DIY_EFI Digest Tuesday, 6 August 1996 Volume 01 : Number 222 In this issue: Alpha-N injection Back flow?(don't tell me this belongs on a sewer!) Re: Alpha-N injection Power Regulators... Re: Alpha-N injection Re: Circuits for magnetic pickups Instruments & such [none] general info. general info. Re: Instruments & such Re: Alpha-N injection Re: general info. Re: Instruments & such Re: Instruments & such Re: Power Regulators... re: back-flow See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- From: James E Staff Date: Mon, 5 Aug 1996 03:56:07 -0500 (CDT) Subject: Alpha-N injection Has anyone here looked at the merits of a system that only knows the position of the throttle plates? And the can use O2, engine temp and air temp values to tune the A/F ratio. This is the system that I'm working on now, and am nearly complete. It has the simplest components. 1 10bit 600ns flash A/D 1 8 bit A/D that is slow and has a analog multiplexer attached 1 O2 sensor 1 Mil spec oil filled conductive plastic POT for a precision voltage divider. Thats the who core system, when I finish my spec sheet I'll provide more info... Later, Jim Staff ------------------------------ From: talltom Date: Mon, 05 Aug 1996 03:41:46 -0700 Subject: Back flow?(don't tell me this belongs on a sewer!) - ----------------------------- > > From: RABBITT_Andrew@xxx.au > Date: Mon, 5 Aug 1996 08:02:16 est > Subject: re: AFMs > > >>Is it a MASS FLOW measurement? > > NO, vortex shedding frequency is a function of flow velocity, > therefore it's only volume flow metering. The pressure and temp. > sensors are only to do the corrections, which alledgedly leads to > messy lookup tables and calculations in the OEM ECU. (yuk!) > > >>Does a problem occur at low (read idle) flow rates (of resolution)? > > I shouldn't think so, it should be just a matter of sizing the vortex > shedder and minimum flow velocity appropriately. (my opinion only) > > >>All this stems from me being a little nervous about using Bosch > hotwires in a high vibration offroad application. > > If you're worried about vibration on a hotwire, try using the bosch > hot-film sensor (HFM-2) as fitted to many late model BMW's and > probably many other European cars. Take a look at the latest 540i > (4.4L V8) which should be good for your application > > Also, the Hitachi bypass meter fitted to most fords (EEC iv) is an > analogue output, not frequency. > > Also, for everyone's info, Bosch has recently started production on a > hot-film meter capable of measuring back-flow (properly!) A neat > piece of design using micro-machined silicon technology. > > Andrew Rabbitt > Orbital Engine Company Hang the hell on here! Are you saying what I think you're saying? This thing can measure air flow in either direction, relatively accurately? If this the case, did anybody else see all those arguments about wild cams up and fly out the window like I just did? ------------------------------ From: cloud@xxx.edu (tom cloud) Date: Mon, 5 Aug 1996 09:12:29 -0500 Subject: Re: Alpha-N injection > > Has anyone here looked at the merits of a system that only knows the >position of the throttle plates? And the can use O2, engine temp and air >temp values to tune the A/F ratio. > > This is the system that I'm working on now, and am nearly complete. It >has the simplest components. > > 1 10bit 600ns flash A/D > 1 8 bit A/D that is slow and has a analog multiplexer attached > 1 O2 sensor > 1 Mil spec oil filled conductive plastic POT for a precision voltage >divider. > > Thats the who core system, when I finish my spec sheet I'll provide >more info... > > Later, > Jim Staff > Jim This describes the Holley aftemarket EFI I have installed on my Bronco. It only uses TPS, engine RPM and temp. as inputs. For ~ $200 one can add EGO (O2) feedback, though I haven't done that yet. It seems that most people in this group are looking to modify the fuel injection system they already have. I would like to take the throttle body injection system I have installed (Holley) and build my own controller, perhaps adding a few more data inputs. But, alas, though I feel I have some idea of how the various bits of data influence the control process, I would like to not have to re-invent the wheel. The development of fuel control systems has obviously consumed thousands of hours of automotive engineers' time -- though probably a large amount was spent on emissions control algorithms. Though I would like to be able to be emissions compliant -- I also want to be able to go fast! Anyway, keep me posted on what you find out. Thanks, Tom Cloud ------------------------------ From: Donald Whisnant