Africa + 27 (11) 402-7750 Fax: 402-7751 ------------------------------ From: "Hans Hintermaier" Date: Thu, 21 Nov 1996 14:01:30 MET Subject: Re: MACHINE DESIGN magazine? > Date: Mon, 18 Nov 1996 07:45:28 -0600 (CST) > From: Robert Van Zant > To: diy_efi@xxx.edu > Subject: Re: MACHINE DESIGN magazine? > Reply-to: diy_efi@xxx.edu > > > > Does anyone know where in Europe I can get the MACHINE DESIGN magazine? > > Or here in the US for that matter? I know it's a trade rag, so > it seems the majority of us are SOL unless some kind sole is willing to > post the article of interest on the net somewhere. While we're on the > subject (and now that the electronic fuel/ignition nut is more-or-less > cracked), is anyone else of the opinion that this is what's *really* > needed for our dream motor? I suppose a diy_valve_train mail list would > be even quieter than this one though. > > bob Hi Bob, If you get any feedback, I would be interested in a DIY_valve_train mailing list! Hans > > mailto:hiha@xxx.de Munich / Germany ------------------------------ From: Mazda Ebrahimi Date: Thu, 21 Nov 1996 08:15:48 -0500 Subject: Re: Diff between theory and practice jon hanson wrote: > > [snip] > >The engine IS most efficient at peak torque, but that is not why he needs > more fuel at > >higher RPMs. If he needed more FUEL PER HORSEPOWER produced, then you are > right. But > >what he is indicating is that he is maintaining constant air fuel ratio > (constant CO), > >and is using more fuel at 6000 RPM. This simply means he is flowing more > air which > >means that: > > > > (vol eff @ 6000)* 3000 * disp > (vol eff @4800) * 2400 *disp > > > > [snip] > > Thanks to all who replied. > The fuel no I talked about is a no between 0 and 255 which this particular > system translates into an injector open time in ms. the larger the no the > more fuel per injection event. > > The above explanation still confuses me as it is based around the rate at which > fuel is being used. As I understand it (and this not neccesarily correct) > at Peak VE each intake stroke draws in the greatest mass of air into the > cylinder > compared to any other rpm which is off peak torque rpm. To maintain the > desired A/F > ratio (in my case 3.5% CO) I then need the greatest mass of fuel per > injection event. > Note i see the whole thing very much as a per > induction/compression/power/exhaust > event and the particular revs of the engine dont come into it. > Rpm comes into it when you are interested in the rate at which you are using > fuel. > ie the more induction/power strokes you make per second the more fuel per > second you use. > But a fuel no of 150 represents an injector open time in ms for each single > injection. > my figures suggest that each induction stroke at 6000 rpm is drawing in a > geater mass of > air than each induction stroke at 4800 rpm and I know the torque peak is > quoted as 4800rpm > I live at 5,500 ft altitude could this affect the breathing characteristics > of the engine? > If I'm being thick please dont hesitate to bash some sense into my head. > > Regards > Jon Hanson > Johannesburg > South Africa Now we are talking about a problem. Since you clarified that your numbers are injector duty cycles, as opposed to fuel flow rate, non of the explanations so far are correct. You have mentioned the CO numbers stay fairly constant. How about the hydrocarbons? CO is only produced when your fuel is burnt. Maybe at 6000 RPM you have higher hydrocarbons which indicate some of your fuel input is comming out of the tail pipe without reacting. If that is the case, you should adjust your spark timing for minimum advance for best torque at each RPM, and then re-compare your CO readings to adjust fuel flow. Good luck ------------------------------ From: dg@xxx.com (David Gould) Date: Thu, 21 Nov 1996 08:26:24 -0800 (PST) Subject: Re: Electromotive TEC-II? > I run a ACCEL/DFI and have had very good luck. My friends run Haltech and > have had very good luck. I've heard some people talk down the ElectroMotive > system, but I have no direct experience with it. With these modern systems, > there's no reason to switch induction systems to meet emissions standards. > Both the Haltech and the DFI can run in closed loop mode for the emissions > test, and then you can load a new program for the track (probably open > loop). I can't speak for the Haltech, but