Bosch ECU Schematic for 1981 BMW 528i

michael glidewell glide at shore.net
Wed May 22 16:27:27 GMT 1996


Werner:  Thanks for taking the time for such a detailed answer.  My L-jet
has most of the same things you stated. I'm sure your right re. the
multiport - I think I mean sequential vs batch. Per Fuel Injection book,
forgot the author unfortunately, the L-jet is batch fired injectors and I
believe 3 at a time ( half the charge each cam revolution). If I had a
schematic I could better tell exactly what's going on.  It has a lambda
sensor and a new air flow meter. I had twiddled with the old flow meter so
much (spring adjust) that I needed to go back to a baseline. 

Hope you don't mind thast I copied the newsgroup with your response - it was
very good basic info.






At 11:51 AM 5/19/96 -0600, you wrote:
>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 at shore.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 at shore.net
KE1CP     BMW 528i      BMWCCA 		http://www.shore.net/~glide/




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