I have been trying to set up the HP tuners scanner so I can get some meaningfull baseline logging before I start changing anything. I started running into some strange readings with the MAP sensor, It showed atmospheric (engine not started) at 78.3kPa, and 6psi of boost at 110kPa. I looked into this a little further just to realize there are 6 MAP readings available, just to confuse things a little more, they come up with different readings!!!
In the PID table, there is the Manifold Absolute Pressure (SAE), the Manifold Air Pressure (kPa), the Manifold Air Pressure (V), not to mention the 2 and 3 bar (I don't think these are available for our platforms.) There is also the Manifold Absolute Pressure available as a sensor.
Could someone please explain the difference of all these to me, as well as their respective relevence?
for the gm sc program , you need to change the map , its set to default on the 1 bar readings
I haven't found a place to change the map settings, just the scale for the guages/charts. The Manifold Absolute Pressure seems to be the most accurate, reading around 140kPa at max boost (6psi). I will start using that reading instead of the others.
My biggest question now is what is the reason for the discrepency in readings. In the same run, I logged the MAP (Manifold Absolute Pressure), the PIDs Manifold Absolute Pressure (SAE), and Manifold Air Pressure, and got 3 different readings.
Under boost, the MAP sensor read 107.7kPa, the MAP SAE read 142.0, and the Manifold Air Pressure read 73.4.
At Idle, they were also different, 25.3, 30.0, 20.7 respectivley.
Why are they different, and what is the difference between Manifold Absolute Pressure, and Manifold Air Pressure?
hp's gauge program is set with a 1 bar map , and you have to edit the gauge to get the 2 bar values
i know its beeen talked about
I should have called in an archeologist to help me dig up this ancient thread....
But i was wondering the EXACT SAME thing... and seeing how in 3 years no one has answered this poor fellow.
Why the heck are there like 6 different entires for air pressure? and more so why do they all read differently?
I have a gauge on my display showing MAP pressure... but found it odd that when playing back my logs, the gauge rarely refelcted the MAP Cell some of my histrgrams were recording in.
Like my gauge was showing 171kpa... but the histogram was being populated in the 200kpa cell of one histogram, and on the 180kpa cell of another.
got looking around... and realized my gauge was showing the Manifold Absolute Pressure SENSOR... and the one histogram was based off of the Manifold Absolute Pressure (SAE) PID.
So i added another gauge.. so now i have one showing the MAP SENSOR, and the other showing the MAP PID... and they are both very different. 171 on one but 206 on the other. when one says 100 the other says 80...
that is a big difference...
And i also have an added EIO Map sensor that i put in myself... and that one is even further off... it shows 119 when the other 2 are at 80 and 100. and they all move differently... one is real jumpy, the other is kinida sluggish.
Which MAP do we use for what and why?
why are they all so far off from eachother?
Looks like the MAP "sensor" is what is used for the VE histograms... so i am imagining that is the important one... but why are the rest there at all? just to confuse us? or do they have a use?
I found this in the HPT help files... but i think i am more confused now after reading it...
HPT Help Files wrote:Note: User defined PIDs are ALWAYS calculated, even if they are not shown in the table display. You should be careful about defining custom PIDs as sensors if they will generate bad data, as sensor's are always averaged. eg. if you create a user defined boost PID (for a boost gauge using EIO input) as a MAP sensor, this data will always be averaged with other MAP sensor PIDs, such as MAP (SAE) even if your boost gauge is not connected. This can cause problems in histograms and charting if they reference sensors for axis. The solution to this issue is not to declare user-defined PID as sensors and reference the PIDs directly in charts if needed.
You can define your own sensors using user defined PIDs as well. User defined PIDs as sensors can make up for sensors some vehicles may lack such as Cylinder Air and others.
Are they saying you can have multiple PID's all contributing data to one common "sensor"? so we could have 4 different MAP sensors on our car... logging them all as a seperate PID... and assign all for to a single sensor.... and it would average the 4 of them together to give you one combined reading? So say you had a v-8 twin turbo... and a map sensor on each turbo bank.... one on the intake manifold, and another after your intercooler... So could reference each one seperately by its PID... or assign them all as the MAP "SENSOR"...
so if you showed 10psi on TurboA 11psi on TurboB 13psi at the intercooler, and 14psi at the mani... your MAP "sensor" would read as 12?
Is that what i am getting out of this? and if so... why do we still have multiple "PIDS" if our cars only have one physical MAP sensor?? and more importantly, why are they all different readings if there is only one physical sensor feeding the computer that info.