the DFI has all kinds of bells & > whistles for AC compressor loading, knock sensor input, relay contact > closure for nitrous, etc. Good luck, Thanks for the info, I will look at the ACCEL/DFI too. Do you have a contact number for them? The reason you have to switch systems for smog check is not the tailpipe sniffer, but the visual inspection. You have to have all (and only) the OEM equipment in place and they do check. - -dg ------------------------------ From: DJohn77284@xxx.com Date: Thu, 21 Nov 1996 12:27:23 -0500 Subject: Re: New member For ignition and 68HC11 processors look towards Tim Drury as on the DIY_EFI home page. Dave. ------------------------------ From: Phil Dorman Date: Fri, 22 Nov 1996 05:02:48 -0800 Subject: Re: O2 Sensor Open/Close Loop Eduard Anna wrote: > > > I have been meaning to make a decent scan tool to watch the O2 controller > > > at work in the ECM under actual driving conditions. I have completely > > > worked out GM ALDL protocol, but am not really a programmer. :-( I am a programer. Self employed and always looking for new projects. I also have a good grounding in the workings of the Infernal Combustion engine and some knowlege of electronics. However I'm only new to EFI and don't get all the acronyms yet. If you're interested in a joint effort let me know. - -- Phil (Mig Pilot) Convenor-Motorcycle Modifiers Register of Australia at http://users.hunterlink.net.au/~ddped/mcmodrau.htm Member-Russian Motorcycle Owner's Association at http://users.hunterlink.net.au/~ddped/rmoa/index.html ------------------------------ From: Phil Dorman Date: Fri, 22 Nov 1996 05:15:12 -0800 Subject: Re: Air Flow Measurement tom cloud wrote: > If you know BAP and MAP, you know delta-P across opening -- granted, > the opening size varies with throttle position, but you've got TPS > for that -- seems that air flow could be rather accurately determined > without much hassle????? Wow ! That might all be very well But ! What the hell are BAP and MAP and delta-P and TPS ??? Are they all TLAs ?? Is there (or should there be) an FAQ ? - -- Phil (Mig Pilot) Convenor-Motorcycle Modifiers Register of Australia at http://users.hunterlink.net.au/~ddped/mcmodrau.htm Member-Russian Motorcycle Owner's Association at http://users.hunterlink.net.au/~ddped/rmoa/index.html ------------------------------ From: Stephen Dubovsky Date: Thu, 21 Nov 1996 14:38:09 -0500 Subject: RE: Air Flow Measurement At 06:15 PM 11/20/96 +0000, you wrote: > >-> Ok, so go buy a $90 vane/rotating type meter that is 1-2% accurate >-> and get a curve for your MAF to linearize it. > > I'd love to. Where can I purchase such a meter? > Ok, A company called alfa electronics @ 1-800-526-2532 sells meters and stuff (are ok quality, but not quite as nice as a fluke). They have 2 anemometers for sale. Here is the rundown: AM-402 $89.95 measures: 0.4-30.0m/s, 1.4-108.8km/h, 80-5910ft/min, 0.8-58.3 knots output: 1mv DC per m/s, km/h, 100ft/min, knots operation temp: 0-50 C accuracy: 2% +- 0.1mV (you obviously need a good meter to keep this accuracy) size: 4x2x1", sensor head 2.8" diam power: 9v AM-4201 $179.95 same as the AM-402 but inlcudes a display accuracy: 2% +- 1digit They also sell other cool stuff like a relitive humidity (RH) gauge for $89.95 that outputs 1mV per 1% RH. (could help in calibrating those MAF sensors since humidity changes the specific heat of the air). Accuracy is 3% +- 1mV. If nothing else, call and get the catalog... Omega also sells an accurate and wide range MAF for ~$800. Is a little steep to put in a vehicle, but for calibration purposes... I think their web site is www.omega.com They have GREAT catalogs on pressure/temp/flow/etc measurement. Each book describes the principles involved and the pros/cons of different techniques. A must have. SMD - -- Stephen Dubovsky dubovsky@xxx.edu 95 Yamaha FZR600 83 Porsche 911SC 84 Jeep Cherokee ------------------------------ From: Phil Dorman Date: Fri, 22 Nov 1996 05:23:33 -0800 Subject: Re: Air Flow Measurement tom cloud wrote: > the MAP / RPM / IAT (speed > >density) nor TPS / RPM / IAT method are as accurate in measuring air flow > what's IAT ? My point exactly ! - -- Phil (Mig Pilot) Convenor-Motorcycle Modifiers Register of Australia at http://users.hunterlink.net.au/~ddped/mcmodrau.htm Member-Russian Motorcycle Owner's Association at