What happened to my A/C Pressure PID?!

[Mr. P.]

OK I've been logging A/C Pressure (GM.ACP) and it has until today been working great, reporting the actual pressure in the system in PSI (I'm tuning my efan hi-speed cut-in points) but now for some reason this PID is returning VOLTAGE instead of pressure?! What Gives? I've gone through the PID settings and units configuration screens trying to see if there's a setting I'm overlooking. How do I log A/C pressure in PSI again? It doesn't do me any good watching the sensor voltage. OH, and btw I don't know if this is a bug but the calculated A/C sensor voltage PID does not work, it just stays at 1.3 volts regarless of whether the A/C is running or not...

Mr. P.

[Blacky]

I presume you have upgraded your software. In one of the recent releases two PIDs were changed:

GM.ACP -> GM.ACP (A/C pressure)
and
GM.EOP -> GM.EOPS (Engine oil pressure)

Both of those PIDs used to be converted internally by the EFILive Scan Tool from volts to psi (and kPa). That worked fine when just the LS1 style controller was supported. However, as we added more controller types (specifically diesel) the conversion that EFILive was doing was wrong for those new controller types.

So now EFILive just returns the voltage as supplied from the controller. It is up to you to create a calculated PID that calculates psi (and/or kPa) for your particular platform.
In order to do that we will try and supply the scaling factors. So far we have the scaling factors for LS1 for A/C and engine oil pressure:


GM.EOPS returns the oil pressure sender’s 0-5V signal,
not kPa or psi.
For most LS1 applications convert the 0-5V value to
kPa or psi use the following expressions:

kPa = V*220.625-110.3125
psi = V*32-16
GM.ACP returns the A/C high side pressure sender’s 0-5V signal,
not kPa or psi.
For most LS1 applications convert the 0-5V value to
kPa or psi use the following expressions:

kPa = V*12.7078-128.907
psi = V*1.84311-18.6964Regards
Paul

[Mr. P.]

Paul can you recheck your math - when I substitute 5V in the AC PSI and kpa formulas I get negative numbers ???

Mr. P.

[mr.prick]

I can not find GM.EOP,
the supported box is unchecked.

[Blacky]

I don't know what drugs I was smoking that day...
After re-investigating, I think this is what the AC pressure should be:

psi = V*94.0479-18.8721
kPa = V*648.4372-130.1184

The psi range is: 0 to about 450kPa
The kPa range is: 0 to about 3000kPa

A minimum of zero is forced by the PCM, even though mathematically it can be negative.

Note: The conversion from V to psi is done via a lookup table in the PCM. The above information is based on me looking at only one vehicle. That means it may not be accurate for every LS1 calibration.

Regards
Paul

[Blacky]

I can not find GM.EOP,
the supported box is unchecked.

There is no EOP PID anymore. The engine oil pressure is only returned by the PCM as V. We used to convert it internally to kPa and psi (when we first supported only a few LS1 controllers).

But as newer LS1 controllers were released the potential for them to have different V->psi scaling was introduced and we could no longer make that conversion accurately in the scan tool.

Regards
Paul

[Ninety8C5]

Try logging GM.EOPS and then use the Calculated PID to convert it to PSI.

[mr.prick]

Unless I overlooked it, there is no oil pressure sensor voltage PID either.
Can the single wire sensor be logged thru an AD input without a ground?

[Ninety8C5]

This works in my "calc_pids.txt" file and follows the Oil Pressure gauge in the car.

*CLC-00-043
PSI 0.0 150.0 0.0 "({GM.EOPS}*32)-16"

CALC.OIL_PRESSURE F043 CLC-00-043 PSI Testing "Engine Oil Pressure"

[mr.prick]

This works in my "calc_pids.txt" file and follows the Oil Pressure gauge in the car.

*CLC-00-043
PSI 0.0 150.0 0.0 "({GM.EOPS}*32)-16"

CALC.OIL_PRESSURE F043 CLC-00-043 PSI Testing "Engine Oil Pressure"


There is no EOP PID anymore. The engine oil pressure is only returned by the PCM as V. We used to convert it internally to kPa and psi (when we first supported only a few LS1 controllers).

But as newer LS1 controllers were released the potential for them to have different V->psi scaling was introduced and we could no longer make that conversion accurately in the scan tool.

Regards
Paul
What version of the software are you using?
I cannot find GM.EOP.
FWIW the OP gauge in my car is totally unreliable,
it does not read the same as a mech gauge I have under the hood and
just sits under 40psi at idle and never breaks 40psi under load.

[Ninety8C5]

What version of the software are you using?
I cannot find GM.EOP.
FWIW the OP gauge in my car is totally unreliable,
it does not read the same as a mech gauge I have under the hood and
just sits under 40psi at idle and never breaks 40psi under load.


I'm using the same software you are. There is no GM.EOP. There is a GM.EOPS.

[mr.prick]

I'm using the same software you are. There is no GM.EOP. There is a GM.EOPS.
I don't have either one. :laugh:
Here is a screen shot with all PIDs in alphabetical order.
http://i235.photobucket.com/albums/ee259/whitespar/GMEOPS.jpg
The one OP PID that is there is not valid for me and is in PSI/kPa not volts
and is not GM.EOP, EOPS, EOPOS or EIO. :hihi:
:nixweiss:

[Ninety8C5]

Maybe it is only available for Corvettes or just the 97/98 PCM? I don't know why but GM.EOPS is valid for me.

[mr.prick]

There's all kinds of PIDs that are not valid for me, Diesel, LS2, E38 ect.
This one's not even there and Paul said:

There is no EOP PID anymore. The engine oil pressure is only returned by the PCM as V. We used to convert it internally to kPa and psi (when we first supported only a few LS1 controllers).

But as newer LS1 controllers were released the potential for them to have different V->psi scaling was introduced and we could no longer make that conversion accurately in the scan tool.

Regards
Paul
GM.EOP or GM.EOPS it's nowhere to be found.
:confused:

[Ninety8C5]

Maybe you need to revalidate your PIDs or I shouldn't revalidate mine? :nixweiss:

[mr.prick]

Re-validated and no change. :bad: Oh well.

[Ninety8C5]

According to this post (last page) it's not available on the F-Body cars.

http://forum.efilive.com/showthread.php?t=7587&highlight=eops&page=3