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SVT Shelby GT500
Gauge for Monitoring Air Fuel - plus other OBD info on a 2010 Shelby
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<blockquote data-quote="Catmonkey" data-source="post: 16601409" data-attributes="member: 124025"><p>I don't use the sensor for vacuum/boost, but I'm pretty familiar with how the gauges work to enable you to trouble shoot. Aeroforce states the MAP sensor is based on 5 volts. You were given a slope and intercept to program into the gauge. These are just conversion factors to take volts and convert them to a digital reading. The slope and intercept for the 3.5 bar is 14 and -14. So if the map sensor is reading 1 volt, the gauge should display 0. You would multiply volts times the slope and add or subtract the intercept. Since the intercept is negative, you would subtract it. So, (1 x 14) - 14 = 0. If the map sensor reads 0 volts, it should read -14 psi (vacuum). If the map sensor is sending a 2.5 volt signal to the gauge, the slope and intercept should convert it to 21 psi = (2.5 x 14) - 14).</p><p></p><p>So if you're seeing 10 psi at idle, I suspect you did not enter the intercept as a negative value, so I would double check the values you entered. At idle, you should be seeing engine vacuum which would be negative values. Based on the slope and intercept, the lowest vacuum reading you can see is -14 psi. I say that because the MAP sensor can't read below 0 volts. However, vacuum isn't measured in negative PSI, but IN HG (inches of mercury). You need to apply a conversion factor to the psi value to read vacuum in inhg. Doubling it is close. -14 psi would be 28 inhg. If you're running stock cams, you should probably see something like -10 psi at idle (20 inhg) . You say you see 10 at idle, but is there a negative sign attached to it?</p><p></p><p>Here are the instructions I'm using to come up with these values. <a href="https://www.aeroforcetech.com/files/3_5_bar_MAP_sensor_kit_instructions.pdf" target="_blank">https://www.aeroforcetech.com/files/3_5_bar_MAP_sensor_kit_instructions.pdf</a></p><p></p><p>Almost all engine sensors are based on a 5 volt output, certainly as it applies to Ford, so what I've written above will apply to any sensor you may be trying to troubleshoot. If you entered the slope and intercept as 0 and 0, it should read volts on the gauge.</p><p></p><p>HTH</p></blockquote><p></p>
[QUOTE="Catmonkey, post: 16601409, member: 124025"] I don't use the sensor for vacuum/boost, but I'm pretty familiar with how the gauges work to enable you to trouble shoot. Aeroforce states the MAP sensor is based on 5 volts. You were given a slope and intercept to program into the gauge. These are just conversion factors to take volts and convert them to a digital reading. The slope and intercept for the 3.5 bar is 14 and -14. So if the map sensor is reading 1 volt, the gauge should display 0. You would multiply volts times the slope and add or subtract the intercept. Since the intercept is negative, you would subtract it. So, (1 x 14) - 14 = 0. If the map sensor reads 0 volts, it should read -14 psi (vacuum). If the map sensor is sending a 2.5 volt signal to the gauge, the slope and intercept should convert it to 21 psi = (2.5 x 14) - 14). So if you're seeing 10 psi at idle, I suspect you did not enter the intercept as a negative value, so I would double check the values you entered. At idle, you should be seeing engine vacuum which would be negative values. Based on the slope and intercept, the lowest vacuum reading you can see is -14 psi. I say that because the MAP sensor can't read below 0 volts. However, vacuum isn't measured in negative PSI, but IN HG (inches of mercury). You need to apply a conversion factor to the psi value to read vacuum in inhg. Doubling it is close. -14 psi would be 28 inhg. If you're running stock cams, you should probably see something like -10 psi at idle (20 inhg) . You say you see 10 at idle, but is there a negative sign attached to it? Here are the instructions I'm using to come up with these values. [URL]https://www.aeroforcetech.com/files/3_5_bar_MAP_sensor_kit_instructions.pdf[/URL] Almost all engine sensors are based on a 5 volt output, certainly as it applies to Ford, so what I've written above will apply to any sensor you may be trying to troubleshoot. If you entered the slope and intercept as 0 and 0, it should read volts on the gauge. HTH [/QUOTE]
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Gauge for Monitoring Air Fuel - plus other OBD info on a 2010 Shelby
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