Date: Mon, 05 Aug 1996 11:08:33 -0400 Subject: Power Regulators... Whoever it was that mentioned the Maxim MAX724 switching regulator, THANKS! ... I just finished designing and building my speedometer that I've been working on for my '85 Grand Prix that I put the '94 4.3L V6 CMFI engine in (with a 4L60E tranny) ... The speedometer was needed because the electronic pickup doesn't work too well for an older mechanical cable style speedometer :) .... I was originally thinking about using the conventional 7805, but did a quick calculation: if ALL segments on the display (128 segments and dps total!) at full power, as much as 2.5 amps could be drawn. This exceeded the limit of the 7805, but I didn't have much board space to spare... So I checked out the MAX724 that someone on this list recommended, and it works great!! -- Now I can run up to 5 Amps and not worry about it! (how's that for a safety margin) ... First time I've put a switching regulator onto one of my projects -- and I was well impressed with it... Also, for those of you looking for good 7-seg display drivers, check out the MAX7219 -- really neat chip... Donald Whisnant dewhisna@xxx.com ------------------------------ From: Jeffrey.Giberstein@xxx.EDU (Jeffrey Giberstein) Date: 05 Aug 96 12:23:09 EDT Subject: Re: Alpha-N injection Does anyone know what the feasibility of using an alpha-N system on a Supercharged engine is? I know it's a no-no for turbos, but I'd guess that it's cool with Sperchargers because intake air characteristics would be throttle angle and RPM-dependent. Does that sound right? Jeff Giberstein ------------------------------ From: Sandy Date: Mon, 05 Aug 1996 10:05:07 -0700 Subject: Re: Circuits for magnetic pickups > >Actually the noise really isn't bad at all.... I've got a 120v power >inverter and have actually put my oscilloscope in the car (had someone else >drive :) and looked at the signal under real-time operating conditions. [SNIP] I think that I will try the simpler op-amp circuit and give it a run in the car with an unconnected sensor to see what happens. I could eliminate a chunk of board space if I use the op-amp instead of the lm1815, not to mention the cost of the lm1815 is a lot more then the op-amp. Good idea with the inverter and the scope, I'll have to get on, as that will make the testing easy! Sandy ------------------------------ From: "Michael T. Kasimirsky" Date: Mon, 5 Aug 1996 15:19:13 -0400 (EDT) Subject: Instruments & such I have a question kind of related to DIY-EFI. I've noticed several list members posting about testing this or that with an oscilloscope or some other high-priced widget. Can anyone recommend a reasonably priced source for such instruments? Is there such a place? Used? Any help would be greatly appreciated. Michael T. Kasimirsky ----> mtk@xxx.edu Days: Staff Engineer or mk4u@xxx.edu ASTM Test Monitoring Center Phi Gamma Delta, Nights: 1992 Suzuki GSX-R750 Pilot NRA Life Member, AMA Member 1991 Suzuki GSF400 Bandit Mechanic DoD #1848 ------------------------------ From: cloud@xxx.edu (Tom Cloud) Date: Mon, 5 Aug 1996 15:14:16 -0500 Subject: [none] ------------------------------ From: cloud@xxx.edu (tom cloud) Date: Mon, 5 Aug 1996 17:33:53 -0500 Subject: general info. I have recently joined your group and have some serious questions. I am trying to add EFI to an older vehicle, not modify an existing unit -- though I have considered going and getting a Ford intake, runners and injectors, and putting them on my 351-W engine. But, I would still be back to the original problem -- how to control it. As I have noted in past postings, I purchased an aftermarket EFI system that proves that one can be quite effective with a minimal amount of features -- specifically, this system basically only uses TPS to determine fuel supply. [It uses RPM to operate the injectors, with more fuel being allowed for greater RPM. Large TPS values are assumed to imply power, so there is an adjustment to control how much enrichment to add for 2/3 or 3/4 throttle to WOT. It also senses the TPS rate-of-change to simulate the carburetor accelerator pump function, and it senses engine temp. to provide "choke" cold start enrichment.] I can say that the unit is very functional and reliable though I do have to tune it (the controls are potentiometers under the dash) periodically to compensate for temperature and altitude changes -- and often I don't know why it needs adjusting. Now, it seems to me that a simple EFI system would start with a fixed injector pulse width. Then increased RPM would give a corresponding increase in fuel. RPM and TPS would also (each) give