Reply to: KE-jetronic closed loop

[Steven Buchholz]

> 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 at brc.ubc.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.
> 
Although the response was generally correct, I wanted to make one clarifi-
cation.  The electro-hydraulic pressure actuator (or frequency valve on 
the older K-jet w/OXS systems) modulates the *control pressure* not the 
system fuel pressure.  The fuel distributor has a pressure regulator which 
supplies the bottom of the fuel distributor's diaphragm.  The control 
pressure opposes the system pressure in such a way as when the control 
pressure is decreased the amount of fuel delivered at a certain airflow 
sensor position will increase.  It turns out that the pressure at the 
injectors is constant.

The control pressure is also modulated for cold-running enrichment ...

Bosch publishes small parperback books on each of the systems it has pro-
duced ... I find them quite useful.  There is another book by Probst that
has a lot of good info on how the FI systems work.  

I don't have ISBNs here, but if someone is interested I am willing to 
look them up and post them.  

Steve Buchholz
s_buchho at kla.com
San Jose, CA (USA)