http://users.hunterlink.net.au/~ddped/rmoa/index.html ------------------------------ From: Mazda Ebrahimi Date: Thu, 21 Nov 1996 15:55:07 -0500 Subject: Re: Air Flow Measurement Phil Dorman wrote: > > tom cloud wrote: > > If you know BAP and MAP, you know delta-P across opening -- granted, > > the opening size varies with throttle position, but you've got TPS > > for that -- seems that air flow could be rather accurately determined > > without much hassle????? > > Wow ! That might all be very well But ! > What the hell are BAP and MAP and delta-P and TPS ??? > Are they all TLAs ?? > Is there (or should there be) an FAQ ? > -- > Phil (Mig Pilot) > Convenor-Motorcycle Modifiers Register of Australia at > http://users.hunterlink.net.au/~ddped/mcmodrau.htm > Member-Russian Motorcycle Owner's Association at > http://users.hunterlink.net.au/~ddped/rmoa/index.htmlHi Phil, I think everyone got tired of spelling everything out, so if you just joined, it looks like a military hand book. Here are some of the common ones off the top of my head: TPS: Throttle Position Sensor MAP: Manifold Absolute Pressure MAF: Mass Air Flow sensor BAP: Barometric Absolute Pressure CLT or ECT: Engine Coolant Temperature IAT: Intake Air Temp. O2: Exhaust Oxygen Sensor HEGO: Heated O2 sensor ECU: Electronic Control Unit EEC: Electronic engine controller (Ford) It is a good idea to compile a list new people can access. I just joined a couple of weeks ago. Maybe there is one somewhere. Anyone care to comment? ------------------------------ From: Stephen Dubovsky Date: Thu, 21 Nov 1996 16:19:05 -0500 Subject: re: Air Flow Measurement alright, someone who knows alot about this stuff, so here are some questions! > ... Some of us dont have access to a dyno (hence the car window idea) ;) although I might be able to schedule some time in the wind-tunnel... ... >The problem is that steady >flow conditions only exist at very low throttle openings. > >As you open the throttle the steady flow starts to become pulsating >flow and if you're unlucky it will turn into reverse flow at some point. >To give you an idea of the magnitude of this, at WOT, 2250 rpm on the >engine I'm working on (4-cyl) flows about 37g/s average, but between 25 >and 54 g/s peak-to-peak. The frequency is twice engine speed for >obvious reasons Ok, why the heck does the airflow change directions? Some sort of shock wave like in a 2cycle tuned pipe exhaust? Wouldn't this just indicate lousy intake manifold/runner (whatever you all call them) design? Seems it would give peaks and valleys to the torque curve (like resonances in the exhaust do). >The problems become apparent when you know that the sensor output is >non-linear, the frequency response is asymmetrical, and any reverse >flow signal will be rectified. This means that the true average >(voltage) signal will not represent the true average airflow. Any >digital approximation to this will only be worse unless you use a few >tricks. Understand that reverse flow would be rectified, no problems there. Yes, the sensor is non linear, watts vs m/s is ideally square or cubic in nature (can't remember w/o my books in front of me.) What do you mean by the freq response being asym? So the sensor has some frequency response, all sensors do. I would expect a low pass filter (LPF) that MIGHT be resonant somewhere (although I cant think of a single reason why this would happen). This could still be dealt w/ easily. I would expect the freq response of a MAF to be really poor compared to computational ability. The fastest thermocouple I can find in the Omega catalog is 0.002" thick (or was that 0.001"?) which means it has VERY little thermal mass and still has a several ms (1-10) response time (slow in my book). I havent seen a Pt element any smaller. This gives a response bandwidth for 100Hz to 1kHz @ -3db which brings me to my next question... >To convert this analogue signal to a useful byte or two, you must >perform some A-D conversion. So you are quantising it not only in >the range, but also in the (time) domain. If you don't do this syn- >chronously (ie you sample in the time domain) you will wind up with >a very noisy (and aliased) signal. If you do it synchronously (in the >crank domain) you have to decide what angle gives you the represent- >ation of the average airflow. Your sample angle cannot be calculated >(easily) and varies significantly with