DIY_EFI Digest Wednesday, 9 October 1996 Volume 01 : Number 306 In this issue: RE: Using PC HW (& Ignition timing reference points) Re: FW: DIY Traction Control? Re: Ignition timing ref points Re[2]: FW: DIY Traction Control? Re: Ignition timing ref points Re: Ignition timing ref points Re: Re[2]: FW: DIY Traction Control? re: Volume of fuel injected Forwarded: Re: Ignition timing reference points re: ignition reference Re: Ignition timing ref points RE: Using PC HW (& Ignition timing reference points) Re: Boost retard Re: Ignition timing ref points Re: PC Hardware Re: Using pc parts RE: drive-by-wire 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: Tue, 8 Oct 1996 17:48:38 -0500 Subject: RE: Using PC HW (& Ignition timing reference points) >On Tue, 8 Oct 1996, tom cloud wrote: > > > ..[Mucho good stuff deleted]... >> >> Now, understand, I really haven't thought about perzactly how to do all >> these things. Just wondering if anyone else has. It is my experience >> that being too much the purist (i.e. a hacker / fanatic trying to make >> the confuser doo it all) puts you way up on the diminishing returns curve, >> when the most expeditious (isn't that a new Ford product?) approach would >> seem to be to use any and all tricks to get what we want. [Now, if what >> you want is to play wid da cornfuser, so be it. As I've said before, I >> wanna D-R-I-V-E !] > > Well put! I have seen both extrems of design in IEEE hardware contests >(one design was *completely* analog - to reprogram, change resistors), & >I think that there is a lot to be sair for a hybrid design. It is >amazing what one can do with a R & a C & a CMOS gate! > > Thor Johnson well, to continue my tirade (feel like a preacher that's just gotten a few strong "amens"): clearly, if you've got lots of moola and major investment in hardware, you'd have a serious development system, flow bench, dyno, etc. but for us 'regular' folks ... a simple R-C filter saves lots of code -- and one can still add software filter routine. A PC is a magnificent and inexpensive (I guess I'm comparing to what an Intel MDS used to cost, not counting the PL-1 software, etc) development bed. You can buy cheep A/D - D/A cards, mock up the hardware, play wid it, build a few peripheral drivers and test 'em (I'm talking the presettable counters for injector and ignition timing, for example). Seems to me you could easily have the ignition timing be totally separate from the cpu exzept for the I/O that loads the counters (they would be driven by a clock that would either generate a fixed rate or a rate determined by rpm (a'la PLL)). If the clock were a multiple of rpm, then the number loaded into the counter would directly correspond to some advance angle. If the period were fixed, the advance would be a function of both the number and the rpm. The injectors could be done the same way, except the clock would be fixed, as the number loaded should directly correspond to a known amount of fuel per pulse. I could ramble for hours about this. What I'm searching for is the 'best' approach. Doing it all cpu may be it?? I just know from personal experience that noise reduction is a whole lot easier using R-C or R-L than digital -- you're always gonna have aliasing probs, esp with varying frequencies (e.g. rpm). Clearly, your hardware can cause serious limitations if it's designed without forethought. In which case all cpu wudda been bedda. I know that if this were assigned to me as a design project, I'd probably do it all cpu (except for the obvious transducers, etc) and then maybe back up and design some peripheral circuits to simplify the design. But, since it's a home project, I guess I think like the scrounge that I am! Tom Cloud ------------------------------ From: William Boulton Date: Wed, 9 Oct 1996 08:59:28 +1000 (EST) Subject: Re: FW: DIY Traction Control? On Tue, 8 Oct 1996 dzorde@xxx.au wrote: > > I know dropping random cylinders is the way used to limit RPM and > regain traction, etc. But I dread everytime I hit the rev limiter in > the Chev, it feels like someone is trying to tear the engine out from > under the bonnet. And there is a similar feeling in the newer sports > cars (ie. relatively powerful cars). Is this normal ?? > > Dan dzorde@xxx.au > > > ______________________________ Reply Separator _________________________________ > Subject: FW: DIY Traction Control? > Author: diy_efi@xxx.edu at INTERNET > Date: 10/7/96 8:06 PM > > > Fully, completely and utterly seconded! All the comments bellow. > > 'cos somdays..... you just got to let the tail end hang out! > > Mark > > ---------- > From: MaxBoost@xxx.com] > Sent: Saturday, October 05, 1996 7:51 AM > To: diy_efi@xxx.edu > Subject: DIY Traction Control? > > How about a DIY traction control system? > > Relatively simple comparison of wheel speeds (most cars have abs these days, > so parts are readily avail). Wire into the injector