DIY_EFI Digest Monday, 20 May 1996 Volume 01 : Number 145 In this issue: Re: Bosch ECU Schematic for 1981 BMW 528i Re: Bosch ECU Schematic for 1981 BMW 528i Reply to: KE-jetronic closed loop Reply to: re: Re: a/f ratio with LPG Reply to: Re: a/f ratio with LPG See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- From: WERNER_HAUSSMANN@xxx.com Date: Sun, 19 May 96 11:51:52 -0600 Subject: Re: Bosch ECU Schematic for 1981 BMW 528i Hi Michael I am a little confused. The L-Jetronic is a multi-port system usually. Maybe I have my terms mixed up. I am not at all familiar with BMW's in general, but here what I know about the L-Jetronic * It is analog (not digital) for the early '80's and a few late '70's. A few late versions were digital, but those are mostly the next generation of EFI from Bosch. I know nothing about them. This is realy nice for us analog guys that don't want to mess with burning in ROMs. * The L-Jetronic ECU, depending on options, has the following inputs - trottle position input in digital (switch) form, idle, part open, >2/3 open - Analog (potentiometer) altitude input - overboost cut out (by switch) - enrichment input (by switch, same as > 2/3 trottle open - Lambda sensor - Air flap meter (with temperature input) or air mass meter on very few. - coolent temperature input. - the spark coil is the only input for timing the injectors * In the system, but not part of the ECU - Cold start injector - Fuel Pump relay that only operates when there is a spark coil signal - Trottle bypass controlled electrically and by engine heat for extra trottle when cold running. * The output is control of low impedance injectors. They are batch fired (all fire at the same time) and they fire once for every revolution of the crank. In terms of modification, I think there are only a couple of options. You can upgrade to a later version with more features, ( go the lambda sensor if you don't have one) or you can tune it for more power or torque if it is running on the Oxygen sensor. But the gains are very small, because it already enriches the mixture at wide open trottle. Still you can enrich mixture a little. You can also increase the responsiveness by loosening the air meter spring by about two notches. This gives it a little better 'accelerator pump action' If you need a schematic of how the L-Jetronic is hooked up, let me know. I have one for a Fuego Turbo. They are all about the same. There are several very good books that describe the operation and general hook up. If anyone has a schematic, I sure would like to see it. Or maybe someone has reverse engineered the L-Jetronic and can share some of the knowledge. Let's hear from all those that have messed around with the L-Jetronic and see what they have to say. I am sure both opinions and facts are welcome. My experience is with an 1800cc engine, and MGB. And it works great but doesn't give more noticeable power. I think the L-Jetronic works well and is easy as an upgrade from carburettors, but to increase its performance beyond the designers intend, you should go for something like the Tech II with an air mass meter and some software to program it. Werner ______________________________ Reply Separator _________________________________ Subject: Re: Bosch ECU Schematic for 1981 BMW 528i Author: Non-HP-glide (glide@xxx.net) at HP-ColSprings,mimegw2 Date: 5/17/96 2:29 PM Werner: Being a EE I look to EFI electronics where I might be able to improve things without major cost impact. I wonder if it would be possible to turn the L-jet into a multiport injection system by firing each injector individually and possibly improve the city fuel consumption (its 12+ mpg). Or maybe I could bring out some of the parameters and adjust for max performance/ economy. Maybe I could repalce with a microprocessor and and do more calculations per second resulting in smoother idle/ economy or performance. I guess I can't leave things well enough alone also. - ---------------------------------------------- Michael Glidewell Boston, Massachusetts glide@xxx.net KE1CP BMW 528i BMWCCA http://www.shore.net/~glide/ ------------------------------ From: cmorris@xxx.com (Charles) Date: Sun, 19 May 1996 15:34:42 -0700 Subject: Re: Bosch ECU Schematic for 1981 BMW 528i Michael Glidewell wrote: >I wonder if it would be possible to turn the L-jet into a multiport >injection system by firing each injector individually and possibly improve>the city fuel consumption (its 12+ mpg). I think you mean "sequential" (vs. batch-fire). It is multiport. I'm not sure about your '81 2.8, but the late 70's 3.0 (i.e. 530i) had horrible gas mileage because the emission control system was a thermal reactor, not a catalyst. A thermoreactor requires about a 10-15% overrich mixture so that the exhaust is rich enough to burn. Also the timing must be retarded to get a hot exhaust. These two factors guarantee lousy mileage... - -Charles ('81 745i) ------------------------------ From: RABBITT_Andrew@xxx.au Date: Mon, 20 May 1996 09:25:22 est Subject: Reply to: KE-jetronic closed loop According to the Bosch Automotive Handbook, the KE-Jetronic uses an 'electrohydraulic pressure actuator' which controls the system fuel pressure. The KE also has an ECU which controls this device from the outputs of various sensors, the O2 sensor being one of them. From: (James Weiler) james@xxx.ca:smtp Date: ## 05/17/96 16:02 ## Hello everyone. A recent discusion has prompted me to ask how an oxygen sensor feeds back on a mechanical injection system? Does it contol a fuel pump relay that alters the pressure? It makes sense how feedback works on an electronic system by altering the pulse width of the injectors. But there is no pulse width in a CIS system. Thanks to anyone who can educate me james@xxx.ca(james wieler) ------------------------------ From: RABBITT_Andrew@xxx.au Date: Mon, 20 May 1996 13:35:08 est Subject: Reply to: re: Re: a/f ratio with LPG SAE paper 930352 describes this (O2, H2, CO sensitivity) phenomenon and is written by two Ford engineers. The problem seems to be in the response of the sensor rather than its ability to measure O2 concentration at steady state conditions (my interpretation from a very brief read of it). It has a reference to a paper (#920289) which may be the paper you are refering to but I couldn't check since we've not got a copy. Hope this helps Andrew Rabbitt Orbital Engine Company From: SRavet@xxx.com:smtp Date: ## 05/17/96 09:53 ## ------------------------------ From: RABBITT_Andrew@xxx.au Date: Mon, 20 May 1996 13:40:22 est Subject: Reply to: Re: a/f ratio with LPG ULEV with CNG can't be really difficult since the methane content of the exhaust is not counted which is essentially all your UHC. How did you control NOx. Was it closed loop stoich. on a TWC? Did you use your CNG modified O2 sensor for feedback? From: (Seth Allen) n9540517@xxx.edu:smtp Date: ## 05/17/96 08:12 ## ------------------------------ End of DIY_EFI Digest V1 #145 ***************************** 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".