engine speed (and to a lesser >extent with throttle position) Ok, if I sample async and the sensor looks like a LPF w/ a corner at 1kHz it will roll off at -20dB/decade. If it is resonant somewhere then put an electrical filter between it and the ADC (a good idea anyway) to make it look like a LPF. I've got 10bit A/Ds which mean I get about 1/1024 = 60dB dynamic range (which is a pretty good approx). The signal would be at -60dB in 3 decades, 1KHz -> 1MHz. Nyquist then says I sample at twice that, 2 MHz, and the aliasd signal gives less than 1 bit error across the entire 1MHz bandwidth. This would be the WORST case, as you could use a multi pole filter to attenuate the signal faster and sample much slower (or digitally decimate to avoid the problems that the phase shift from high order analog filters would cause). Anyway, sampling wouldn't be a problem (and I could always use the signal in the analog domain). > >I guess what I'm trying to suggest is that (from my experience at >least) the MAF is no slap-it-on-and-go solution. A MAP sensor on >the other hand is linear, can be throttled to give a physical average >or can be sampled and averaged/filtered in the time domain without >difficulty. It has it's disadvantages, but... > >There's heaps more to be said about this subject but I hope it's >useful to share this with you guys. If anyone has any other ideas or >experience on getting MAF's to work well, I'd love to hear from them. > >Andrew Rabbitt >Orbital Engine Company >Perth, Western Australia Ok, if the flow reverses direction, can't you just move the sensor 'upstream' (even past the air filter)? I know it would delay the response time, but if you looking for accurate measurements it seems that a MAF can't be beat. Sure seems a lot better than using MAP and some magical 'volmetric efficiency'. Could always use the TPS or MAP to help response time (as discussed in some other thread to get TPS to help the MAP). Another question/problem. How affected are MAFs by the relative humidity. Since it works on an energy loss principle, the reynolds number and other stuff are important, but so is the specific heat of the fluid being measured. RH changes the sp. heat of air. When the humidity goes up, so does the sp.heat, and the energy lost from the sensor, giving a false high reading of the air mass. It actually measured the air mass + some desired/undesired H2O(g). Curious to know if this is a big problem. Plz dont take any of this the wrong way, Im just looking for a couple of answers and you seemed to know too much practical stuff about MAFs;) SMD - -- Stephen Dubovsky dubovsky@xxx.edu 95 Yamaha FZR600 83 Porsche 911SC 84 Jeep Cherokee ------------------------------ From: Walters Chris Date: Thu, 21 Nov 96 14:34:00 MST Subject: Distributed processing articles in EETimes The 11/04 issue of Electronic Engineering Times has a special section on Distributed Processing with special emphasis on automotive control. Has articles on getting away from the single fast CPU approach to building a hiearchial ECU where each process runs on its own microcontroller, using the Controller Area Network data bus to link all sensors and processors in a car (already being done in Europe), other good stuff. ------------------------------ From: Mazda Ebrahimi Date: Thu, 21 Nov 1996 18:33:47 -0500 Subject: Re: Air Flow Measurement Stephen Dubovsky wrote: > > Ok, why the heck does the airflow change directions? Some sort of shock > wave like in a 2cycle tuned pipe exhaust? Wouldn't this just indicate lousy > intake manifold/runner (whatever you all call them) design? Seems it would > give peaks and valleys to the torque curve (like resonances in the exhaust do). > The change of direction in air flow is a result of compromises you have to make in living with one cam profile over the RPM range of the engine. Intake valves are left open for the first few degrees of the compression stroke, because the air flow comming into the cylinder has a positive momentum. So even as the piston is on its way up, you manage to pack more air into the cylinder. This momentum effect is much less pronounced at lower loads, and since the camshaft is also rotating slower, it allows some air to be pumped back into the intake runner. I have seen the results of one experiment, where at low RPM, as much as 50% of the air volume in an individual intake runner