Oem Map Sensor And Boost

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How much Boost can a Stock (OEM) Honda MAP (Manifold Absolute Pressure) Sensor Read?​

On a stock map sensor, the amount of boost you can run is limited due to the fact that it doesn't know what to do with values out of it's voltage range and the result is the ECU throwing a code and putting your car into limp mode.

The OEM Honda MAP sensors are roughly ~1.7 bar sensors (details below)
1 bar is 1 atmosphere of pressure, or roughly 14.7 psi at sea level. There is natural variance in these values based on altitude as well. So, that leaves less than 1 bar available for boost.

OBD 0​

OBD0 OEM Map Sensor supports .65 KG/cm2 or, 9.24 PSI

OBD1 and OBD2​

OBD1 and OBD2 OEM Map Sensors support .75 KG/cm2 or, 10.66 PSI

Any boost over this limit cause the ECU to go into limp mode.

If you want more boost than that, you need to run a GM 3-bar map sensor (common) or others like the gm 2.5 bar, the AEM 3.5, or the skunk2 4 bar map sensor. There are other super large ones out there like 5 or 6 bar but unless you're making 50 psi or more are completely unnecessary.

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Remember, your tuning software must have the proper voltage assigned to the sensor. Both stock, 2.5 bar, 3 bar, and 5 bar maps operate on a fixed voltage range (0-5volts), but each psi moves a different amount of voltage over. Therefore it is imperative to be using the right map sensor's output voltage range when you're tuning, and thus in your software.

It is also advisable to choose one closer to your expected boost range. You loose granularity and accuracy in larger spread. If you are only planning to run 6 lbs of boost, there's no need to get a 5 bar map sensor. In fact, your stock map sensor will work just fine. If you're going to 12 lbs, you should be looking for a 2.5 or 3 bar sensor. But if you're planning to run 30 psi, you will need to be able to handle that range with one of the big 5 or 6 bar MAPs.

An illustrative example (not accurate numbers, just for display purposes) of how the voltage corresponds to a psi reading. Of course, there's a negative side (vac) to indicate vacuum.

0-------------------2.5-------------------5v (Voltage Reading at psi)
-vac----0----1----3-----5------7------9-----11 psi (oem)
-vac----0-1--3--5--7--9---13--15--19---21---25 psi (3bar)
-vac----0-5--10--18--23--27--32--38--41--48-56 psi (5bar)

If you try to feed 11 psi into the oem sensor, it creates a 'Voltage over range' effect which triggers the ecu to error out and go into limp mode to protect itself.
See also: How to wire in the 3 bar map sensor