a relative indication of the expected operating needs of the engine, a "typical" correlation between the two being empirically determined. Then a large disparity between RPM and TPS could assume a need for more fuel (TPS > RPM) or for less than the "normal" amount. Engine temperature could be used to increase the pulse width at lower RPM for cold operation. Now comes feedback. EGO supposedly tells when conditions are optimum for the most complete burning of the fuel (stoichiometric, or A/F of 14.7:1). But, economy is achieved at about 18:1 while maximum power is found at about 11:1. From recent discussions in this group, it appears that the EGO sensor is useless at determining anything but 14:7 -- is this right? And even then how, specifically, is it's output used? I have an O2 sensor connected to a DPM and use it to tune my EFI system. The writings that I have seen say that its output swings back and forth between a high level and a low one, with an average of about .5 volt being sought. My DPM shows no pulsating. Can the EGO sensor's output be filtered to average or integrate the pulses and provide a steady control signal? Other sensors that I know of are the MAP, BAP and MAF. I can see how a reduced manifold pressure would imply an increased need for fuel and would modify the previous RPM / TPS determined pulse width, but how does BAP (barometric atmos. press.) modify that, and is it necessary? Apparently BAP is not needed if MAF is used. I can see that, with MAF, one could actually determine the amount of air entering the engine and therefore more correctly ascertain the amount of fuel to add. How hard is it to add? How could it be added to a TBI system? Why isn't manifold pressure and throttle position an adequate indication of air intake volume? In fact, since MAF sensors seem to be a pain, it would seem to me that air volume could be determined quite well from knowing BAP (the available air density), TPS (the size of the opening the air is trying to get through, and MAP (the amount of pressure on the opening). Then there's my question about EGR. This is not a sensor, but it has a marked effect on engine operation. It seems to give a higher effective octane thereby allowing the timing curve to be more advanced than without it. What that means is that anyone monkeying with the EGR will end up with pinging at rpm under load and a loss in power. This is a particularly onerous problem for anyone trying to increase engine performance with aftermarket products -- specifically intake manifolds or, as in my case, a carburetor-to- fuel injection upgrade. I would like to know if anyone has any control algorithms (digital or analog) to share, as studying what you've discovered will help me. I would like to know any correlations between sensor readings and fuel control and I need sources of engineering specs. on the various sensors. That pretty well sums my rather large ignorance of the subject. Can anyone help? Thanks Tom Cloud ------------------------------ From: cloud@xxx.edu (tom cloud) Date: Mon, 5 Aug 1996 18:11:50 -0500 Subject: general info. I have recently joined your group and have some serious questions. I am trying to add EFI to an older vehicle, not modify an existing unit -- though I have considered going and getting a Ford intake, runners and injectors, and putting them on my 351-W engine. But, I would still be back to the original problem -- how to control it. As I have noted in past postings, I purchased an aftermarket EFI system that proves that one can be quite effective with a minimal amount of features -- specifically, this system basically only uses TPS to determine fuel supply. [It uses RPM to operate the injectors, with more fuel being allowed for greater RPM. Large TPS values are assumed to imply power, so there is an adjustment to control how much enrichment to add for 2/3 or 3/4 throttle to WOT. It also senses the TPS rate-of-change to simulate the carburetor accelerator pump function, and it senses engine temp. to provide "choke" cold start enrichment.] I can say that the unit is very functional and reliable though I do have to tune it (the controls are potentiometers under the dash) periodically to compensate for temperature and altitude changes -- and often I don't know why it needs adjusting. Now, it seems to me that a simple EFI system would start with a fixed injector pulse width. Then increased RPM would give a corresponding increase in fuel. RPM and TPS would also (each) give a relative indication of the expected operating needs of the engine, a "typical" correlation between the two being empirically determined. Then a large