was being pumped back into the intake plenum! At part throttle, the butterfly shields the MAF sensor from flow reversion, but at lower RPMs and WOT, flow reversion past the MAF could be a problem. I think this is what you guys are talking about. That's my two cents worth! ------------------------------ From: cloud@xxx.edu (tom cloud) Date: Thu, 21 Nov 1996 17:56:56 -0600 Subject: Re: Air Flow Measurement >tom cloud wrote: >> If you know BAP and MAP, you know delta-P across opening -- granted, >> the opening size varies with throttle position, but you've got TPS >> for that -- seems that air flow could be rather accurately determined >> without much hassle????? > >Wow ! That might all be very well But ! >What the hell are BAP --- barometric absolute pressure and MAP --- manifold absolute pressure and delta-P --- pressure change or differential and TPS --- throttle position sensor pretty standard terms for efi ??? Now, what the heck is TLA ??? >Are they all TLAs ?? >Is there (or should there be) an FAQ ? >-- >Phil (Mig Pilot) Tom Cloud ------------------------------ From: cloud@xxx.edu (tom cloud) Date: Thu, 21 Nov 1996 18:00:47 -0600 Subject: Re: Air Flow Measurement >tom cloud wrote: >> the MAP / RPM / IAT (speed >> >density) nor TPS / RPM / IAT method are as accurate in measuring air flow >> what's IAT ? > >My point exactly ! there is a FAQ (somewhere) with all the pertinent terms in it. I have it, guess I could find it, but it's on the efi board. BTW I don't know what ADL? or whatever is either (for GM controller ??) Tom Cloud ------------------------------ From: "Scot A. Sealander" Date: Thu, 21 Nov 1996 18:39:59 -0800 Subject: Re: Air Flow Measurement oecar1@xxx.au wrote: [big snip] > There's heaps more to be said about this subject but I hope it's > useful to share this with you guys. If anyone has any other ideas or > experience on getting MAF's to work well, I'd love to hear from them. Andrew, I think you did a great job describing some of the problems! As to average MAF value with big sample to sample deltas in normal use, I have seen OEM code that addresses this. There is often a delta rate limiter (can be asymmetric) that can keep the sample to sample variation under control. I have never plotted the Raw MAF to gps tables to see what the actual curve looks like. It is very obvious that it is not linear. Maybe when I get some time..... It seems the frequency type MAF (digital) may have better resolution than the 0 to 5 V MAF, but that resolution may not be useful :-) As far as MAP's, I have also seen OEM code that attempts to keep the MAP samples taken about the same time in the engine cycle. It seems that this would make for less sample to sample variation. (That could be all wrong....) > Andrew Rabbitt > Orbital Engine Company > Perth, Western Australia Scot Sealander In northeast PA....USA ------------------------------ From: "Scot A. Sealander" Date: Thu, 21 Nov 1996 18:58:19 -0800 Subject: Re: Spark signal generation Dave Zug wrote: > to get my ECM to run on a bench, i think i read that some sort of > feedback spark reference is needed to simulate a "running" engine, in > addition to, of coarse, key sensors attatched, or POTs. can someone > explain what is basically needed and how it can be simulated? It depends on what you want to do. The C3's will accept a 5 v square wave at the distributor reference input and accept it as engine running. I don't remember the last P4 I looked at... I do remember that the P4 would not accept the 5V square wave as the VSS input. > you should see the image in my head of my test bench! the wife is gonna > freak! who has the best " i thought she was gonna kill me when i ..." > story? (20 words or less, and limit it to EFI) :-) Ah, been there, done that, am still living.... That is only 8 words! I think most of the wrath came from spending so much time in junkyards looking for all those ECMs. ;-) And then bringing all that junk home. (Our five year old twin girls did enjoy unwrapping all the black tape from some of the harnesses.) To make ECM interface easier, I hacked out the ECM portion of the wiring harness at one of those U-Pull-It places. I think it cost 5 bucks... An aluminum bud box and a bunch of binding posts now make ECM bench connections real easy. It will save you time if you do this. It is about 20-25 dollars for the bud box, a lot more