DIY_EFI Digest Wednesday, 7 August 1996 Volume 01 : Number 223 In this issue: Re: DIY_EFI Digest V1 #222 Re: general info. more musings on EFI controllers Re: general info. Nuts & Volts Re: Instruments & such Re: Instruments & such Re: Instruments & such Unable to deliver Re: more musings on EFI controllers See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- From: talltom Date: Tue, 06 Aug 1996 03:39:29 -0700 Subject: Re: DIY_EFI Digest V1 #222 > 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? > Well I hope you'll indulge my ignorance, but why do you care about some known Flow? Maybe I'm 9 clouds out of orbit, but it would seem to me that one could set up some sort of graph with the differential output as one axis and fuel injector pulse as the other and set the pulse width on a laptop once you put it on whatever the application is. One possible complication I can see is that pulsing across AFM could cause radical sensor outputs, but as long as the output differential was used It would have to be accurate. One may need to cook up some sort of filter to slow up pulses if idle gets erratic, but you know that more air has to go in than out unless it pukes, at which point the backfire will have heated the outgoing air and read as incoming which will in effect richen the mixture. At that point the tendency to puke will have been reduced. Kinda automatically screws up in the right direction! Even a bunch of burned intake valves shouldn't keep this thing from working, as still more air has to go in than come out. Alright, let the flames begin! ------------------------------ From: Alexander.M.Lichstein@xxx. Lichstein) Date: 06 Aug 96 09:06:53 EDT Subject: Re: general info. EFI is used to maintain a desired A/F ratio under all conditions. This might mean 12.5:1 under power conditions (WOT, deltaTPS) and 14.7:1 under normal conditions (TPS <60%, [IDLE]) Since we must estimate the amount of air entering the engine in order to allow the correct fuel, we need to know how it sucks it's air. While higher RPM does imply more fuel... the pulse widths will be roughly the same. This is b/c these pulses are working once per engine event... it's just that these engine events are happening more often. This is not entirely true, however, b/c the engine gets more or less efficient at pumping air at different engine speeds. This is dependant on the physical layout of manifold (tuning lengths...) and valvetrain (overlap...). This is roughly called VE or volumetric efficiency. You will have seen a thread about this early last month. The accelerator pump concept is merely an effect of the above. High deltaTPS or WOT will tell us that the driver would like us to go faster (or, make more power). We can do that by changing our fuel ratio from 14.7:1 (cruise), to 12.5:1 or the like. [You mentioned 11:1 which you may find way past your peak power and *very* inefficient] Anyway, this change alone can acount for the benefits from an accelerator pump. However, the more subtle one is the manifold fuel film issue which is most pronounced in a TBI or wet-flow manifold like yours. You must figure out how much of the fuel you inject is actually getting into the cylinders when you want it. An analysis of the liquid fuel stickiing to the walls will tell you that you must overshoot fuel as you switch to 12.5:1, and then ease up as this "flood" of fuel makes it's way as vapour to the cylinder. The O2 sensor will only bounce back and forth is the engine is bouncing back and forth. In OEM systems, it is designed to do this. In yours, it may be doing this from inaccuracy. However, you would not be able to see it on a DVM. As for interpreting O2... I'll leave that to another as I am stilll working out the bugs on mine. MAP - higher the MAP (less vacuum) the *MORE* fuel is needed since the air pump (engine) is trying to suck this air in. The lower the P1, the lower the P2, this the lower the mass of air. MAP sensors are usually set up to measure the static pressure and ignore the velocity pressure of the incoming air. By knowing the diameter of the tube across which it is looking, all that is needed is the temperature in order to know the mass-flow. Ambient pressure is inconsequential... although it might give a way to correlate TPS with MAP more easily. BAP - affects the backpressure on the exhaust side. Since a MAP based system is estimating how much aire the engine can pull at that level of Manifold vacuum and it is *Absolute, the backpressure at the exhaust will affect how much air is left in the cylinders when it comes around again... again affecting the mass air to be burned. While we're at it, don't forget HUM. - - Z ------------------------------ From: cloud@xxx.edu (tom cloud) Date: Tue, 6 Aug 1996 11:00:59 -0500 Subject: more musings on EFI controllers The following is an excerpt of a missive I just sent to Michael Kasimirsky and is a continuation of my rambling thoughts on EFI control. > > [ snip ] > >several ideas on overall logic of the system. The big question I have is >on the electronics to control the system. I'd like to use a >microcontroller of some sort; probably a Motorola of some sort. > I am in the research mode myself. The Motorola 68HC11 is a super controller, and is apparently the backbone of some commercial EFI controllers, but I am not sure what is really needed for EFI. I'll tell you, if cost is not a major factor, I would check out the aftermarket genre -- esp. Holley and Accel. Holley tech. line: 502-781-9741 (9:30 - 11:30 & 12:30 - 3:30 -- I think CST). Maybe they would help you and sell you one of their controllers only (since I don't think they make throttle bodies for motorcycles). [Trust me, if you have no experience writing assembly, C, FORTH or some such, you don't know what you're asking for trying to develop a complete hardware and software system -- either one alone is a major under- taking. So, you can realistically either choose to ride it or spend the next few years working on it.] For me, I honestly think that a reasonable alternative is to build an analog controller. The reasons for using digital logic and microprocessors: they're "neat", well defined, reproducible. They appeal to our egos because we can actually "control" something. Analog tends to be "fuzzy", irritating and often is the controller rather than the controllee. But, it has the advantage of being faster to develop, easier to implement (depends on the complexity of the system), cheaper, and easier to "twiddle". I think that if one evaluates his priorities and finds performance at the top, with economy and emissions some- where further down the list (?), then an analog system becomes very practical. If you'll read my latest posting, you'll see that I use a Holley aftermarket EFI throttle body system that is analog (well, the timing for the injection pulse, etc. is probably a digital function) and uses the minimum of sensors: namely TPS and temperature. This system works very well (it costs about $600 for everything) when you consider that their next more sophisticated (read digital) system costs double that. So, with some linear circuits (i.e. analog) measuring TPS and RPM one should be able to calculate an injector pulse width to give an effective fuel mixture to operate. Keep in mind that TPS represents the amount of opening of a butterfly valve, which is a non-linear function of area and therefore air delivery (correcting this non- linearity is probably "easier" with a micro-controller). With a simple differentiator, a temporary extra shot of fuel can be added for a positive delta of TPS (indicating acceleration). Now, if you're interested, here's my very preliminary thoughts on how to achieve this (hope you have someone with a little electronic circuit know-how available). Take a linear ramp generator (I-constant circuit charging a cap) and reset it with each ignition pulse. This ties it to RPM. The rate of rise of this ramp is controlled by the voltage (or current) at the input to the op-amp. The injector is opened by the ignition pulse (set a FF) and closed (reset the FF) by the ramp crossing some pre-determined level (a comparator), so the amount of fuel given the engine is already greater for higher RPM, since the injector open time is constant. The controllable points are the V or I input to the op-amp and the level to the comparator that resets the FF. Now, take TPS and process it (can be a linear function, logarithmic, or whatever) and feed it into the ramp generator, changing the slope of the ramp -- steeper ramp = less on time of injector, and vice-versa. Also