DIY_EFI Digest Thursday, 8 August 1996 Volume 01 : Number 224 In this issue: Re: more musings on EFI controllers Contact Re: Contact Manufacturer of a small EFI system... Re: more musings on EFI controllers Re: more musings on EFI controllers Re[2]: more musings on EFI controllers Re: more musings on EFI controllers 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: cloud@xxx.edu (tom cloud) Date: Wed, 7 Aug 1996 07:45:39 -0500 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 > > No, Ignoring inductors (for practical purposes, they are too large and too expensive, so most circuits just use R-C combos) a circuit with R connected between the source and load and the C connected in shunt across the load is called either a low-pass filter or an integrator -- depending on what you're trying to do. ----- R ------- IN | OUT C lo-pass / integrator | --------------- A circuit with C connected between the source and the load and the R shunted across the output is called either a high-pass filter or a differentiator -- depending on what you're trying to do. ----- C ------- IN | OUT R hi-pass / differentiator | --------------- If the integrator were perfect, a square wave input would yield a triangular wave output -- but it isn't and it doesn't. If the differentiator were perfect, a square wave input would yield an infinitely large pulse with an infinitely short width at each transition, in the direction of the transition -- but it isn't and it doesn't. With a square wave input, the simple R-C integrator yields a sawtooth output while the R-C diff. gives a pulse no greater than the applied voltage and a trailing decay (time constant). thanks, Tom Cloud ------------------------------ From: Jonathan Lloyd Date: Tue, 6 Aug 1996 18:36:38 +0100 Subject: Contact Has anyone managed to write to Mr Kirk Arwood? He has a page on the EFI web and says willing to talk about Ford EEC. I've posted several times and even with a deliberately wrong email address and still got no "failed mail" message back. - -- Jonathan Lloyd ------------------------------ From: "Edward C. Hernandez" Date: Wed, 07 Aug 1996 11:21:37 -0400 Subject: Re: Contact Jonathan Lloyd wrote: > > Has anyone managed to write to Mr Kirk Arwood? He has a page on the >EFI > web and says willing to talk about Ford EEC. I've posted several >times > and even with a deliberately wrong email address and still got no > "failed mail" message back. > -- > Jonathan Lloyd What email address is he listed under? - -- Ed Hernandez Ford Motor Company ehernan3@xxx.com ------------------------------ From: "David W. Taylor" Date: Wed, 07 Aug 1996 09:57:20 -0700 Subject: Manufacturer of a small EFI system... Does any body have exxperience with an outfit called Simple Digital Systems?? They have a web-site (http://www.sdsefi.com/) and they make some interesting claims,,, Their system could work well in my application (not to mention saving me a LOT of work) since it supposedly supports positive manifold pressure . Any comments?? - -- David Taylor dwtaylor@xxx. My opinions are mine ,, and nobody elses. ------------------------------ From: "Paul E. Campbell" Date: Wed, 7 Aug 1996 14:18:20 -0400 (EDT) Subject: Re: more musings on EFI controllers > 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". Not anymore. It takes a while to get used to some of the "tricks" that one does with digital circuits. Also, you can "twiddle" digital just as easily via computer. I always use battery backed SRAM's or EEPROM's in all my projects because it takes seconds to reprogram them. Since Lattice came out with their ISP stuff, I can just plug in a $20 chip and infinitely reprogram it using a PC and $100 for the starter's development package. In short, digital stuff is now just as easy to implement and just as easy to twiddle. Other than if you've got a 4 op-amp circuit, I don't think analog is all that much cheaper, either. However, the "way to do things" is not necessarily obvious. All-hardware PLL's, tricks with counters, and such are not necessarily obvious at first. If you can't handle that sort of thing, you'll probably go the route that all the regular manufacturers do; do it 99% in software. This costs more than hardware assisted software or all hardware unless your application is trivial enough to run on a PIC microcontroller or the complexity is pretty steep. > 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. Okay..assuming you can get a throttle body that works, the next issue is which sensors to use and such. Fuel injectors will cost you say $30 (using a J.C. Whitney catalog and rounding up a little). The little driver chip is around $5-$10; just a high current driver transistor with some extra smarts. As for the digital/analog end of controlling it, for analog, you'd use a ramp generator and a comparator. In digital, you'd use a countdown clock with a programmable start point. Programming the "curves" can be as simple as using a ROM or a GAL. Either way, this is also low cost. The temperature sensors are thermistors. The TPS is just a potentiometer. Now, here the TPS might be a bigger problem. Unless you switched the TPS for an optical encoder of some sort, you're going to have to deal some sort of ADC. Analog just uses the potentiometer directly. Course analog circuitry has to deal with the nonlinearity problem, too. Same is true with the thermistor. Recommended route here since neither of these are tremendously high speed is a slope detector ADC or something else equally cheap. Temperature sensors are around $5. TPS sensors are $5 and usually come with the throttle body. I could scrape a system identical to the Holley together for less than $200, excluding the throttle body itself. I have no idea who makes custom throttle bodies or where to get one, so I'd head to the local junk yard. Now on the "processing" end, practically everything in your "simple" system is a matter of programming the fuel pulse map. The easiest way to do this is to simply generate the fuel map in a ROM and use the ROM for your pulse width mapping. There is no "processor" as such. EPROMs are as cheap as the op-amp circuit and they will trivially handle nonlinearities of any conceivable sort. So