for the binding posts. > oh, > wanted: > > 1) "pathfinder II" cartridge for OTC 2000 scan tool. (89 P4-MAP). > sell me one or offer a lead to one please. Maybe a custom built scan tool. ;-) > 2) an eprom burner that'll do 27c256's. work took my toys back. I bought "The Pocket Programmer" from Intronics, Inc. in Edwardsville, KS. It connects to the printer port, so it works easily with the laptop. That was only 129 dollars. > 3) all of GM's source code, and a code calibrator hog tied and > delivered to MD, USA. Tall order! Can't help there. Scot Sealander Sealand@xxx.com ------------------------------ From: "George M. Dailey" Date: Thu, 21 Nov 1996 18:20:48 -0600 (CST) Subject: Re: Spark signal generation At 10:15 PM 11/20/96 -0500, you wrote: >to get my ECM to run on a bench, i think i read that some sort of >feedback spark reference is needed to simulate a "running" engine, in >addition to, of coarse, key sensors attatched, or POTs. can someone >explain what is basically needed and how it can be simulated? > I "emulated?" my GM TPI and TBI engines by simply connecting them to a distributer and spinning it with my power drill. Worked great in both cases. Used a 555 timer to fool the vats. The best way to fool an ecm is to find out what it wants to see and then generate those signals by the cheapest means necessary. GMD ------------------------------ From: Mark Mason Date: Thu, 21 Nov 1996 19:25:32 -0500 Subject: Re: Spark signal generation Dave Zug wrote: > > to get my ECM to run on a bench, i think i read that some sort of > feedback spark reference is needed to simulate a "running" engine, in > addition to, of coarse, key sensors attatched, or POTs. can someone > explain what is basically needed and how it can be simulated? It depends on the type of pickup circuitry used. If your ECM receives the spark reference directly, you can use a sine wave generator to simulate the signal because the ECM will turn this into a square wave and sense the falling edge as the spark reference. If the pickup is amplified with a module, you can use a square wave generator with its DC offset adjusted so the signal swings from 0 to 12 or so volts. For a GM product, you'd use the square wave. The frequency in hertz for a given RPM would then be : RPM x 8 - ------------ 60 x 2 Hope this helps. Mark. ------------------------------ From: Todd Knighton Date: Thu, 21 Nov 1996 17:04:12 -0800 Subject: Re: ATTN: Todd Knighton Paul.J.Timmerman@xxx.gov wrote: > > Todd, > > Has your website moved? I was going to email you > about some EFI stuff and my bookmark is now bogus. > Please update me. > Yup, http://net-quest.com/~knighton/ knighton@xxx.com Todd Knighton Protomotive Engineering ------------------------------ From: Todd Knighton Date: Thu, 21 Nov 1996 17:28:10 -0800 Subject: Re: Diff between theory and practice Some other things to consider. On some of the Twin-Turbo Porsche stuff we do, we commondly run out of fuel. Check your fuel pressure, is it staying up. Are you compensating for a fuel pressure drop by opening the injector longer. What we've observed has been a fuel curve that's almost identical to the torque curve on a ms based injector opening time based map. Should be the same for most others. You will use more fuel at 6000 than at 5500 because your firing the injector more often, however, if the peak torque has reduced, your fuel requirements should also, unless something wacky is going on. Spark is going away, valve float maybe, or as I suggested above, fuel pump is giving it up. Just a note Todd Knighton Protomotive Engineering ------------------------------ From: Ross Forgione Date: Fri, 22 Nov 1996 12:45:58 -0600 (CST) Subject: Re: Air Flow Measurement > > Now, what the heck is TLA ??? > > >Are they all TLAs ?? > >Is there (or should there be) an FAQ ? > >-- > >Phil (Mig Pilot) > > > Tom Cloud > > Three Letter'd Acronym ..... By the way, this is a TOP list. Much learnt to date. Still a little shy to conribute. Ross Forgione. ------------------------------ From: Doug Robson Date: Fri, 22 Nov 1996 13:47:58 +1100 Subject: Fuel vs advance the other day i said in my race car that when i added more fuel to my efi table to get lambda from .95 to .9 and i lost power. I spoke to Richard AAubert who desinged the autronic and he said he would have put advance up to 34-35 degrees for my type of high crown ( Isuzu 8valve