take TPS and couple it through a capacitor (differentiate it), process this signal (read adjust the gain and time constant) and sum it in also. This gives the acceleration / deceleration adjustments. The signal from temp. would also be summed in (though you'd want to figure out how to remove it once operating temp. was achieved and at higher RPM). Now, the advantage of this system is that you could put potentiometers allowing adjustment of how much each of these factors contributed and they could be placed where you could easily access them so real-time adjustments could be made -- and wouldn't require a computer in your lap, much less re-programming and assembling or compiling. But how, exactly, to do this? I haven't worked on it. I am fairly certain though that that's how the Holley system works. The complexity increases exponentially (same with a digital system) as more control is attempted (read more sensors and therefore more calculations). Adding EGO feedback would be done in the same manner as before (remember, this is my speculation only, not gospel). The signal would be processed and summed into the ramp generator, but now there's a serious problem -- the EGO output is extremely non- linear, and that becomes a B-I-G problem with analog. (With micro- controller, one can store values in a lookup table for curve correction.) Calculating A/F ratio (i.e. the rate of rise of the ramp generator / injector pulse width versus the air entering the system) was guessed at and an acceptable compromise set with the above-mentioned system (this is called speed density -- where the A/F ratio is assumed from the position of the throttle (TPS) and the speed of the engine (RPM)). Now, should one want to get more exact (and I'm not sure why you'd want to, unless you were trying to maintain tight emission controls) one would attempt to determine A/F more precisely. Enter MAF, etc. As in my previous post, it would seem to me that the air charge could be determined just as well -- maybe even better -- by using baro- metric pressure, manifold pressure (establishing a pressure diff.), and throttle position (aperture size, though this is a non-linear function unless throttle slides are used). Well, it seems to me that the point of diminishing returns is rapidly found. But, if the objective is to go fast, it is much less complicated. If consistency is desired -- more complicated. Stoichiometry -- even more complicated. So, it seems to me that the choice is relatively easy: go fast, with varying climatic conditions and altitudes, with some acceptable consistency (for me, I'd like to not have to adjust the system, except maybe with the exception of major climatic or altitude changes -- and even then, I want to do it in a well defined, easily accomplished manner, like adjust a pot). > Can you >suggest some reference materials on microcontrollers where I can learn >how to both set up the circuits as well as program the system? I think >I've got a general idea how the system should work, but I've got a long >way to go. Since you've taught electronics, hopefully you can recommend >a good text to get me started. As far as literature -- let me check and get back to you on a source. When I need it, I'll find one of our students or a friend who works at the Motorola plant here. But, for you, best bet might be to contact their literature dist. center (used to be one here in Austin). Check out: "http://motserv.indirect.com" "http://www.motorola-powered.com/" Motorola product info and tech. info. : 800-668-6765 Motorola literature distrib. center (MST zone) : 800-441-2447 for 68HC11: http://129.38.232.2/hc11/home.html Even easier might be to post request on EFI group. (There are FAQ's about 68Hxx also.) As far as texts, the ones we use are extremely basic: like how a CPU, ALU, etc. works, memory addressing schemes, instruction sets, subroutines, parameter passing (note that this is all done in assembly code). Interrupt handling is not covered at all. You want something that gives you actual examples of code and block and schematic diagrams of actual hardware. I don't know of such right now. Anyone want to chip in? Tom Cloud ------------------------------ From: cloud@xxx.edu (tom cloud) Date: Tue, 6 Aug 1996 11:18:37 -0500 Subject: Re: general