Bosch LE/2 Jetronic (info and problems)

[Christian Hack]

> 
> Date: Mon, 15 May 2000 00:19:27 +1200
> From: Steve Spiers <s.spiers at xtra.co.nz>
> Subject: Bosch LE/2 Jetronic (info and problems)
> 
> I have one major problem with the system at the moment. I get extreamly bad fuel
> economy, like 10MPG! I need to solve this first, anyone know what could be causing
> this? The engine runs fine, the top end seems a little soft (but so do most std
> turbocharged cars).
> 
> How dependent is the ECU on coolant temperature? I suspect that the thermostate is
> either stuck open or has been removed. The temp gague will only just get off the
> absolute bottom of the scale. Could this be the sole problem causing the ecu to
> run in "cold start" mode?
> 
> Thanks for any help in advance
> 
> Steve
> 

Well I can't say for sure about that ECU, but pretty much any ECU worth it's salt
will have a coolant temperature sensor to allow for cold starting etc. This is
how it emulates a choke on a carbed engine. Rather than choke the air, it adds
more fuel for a rich mixture.

If your engine is running too cold, it is probably running permanently in cold start
mode which would probably explain your high fuel consumption. Again I have
no idea on what your consumption should be but remember turbo cars can
be quite thirsty when driven "enthusiastically" (I know this first hand). I don't
even know what 10MPG works out to in l/100km. I'm a metric person.

One thing to consider though - are you sure the guage isn't buggered? If you
have access to a decent temperature sensor (multimeter with a K type thermo
couple), you could try measuring the engine temperature to make sure it is
running the right temps. From what I hear 80-100C is about the right range.

Some guys remove the thermostat or replace it with a lower temp one on turbo
cars to help prevent detonation. Perhaps the previous owner went to the extreme
and remove the thermostat completely.


Christian Hack
DESIGN ENGINEER
christianh at edmi.com.au
EDMI Pty Ltd
Ph : (07) 3888 3066
FAX : (07) 3888 3583


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