DOHC 2 litre ) rather than the 30 degree,s i was running . I had adjusted the fuel multiplier from 13 to 13.7 to get the lambda down regards - -- |===============================================================| | When I die, | | I want to go in my sleep, like my grandfather, | | not screaming like the passengers in his car. | |---------------------------------------------------------------| | Doug Robson (H) mailto:doug@xxx.au | | (W) mailto:Doug.Robson@xxx.com | | Sydney, Australia http://www.cia.com.au/doug | |---------------------------------------------------------------| | Club Car Racing Register of NSW | Thank God | | 1992/93 Under 2 litre State Champion | for | | http://www.clubcars.org.au | Gravity | |===============================================================| ------------------------------ From: Kalle Pihlajasaari Date: Fri, 22 Nov 1996 06:27:38 +0200 (sat) Subject: Some (late) breaking news Hi All, >From another mailing list I'm on. Cheers > From: David Kraft > To: stamps@xxx.com > Subject: Re: [STAMPS] Stamps Newbie > > > The project is to aid in the tuning of a fuel-injected car. I need to > > pick up RPM from the coil and voltage from the Oxygen sensor and spit them > > out of a serial port as a pair. The RPM will be picked up as a pulsed > > ground signal, as it is actually the pulse that fires the coil. The Oxygen > > Check out the December 1996 Dr. Dobbs Journal. > Page 50 " Inside Motorola's TPU" > It is a bit advanced, but provides great insight on what they are really > doing > in there on the engine tuning. > > - To subscribe -or- unsubscribe send e-mail to majordomo@xxx.com and > - put SUBSCRIBE stamps -or- UNSUBSCRIBE stamps in the body of the message - -- Kalle Pihlajasaari kalle@xxx.za Interface Products P O Box 15775, DOORNFONTEIN, 2028, South Africa + 27 (11) 402-7750 Fax: 402-7751 ------------------------------ From: oecar1@xxx.au Date: Fri, 22 Nov 1996 13:22:39 +0800 (WST) Subject: re: Air Flow Measurement >Some of us dont have access to a dyno (hence the car window idea) ;) >although I might be able to schedule some time in the wind-tunnel... I guess I'm trying to demonstrate that even with access to all the toys, it's still difficult (for me anyway!) to get working acceptably. >Ok, why the heck does the airflow change directions? Some sort of shock >wave like in a 2cycle tuned pipe exhaust? Wouldn't this just indicate lousy >intake manifold/runner (whatever you all call them) design? Seems it would >give peaks and valleys to the torque curve (like resonances in the exhaust do). The inlet system is usually tuned to optimise peak torque. I can't easily describe it this in detail, but imagine the momentum of the flow pulses used to increase VE at peak torque are also being reflected off closed inlet valves at other speeds. I know from practice, its very dependent on cam timing. >What do you mean by the freq response being asym? The response to a step increase is faster than a step decrease in airflow. This means that if you have pulsating airflow, the signal is skewed upwards, including the average. >I would expect the freq response of a MAF to be really poor compared to >computational ability. t63 for a 3 to 85 g/s step is about 5-10ms depending on the design. >Ok, if I sample async and the sensor looks like a LPF w/ a corner at 1kHz >it will roll off at -20dB/decade. If it is resonant somewhere then put an >electrical filter between it and... [snip...] >...twice that, 2 MHz, and the aliasd signal gives less... [snippety snip..] >...high order analog filters would cause). Anyway, sampling wouldn't be a problem (and I could always use the signal in the analog domain). A lot of this went over my head, but 2MHz is out of the question for an automotive spec ECU. I'd be lucky to sample at 1kHz, but I'd prefer to sample at a lot less. Remember you've got to do more than just measure airflow :) If you just 'average' it with analogue circuitry (or even fast ADC and DSP), the point I raise is that the average signal is not representative of the average airflow because of the linearity, response and rectification issues that I described before. >Ok, if the flow reverses direction, can't you just move the sensor >'upstream' (even past the air filter)? I use an 1000 Litre volume between the airbox and the reference meter. Even with this you will see some pulsations in the