info. > [ SNIP ] > >While we're at it, don't forget HUM. > HUM ?? ------------------------------ From: catapult@xxx. Gleason ) Date: Tue, 6 Aug 1996 10:12:34 -0700 Subject: Nuts & Volts Todd (and any others interested), Nuts & Volts can be reached at: http://www.nutsvolts.com/ Phones: 909-371-8497 (Voice) 909-371-3052 (Fax) Mike ------------------------------ From: cloud@xxx.edu (tom cloud) Date: Tue, 6 Aug 1996 14:15:33 -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. > > [ snip ] Some places we use: ****** equipment: Techni-Tool; 800-832-4866; http://www.techni-tool.com Extech Instruments;617-890-7440; FAX 617-890-7864; extech@xxx.com; http://www.extech.com ****** components: Active Electronics (quality, name-brand semiconductors and other discretes at reasonable prices); 800-677-8899 Digi-Key (discrete components at good prices; mail-order type); 800-344-4539; http://www.digikey.com Mouser Electronics (discretes, some top quality, some not -- be careful; assortment of mechanical stuff others don't carry, like rotary switches, transformers, cabinets, tools); 800-346-6873; http://www.mouser.com ****** hobbyist / mail order Hosfelt Electronics; 800-524-6464 Edlie Electronics; 800-647-4722 RSR / Electronix Express (cheap parts) 800-972-2225 ****** replacement parts Parts Express; 800-338-0531 MCM Electronics; 800-543-4330 ****** disregard previous post about Fordham, the 800 number belongs to someone else, and they are not listed with 800 info. BUT, if someone knows about them, let me know. They were an excellent source of test equipment (Fluke, Hitachi, Simpson, Tektronix, etc) at good prices. ****** hope this helps Tom Cloud ------------------------------ From: cloud@xxx.edu (tom cloud) Date: Tue, 6 Aug 1996 14:25:58 -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. > > [ snip ] darn, I left a couple of goodies out of previous: Berg (little gears, drive belts, rods, clutches, linkages, etc.) 516-596-1700 Kelvin (lots of neat stuff, kits for kid's robotics and auto projects, fiber optics, aeronautics, etc.) 800-535-8469 hope this helps (too) Tom Cloud ------------------------------ From: cloud@xxx.edu (tom cloud) Date: Tue, 6 Aug 1996 14:25:58 -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. > > [ snip ] darn, I left a couple of goodies out of previous: Berg (little gears, drive belts, rods, clutches, linkages, etc.) 516-596-1700 Kelvin (lots of neat stuff, kits for kid's robotics and auto projects, fiber optics, aeronautics, etc.) 800-535-8469 hope this helps (too) Tom Cloud ------------------------------ From: "QMGATE" Date: 6 Aug 1996 11:18:44 -0700 Subject: Unable to deliver Mail*Link¨ SMTP RE>general info. > [ SNIP ] > >While we're at it, don't forget HUM. > HUM ?? - ------------------ RFC822 Header Follows ------------------ Received: by qmgate.trw.com with SMTP;6 Aug 1996 11:05:13 -0700 Received: from coulomb.eng.ohio-state.edu by mailhub1.trw.com; Tue, 6 Aug 96 11:13:04 -0700 Received: by coulomb.eng.ohio-state.edu (940816.SGI.8.6.9/940406.SGI) id QAA22567; Tue, 6 Aug 1996 16:18:47 GMT Received: from hagar.ph.utexas.edu by coulomb.eng.ohio-state.edu via SMTP (940816.SGI.8.6.9/940406.SGI) for id MAA22562; Tue, 6 Aug 1996 12:18:40 -0400 Received: from slip-22-10.ots.utexas.edu by hagar.ph.utexas.edu (AIX 3.2/UCB 5.64/4.03) id AA41814; Tue, 6 Aug 1996 11:18:37 -0500 Date: Tue, 6 Aug 1996 11:18:37 -0500 Message-Id: <9608061618.AA41814@xxx.edu> X-Sender: cloud@xxx.edu X-Mailer: Windows Eudora Version 1.4.4 To: diy_efi@xxx.edu From: cloud@xxx.edu (tom cloud) Subject: Re: general info. Sender: owner-diy_efi@xxx.edu Precedence: bulk Reply-To: diy_efi@xxx.edu ------------------------------ From: "William A. Sarkozy" Date: Tue, 06 Aug 1996 21:25:28 -0700 Subject: Re: more musings on EFI controllers At 11:00 AM 8/6/96 -0500, you wrote: >The following is an excerpt of a missive I just sent to Michael >Kasimirsky and is a continuation of my rambling thoughts on EFI >control. > >> >> [ snip ] >> >TPS and couple it through a capacitor (differentiate it), process this Don't we INTEGRATE by coupling through a capacitor & DIFFERENTIATE by coupling through an inductor? Bill ------------------------------ End of DIY_EFI Digest V1 #223 ***************************** 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".