Running too rich or lean?
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Any I/H/E part that actually helps air flow through engine (be careful because a lot of the aftermarket crap actually hurts flow on f20) will tend to make the engine run leaner (fuel wise) unless you modify the VAFC/ECU to add more fuel. More air with same fuel = lean = hi temps. Be careful about adding more air unless you OR the ECU can add more fuel to maintain safe fuel/air ratio.
Be careful of the difference between air/fuel ratio (lower # means rich fuel-wise) and fuel/air ratio (lower # means lean fuel-wise. Some guages display in lambda value (the ratio of current a/f ratio divided by stoichiometric a/f ratio of 14.7). Now that I think of it lambda may be ratio of f/a to stoichiometric. So I'm not sure if a lower lambda # is richer or leaner fuel-wise. Anyway . . .
When taking someone's advice on 'richer' or 'leaner', be sure you know wether they mean fuel-wise or air-wise. I think fuel-wise is more intuitive, because you are normally adding or subtracting fuel during tuning, and you can't adjust air flow except by rpm.
So if you are too low F/A ratio, you add more time to injector's pulsewidth, which (at a given fuel rail pressure) gives more fuel. THis keeps me form getting confused. Hope it helps. BTW . . .
A/F ratios are measured by an O2 sensor that measures the amount of excess (unburned) oxygen in the exhaust. Stock OEM uses a narrow-band sensor that's only accurate right around stoichiometric. That's why the stock ECUs only go into closed loop mode (trim fuel based on O2 reading) at idle, when it's safe to rely on the narrow-band O2 sensor.
Aftermarket has wide-band O2 sensors that accurately measure a wider range of A/F ratios. These are an absolute MUST have item to safely tune engine after modifications are made to engine. Of course you have to know if the display is A/F or F/A ratio, so you know if you are rich or lean, and wether you need to add or subtract fuel.
Be careful of the difference between air/fuel ratio (lower # means rich fuel-wise) and fuel/air ratio (lower # means lean fuel-wise. Some guages display in lambda value (the ratio of current a/f ratio divided by stoichiometric a/f ratio of 14.7). Now that I think of it lambda may be ratio of f/a to stoichiometric. So I'm not sure if a lower lambda # is richer or leaner fuel-wise. Anyway . . .
When taking someone's advice on 'richer' or 'leaner', be sure you know wether they mean fuel-wise or air-wise. I think fuel-wise is more intuitive, because you are normally adding or subtracting fuel during tuning, and you can't adjust air flow except by rpm.
So if you are too low F/A ratio, you add more time to injector's pulsewidth, which (at a given fuel rail pressure) gives more fuel. THis keeps me form getting confused. Hope it helps. BTW . . .
A/F ratios are measured by an O2 sensor that measures the amount of excess (unburned) oxygen in the exhaust. Stock OEM uses a narrow-band sensor that's only accurate right around stoichiometric. That's why the stock ECUs only go into closed loop mode (trim fuel based on O2 reading) at idle, when it's safe to rely on the narrow-band O2 sensor.
Aftermarket has wide-band O2 sensors that accurately measure a wider range of A/F ratios. These are an absolute MUST have item to safely tune engine after modifications are made to engine. Of course you have to know if the display is A/F or F/A ratio, so you know if you are rich or lean, and wether you need to add or subtract fuel.
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Originally Posted by snakeeater,Feb 23 2006, 01:45 PM
Any I/H/E part that actually helps air flow through engine (be careful because a lot of the aftermarket crap actually hurts flow on f20) will tend to make the engine run leaner (fuel wise) unless you modify the VAFC/ECU to add more fuel. More air with same fuel = lean = hi temps. Be careful about adding more air unless you OR the ECU can add more fuel to maintain safe fuel/air ratio.
Be careful of the difference between air/fuel ratio (lower # means rich fuel-wise) and fuel/air ratio (lower # means lean fuel-wise. Some guages display in lambda value (the ratio of current a/f ratio divided by stoichiometric a/f ratio of 14.7). Now that I think of it lambda may be ratio of f/a to stoichiometric. So I'm not sure if a lower lambda # is richer or leaner fuel-wise. Anyway . . .
When taking someone's advice on 'richer' or 'leaner', be sure you know wether they mean fuel-wise or air-wise. I think fuel-wise is more intuitive, because you are normally adding or subtracting fuel during tuning, and you can't adjust air flow except by rpm.
So if you are too low F/A ratio, you add more time to injector's pulsewidth, which (at a given fuel rail pressure) gives more fuel. THis keeps me form getting confused. Hope it helps. BTW . . .
A/F ratios are measured by an O2 sensor that measures the amount of excess (unburned) oxygen in the exhaust. Stock OEM uses a narrow-band sensor that's only accurate right around stoichiometric. That's why the stock ECUs only go into closed loop mode (trim fuel based on O2 reading) at idle, when it's safe to rely on the narrow-band O2 sensor.
Aftermarket has wide-band O2 sensors that accurately measure a wider range of A/F ratios. These are an absolute MUST have item to safely tune engine after modifications are made to engine. Of course you have to know if the display is A/F or F/A ratio, so you know if you are rich or lean, and wether you need to add or subtract fuel.
Be careful of the difference between air/fuel ratio (lower # means rich fuel-wise) and fuel/air ratio (lower # means lean fuel-wise. Some guages display in lambda value (the ratio of current a/f ratio divided by stoichiometric a/f ratio of 14.7). Now that I think of it lambda may be ratio of f/a to stoichiometric. So I'm not sure if a lower lambda # is richer or leaner fuel-wise. Anyway . . .
When taking someone's advice on 'richer' or 'leaner', be sure you know wether they mean fuel-wise or air-wise. I think fuel-wise is more intuitive, because you are normally adding or subtracting fuel during tuning, and you can't adjust air flow except by rpm.
So if you are too low F/A ratio, you add more time to injector's pulsewidth, which (at a given fuel rail pressure) gives more fuel. THis keeps me form getting confused. Hope it helps. BTW . . .
A/F ratios are measured by an O2 sensor that measures the amount of excess (unburned) oxygen in the exhaust. Stock OEM uses a narrow-band sensor that's only accurate right around stoichiometric. That's why the stock ECUs only go into closed loop mode (trim fuel based on O2 reading) at idle, when it's safe to rely on the narrow-band O2 sensor.
Aftermarket has wide-band O2 sensors that accurately measure a wider range of A/F ratios. These are an absolute MUST have item to safely tune engine after modifications are made to engine. Of course you have to know if the display is A/F or F/A ratio, so you know if you are rich or lean, and wether you need to add or subtract fuel.
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