reference signal (another MAF in this case). Flow pulsations appear to be seriously hard to get rid of. I think you have to live with them and work your way around them. >Sure seems a lot better than using MAP and some magical 'volmetric >efficiency'. I'd prefer to use MAP and learn (and adapt) the VE function using closed loop A/F control if I didn't need EGR (and lots of it - I'm working on a DISC engine project). >How affected are MAFs by the relative humidity. At 20degC, according to my calcs, the specific heat capacity of air (+H2O) varies about 2% from 0 to 100%RH. Andrew Rabbitt ------------------------------ From: Darrell Norquay Date: Fri, 22 Nov 1996 06:10:25 GMT Subject: Re: DIY vacuum canister At 09:59 PM 11/20/96 -0500, you wrote: >Speaking of a vacuum canister, any ideas on where I could source something >like that? I recently ported the motor on my RX-7 and I think that the map >sensor is getting a little confused so I'd like to play with a vacuum >accumulator or something of the sort. > >Justin "Tuck" Cordesman 1. Obtain bottle of Vodka. 2. Obtain can of Clamato juice (extra spicy). 3. Punch two holes in the Clamato juice can on one end. 4. Drain Clamato into a *LARGE* glass. 5. Add Vodka, tabasco, celery salt, and ice to taste. 6. Drink Caesar, while soldering two vacuum hose barbs into holes previously punched in can. 7. Voila! Vacuum reservoir. To dress up engine compartment, leave label on can. 8. Wait until sober for road test. regards dn dnorquay@xxx.com ------------------------------ From: jon hanson Date: Fri, 22 Nov 1996 10:26:11 +0200 Subject: Re: Programmable ECU for 4A_GE snip >The reason I ask is, that I have a GEMS unit mounted in a AE86 with a 4A_GE >engine, but I can get the engine to idle when it is hot and if I touch the >throttle, then the engine stops. >Any good ides ? > >Best Regards >Rene Pedersen >74714.701@xxx.Com > > Thanks to Mazda and Tom for the sound advice, I new something was out of kilter. At least now I know what sort of things to investigate once my wallet has recovered from the shock of buying some dyno time. Hi Andrew, the system is a MIC (Micro Injection Controller) from a Johannesburg based company Digital Data Systems. Their phone no is 011 793 1151 ask for Klaus or Peter and mention that your interested in the MIC (there main business is actually UPS's). Hi Rene , The car is USA spec LHD 1985 Toyota MR2 MkI. The original system was the Toyota Computer Control System (TCCS) which I suspect is a NipponDenso licensed version of Jetronic. The car used a flap type air flow meter but this has been discarded the EGR kit has been removed and blanked off, O2 sensor as well. I still use the std throttle body and inlet manifold but the TVIS flaps have been removed ( I didn't want to do this as the engine is lazy enough at low revs in std form but I had no way of controlling them) Mic is a sort of hybrid system, I've never read of anything like it It is essentially a Throttle posn (Alpha-N) based system. ie in the main fuel map the rows are RPM and the columns are Throttle posn's for Load. However it also has a map Sensor which is connected to the Plenum chamber near the throttle body. The Map readings are used to modify the fuel curve There is a small table where you associate Map readings with a Map fuel factor which is used in calculating injector open times. The map sensor is also used to give ignition advance/retard based on load. ie you have a base advance curve table based on engine rpm this is modified by a table which has advance/retard based on the Map reading. ie NO true three dimensional spark mapping. As far as idling goes, I have learnt some tricks but they might not apply to the GEMS system. are you saying that when idling with a hot engine and you touch the throttle the engine dies. What happens when the engine is still Warming up. In the MIC it is very important that even a very small throttle movement from idle posn will move the fuelling from col 0(idle) to column 1 where there is quite a sharp increase in fuelling to take up the initial load Let me know how gems works and maybe I can help I'd be interested in comparing ign advance figures with you Regards Jon Hanson Johannesburg South Africa. ------------------------------ End of DIY_EFI Digest V1 #356 ***************************** 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".