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^this. I was going to say something similar. I'm positive you can read oil pressure with a Dashlogic and in HPtuners on LFX cars. Even the most basic of GM ecu's have an oil pressure PID. Its just getting that PID programmed in the Racepak which is the real battle. I've heard a few stories about Racepak being unhelpful in that regards similar to what's mentioned in the link above.
Just a head up... data from a stock vehicles ecu isn't always "real". For instance if an iat were to short to ground, the ecu may spit something out like 100 degrees. The ecu would see the short, flip on the MIL and use a default value. Hopefully the tuning software you are useing disables this "feature".
Only telling you this in case something goes wrong in the future and something just doesn't add up. I've always been taught; scan tools are liars until proven otherwise. I've been bit before by this sort of thing.
im not trying to scare you away from using the obd2 port. I'd probably do it that way to. Just thought you should know oe ecu's have the ability to reject reality and substitute their own. Then again, if the tuning software disables it, you have nothing to worry about.
Good notes, thanks guys. This is not my area of expertise so I'm figuring some of the wiring/electronics stuff out as I go.
I spoke with Racepak this morning. Explanation for oil pressure not coming through the OBDII plug is that the Racepak dash can only read the "standard" OBDII PIDs. There are additional "enhanced" PIDs added by GM which are not required part of the standard/required OBDII data. HPTuners and similar can read those enhanced PIDs but the dash cannot.
Worst-case scenario is having to run a second OP sensor for the dash. However, I asked about piggy-backing off the factory sensor and they said because the factory sensor is a 3-wire unit, one of those wires should be a 0-5V signal wire and there shouldn't be any issues with splicing into that wire to connect to the dash's OP input wire on its harness. Then, it's a matter of configuring the dash for that sensor which requires knowing the scaling of the factory sensor - info with should be in the factory service manual. So, sounds hopeful-ish...
Worst-case scenario is having to run a second OP sensor for the dash. However, I asked about piggy-backing off the factory sensor and they said because the factory sensor is a 3-wire unit, one of those wires should be a 0-5V signal wire and there shouldn't be any issues with splicing into that wire to connect to the dash's OP input wire on its harness. Then, it's a matter of configuring the dash for that sensor which requires knowing the scaling of the factory sensor - info with should be in the factory service manual. So, sounds hopeful-ish...
I would test the sensor first while sending data to the ECU and Racepak. Being able to split analog signals is dependent on the output and input impedance of the sensor/loggers, all of which I am not sure how to figure out. I have successfully split a signal, though. We split an amplified load cell signal (0-5v) between a hydraulic controller and a data acquisition box (Dewesoft). We found that the sensitivity remained the same (lb/V), while the offset changed (voltage at zero load) when the signal was connected to both sides. This was verified by re-calibrating the load cell. If this theory held true to the pressure sensor (same circuitry as the load cell), then you would have to adjust the offset in Racepak and the factory ECU (if that's possible in HPTuners).
I would think the most robust solution would be to run a redundant sensor.
So they said racepack can't do mode 22 PID's? Cuz I have some of those documented - but I use the broadcast GMLan data for my solution. The oil pressure data is "real" (there's still a floating value at 0psi to deal with), but the oil temperature is "calculated".
Mode 22, Pid 14. I didn't bother figuring out the scaler value since I was focusing on non-OBDII pids.
Last edited by gooflophaze; 02-02-2017 at 02:16 PM.
I would test the sensor first while sending data to the ECU and Racepak. Being able to split analog signals is dependent on the output and input impedance of the sensor/loggers, all of which I am not sure how to figure out.
Should be pretty easy to find DC (or anything really low-frequency) input impedance to ground of the sensor inputs using a 2-resistor voltage divider. More resistors and a DMM should also work for the output impedance of the sensors.
Would be pretty damn surprising if Racepak inputs weren't extremely high (~1M) impedance, though.