disparity between RPM and TPS could assume a need for more fuel (TPS > RPM) or for less than the "normal" amount. Engine temperature could be used to increase the pulse width at lower RPM for cold operation. Now comes feedback. EGO supposedly tells when conditions are optimum for the most complete burning of the fuel (stoichiometric, or A/F of 14.7:1). But, economy is achieved at about 18:1 while maximum power is found at about 11:1. From recent discussions in this group, it appears that the EGO sensor is useless at determining anything but 14:7 -- is this right? And even then how, specifically, is it's output used? I have an O2 sensor connected to a DPM and use it to tune my EFI system. The writings that I have seen say that its output swings back and forth between a high level and a low one, with an average of about .5 volt being sought. My DPM shows no pulsating. Can the EGO sensor's output be filtered to average or integrate the pulses and provide a steady control signal? Other sensors that I know of are the MAP, BAP and MAF. I can see how a reduced manifold pressure would imply an increased need for fuel and would modify the previous RPM / TPS determined pulse width, but how does BAP (barometric atmos. press.) modify that, and is it necessary? Apparently BAP is not needed if MAF is used. I can see that, with MAF, one could actually determine the amount of air entering the engine and therefore more correctly ascertain the amount of fuel to add. How hard is it to add? How could it be added to a TBI system? Why isn't manifold pressure and throttle position an adequate indication of air intake volume? In fact, since MAF sensors seem to be a pain, it would seem to me that air volume could be determined quite well from knowing BAP (the available air density), TPS (the size of the opening the air is trying to get through, and MAP (the amount of pressure on the opening). Then there's my question about EGR. This is not a sensor, but it has a marked effect on engine operation. It seems to give a higher effective octane thereby allowing the timing curve to be more advanced than without it. What that means is that anyone monkeying with the EGR will end up with pinging at rpm under load and a loss in power. This is a particularly onerous problem for anyone trying to increase engine performance with aftermarket products -- specifically intake manifolds or, as in my case, a carburetor-to- fuel injection upgrade. I would like to know if anyone has any control algorithms (digital or analog) to share, as studying what you've discovered will help me. I would like to know any correlations between sensor readings and fuel control and I need sources of engineering specs. on the various sensors. That pretty well sums my rather large ignorance of the subject. Can anyone help? Thanks Tom Cloud ------------------------------ From: catapult@xxx. Gleason ) Date: Mon, 5 Aug 1996 16:53:03 -0700 Subject: Re: Instruments & such You wrote: > >I have a question kind of related to DIY-EFI. I've noticed several list >members posting about testing this or that with an oscilloscope or some >other high-priced widget. Can anyone recommend a reasonably priced >source for such instruments? Is there such a place? Used? Any help >would be greatly appreciated. > >Michael T. Kasimirsky ----> mtk@xxx.edu >Days: Staff Engineer or mk4u@xxx.edu > ASTM Test Monitoring Center Phi Gamma Delta, >Nights: 1992 Suzuki GSX-R750 Pilot NRA Life Member, AMA Member > 1991 Suzuki GSF400 Bandit Mechanic DoD #1848 > You might try Nuts & Volts, a monthly magazine. They have a ton of ads for electronics/hobby stuff and a lot of test equipment. The magazine can be found at some electronic or ham radio stores. They also have a web page, but I don't have the address handy. If you need the address, I'll find it for you. M.G. ------------------------------ From: Todd Knighton Date: Mon, 05 Aug 1996 17:35:13 -0700 Subject: Re: Alpha-N injection James, We have modified Bosch Motronics units from Air Flow meter to Alpha-n type systems. We typically have done this for radically cammed engines where airflow measurement is unreliable. It has worked out well If we can help you let us know. Todd Knighton Protomotive Engineering Email: knighton@xxx.com James E Staff wrote: > > Has anyone here looked at the merits of a system that only knows the > position of the throttle plates? And the can use O2, engine temp and air > temp values to tune the A/F ratio. > > This is the system that I'm working on now, and am nearly complete. It > has the simplest components. > > 1 10bit 600ns flash A/D > 1 8 bit A/D that is slow and has a analog