ground circuit back to > the ecm and drop cylinders as needed. Use a pic processor and some drivers > to interupt the ground circuit. > > Also need an on off switch on the dash as well as a pot to adjust the > percentage of slip allowed. (got to have the switch so you can turn it off > and roast the tires :) > > Max. > > > Dan I don't think you should have to tolerate destruction of engine mounts just to have a rev limiter, after all, old L-Jetronics could do it without even the tinest shudder. It sounds to me as if no "soft" cut is activated before the full hard cut. Can that be enabled on your system? BTW what system are you using? As for "random" cylinder cuts; there are plenty of other ways of doing it with almost no side effects. Bill Boulton ------------------------------ From: Todd King Date: Tue, 08 Oct 96 16:27:00 PDT Subject: Re: Ignition timing ref points <<< From: Kalle Pihlajasaari Date: Tue, 8 Oct 1996 12:39:54 +0200 (sat) Subject: Ignition timing reference points ... I was thinking of adding a 256 or 360 slot optical interrupter disk into my distributor to give double the that number of edges every rev of the dizzy (or the same resolution on the crank). Is one degree on the crank accurate enough for a totally digital one or two of design for a mapped ignition. Interrupter disks like this are >>> Well again, you can do alot with less firepower than this. Not to imply that this is the only or best way to do it, but for example the GM SFI system on the turbo Regals has a best resolution of only 6 edges per crank rev (3 rise and 3 fall); The Crankshaft Position Sensor (CPS) is just an interrupter wheel that has 3 slots that gives 3 rising (and falling) edges per 360 degrees of rotation. We accelerate the cr*p out of the poor little things (231" V-6; 600 hp and 600 ft lbs is pretty easy to get) and things seem to work pretty well without 1 degree resolution ability :-) A cam position sensor is used to reference no.1 cylinder, providing a "blip" every 720 deg. That's it. Consider the real resolution requirements carefully for your design! Just how fast does the crank actually accelerate (and thus throw off the timing accuracy) compared to the number of firing events per rev is a good problem to ponder... Best I ever came up with was that down in the 3 timing events per rev scale the crank accel was pretty negligible; 'Course I'd welcome some more precise input on this! Todd Todd_King@xxx.com ------------------------------ From: dzorde@xxx.au Date: Wed, 09 Oct 96 08:32:07 Subject: Re[2]: FW: DIY Traction Control? This is only cutting fuel to the cylinder at the moment, I haven't got the ignition side connected yet, so I don't know if it would also cuts spark (don't think so). Anyway I'm using the AEMS Wolf 3D unit (there you go Rob, a little plug for you if you are still on the list). There is no feature for setting a soft cut-out, but it may be in the algorithm (Rob send me a mail if you are still there). Apart from this minor hitch the system is very good. I now have it set just above where I change gears, so I just keep an eye on the tacho and change before I hit the limiter. Although, I went for a drive in a friends VR Commodore Wagon (GMH product for those not in AU or NZ), a '94 model, 3.8L V6. And when he hit the rev limiter, it was the same feeling. So obviously car manufacturers don't seem to worried about this. Dan dzorde@xxx.au ______________________________ Reply Separator _________________________________ Subject: Re: FW: DIY Traction Control? Author: diy_efi@xxx.edu at INTERNET Date: 10/9/96 8:10 AM I don't think you should have to tolerate destruction of engine mounts just to have a rev limiter, after all, old L-Jetronics could do it without even the tinest shudder. It sounds to me as if no "soft" cut is activated before the full hard cut. Can that be enabled on your system? BTW what system are you using? As for "random" cylinder cuts; there are plenty of other ways of doing it with almost no side effects. Bill Boulton ------------------------------ From: Kalle Pihlajasaari Date: Wed, 9 Oct 1996 02:56:28 +0200 (sat) Subject: Re: Ignition timing ref points Hi Todd, > <<< From: Kalle Pihlajasaari > Date: Tue, 8 Oct 1996 12:39:54 +0200 (sat) > Subject: Ignition timing reference points > ... > I was thinking of adding a 256 or 360 slot optical interrupter disk into > my distributor to give double the that number of edges every rev > of the dizzy (or the same resolution on the crank). Is one degree > on the crank accurate enough for a totally digital one or two of > design for a mapped ignition. Interrupter disks like this are >>> > > Well again, you can do alot with less firepower than this. Not to imply that > Best I ever came up with was that down in the 3 timing events per rev scale > the crank accel was pretty negligible; 'Course I'd welcome some more precise > input on this! Everything you say is