1KillerSS

I want to log boost in HPT, I know this is kinda an easy remedial topic, I have searched and all I can come up with is the PID to do it, not topics for the readings being off.

I setup my PID using [PID.11.PSI]-14.5 But like the title says, my boost gauge will show -20 and my datalog will show like -9 or close that +/- a few.

I am running a 2 bar operating system, and scaled properly. I am also using a AEM Tru Boost for my Gauge/controller.


Any help will be appreciated, and thank you in advance for reading.

93camaro_zzz

iTrader: (13)

Try out ([PID.11]/6.89476)-14.7

or if that doesn't work try:

([PID.2333]/6.89476)-14.7

RonSSNova

iTrader: (3)

Any chance you have both the 2 bar and std map in your table display?
If so, delete the std map PID.

Personally, I just read in KPA and convert in my head.....or cheat and use my conversion spreadsheet.

1KillerSS

Tried the first PID seems to give me the same reading as the original one I was using. The second PID I get unsupported parameter.

1KillerSS

This is probobally my issue, I never knew there was a difference. How do I change to the 2bar. I am sure I am still using the std.

93camaro_zzz

iTrader: (13)

Like Ron said, to change it to 2 bar, just delete the PID that says "Manifold ABsolute Pressure" that is in your table display. Only keep the one that specifically says 2 bar in it. On my car, the 2 bar would read correctly. On my last run it would read 185kpa, yet the regular one would read 140kpa. The 185 was correct in my situation.

1KillerSS

I can't find PID that is for a 2bar. The only MAP I have listed is the standard "MAP SAE". My operating system is definately a 2bar OS. I just cant see anything in my scanner that shows anything specifically for a 2bar operating system.

1KillerSS

Here is my boost PID and my options for MAP PID's

1KillerSS

Ok sorry guys, must have had a blond moment. I found the 2bar MAP sensor, however its telling me its an unsupported parameter so I must be typing in the PID incorrectly.

1KillerSS

I actually feel like a fool, and now feeling even less intelligent lol. The PID I am using is exactly [AUX.20021] Still coming out as "unsupported parameter"

Am I entering it with the wrong characters?

RonSSNova

iTrader: (3)

Once you enter it into the table, hook the scanner to the car. Ign in but not running. Start a scan. The scanner should poll the PCM for available pids. Then it should work from then on.

1KillerSS

According to my tuner I dont need to select the 1 or 2 bar map sensor, because the 3 bar map sensor I have now is a factory sensor. The PID that 93camaro_zzz gave me worked fine for logging at WOT. Its just the readings of the boost gauge and of the map sensor don't match up. Still not sure why, but when I log my boost using that pid, I read the same on the scanner as what my gauge says. Also what's wierd is my table display has MAP (SAE) and my chart display just uses MAP. When my boost gauge reads 13psi my table display reads 191.0 kpa from the SAE pid and my chart display reads 140.3 kpa. I'm lost...as if that's not obvious!

RonSSNova

iTrader: (3)

Lost me. Not sure why you would be using s 3 bar map sensor and a 2 bar tune?

1KillerSS

E38 only supports a 2.5 bar map sensor, so it must be a 2.5 bar. I got ahold of My tuner and spoke with him about the issues I was having. He was on the dyno at the time and told me it was a 3 bar, maybe his mind was somewhere else, or he really did install a 3 bar sensor. The tune is scaled to 312.50kpa with a linear offset of -11.31.

1KillerSS

After doing some research, I found this:


Quote Originally Posted by Chris@HPTuners
the 2.5 bar program can be used with a 2bar or 3bar sensor (with the 3bar you can only read boost up to 255kpa obviously). Be careful with the cobalt sensor cos it has an integrated IAT sensor as well, although it is a true 2.5bar sensor.

The boost VE table uses the value of whatever is being shown in the scanner for the MAP PID.

The MAP Sensor calibration (Linear and Offset) are used to calibrate the MAP sensors pressure/voltage characteristic. Typically the 5V output pressure is the Linear + Offset. so if you have Linear at 200kpa, offset at 10kpa then at 5V the PCM will assume 210kpa. Depending on the sensor type the default values are usually ok. some sensors have a 185/5 or 190/8 etc. but usually 200/10 is good enough for most 2bar sensors. To get is exact you need the manufacturers datasheet for the MAP sensor where it gives you the linear curve for the pressure/voltage characteristic.

Load up one of the Boost VE histograms to see where you are on the Boost VE table at any time. if your kit is making around 10-12psi you will be around the 170-185kpa mark.


I dont know if he actually did use a 3bar or not, if he did I dont know why. How do I tell for sure? One thing I did notice is what Chris said, that " if your kit is making around 10-12psi you will be around the 170-185kpa mark." That is true for me, infact that is almost exactly what my boost pid reads compared to my map pid.

Ill contact Matt tomorrow and verify that it is or is not a 3 bar map.

RonSSNova

iTrader: (3)

Got it. I don't know didly squat about the E38 controller.

Your guy will be able to explain it. I'm guessing that as long as the system is happy, you are good. Just might have to do some trickery to get boost reading correctly in your log.
Which of course is what you aksed in the first place......

1KillerSS

For anybody else that comes accross this issue in the future. My readings were only different at idle, not WOT. My boost at WOT and on my data logs were spot on. For anybody else that comes across this thread. The reason their off is because at idle the AEM Tru Boost gauge, reads inches of vacuum of InHg. So of course its different. I just assumed that it was incorrect at WOT. When I realized that they were the same at the top it still took me a good long while to hear the "pop". That was the sound of my head coming out of my ***. Duh...