Determining appropriate A/F ratios.
10-19-2007, 02:21 PM
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Determining appropriate A/F ratios.
You dont have a dyno, and you dont have a knock sensor.
How is tuning accomplished? what is a generally accepted target A/F ratio? Is A/F ratio constant throughout the rev range? How do you know what A/F ratio should be if you are cruising? If a turbo makes full boost at 3000rpm and you are cruising at 4000rpm, the engine doesn't make boost until you step on it?
I am trying to visualize the fuel tables that I see screen shots of, and if I remember correctly it was boost vs rpm. What data and, in what measurement, is filled into the table?
How is tuning accomplished? what is a generally accepted target A/F ratio? Is A/F ratio constant throughout the rev range? How do you know what A/F ratio should be if you are cruising? If a turbo makes full boost at 3000rpm and you are cruising at 4000rpm, the engine doesn't make boost until you step on it?
I am trying to visualize the fuel tables that I see screen shots of, and if I remember correctly it was boost vs rpm. What data and, in what measurement, is filled into the table?
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10-19-2007, 02:37 PM
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cause 14.7:1 is the optimal burning ratio for gasoline.
Richening up the mixture to 12:1 results in a slower burn, moving the pressure peak later where there is more leverage and more torque. Anything richer is a waste of gas; it cannot provide any real additional cooling or slow the burn. Anythign leaner and the peak pressure increase, the spark ignites closer to TDC, the air charge is not cooled and you risk detonation.
Richening up the mixture to 12:1 results in a slower burn, moving the pressure peak later where there is more leverage and more torque. Anything richer is a waste of gas; it cannot provide any real additional cooling or slow the burn. Anythign leaner and the peak pressure increase, the spark ignites closer to TDC, the air charge is not cooled and you risk detonation.
Last edited by Braineack; 10-19-2007 at 03:18 PM.
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10-19-2007, 02:52 PM
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cause 14.7:1 is the optimal burning ratio for gasoline.
Richening up the mixture to 12:1 results in a slower burn, moving the pressure peak later where there is more leverage and more torque. Anything richer is a waste of gas; it cannot provide any real additional cooling or slow the burn.
Richening up the mixture to 12:1 results in a slower burn, moving the pressure peak later where there is more leverage and more torque. Anything richer is a waste of gas; it cannot provide any real additional cooling or slow the burn.
What about the numbers in the tables?
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10-19-2007, 04:16 PM
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no. i thought the op was being smart with me. i didnt even realize it was someone else.
about the tables. they are a % of fuel. based on rpm vs. MAP. only there to supply to fuel so you can tune it to your given AFR.
about the tables. they are a % of fuel. based on rpm vs. MAP. only there to supply to fuel so you can tune it to your given AFR.
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10-19-2007, 04:32 PM
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So is there some sort of mathematical formula you can use to determine the percentage of fuel you would need to create a specific AFR based on rpm and map or is it unique to every car? I know its somewhat interchangeable between miatas, but never perfect unless cars are identical.
I ask because i am curious, can you measure your AFR only once the car is in motion or can you estimate it on the drawing board?
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