probably spot on. I however like to overkill where possible to avoid problems later. As it is a one or two of design the thing does not have to be particularly 'consumer' priced. I want to do the timing with no interpolation so that the counter can be very dumb and just count pulses ant any RPM and then go blip. Cheers - -- Kalle Pihlajasaari kalle@xxx.za Interface Products Box 15775, Doornfontein, 2028, South Africa +27 (11) 402-7750 Fax: +27 (11) 402-7751 ------------------------------ From: "George M. Dailey" Date: Tue, 8 Oct 1996 20:28:13 -0500 (CDT) Subject: Re: Ignition timing ref points At 04:27 PM 10/8/96 PDT, you wrote: ...snip... > Well again, you can do alot with less firepower than this. Not to imply that > this is the only or best way to do it, but for example the GM SFI system on > the turbo Regals has a best resolution of only 6 edges per crank rev (3 rise > and 3 fall)... 'Course I'd welcome some more precise > input on this! > > Todd Todd_King@xxx.com My thoughts exactly, If GM can do it on millions of TPI's, MPI's, and forced induction EFI's, it simply must be adaquate. Is it just me, or does it seem this way to the rest of you also, that GM has the simplest hardware available. Smaller, simpler, ignition modules, ECMs with no "Power Modules" as some companies use, changable EPROMS, etc. etc. NO, I don't work for GM or get any type of kick back from them. I was just wondering. GMD ------------------------------ From: "Stuart Woolford" Date: Wed, 9 Oct 1996 14:59:48 +1100 Subject: Re: Re[2]: FW: DIY Traction Control? my toyota supa 3l turbo (ex-japan) speed limits hard at 180Km/h (US ones go a LOT faster.) I have enlarged turbo/exhaust/etc, so it is still making a LOT of power as 180 approaches. The speed cut is perfectly smooth, you just slow accelleration as you reach 180, and go no faster. no shudder, no fuss, etc. > This is only cutting fuel to the cylinder at the moment, I haven't got > the ignition side connected yet, so I don't know if it would also cuts > spark (don't think so). Anyway I'm using the AEMS Wolf 3D unit (there > you go Rob, a little plug for you if you are still on the list). > > There is no feature for setting a soft cut-out, but it may be in the > algorithm (Rob send me a mail if you are still there). Apart from > this minor hitch the system is very good. I now have it set just > above where I change gears, so I just keep an eye on the tacho and > change before I hit the limiter. > > Although, I went for a drive in a friends VR Commodore Wagon (GMH > product for those not in AU or NZ), a '94 model, 3.8L V6. And when he > hit the rev limiter, it was the same feeling. So obviously car > manufacturers don't seem to worried about this. > > > Dan dzorde@xxx.au > > > ______________________________ Reply Separator _________________________________ > Subject: Re: FW: DIY Traction Control? > Author: diy_efi@xxx.edu at INTERNET > Date: 10/9/96 8:10 AM > > > > > I don't think you should have to tolerate destruction of engine mounts > just to have a rev limiter, after all, old L-Jetronics could do it without > even the tinest shudder. > > It sounds to me as if no "soft" cut is activated before the full hard cut. > Can that be enabled on your system? BTW what system are you using? > > As for "random" cylinder cuts; there are plenty of other ways of doing it > with almost no side effects. > > Bill Boulton > > > > - ---------------------------------------------------------------------- Stuart Woolford, stuart@xxx.nz >>>>In VI Where Available<<<< - ---------------------------------------------------------------------- ------------------------------ From: RABBITT_Andrew@xxx.au Date: Wed, 9 Oct 1996 10:08:46 est Subject: re: Volume of fuel injected > why wouldn't you fire it 100 or 1000 times into a graduated cylinder > and divide the volume by that number?? This would be a way to determine your turn-on and turn-off delays. If you were to plot a graph of flow -v- pulse width, then the line would be offset by some pulse width which would represent your turn on/off delays. The slope would be your continuous flow rate. ------------------------------ From: RABBITT_Andrew@xxx.au Date: Wed, 9 Oct 1996 09:58:48 est Subject: Forwarded: Re: Ignition timing reference points nissan use a 360 tooth optical encoder mounted in the dizzy on some of their 6-cylinder models (not sure which ones though) which would give you 2degCA resolution. From: EAXMJHI@xxx.uk:smtp Date: ## 10/08/96 17:01 ## > From: Kalle Pihlajasaari > > I was thinking of adding a 256 or 360 slot optical interrupter disk into > my distributor to give double the that number of edges every rev > of the dizzy (or the same resolution on the crank). Is one degree > on the crank accurate enough for a totally digital one or two of > design for a mapped ignition. Interrupter disks like this are > available alone and have usually got an index mark at another > radius. I could then just replace the cam section with a nice > shaft without the centrifugal advance (will the rotor still point > close enough to the correct cap electrode if the rotor is not > advanced at all and the timing is ? > > Just a few thoughts. This is far more than enough for a digital system. Most systems these days use a 36 tooth wheel with one tooth missing to signify TDC. With the computer it is possible to get accurate enough timing form this. 360 teeth would provide so much information you would need a faster processor to keep up. Martin ------------------------------ From: jac@xxx.us Date: Tue, 8 Oct 96 18:41:59 PDT Subject: re: ignition reference My experience is that one is more likely to build a robust, high quality timing disk with six or eight accurately spaced notches or vanes than one with 360 or 256 notches and I do have access to numerically controlled equipment. It is far better to improve the quality of the inputs than to depend on many more, less accurate inputs. Quantity certainly does not imply quality in this instance. The most precise measurement you have available in a typical ignition system is the record of time in a 16 bit counter. If you divorce you mind from thinking in terms of degrees advance and instead consider ignition TIME before TDC or some other datum, ignition calculation is much simplified. The time advance bears a near inverse linear relationship to manifold pressure. It is the different rotational speeds that make calculation if the ignition position touchy. I time the interval between say 120 and 60 degrees BTDC. The complement of this number, less a calculated or lookup number based solely on MAP will yield a timer load value that will interrupt exactly when you need a spark. The processor dependent details of the timer dictate whether the number is counted up or down, but the principle remains the same. If you have two timers and an edge sensitive timer and interrupt available as in an 8051, this is really a snap to implement. First clear a counter register and set it to count while a signal is high. When the 120 BTDC vane hits it will begin to count cycles and stop counting and interrupt when the vane passes at 60 BTDC. At the interrupt indicating the vane has passed, start the second counter that counts down to a spark. This register has been previously loaded with a calculated value. While waiting for the timer to run out and interrupt for a spark, use the contents of the first timer to calculate the load value for the next cylinder. It is necessary to pick a clock speed that allows sufficient counts to register at the highest RPM so that there is reasonable time resolution available at the top RPM. A 12 Mhz 8052 works fine up to 8,000 or so. The flip side of this consideration is that at low speeds the time register may roll over. The roll overs at low speed necessitate some accommodation but fortunately there is lots of time available to figit around with the extra interrupts. I find that a 15:1 speed ratio can be easily accommodated and still have good resolution at the top end. As the top speed of the engine increases, the processor must be slowed. All of the calculations and interrupts are easily handled with a minor fraction of the 8052's time at the highest RPM. There is lots of time to calculate advance modifiers for everything from humidity to lunar phase and fuel strategy, but a fail safe, fall back value is easily and reliably produced from MAP. The system is easily modeled with a spread sheet. All of the values can be worked out and if you insist, a degrees advance curve can be displayed as you work. The lookup table for the assembler program or ROM can be produced directly from the spread sheet I use the Phillips 87C550 variant of the 8052 because they are available in all temperature ranges, have six or eight A/D channels, a variety of packages and 8052 development tools work well with them. The DIP package plugs in to a typical 8031 - 8052 socket. The startup code is not trivial, but it is best to spark at or after TDC while the engine is cranking anyway. This sketch certainly does not solve all of the details, the intent is to suggest that the timing calculation need not be tedious, require excessive processor power or be a mystery. Befor the rock throwing begins, let me point out that this scheme works well and has accumulated thousands of hours of service. - ------------------------------------- john carroll jac@xxx.us ------------------------------ From: Todd Knighton Date: Tue, 08 Oct 1996 19:52:53 +0000 Subject: Re: Ignition timing ref points Kalle Pihlajasaari wrote: > > I want to do the timing with no interpolation so that the counter > can be very dumb and just count pulses ant any RPM and then go blip. > Well, about the simplest system I've seen for that has to be the early Bosch Motronics. On a six cylinder, the use a 129 tooth flywheel