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Old 02-25-2007, 10:11 AM   #1
Cassim
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Exclamation Engine Tuning - Discovery 1 V8 i - 3.9

How do I adjust the air fuel ratio on my disco. Where is the adjustment screw located.

Also, I had my coil replaced, distributor cap, rotor , ignition module and injectors replaced. Now I hear a constant clicking from the top of the coil. Sounds like it's losing fire.

Please help!
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Old 02-25-2007, 10:38 AM   #2
byronAU
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Red face Re: Engine Tuning - Discovery 1 V8 i - 3.9

Quote:
Originally Posted by Cassim
How do I adjust the air fuel ratio on my disco. Where is the adjustment screw located.

Also, I had my coil replaced, distributor cap, rotor , ignition module and injectors replaced. Now I hear a constant clicking from the top of the coil. Sounds like it's losing fire.

Please help!
The fuel/air ratio of your engine is completely controlled by the ECU [14 CUX type] and you can't effectively alter it.......its part of the hard/core programming of the ECU, its values derived from various sensors and changing constantly all the time.

Sorry , but YOU can't do it except maybe with a whole lot of specialised equipement including a twin roller dynomometer or a rolling road and the permanent installation of a more sophisticated [expanded memory] "piggy back" ECU.......it ain't just a screw adjustment that you can set "by ear"!

Last edited by byronAU; 02-25-2007 at 10:40 AM.
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Old 02-25-2007, 11:04 AM   #3
ptschram
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Default Re: Engine Tuning - Discovery 1 V8 i - 3.9

A/F ratio is controlled by the ECU responding to signals from the oxygen sensors.

The easiest way to control it is to switch to mega-squirt EMS and then, you can program your fuel map as you wish via your PC. There are other ECUs that are user-programmable, but none are plug-n-play.

There are a coupla companies producing replacement proms that allow for a fixed fuel map substitution.

PT
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Old 02-25-2007, 03:11 PM   #4
Chris-St Louis
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Default Re: Engine Tuning - Discovery 1 V8 i - 3.9

Actually, A/F CAN be leaned/riched with a screw on your MAF. However, that is something if done wrong can go really bad.
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Old 02-25-2007, 03:30 PM   #5
ptschram
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Default Re: Engine Tuning - Discovery 1 V8 i - 3.9

Manipulating the A/F ratio by meddling with the MAF calibration is NOT the correct way to modify one's A/F ratio!

Yes, it can be done, but all one achieves is an offset from the original fuel map that can result in bad things happening at various points in the fuel map.
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