multiplexer attached > 1 O2 sensor > 1 Mil spec oil filled conductive plastic POT for a precision voltage > divider. > > Thats the who core system, when I finish my spec sheet I'll provide > more info... > > Later, > Jim Staff ------------------------------ From: Todd Knighton Date: Mon, 05 Aug 1996 17:53:43 -0700 Subject: Re: general info. tom cloud wrote: > > Now, it seems to me that a simple EFI system would start with a fixed > injector pulse width. Then increased RPM would give a corresponding > increase in fuel. RPM and TPS would also (each) give a relative > indication of the expected operating needs of the engine, a "typical" > correlation between the two being empirically determined. Then > a large disparity between RPM and TPS could assume a need for more > fuel (TPS > RPM) or for less than the "normal" amount. Engine > temperature could be used to increase the pulse width at lower RPM > for cold operation. > YUP. > Now comes feedback. EGO supposedly tells when conditions are > optimum for the most complete burning of the fuel (stoichiometric, > or A/F of 14.7:1). > But, economy is achieved at about 18:1 Maybe in a diesel application, most 4 stroke gas motors won't tolerate much over 15:1 without lean misfire, unless your HONDA with a CVCC. > while maximum power is found at about 11:1. We don't even get there at 20 psi on an air cooled Porsche Motor, Max power is still at 11.6:1 or so. Normally Aspirated Max power can usually be found from 12.8:1 to 13.3:1 > From recent discussions in this group, it appears that the EGO > sensor is useless at determining anything but 14:7 -- is this right? > And even then how, specifically, is it's output used? They do work typically from 23.5 to 11:1, at least a Bosch 4 wire sensor does, typical 1 or 3 wire sensors are not very good beyond 12 to 17:1 > I have an O2 sensor connected to a DPM and use > it to tune my EFI system. The writings that I have seen say that > its output swings back and forth between a high level and a low one, > with an average of about .5 volt being sought. My DPM shows no > pulsating. This in on cars that are being controlled, not very well, by a Microcontroller. > Can the EGO sensor's output be filtered to average or > integrate the pulses and provide a steady control signal? Yup. > > Other sensors that I know of are the MAP, BAP and MAF. I can see how > a reduced manifold pressure would imply an increased need for fuel and > would modify the previous RPM / TPS determined pulse width, but how > does BAP (barometric atmos. press.) modify that, and is it necessary? To maintain specific air/fuels at specific gauge pressures typically on emmissions control type stuff. > > Apparently BAP is not needed if MAF is used. I can see that, with > MAF, one could actually determine the amount of air entering the > engine and therefore more correctly ascertain the amount of fuel to > add. How hard is it to add? Fairly easy to compute with a MCU > How could it be added to a TBI system? Depends on the system > Why isn't manifold pressure and throttle position an adequate > indication of air intake volume? It is until there is a change over time. Pressure lags behind air flow and thus has to be compensated for. But with throttle position that can be calc'd. > In fact, since MAF sensors seem to be a pain, > it would seem to me that air volume could be determined quite well > from knowing BAP (the available air density), TPS (the size of the > opening the air is trying to get through, and MAP (the amount of > pressure on the opening). YUP. > > Then there's my question about EGR. This is not a sensor, but it > has a marked effect on engine operation. It seems to give a higher > effective octane thereby allowing the timing curve to be more > advanced than without it. What that means is that anyone monkeying > with the EGR will end up with pinging at rpm under load and a loss > in power. This is a particularly onerous problem for anyone > trying to increase engine performance with aftermarket products -- > specifically intake manifolds or, as in my case, a carburetor-to- > fuel injection upgrade. Unfortunately EGR also decreases the effective oxygen in the combustion chamber, thus decreasing power output. IF you removed the EGR and recalibrated the timing, an overal net increase in power would be the result. > > I would like to know if anyone has any control algorithms (digital > or analog) to share, as studying what you've discovered will help > me. I would like to know any correlations between sensor readings > and fuel control and I need sources of engineering specs. on the various > sensors. > Pressure