On board map

[obxtsi]

Why would the onboard map sensor calibrate but shows 4 to 5 psi on start up and idle? 

[Confused]

MAP = Manifold Absolute Pressure, this is how far above absolute vacuum, it's always positive.

You're probably confusing it with MGP (Manifold Gauge Pressure), which is relative to your current atmospheric pressure, negative for values below this (in vacuum) and positive for values above this (in boost)

[obxtsi]

I assume this is normal at sea level. My vacuum should be like 19 not 9 on my car based on my scg1 gauge.

[castillaricardo]

Those seem like normal numbers. The gauge reads psi on boost and inHg on vacuum. The ecu sees -9.7psi which is 19.7inHg at idle. Assuming your BAP is 14.6psi (MAP+abs(MGP)), your sensors seem to be working fine.

[obxtsi]

Ok. Thanks.  I come from ecmlink which is definitely different in how things are displayed. 

[koracing]

The confusion here I think is in units as inches of mercury (inHg) is not the same as psi (pounds per square inch).  14.7psi = 29.9inHg. In the vacuum range where gauge pressure (MGP or manifold gauge pressure) is negative psi - you can roughly double that value to know what it is in inches of mercury.  Alternatively you can set up a math channel to display vacuum values in inches of mercury with a simple scalar multiplier.

Personally I prefer to look at everything in kpa absolute values, and set up PSI math channels for certain display values if desired.

Trying to set up an example of a math channel to do this, I run into the equation character limit, but I think that is being expanded in the next release. 

Math 1:  a=MGP in psi
Equation: a*((a<0)*(-2.036)+(a>0)) 

to do in 2 math channels:
Math 1: a=MGP in psi --> a*((a<0)*(-2.036))
Math 2: a=Math 1, b=MGP --> a+b*(b>0)

I don't know if the MGP value is actually evaulated in the currently displayed units or it defaults in the background to kpa or something, however.  If it's the latter - the math will change a bit.

[Vaughan]

6 hours ago, koracing said:

I don't know if the MGP value is actually evaulated in the currently displayed units or it defaults in the background to kpa or something, however.  If it's the latter - the math will change a bit.

Math blocks do the calculation in SI units (kPa for MGP), the ECU has no idea what units you are viewing the values in that is done entirely in PCLink

[koracing]

Ok so if it's in SI units:

to do in 2 math channels given SI units:
Math 1: a=MGP in kpa --> a*((a<0)*(-.2953))
Math 2: a=Math 1, b=MGP --> a+b*(b>0)*.14504