DME adjustment for fuel quality
03-31-2004, 06:33 PM
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DME adjustment for fuel quality
All,
I seem to remember that the DME has a switch that can be used to modify the ignition timing characteristics to account for fuel quality.
I've quickly searched the archives but can't find any references. Does anyone have any information on this?
Doug
I seem to remember that the DME has a switch that can be used to modify the ignition timing characteristics to account for fuel quality.
I've quickly searched the archives but can't find any references. Does anyone have any information on this?
Doug
03-31-2004, 07:45 PM
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i think you are thinking of the older DME (Pre-964's) which i believe did have an external switch on them.
the 964 DME does not have an external switch on it
the 964 DME does not have an external switch on it
03-31-2004, 11:27 PM
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I thought I had read something on this subject before and referred to Adrian's book.
"Fuel Selector Switch"
In certain Countries fuel octane levels lower than the recommended RON95 may be mandated for use in automobiles. In order to avoid random ignition taking place in the engine, the ignition timing may be retarded by up to 2.3 degree at certain engine loads. A 2-pin octane code plug (part number 944 612 525 01) is connected to pin 4 of the ignition control unit.
On my 928 there is a green wired connector which comes out of the ECU unit under the passenger footwell. When low fuel grades are encountered you simply plug the 2 ends together and this gives you about a 3 degree retard on the timing.
In the later cars there is a "knock sensor" which automatically retards the ignition when the engine "senses" the detonation in the cylinder.
Hope this helps,
Ken Bigham
"Fuel Selector Switch"
In certain Countries fuel octane levels lower than the recommended RON95 may be mandated for use in automobiles. In order to avoid random ignition taking place in the engine, the ignition timing may be retarded by up to 2.3 degree at certain engine loads. A 2-pin octane code plug (part number 944 612 525 01) is connected to pin 4 of the ignition control unit.
On my 928 there is a green wired connector which comes out of the ECU unit under the passenger footwell. When low fuel grades are encountered you simply plug the 2 ends together and this gives you about a 3 degree retard on the timing.
In the later cars there is a "knock sensor" which automatically retards the ignition when the engine "senses" the detonation in the cylinder.
Hope this helps,
Ken Bigham
04-01-2004, 01:56 AM
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Dear Ken,
Would you be so kind as to provide the page numbers for any quotes attributed to myself.
You will find that this statement applies to the Turbocharged 964s.
There is no such connection on a 964 normally aspirated engine management system "Motronic" because it is fitted with knock sensors.
Ciao,
Adrian
964C4
Would you be so kind as to provide the page numbers for any quotes attributed to myself.
You will find that this statement applies to the Turbocharged 964s.
There is no such connection on a 964 normally aspirated engine management system "Motronic" because it is fitted with knock sensors.
Ciao,
Adrian
964C4
