DIY_EFI Digest V5 #215

[Bill Shaw]

Hi Toby,  Welcome to the list.

Interesting project,  I'm working on something sort-of similar,  I'm replacing the
carb on my Fiat Spider first with a L-Jet to get the FI working, and then with a
replacement ECU I'm working on.  The replacement will accept the L-Jet's wiring
harness and use as many of the Bosch FI components as possible.

Having the parts from a donor helps a lot,  but  I think you'll have better luck
using an ECU from an engine that's more like yours.  If you're bent on using a
L-Jet  maybe a Fiat X-19 or some other small displacement 4 banger's ECU.  One of
the L-Jet's main drawbacks is the fact that it's an analog system and difficult to
modify,  which is why I'm planing on replacing mine before it's even installed. I'm
considering both the GM '749 and the EFI332,  the jury's still out.

And yes,  the air flow meter IS a big restriction,  which is another reason I'm
switching from the L-Jet to a MAP system.

Info on hacking the L-Jet can be found at:
http://www.students.tut.fi/%7ek124775/Injection.html

and info on the Fiat L-Jet :
http://www.geocities.com/MotorCity/Downs/5479/index.html


Bill
'94 Z28
'78 Fiat 124 Spider
http://www.connix.com/~bshaw/fiatefi.html

Toby wrote:

>
>
> Date: Tue, 13 Jun 2000 00:06:19 +0100
> From: "TVS" <TKMVS at clara.net>
> Subject: New to the list...
>
>     New to the list and could do with some advice regarding a EFI project!
>   I'm in the process of fitting, and modifying, a Bosch L Jetronic EFI to a
> MG Midget. I've got most of the bits including the ECU from Jaguar XJ6.
>
> In order to recalibrate the system I'm planing on reading the analogue
> output from the airflow metre with a laptop PC. The PC will then use a
> lookup table for airflow and rpm to find a new value which will be converted
> to analogue and sent to the ECU. I'm also going to fit a O2 sensor to ether
> help me build up a map or run in  closed loop with the PC. Can anybody tell
> me if I'm missing something important or got something fundamentally wrong?!
>
> I've got a few more plans/questions:
> 1) The O2 sensor has 4 wires (From a Bosch Motronic I think) 2 white going
> to a red plug... power? and a grey and black... out put with black ground?
>
> 2) How many times persecond should the PC be able to read the data/look up
> value/output data? I was considering about > 10Hz if possible.
>
> 3) What sort of resolution should the look-up-table/map have? Again I
> reckoned on 0.1V from the airflow metre (2.5V to 7.5V I think) and 50rpm.
> RPM range from 500-7500rpm so giving me around 7000 values in a 140/50
> table?
>
> 4) If I have sufficient processor time left mapped ignition would be nice...
> but I'm running out of ports on a laptop! (only one parallel port)
>
> 5) Oh, and perhaps most important... the ECU fires the injectors every 3rd
> ignition pulse as it from a 6 cylnd. engine. I need it to fire every 2nd.
> Can I modify the 'divide by 3' bit in the ECU or should I fit a sensor in
> the dizzy/on the crank to send 3 pulses per rev to it?
>
> 6) As the flap airflow metre looks like it's going to be quite a restriction
> on the flow... I was wondering if I could use a hot wire meter from a JE
> system. Are these self contained units? i.e. do I just supply it with power
> and it gives a voltage out like a flap meter? Or does the ECU from these
> systmes need to do some clever suff as well?!
>
> All advice other than 'Don't do it!' ( I have had that in the past ;-)
> gratefully received... Please excuse any spelling mistakes that make it past
> the checker...Dyslexic :-(   Many thanks, Toby.
>

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