DIY_EFI Digest Sunday, 28 January 1996 Volume 01 : Number 024 In this issue: Re: efi555 Re: efi555 Re: efi555 Re: efi555 Re: efi555 See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- From: dn Date: Sat, 27 Jan 96 13:50:54 MDT Subject: Re: efi555 Peter Wales wrote: > one on a race car and know it works so ask questions when you have problems > and I will do my best to help > Peter: And so it begins. The questions, I mean. I think I have a pretty good handle on how this thing would work, but I have a few specific questions on the circuitry. From what I have read, the unit just uses pulses from the MAF to fire an injector with a fixed duty cycle (at least for now) every X pulses (essentially every so many litres of air). Essentially a fixed pulse width, variable frequency system. Later, a CPU could be added to modulate the injector pulse width to compensate for temperature, acceleration enrichment, etc. So far so good? Ok, now for the guts of the thing. Is the 555 run as a one shot, triggered by the MAF pulse, with duty cycle adjustable by the control pin? How do you determine the number of MAF pulses per injector firing? What kind of frequency range does the MAF put out? Since the system is essentially asynchronous with engine firings, how do you ensure that the engine does not just get a slug of fuel on one cylinder, then nothing on the next, etc. Do you fire the injector many small pulses per revolution, or what? As the engine speeds up, you would have more cylinder firings per second, and also more MAF pulses due to increased airflow with RPM. Do these need to by synchronized somehow, or does it not matter? Or do you use a 5 gallon bucket for an intake plenum to smooth it all out? Lastly, some questions on the MAF sensor you recommended. I am not familiar with a Starion, They may not sell the model under that name here in Canada. (Then again, I don't follow the new car lines much, I'm a 60's +70's vintage kinda guy). Some details on what other models, makes, and years used this MAF would be helpful in a junket to the local boneyard. Will this thing handle the required airflow for a V8 making 400+ HP? I'll try not to pester you too much with this, but it sounds almost too good to be true. I'll be hunting down parts over the next few weeks, and I'll post my results to the list if anyone's interested. Thanks in advance for any info. Regards dn - -- - ------------------------------------------------------------------------ Darrell A. Norquay Internet: dn@xxx.ca Datalog Technology Inc. Bang: calgary!debug!dlogtech!darrell Calgary, Alberta, Canada Voice: +1 (403) 243-2220 Fax: +1 (403) 243-2872 @ + < __/ "Ain't no substitute for clock speed or compression ratio" ----------------------------------------------------------------------- ------------------------------ From: "George M. Dailey" Date: Sat, 27 Jan 1996 20:48:02 -0600 Subject: Re: efi555 At 01:50 PM 1/27/96 MDT, Darrell A. Norquay wrote: >And so it begins. The questions, I mean. >I'll try not to pester you too much with this, but it sounds >almost too good to be true. I'll be hunting down parts over the >next few weeks, and I'll post my results to the list if anyone's >interested. Thanks in advance for any info. Darrell A. Norquay Darrel, before you start your holy pilgrimage for discrete electronics, let's kick one more idea around. Back in '87 or so, I built a 555 based FI control unit with only one variable resistor controlling the pulse width. The timer was configured in a monostable mode to fire the injector twice per revolution. On the bench, the electronics worked like a charm. I never got around to testing the electronics on an engine with actual injectors. I started reading about how the GM EFI systems worked and those OEM parts were starting to show up in the salvage yards in large volumes at low prices. I convinced myself that OEM was the way to go. I started having the same questions that are circulating around now about the 555. If I were still interested in building an EFI control unit from scratch. I would seriously consider the Basic Stamp microcontroller by Parallax. With 8 i/o's, you would have a lot more flexibility than the 555. Imagine: i/o 1 = injector driver i/o2 = rpm input (this could be a permissive to prevent that theoretical engine run away) 3 = MAP input 4 = MAF input 5 = you get the idea.... It's a lot easier to connect the Stamp to your PC and modify the program, than to fiddle with resisters, capacitors, and other discrete devices. I haven't used the stamp yet, but it seems ideal for this application. They are priced around $29 - $39 (I THINK). Check out their web page. One more thing, the Stamp might work best in the astable mode. I'm not sure if it would be fast enough for 'real time' reactions of less than 20 ms. But I could be wrong. Keep us posted and good luck. George M. Dailey gmd@xxx.com ------------------------------ From: pjwales@xxx.net (Peter Wales) Date: Sat, 27 Jan 1996 23:58:30 -0500 Subject: Re: efi555 At 01:50 PM 1/27/96 MDT, diy_efi@xxx.edu wrote: >And so it begins. The questions, I mean. I think I have a pretty >good handle on how this thing would work, but I have a few >specific questions on the circuitry. From what I have read, the >unit just uses pulses from the MAF to fire an injector with a >fixed duty cycle (at least for now) every X pulses (essentially >every so many litres of air). Essentially a fixed pulse width, >variable frequency system. Later, a CPU could be added to >modulate the injector pulse width to compensate for temperature, >acceleration