L-jetronic

Fri Mar 15 15:26:31 GMT 1996

Hi Orin

The Bosch trottle position comes in both rotations.  The Weber trottle body 
used on the Renault is the opposite rotation of the Ford trottle body as 
you know.  The German cars (BMW) have the trottle body switches in the 
other directioin.  Even so I was not happy with the fit, and I prefer to 
sense the manifold pressure to go to enrichment.  The manifold pressure 
switch was used on Volvo's and on late Renaults using the LU-jetronic. But 
I still don't know a PN or where I can get one.  Nor do I know at what 
pressure the switch closes/opens.

The trottle body injector I use for the MGB (1800cc) is a E43-AC, 
~752cc/min @ 14.7lb/sqin.  It's about 4 times the injector flow of the port 
injectors for  the Renault i18 or Fuego.

The MGB engine and manifold can't take the lean running condition of the 
design value for the L-Jetronic.  It therefore idled poorly (too lean) and 
hesitated when accelerating.  I was able to overcome all of that by 
loosening the spring of the air flow meter by two notches, and by 
increasing the fuel pressure to 17 lb/squin.  The key for good idle and 
operation is to run at the design mixture level the  engine and manifold.  
This means no lamda (O2) sensor.

Decreasing the spring force on the air meter decreases the maximum air 
measuring capability (runs lean at wide open trottle), so I also toyed with 
the calibration of the air meter.  Depending on the air meter you can 
increase the fuel flow by changing one of the reference resistor values in 
the air meter (thats the resistor that feeds the potentiometer).

The last and best way is to modify the computer to put out more fuel by a 
fixed percent across the whole range of operation.  This is a little more 
tricky and beyond my ability to describe here.  With any of the changes 
above, the car ran good and idled just fine cold or hot.

I never had any cold start problem with the system.  It starts easily with 
at -10F. You might check the cold start injector circuit, and be sure that 
the cold start injector is designed for the fuel pressure you are using.  
You need a low pressure injector.  You can get one from the old VW's that 
use trottle body injection.

I really like the Electromotive unit.  Did you program it, or are you using 
the program that comes with it.  

Werner

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Subject: Re: L-jetronic

Werner,
Did you ever find out what the flow specs. are for the Ford (Bosch) 
injectors are???  I remember you said that you were having trouble with the 
system running lean on the "B"..I had the same problem when I tried your 
approach and never could get the thing to run as I would like.  I also 
never overcame the cold start problems..You know, on very cold days it 
would idle very rough...Warm days ok, but cold days really bad.  I have 
switched over to the Electromotive TEC II and it runs fine, although a 
little lean, but the system is very expensive and defeated the real 
purpose...A cheap replacement for the SU's or Zenith carbs...Let me know 
how you're making out ...

Orin

Hi Werner,
I also had a hard time fitting a switch to the Ford throttle body and what 
I finally used were 2 micro switches on a bracket that I mounted where the 
idle air motor had been mounted.  I never did like this approach.  I looked 
into using the Bosch switch but as you know it's rotation is backwards and 
I never really came up with a good solution.  The vacuum switch sounds like 
a good alternative.

You never gave me the injector part number.  You said you thought it was 
green color coded but when I talked to you, you couldn't remember.  If you 
have time, please look it up and send it to me.  If you know it's flow 
rate, please let me know that also.

I also upped the fuel pressure to 17 or 18 PSIG and it did help a lot.

You didn't say how you had overcomed the poor idle when cold problem.  What 
have you done there??

Orin