that gives you 1.4 degree resolution. They just count to the proper tooth, then wait for the proper rising or falling edge to fire the thing. No counters wasted, very simple, no interpolation, no problems with crank angle acceleration because it always references the crank not a timer. The only problem is interrupt time. At high rpm the interrupt starts taking up a lot of time, but it will go to about 8500 rpm's or so with an old 8051 and a 6mhz oscillator, the same deal with a faster processor and upped oscillator could easily go to the 20,000 rpm range. Just my two cents, have fun. Todd Knighton Protomotive Engineering ------------------------------ From: pantera@xxx.com (David Doddek) Date: Tue, 8 Oct 1996 22:13:05 -0500 Subject: RE: Using PC HW (& Ignition timing reference points) Was written by somebody: >>BTW--I'd be glad to share my experiences/ideas offline until I get >>something going. Many of the DIY_EFI Motorola guys are working on real >>projects and I'm not going to interject my stupidity until I feel better >>about proving my thoughts with a running motor. Could be the wrong >>attitude, but then again...I'm just tinkering with very little time >>and even less money. >> Don't think ideas are just stupid because of a lack of experience. If that was the case, then technology would go nowhere. And a little time and even littler money was the way I started. >Time honored 'dumb' question: >"Why is the sky blue?" >answer: Clearly that's a two part question. ... "Why?" Well, we'd all >like to know that. And "Is the sky blue". Yes. And just for those that do not know, The blue color of the sky is the result of the light in the blue wave length is filtered and reflected by part of the particles that exhist in the upper atmosphere. The light we actually receive on earth is slightly deficient of blue. David J. Doddek |pantera@xxx.com Owner SGD Electronics & Development Engr for Caterpillar |h 309 685-7965 Formula SAE Team Sidewinder 94-95 |w 309 578-2931 89 T-bird SC, 69 Fairlane w/SGD EFI |fx 217 428-4686 74 Pantera w/Electromotive Tec-II Twin turbos and Nitros | Hey, If you are going to go fast, go REEEAAL FAST. | ------------------------------ From: pantera@xxx.com (David Doddek) Date: Tue, 8 Oct 1996 22:13:08 -0500 Subject: Re: Boost retard alain wrote: > >I would like to build a simple ign retard box similar to the ones by Jacobs >and many others, i have a >84 RX-7 GSL-SE this is the first year they put a 13B with fuel injection., i >will be adding a Vortech supercharger soon and i was thinking a using a MSD >with boost retard but hey this list is up to this task. >The rotary engine has a similar firing as a 4Cyl engine so don't be afraid >of it ! > >I would prefer to use a 68HC11, i have a proto board for this. > >I plan on locking the mechanical and vacuum advance and us a lookup table. > >The ign pulse would come from the magnetic pickup process it, then send it >to the amplifier and to the coil. > >Ultimately there would be a knock sensor just for safety if ever i go over >board with the timing or get a bad batch of gasoline, but the main input for >controlling the amount of retard would be vacuum/boost and RPM. > >If this is to complex maybe just have everything left alone and retard the >timing proportional to boost. > >I could build the board program EPROM's but where i lack the most is in the >software skills kneaded for this type of project any one interested give me >a buzz. The software is really not all that hard. Your mag pickup will have some number of pulses per revolution. Since you said it is like a 4 banger, it would be 2. This gives you an input of information about crank position every 180 degrees, which is where you need to fire. Now if you set the distributor to give these pulses 90 degrees before TDC or what it would be in the case of a rotary, you have a starting point for timing. Using an input capture, measure the time between two successive input pulse sets (actually this will be three pulses with one being at 0 time). Take the newest or latest time and subtract the ondest or first time. This will give an indication of the acceleration of deceleration rate of the crankshaft. Now take the newest time and add/subtract this delta time to predict what the next time period will be. You now have the time for the engine to turn 180 degrees. If you divide this time by 180, then you have the amount of time per degree. Follow closely here. Take 90 degrees and subtract off the desired timing ie 15 degrees. This will leave the amount of time to delay before turning the coil off. Multiply the time for 1 degree times the amount of degrees to delay and add this time to the time that the last distributor pulse was seen. Send this time to an output capture set to turn off. I will leave it up to you how to calculate the time to turn the coil on for dwell. See, timing is not all that hard. Hope I