enrichment, etc. So far so good? Correct > >Ok, now for the guts of the thing. Is the 555 run as a one shot, >triggered by the MAF pulse, with duty cycle adjustable by the >control pin? Yes > >How do you determine the number of MAF pulses per injector firing? >What kind of frequency range does the MAF put out? We used 12 air pulses per injection on a 2 injector 4 cylinder 330HP engine > >Since the system is essentially asynchronous with engine firings, >how do you ensure that the engine does not just get a slug of fuel >on one cylinder, then nothing on the next, etc. Snip Lots of injections per revolution will elad to problems at higher RPMs due to the approx 1.5 mS dead time on the injector. If you consider the system as a carburettor which has an uneven fuel flow, everything will fall into place. Yes there are cylinders which don't get their full fuel supply and others which get too much, but the variations are so small it seems not to bother the engine at all. For example, if in a full cycle of a V8 there are only 7 injections but the total fuel matches the total air requirement to maintain a correct A/F ratio, over a period of 8 cycles, all cylinders will have had the correct amount of air and fuel. However, if this is something which worries you, then arrange the number of air pulse to match the number of sparks. I repeat that this system was used in a race car to ge t330HP from an engine designed to give 200HP and it survived quite well. It won races and was never less than 2nd. >Lastly, some questions on the MAF sensor you recommended. I am >not familiar with a Starion, Dodge Conquest or any Mitsubishi Turbo car or even normally aspirated for all I know. Some details >on what other models, makes, and years used this MAF would be >helpful in a junket to the local boneyard. >Will this thing handle >the required airflow for a V8 making 400+ HP? > Yes, simply bypass the meter and measure a percentage of the air entering the engine to get the pulse rate you want. Ours went upto 4 KHz with the bypasses increased by 25% Peter Wales President Superchips Inc Chairman Superchips Ltd "Timing is everything" Superchips home page with all the answers http://www.superchips.com ------------------------------ From: arthurok@xxx.com (ARTHUR OKUN ) Date: Sat, 27 Jan 1996 20:03:13 -0800 Subject: Re: efi555 You wrote: > >At 01:50 PM 1/27/96 MDT, Darrell A. Norquay wrote: > >>And so it begins. The questions, I mean. >>I'll try not to pester you too much with this, but it sounds >>almost too good to be true. I'll be hunting down parts over the >>next few weeks, and I'll post my results to the list if anyone's >>interested. Thanks in advance for any info. > >Darrell A. Norquay > > > >Darrel, before you start your holy pilgrimage for discrete electronics, >let's kick one more idea around. Back in '87 or so, I built a 555 based FI >control unit with only one variable resistor controlling the pulse width. >The timer was configured in a monostable mode to fire the injector twice per >revolution. On the bench, the electronics worked like a charm. I never got >around to testing the electronics on an engine with actual injectors. I >started reading about how the GM EFI systems worked and those OEM parts were >starting to show up in the salvage yards in large volumes at low prices. I >convinced myself that OEM was the way to go. > >I started having the same questions that are circulating around now about >the 555. >If I were still interested in building an EFI control unit from scratch. I >would seriously consider the Basic Stamp microcontroller by Parallax. With >8 i/o's, you would have a lot more flexibility than the 555. Imagine: > >i/o 1 = injector driver >i/o2 = rpm input (this could be a permissive to prevent that theoretical >engine run away) > 3 = MAP input > 4 = MAF input > 5 = you get the idea.... > >It's a lot easier to connect the Stamp to your PC and modify the program, >than to fiddle with resisters, capacitors, and other discrete devices. I >haven't used the stamp yet, but it seems ideal for this application. They >are priced around $29 - $39 (I THINK). Check out their web page. One more >thing, the Stamp might work best in the astable mode. I'm not sure if it >would be fast enough for 'real time' reactions of less than 20 ms. But I >could be wrong. > >Keep us posted and good luck. > >George M. Dailey gmd@xxx.com > >im thinking of building one using a pic 16 which is the basis of the basic stamp since i already have a programmer for one ------------------------------ From: pjwales@xxx.net (Peter Wales) Date: Sun, 28 Jan 1996 00:04:34 -0500 Subject: Re: efi555 At 08:48 PM 1/27/96 -0600, diy_efi@xxx.edu wrote: >It's a lot easier to connect the Stamp to your PC and modify the program, >than to fiddle with resisters, capacitors, and other discrete devices. I have to disagree with you there! All you have is one resistor, one capacitor and a pot. Thats about as simple an injection system as you can get. Certainly simpler than using any micro, no matter how much work is already done for you. Not as sophisticated perhaps, but that is the idea, and we are proposing to put a cpu on the end of this system anyway, at some future date, but not to have any major control function. Peter Wales President Superchips Inc Chairman Superchips Ltd "Timing is everything" Superchips home page with all the answers http://www.superchips.com ------------------------------ End of DIY_EFI Digest V1 #24 **************************** 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".