[Gmecm] Re: [Diy_efi] Jetronic

Tue Feb 28 05:52:59 UTC 2006

Yeah D-Jet is pretty fascinating. I had one of those systems from the  
factory on my 1977 Jaguar XJ12. It was a piece of engineering to be  
sure. The pump-shot TPS was one of the cleverest designs ever. It  
even had a little reed switch on the wiper arm so that it would only  
produce pump shots on throttle opening.

The biggest shortcomings were the lack of any feedback loop and the  
very coarse fuel mapping. The system was designed to run rich pretty  
much all the time with an air pump to keep the catalytic converters  
fired up. At idle the ignition timing had to be retarded 4 degrees  
AFTER top dead center, supposedly to keep the air flow (and therefore  
BPW) up to a level that was controllable by the computer and would  
produce acceptable emissions. The system was certainly a marvel in  
it's day, but things have improved a lot since then.

FWIW, I have 1983 Toyota truck that is now running the Nippondenso- 
licensed version of Bosch L-Jet. It's analog like D-Jet but has O2  
sensor feedback and it works absolutely brilliantly. German  
engineering + Japanese assembly = EFI bliss.

So I am convinced that analog fuel injection can work, and work well,  
but D-Jet wasn't quite it in my expereince.

-Gary

On Feb 27, 2006, at 8:48 PM, David Allen wrote:

>   Anyone remember the old D-Jet system?  It was the grandfather of our
> modern speed-density systems.  Had a fascinating magnetic / mechanical
> pressure transducer for measuring density; and sets (yes- setS) of  
> breaker
> points (early version) for the speed sensor! Electronic ignition,  
> but points
> for the EFI... Leave it to Bosch!    The throttle switch would  
> pulse on and
> off as the throttle moved open and create extra injector pulses for
> pumpshot.   The ECU was fully analog.  There ARE people who re-map  
> these
> units by changing resistors, etc.
>   I saw one of these on an older Mercedes V8. It was an early 70's  
> model
> IIRC.   I'm not the type to scrap a unique system like this if  
> there is any
> hope.  I would try to repair if feasible, but if not, it would sure be
> tempting to install a Delco 1226869 (or similar).  The distributor  
> had a VR
> pickup directly compatible with an HEI ignition module. You could  
> hull out
> the transducer, and there might be enough room inside to "hide" a  
> modern
> Delco MAP sensor.  The injector impenence would be an unknown, as  
> would be
> mounting the TPS.  After taking the time to develop a good  
> calibration;
> you'd have quite a system.  It would appear to be original, but  
> with the
> advantage of fully mapped fuel and ignition.
>   Fun to think about anyway!
> David
>
>
>
> ----- Original Message -----
> From: "Bill Washington" <bill.washington at nec.com.au>
> To: <diy_efi at diy-efi.org>
> Sent: Monday, February 27, 2006 5:11 PM
> Subject: [Diy_efi] Jetronic
>
>
>> One minor addition to Torbj?rn's information:
>> In the analog systems from mid 80s on there were also LE2 and LU2  
>> - (LE
> refers
>> to European spec and LU refers to USA spec) and LE2 and LU2 both have
> closed
>> loop lambda control. The Bosch part number on my LE2 is 0 280 000  
>> 344.
>> For years I have been trying to obtain a circuit of the Pinted  
>> circuit
> board in
>> the ECU to repair, and modify a faulty one I have, but these  
>> schematic
> appear to
>> have been printed on a very rare material called 'unobtanium'.
>> These later LE2 Jetronic ECUs use a single printed circuit board with
> leaded
>> components on one side (including a couple of hybrid modules) and  
>> very
> dense
>> surface mount components on the other and a 25 pin connector to  
>> the wiring
> loom.
>> I have found one early LE Jetronic ECU schematic for a BMW on the web
>> (0 280 001 310) but it is significantly different from my ECU, and is
> therefore
>> of little assistance....
>>
>> Regards
>> Bill
>>
>>>
>>> Subject:
>>> Re: [Diy_efi] Motronic hacking...
>>> From:
>>> Torbj?rn Forsman <torbjorn.forsman at gengas.nu>
>>> Date:
>>> Sun, 26 Feb 2006 23:55:41 +0100
>>> To:
>>> diy_efi at diy-efi.org
>>>
>>> To:
>>> diy_efi at diy-efi.org
>>>
>>>
>>> It is not very precise to call an injection system "Jetronic".  
>>> This is a
>>> brand name that Bosch uses for all systems that only deal with fuel
>>> injection, not ignition.
>>>
>>> Analog systems are D-jetronic (manufactured from about 1969 to  
>>> 1974),
>>> L-jetronic (1974 to mid-80's), most LE-jetronic (1981 to early  
>>> 90's) and
>>> all LU-jetronic (the same as LE but with closed-loop lambda  
>>> control).
>>>
>>> Digital systems are LH-jetronic (from early 80's to mid 90's,  
>>> most of
>>> them but not all have closed-loop, LH 2.4 and later have adaptive  
>>> lambda
>>> correction and some diagnostic features), LE3-jetronic (the last
>>> non-closed loop system, the ecu is integrated in the air flow  
>>> meter) and
>>> Mono-jetronic (a TBI system, only used with closed-loop and adaptive
>>> lambda correction).
>>>
>>> The K-jetronic, an all-mechanical system should also be  
>>> mentioned. It
>>> may have a closed-loop add-on and is then called K-lambda- 
>>> jetronic. A
>>> similar but newer variant is called KE-jetronic, it exists both  
>>> without
>>> and with closed-loop. Most KE systems are analog but the KE3 is  
>>> digital
>>> (and then uses an ecu that is very similar to the Mono-jetronic  
>>> ecu).
>>>
>>> Most digital Jetronic systems use an Intel MCS-51 CPU. Either a  
>>> standard
>>>  8051/8031 with a separate A/D converter, or an 80535/80C535. In  
>>> some
>>> cases, mask programmed 8051's may be found but they more commonly  
>>> have
>>> an external eprom. Anyway, all PCBs are designed for external  
>>> eprom so
>>> it is a simple task to solder an eprom socket and the address  
>>> latch in
>>> place, and change the jumper for the CPU's EA signal.
>>> The eprom may be socketed or soldered in place depending on  
>>> requirements
>>> from each car manufacturer.
>>>
>>> Some older LH-jetronic (in particular, LH 2.2) use instead an  
>>> 8049 CPU.
>>> The very earliest LH systems might have an RCA 1802, like the early
>>> Motronic systems.
>>>
>>> The simplest way to identify a Jetronic system is to look at the  
>>> Bosch
>>> part number of the ECU.
>>> I.e. 0 280 000 561. The first six digits tell just that it is a  
>>> Jetronic
>>> CPU. The seventh digit indicates the number of cylinders, 0 means 4
>>> cylinders, 1 means 6 cylinders and 2 means 8 cylinders. The  
>>> eighth digit
>>> indicates the variant. 0 means D-jetronic, 1 and 2 means L- 
>>> jetronic, 3
>>> means LE- and LU-jetronic, 5 and 9 means LH-jetronic, 7 means
>>> Mono-jetronic and 8 means K-lambda and KE. The two last digits are a
>>> leap number.
>>>
>>> So, when asking about a "Jetronic" system, be sure to include the
>>> variant of the system. I.e. mention that you have an LH 2.4 with
>>> closed-loop.
>>>
>>> Best regards
>>>
>>> Torbj?rn Forsman
>>>
>>
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