[alfa] RE: Alfa perfprmance chip

["John Fielding" <johnf@xxxxxxxxxxxxxxx>]

Hi Ben,

I saw your query on the Alfa Digest.

In a petrol engine the  ECU monitors the air inlet temperature.  Cold air is denser and
hence needs more fuel, hot air is less dense and needs less fuel.  Therefore fooling the
ECU to think the air is hotter than it actually is  makes the engine run lean.  IMHO not a
clever idea!

Most Motronic ECU have a "fuel quality switch" which has 8 settings.  On the Alfa
Motronics it is a behind a plastic plug in the side of the ECU.  By turning the switch you
can adjust the timing by plus or minus 2 or 4 degrees and the fuel by plus or minus 2 or
4%.  The switch must be changed with the ignition switched off.  The ECU when it boots
goes and checks the position of the switch.  If the switch is changed with the engine is
running nothing changes.

Similarly the water temperature has a big effect on the fuel.. A cold engine requires more
fuel, this is the "automatic choke" function.  As the engine warms up the fuel is reduced
towards the hot running state.  To deliver more fuel you can fool the ECU to think the
engine is not fully warmed up.  However, in the Motronic ECU this also causes the ignition
timing to be retarded until the engine reaches full operating temperature, so the power
gained is next to zero!

IMHO the only way to get extra performance from a Motronic ECU is to toss it and fit
something more appropriate such as an after-market ECU that can be adjusted by the tuner.

John
Durban
South Africa
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