helped. David J. Doddek |pantera@xxx.com Owner SGD Electronics & Development Engr for Caterpillar |h 309 685-7965 Formula SAE Team Sidewinder 94-95 |w 309 578-2931 89 T-bird SC, 69 Fairlane w/SGD EFI |fx 217 428-4686 74 Pantera w/Electromotive Tec-II Twin turbos and Nitros | Hey, If you are going to go fast, go REEEAAL FAST. | ------------------------------ From: Jeffrey.Giberstein@xxx.EDU (Jeffrey Giberstein) Date: 08 Oct 96 23:48:17 EDT Subject: Re: Ignition timing ref points My buddies and I have built an EFI unit for a Honda CBR600. The stock engine takes its ignition timing pulses off of an 8-toothed gear with one tooth missing (so it's got 7 teeth) with a variable reluctance sensor reading it. We time our injection events off this wheel, and are now looking to do custom ignition off this wheel. If this wheel has enough resolution for Honda to do it's spark maps, will it have enough resolution for me? We do engine tracking with an SSI 67F687, so the engine angle interpolation functions while between teeth ought to be first rate, but I'm hearing all this stuff about 100-toothed wheels, etc. so you've got me worried. There's no concern about interrupt times because the SSI manages all that stuff - -- we just have to upload firing angles to the SSI and make sure that all that dwell time stuff is cool. Please let me know what you think before we put tons of time in on a system that won't work! Thanks, Jeff Giberstein ------------------------------ From: Stuart Baly Date: Wed, 9 Oct 96 15:10:12 EST Subject: Re: PC Hardware A few thoughts: >But if I was really heavy into pain, and I had back door access to a major >game house, I'd take a real close look at SEGA or PLAYSTATION or similar >wazoo >high end game box. Lot of potential there - if you can get the info >somewhere. In Japan, Sony have released a modified Playstation with PC link to allow owners to write their own programs. The Playstation has a 34MHz NEC RISC processor, 2M of RAM, and a super-duper graphics chipset (from SGI, if I remember rightly) - about 500MIPS total processing power. A 68332 might be better suited to engine control, but a Playstation would make a thumper of a glass panel. There is information on the Web, or at least information on how to buy the information. Another suggestion for a no-frills controller - a Gameboy. A 4.2MHz nearly-a-Z80 might not be fast enough for some, but it has a handy LCD screen, and it wouldn't be all that hard to add I/O and memory using the game cartridge port. Being brat-proof, it'd presumably be fairly durable. It's also dirt cheap. Check out http://fly.hiwaay.net/~jfrohwei/gameboy/home.html ========================================================= Stuart Baly (S.Baly@xxx.au) '71 Datrat 1600, '89 Kawasaki GPz900R, '81 Yamaha RD350LC ========================================================= ------------------------------ From: talltom Date: Tue, 8 Oct 1996 22:21:05 -0700 (PDT) Subject: Re: Using pc parts I for one would be inteested in the pc parts approach, primarily on account of entirely to much expierience with propietary junk. Yes, this means that if it costs more thats to damn bad. When my chip burns up at 7:30am on Saturday in Clovis New Mexico, I want to be back on the road within 30 min. after radio shack opens! Not only the much better parts supply situation, but the computing power and flexibility should be much greater. So you pc types, I'm all ears!(this comes from a guy that drives a cornbinder!) >>---------------------------------CUT-------------------------------------- - ----<< "a society that will trade a little freedom for a little order deserves neither" Thomas Jefferson Clinton doesn't want anything Hitler didn't have. What do you get with Bob Dole, Bill Clinton, and Dolly Parton in the same room? Two boobs and a country singer! Harry Browne for US president 96! Talltom ------------------------------ From: dave.williams@xxx.us (Dave Williams) Date: Tue, 08 Oct 1996 20:01:00 +0000 Subject: RE: drive-by-wire - -> BMW made (no successful) experiments somewhen in the seventies with - -> octagonal ceramic pistons. I don't know why they used that shape and - -> how they machined the rings. Ceramic was not far enough in those - -> times and the pistons cracked when temperature changed rapidly. ??? I haven't come across that one yet, but I'd imagine the flat-sided piston let them use spring loaded seals similar to those in a Wankel. It would neatly sidestep the problems of doing an elliptical bore. ====dave.williams@xxx.us========================DoD#978======= can you help me...help me get out of this place?...slow sedation... ain't my style, ain't my pace...giving me a number...NINE, SEVEN, EIGHT ==5.0 RX7 -> Tyrannosaurus RX! == SAE '82 == Denizens of Doom M/C '92== ------------------------------ End of DIY_EFI Digest V1 #306 ***************************** 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".