BMW 3 Series E30 Airflow Meter Adjustment

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The meter can be tweaked to maximise fuel economy or performance. Unless the unit has been adjusted incorrectly previously you wont see substantial gains either way you wish to set it, however, you should notice a good difference considering the price of it which is... FREE!!

First of all you will want to remove the airflow meter from the car and remove the plastic lid on the top part of it.
You will then see this:

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Ideally you would want to be able to record air/fuel ratios, power/torque and mpg for each adjustment to end up with the best possible setting for your particular car but since were not all millionaires you can DIY and still get a good improvement in most cases. On my own car using the trusty butt dyno I came to the conclusion that for performance there is no point in adjusting the toothed wheel more than 2 teeth to the rich side. I actually have had it set at only 1 tooth richer for some time now. MPG has not dropped enough to warrant mentioning and the engine feels stronger accelerating. I did try 2 teeth to the rich side but noticed no further improvement and MPG was suffering. Allthough I have not tried to set the meter for better fuel economy the idea is the same simply instead of moving a tooth more rich you will be moving a tooth, or 2 if your feeling adventurous, to the lean side. If your car has an onboard computer with MPG readout you can reset that and test before/after each adjustment to see what works best for you. Ensure temp sensor and carbon tracks/contacts are clean and in good working order. Unless you are setting up the unit for emissions testing or really know what your doing I wouldnt adjust anything other than the toothed wheel.
I must stress you want to adjust 1 tooth at a time and test after each and you should mark the standard location before making any adjustments. You do this completely at your own risk.
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