the simplest solution on the electronics end of things is a voltage regulator, an EEPROM, a 2 channel ADC, a buffer (for the ADC outputs), a programmable count down timer, a clock, an injector driver, and some glue logic. Although the EEPROM may be separate, the buffer, clock, counter/timer, and glue logic could probably be fit into a GAL or other programmable logic chip. How's that for simple? > 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. Ahh! You got me there. I've still got a reprogramming step. But a computer in your lap isn't really that bad. Everybody around here is an expert at balancing a beer can in one hand, shifting with the other, and steering with their knees. You'd have to put down the beer can and fool with the computer. On the other hand, you could route the serial cable back into the cab trivially. > 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.) It doesn't become exponentially more complex. Once you've gotten to the level that you're going to have to use a DSP instead of the trivial stuff you and I mentioned, then there's no inherent added complexity to the hardware end. Simply add more sensors and/or actuators. On the software side, things can get as bad as you want them to. In what I've learned so far, it appears that if you want to do anything very exotic and still be cost effective, you might as well give in to the idea that you HAVE to have a DSP, not an 803x, 805x, 68xx, 80xx, 80x86, or 68xxx microcontroller. Analog Devices makes it a trivial choice with their ADSP-21xx family that has a $100 starter's kit and $15 processors at the bottom end that are hardly "bottom end". I'm sure TI, Acorn, and others will follow suit. Motorola will keep catering to the high end of course. > 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. Yeah, get a carburator. Screw fuel economy. Just run rich. My objective is to upgrade my trail machine (Bronco with 36" swampers). It's a carburated straight 6. No such thing as "aftermarket EFI" unless I buy a funky intake manifold that bolts to 4 barrel carbs and Holley's 4 barrel carb EFI replacement unit or move up to a V8. So my choice is going to be limited to whose throttle body will fit on the carburator's inlet and can I afford 6 separate fuel injectors unless I try to get one of those GM single injector things working. ------------------------------ From: Robert Van Zant Date: Wed, 7 Aug 1996 17:37:10 -0500 (CDT) Subject: Re: more musings on EFI controllers > So the simplest solution on the electronics end of things is a voltage > regulator, an EEPROM, a 2 channel ADC, a buffer (for the ADC > outputs), a programmable count down timer, a clock, an injector driver, > and some glue logic. Although the EEPROM may be separate, the buffer, > clock, counter/timer, and glue logic could probably be fit into a GAL > or other programmable logic chip. How's that for simple? Sounds good, but I'm still looking for the hole to plug my one must-have item into. Limp Home Mode. For my particular application, LHM is crucial to the point that I've been dreaming up digital-over- analog EFI's, at least that's the best term I can give it, but the concept should be obvious. Before I wander too far here, has any work been done along these lines? bob ------------------------------ From: dzorde@xxx.au Date: Thu, 08 Aug 96 08:24:17 Subject: Re[2]: more musings on EFI controllers If its so cheap, forget about LHM. Just build a second unit and carry it in the car for emergency situations. Dan dzorde@xxx.au ______________________________ Reply Separator _________________________________ Subject: Re: more musings on EFI controllers Author: diy_efi@xxx.edu at INTERNET Date: 8/8/96 8:07 AM > So the simplest solution on the electronics end of things is a voltage > regulator, an EEPROM, a 2 channel ADC, a buffer (for the ADC > outputs), a programmable count down timer, a clock, an injector driver, > and some glue logic. Although the EEPROM may be separate, the buffer, > clock, counter/timer, and glue logic could probably be fit into a GAL > or other programmable logic chip. How's that for simple? Sounds good, but I'm still looking for the hole to plug my one must-have item into. Limp Home Mode. For my particular application, LHM is crucial to the point that I've been dreaming up digital-over- analog EFI's, at least that's the best term I can give it, but the concept should be obvious. Before I wander too far here, has any work been done along these lines? bob ------------------------------ From: Alexander.M.Lichstein@xxx. Lichstein) Date: 07 Aug 96 21:42:07 EDT Subject: Re: more musings on EFI controllers I was thinking tha the simplest might be one of Signetics' 8x751 (24-pin DIP) with a frequency based MAF... Could be real cheap, and super tiny (4/5 skinny dip chips... maybe 80 pins total) ------------------------------ From: Ryan Minnig Date: Wed, 07 Aug 1996 21:58:35 -0500 Subject: Re: more musings on EFI controllers Robert Van Zant wrote: > > > So the simplest solution on the electronics end of things is a voltage > > regulator, an EEPROM, a 2 channel ADC, a buffer (for the ADC > > outputs), a programmable count down timer, a clock, an injector driver, <-- > > and some glue logic. Although the EEPROM may be separate, the buffer, \ > > clock, counter/timer, and glue logic could probably be fit into a GAL \ > > or other programmable logic chip. How's that for simple? | > | > Sounds good, but I'm still looking for the hole to plug my one | > must-have item into. Limp Home Mode. For my particular application, | > LHM is crucial to the point that I've been dreaming up digital-over- | > analog EFI's, at least that's the best term I can give it, but the | > concept should be obvious. Before I wander too far here, has any | > work been done along these lines? | > | > bob | | yeah, digital is the only way to go_____________________________________________| that is if you know what you are doing. ANYTHING that can be controlled, can do with digital. Analog is too touchy and needs TLC, give me digital, on, off and ADC. ------------------------------ End of DIY_EFI Digest V1 #224 ***************************** 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".