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MAP Voltage / kPa Correlation?

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Old Dec 30, 2005 | 08:34 PM
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Willie's Avatar
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From: Tucson, Arizona USA
Car: 1987 Z28 Convertible
Engine: 305 TPI
Transmission: 5-speed
MAP Voltage / kPa Correlation?

Unfortunately my scanner displays MAP voltage, not MAP kPa. Is there a conversion formula to derive kPa's from voltage?
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Old Dec 30, 2005 | 08:48 PM
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89 Iroc Z's Avatar
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From: Costal Alabama
Car: 1989 Iroc-Z
Engine: 350, ZZ4 equivalent
Transmission: Pro-Built Road Race 700R4
Axle/Gears: 3.23 Dana 44
here's the conversion table...
Attached Thumbnails MAP Voltage / kPa Correlation?-maptable.gif  
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Old Dec 30, 2005 | 09:35 PM
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From: Tucson, Arizona USA
Car: 1987 Z28 Convertible
Engine: 305 TPI
Transmission: 5-speed
Thanks! Looking at it made me think of something else. This table is true only for a 1-bar MAP, correct? How does the 2 and 3-bar MAP sensors compare?

Willie
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Old Dec 30, 2005 | 10:27 PM
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From: Hurst, Texas
Car: 1983 G20 Chevy
Engine: 305 TPI
Transmission: 4L60
Axle/Gears: 14 bolt with 3.07 gears
On the two bar, double the KPA for the same voltage. On a three bar, triple it. May not be exact, but it is in the ballpark.
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Old Dec 30, 2005 | 11:00 PM
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1Bar
MAP(kPa) = (0.369 x N) + 10.354

2Bar
MAP(kPa) = (0.781 x N) + 8

3Bar
MAP(kPa) = (1.22 x N) + 2.2


Where N = (Volts/5) * 255
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Old Jan 4, 2006 | 09:25 PM
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Thats pretty helpfull..

Also, datamaster the beta software has really nice lookup tables in the help file. You must download the beta software to get it though.
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Old Jan 9, 2006 | 10:25 AM
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Be careful with that table. I posted that a long time ago as an explanation to a question. While that table should be close (it is a theoretical table) most MAPs aren't quite that linear. You can test with a voltmeter and vacuum pump, and many MAPs are off by ±0.5V or more. Some are high, some are low, but most tend to output a slightly higher voltage than the table indicates at the middle ranges.
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