EVAP Vacuum/Pressure resources Sheets
- Atmospheric Pressure Barometric Pressure= Approx. 14.7 Psi, 29.9 In Hg, 1 Bar, 100kPa
- Gauge vs Absolute Pressure: Gauge pressure has Atmospheric pressure equal to zero and reads pressure/vacuum from that zero mark, while Absolute pressure (actual pressure) is not at zero and reads actual pressure.
EVAP Conversion Tables
These Tables display a very narrow range Pressure/Vacuum. Typical EVAP system pressure or vacuum is only approx. .75 InHg. (For example, normal engine manifold vacuum is 20 InHg gauge, or 10 InHg absolute) Therefore these tables only show what you might see during normal EVAP system testing or operation. (Using shop air or anything high pressure or vacuum is beyond the safe limits of an EVAP system!)
Gauge Pressure/Vacuum Conversion Table
| In Hg | In H2O | Mm Hg | mBar | PSI | kPa |
|---|---|---|---|---|---|
| 0 | 0 | 0 | 0 | 0 | 0 |
| 0.1 | 1.36 | 2.53 | 3.38 | 0.05 | 0.34 |
| 0.2 | 2.71 | 5.07 | 6.75 | 0.1 | 0.68 |
| 0.3 | 4.07 | 7.6 | 10.13 | 0.15 | 1.01 |
| 0.4 | 5.43 | 10.13 | 13.51 | 0.2 | 1.35 |
| 0.5 | 6.79 | 12.66 | 16.88 | 0.25 | 1.69 |
| 0.6 | 8.14 | 15.2 | 20.26 | 0.29 | 2.03 |
| 0.7 | 9.5 | 17.73 | 23.64 | 0.34 | 2.36 |
| 0.8 | 10.86 | 20.26 | 27.02 | 0.39 | 2.7 |
| 0.9 | 12.21 | 22.79 | 30.39 | 0.44 | 3.04 |
| 1 | 13.57 | 25.33 | 33.77 | 0.49 | 3.38 |
| 1.1 | 14.93 | 27.86 | 37.15 | 0.54 | 3.72 |
| 1.2 | 16.28 | 30.39 | 40.52 | 0.59 | 4.05 |
| 1.3 | 17.64 | 32.93 | 43.9 | 0.64 | 4.4 |
| 1.4 | 19 | 35.46 | 47.27 | 0.69 | 4.73 |
| 1.5 | 20.36 | 38 | 50.65 | 0.74 | 5.07 |
| 1.6 | 21.71 | 40.52 | 54.03 | 0.78 | 5.4 |
| 1.7 | 23.07 | 43.05 | 57.41 | 0.83 | 5.74 |
(Scan tool PIDs is implied for vacuum)
Absolute Pressure Conversion Table
| In Hg | In H2O | Mm Hg | mBar | PSI | kPa |
|---|---|---|---|---|---|
| 29.93 | 406.16 | 758.03 | 1011 | 14.66 | 101.07 |
| 29.9 | 405.76 | 757.7 | 1009 | 14.64 | 100.96 |
| 29.8 | 404.4 | 754.74 | 1006 | 14.59 | 100.63 |
| 29.7 | 403.04 | 752.2 | 1003 | 14.54 | 100.29 |
| 29.6 | 401.68 | 749.67 | 1000 | 14.49 | 99.96 |
| 29.5 | 400.33 | 747.14 | 996 | 14.44 | 99.61 |
| 29.4 | 398.97 | 744.61 | 992 | 14.39 | 99.28 |
| 29.3 | 397.61 | 744.2 | 989 | 14.35 | 98.94 |
| 29.2 | 396.25 | 741.7 | 986 | 14.3 | 98.6 |
| 29.1 | 394.89 | 737.01 | 982 | 14.25 | 98.26 |
| 29 | 393.54 | 734.47 | 979 | 14.2 | 97.93 |
| 28.9 | 392.18 | 731.94 | 975 | 14.15 | 97.59 |
| 28.8 | 390.83 | 729.4 | 969 | 14.1 | 97.25 |
| 28.7 | 389.47 | 726.87 | 969 | 14.05 | 96.91 |
| 28.6 | 388.11 | 724.34 | 965 | 14 | 96.57 |
| 28.5 | 386.75 | 721.81 | 962 | 13.95 | 96.24 |
| 28.4 | 385.39 | 719.27 | 958 | 13.9 | 95.9 |
| 28.3 | 384.04 | 716.74 | 955 | 13.86 | 95.56 |
Fuel Tank Pressure Sensor Specifications
Polarity- All manufactures (FTP) sensors have the same polarity except for GM
- ALL Except GM: Voltage falls with vacuum and rises with pressure
- GM: Voltage rises with vacuum and falls with pressure
GM - Typical FTP voltage to Pressure Table
| FTP Voltage | Indicated Pressure | FTP Voltage | Indicated Pressure |
|---|---|---|---|
| 0.5 Volts | 5.0- In H2O | 3.1 Volts | -8.6- In H2O |
| 1.0 Volts | 2.6- In H2O | 3.3 Volts | -9.7- In H2O |
| 1.5 Volts | 0 In -H2O | 3.5 Volts | -10.8- In H2O |
| 2.0 Volts | -2.5- In H2O | 3.8 Volts | -12.9- In H2O |
| 2.7 Volts | -6.7- In H2O | 4.2 Volts | -14.5- In H2O |
| 2.9 Volts | -7.8 -In H2O | 4.5 Volts | -16- In H2O |
(Italics voltage represents Cap-Off value)
Fuel Tank Pressure Senor Cap-Off Values (+/-) 200 mV
| Manufacturer | Cap-Off Voltage |
|---|---|
| Acura, Ford, Honda, Hyundai, Kia, Subaru | 2.5 Volts |
| Mazda | 2.6 Volts |
| Nissan, Infiniti | 3.3, 3.8, or 4.2 Volts |
| Toyota, Lexus, Scion | 3.3 Volts |
| General Motors | 1.5 Volts |
| 2.9 Volts | -7.8 -In H2O |
Cap-Off values represent what sensors should read at atmospheric pressure