Sensing: PV=nRT basically sums it up MAF: Pain to calc. Need to air flow by rpms to generate a load value. It almost reverts back to pressure sensing. Low rpms have poor resolution on large MAF sensors due to relative low change in air flow from small to large throttle openings. AFM: Just like MAF though measures CFM not Mass, needs barometric and temperature compensation. TPS: Crude but effective, recommended only when other methods won't work well, i.e. large cams, independent throttle bodies. Motorola is a good source for specs and pressure sensors. Siemens has some good temp stuff. Bosch makes good TPS sensors > That pretty well sums my rather large ignorance of the subject. > > Can anyone help? > > Thanks > Tom Cloud ------------------------------ From: cloud@xxx.edu (tom cloud) Date: Mon, 5 Aug 1996 20:52:41 -0500 Subject: Re: Instruments & such >I have a question kind of related to DIY-EFI. I've noticed several list >members posting about testing this or that with an oscilloscope or some >other high-priced widget. Can anyone recommend a reasonably priced >source for such instruments? Is there such a place? Used? Any help >would be greatly appreciated. > >Michael T. Kasimirsky ----> mtk@xxx.edu >Days: Staff Engineer or mk4u@xxx.edu > ASTM Test Monitoring Center Phi Gamma Delta, >Nights: 1992 Suzuki GSX-R750 Pilot NRA Life Member, AMA Member > 1991 Suzuki GSF400 Bandit Mechanic DoD #1848 > Fordham Electronics (don't have catalog handy right now -- may be out of business) ... pretty good prices on quality new instrumentation (if you're looking for Tektronix, tell me) Tucker Electronics; www.tucker.com; 800-527-4642 ... new and used stuff ------------------------------ From: cloud@xxx.edu (tom cloud) Date: Mon, 5 Aug 1996 21:36:35 -0500 Subject: Re: Instruments & such >> 1991 Suzuki GSF400 Bandit Mechanic DoD #1848 [ snip ] >> >Fordham Electronics (don't have catalog handy right now -- may be out of > business) > ... pretty good prices on quality new instrumentation (if you're > looking for Tektronix, tell me) ... found a number for "a" Fordham Radio, don't know if it's the same one I am talking about: 800-648-2626. > >Tucker Electronics; www.tucker.com; 800-527-4642 > ... new and used stuff Hope this helps, Tom Cloud ------------------------------ From: Darrell Norquay Date: Mon, 5 Aug 96 20:30 PDT Subject: Re: Power Regulators... At 11:08 AM 8/5/96 -0400, Donald Whisnant wrote: >Whoever it was that mentioned the Maxim MAX724 switching regulator, That was probably me. I had the same Eureka Syndrome - first time I tried using one, it worked great, was totally painless to design, dissipates way less than a linear regulator, and puts out more power than you'll ever need. BTW, the MAX726 is a 2A version of the 724, all other specs the same. Linear Technologies also makes a direct replacement, the LT(C?)1074/76. Buy some today! regards dn dnorquay@xxx.com ------------------------------ From: RABBITT_Andrew@xxx.au Date: Tue, 6 Aug 1996 08:10:10 est Subject: re: back-flow >> >> Also, for everyone's info, Bosch has recently started production on >> a hot-film meter capable of measuring back-flow (properly!) A neat >> piece of design using micro-machined silicon technology. >> > > >Hang the hell on here! Are you saying what I think you're saying? >This thing can measure air flow in either direction, relatively >accurately? If this the case, did anybody else see all those >arguments about wild cams up and fly out the window like I just did? > I'm not kidding you here. Take a look at SAE paper #950433. For those who haven't got access to it, it works something like this. A heater is embedded onto a piece of silicon (somehow) with two platinum temp probes, one upstream and one down stream. At zero flow, they both sense the same temperature, but as the flow increases from zero, the boundary layer flow cools the upstream sensor somewhat, but the downstream sensor remains relatively constant due to the air passing over the heater first. Thus the airflow rate is a function of the temperature differential between the two sensors. Obviously the sign of the differential is related to the flow direction. Neat eh! Trick is now, how do you sample these devices given that the flow is likely to be oscillating, sometimes to the extreme, and the sensor output is non-linear? I suggest sampling in the crank domain, however you've still got to reference it to some known flow to work out where the correct sample angle is. Any ideas? ------------------------------ End of DIY_EFI Digest V1 #222 ***************************** 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".