I would test the sensor first while sending data to the ECU and Racepak. Being able to split analog signals is dependent on the output and input impedance of the sensor/loggers, all of which I am not sure how to figure out. I have successfully split a signal, though. We split an amplified load cell signal (0-5v) between a hydraulic controller and a data acquisition box (Dewesoft). We found that the sensitivity remained the same (lb/V), while the offset changed (voltage at zero load) when the signal was connected to both sides. This was verified by re-calibrating the load cell. If this theory held true to the pressure sensor (same circuitry as the load cell), then you would have to adjust the offset in Racepak and the factory ECU (if that's possible in HPTuners).
I would think the most robust solution would be to run a redundant sensor.
That is my worry, in less technical terms, that the additional wire will skew the info the ECU sees and cause more trouble than it's worth.
Any other sensor type and I'd be happy to do a redundant sensor, but the aftermarket OP sender is a big honkin' thing that I'd love to leave in the trash bin. Might have to just accept it as the easiest solution with the least chance of complications though.
The easy button would be Racepak's V-Net OP sensor. Pre-wired and a snap to configure with the dash. Not cheap. https://www.racepak.com/products/oil...nt=17415603907 They have the same sensor in non V-net version for $190
That GM sensor is a whole lot more compact, lighter, and more reliable than the aftermarket 1-wire sender the Racepak came with. Looks like I'm probably going to just run two identical sensors side by side so the ECU and dash each get their own undisturbed signal.
I would just get some sort of 0-5v pressure sensor and run it to the dash. You should be able to use the existing oil pressure inputt on the street harness, and run the signal there. Then change the sensor calibration to handle the new sensor type.
Affirmative. Handy little things that make the assembly process much easier.. only issue I've run into is some mfg's hose ends are a hair too long for the tool.
which vendor's fitting give you grief when using the koul tool?
I would just get some sort of 0-5v pressure sensor and run it to the dash. You should be able to use the existing oil pressure input on the street harness, and run the signal there. Then change the sensor calibration to handle the new sensor type.
Forgive my ignorance but is the GM 3-wire sensor not a 0-5v sensor? My understanding is that the 3 wires on those are ground, +12V and signal (0-5V)
I think so? If so you just need to make sure it is either linear, or some sort of curve the racepak expects. Though they also allow user calibration with a big calibration table. Brief googling doesnt tell me the answer but I would bet on it being linear.
So yeah, just use the 5v/Gnd outputs on the racepak harness, and connect the signal to the oil pressure input.
Harness Type: Engine
• OEM Connector: 12065287
• Service Connector: 88988301
• Description: 3-Way F Metri-Pack 150 Series (BK)
The question is begged - Any reason to run the stock sensor at all? Pretty sure you could mute the MIL in hptuners - and the oil controlled cams should be closed loop not watching the oil pressure for data. I can't seem to find it, but I think the stock oil pressure is 0-120psi (though my math on the PID I monitor indicates 0-150psi). https://www.alibaba.com/product-deta...424792154.html puts it at 0.9mpa which is 130psi.
And yes, ground, 5v, and signal.
Last edited by gooflophaze; 02-02-2017 at 05:42 PM.
Forgive my ignorance but is the GM 3-wire sensor not a 0-5v sensor? My understanding is that the 3 wires on those are ground, +12V and signal (0-5V)
Most 3-wire 0-5V sensors are +5V supply. In some of them ("ratiometric" types), the output is relative to the supply/VREF voltage, so +12V in would definitely not be good.
If you want a compact 0-5V pressure sensor, take a look at the Honeywell PX3 series. PX3AN2BS100PAAAX is a good part for OP (0-100psia, 1/8NPT); it uses a Metri-pack connector, but some of the parts have molded-in 3-wire cables that make them even more compact.
As others above said, it's likely a 5V input. I know the LS series oil pressure sensors are. If it simplifies wiring, you can find a 12V input sensor that has an internal 5V regulator.
The Honewell that afm suggested is a nice choice. I use the Honeywell MLH series at work when I need a robust cheap sensor.
The 1-wire input into Racepak is a resistive signal, likely with a pullup to make it a voltage divider. If this is a software selected pullup and that can actually take in a 0-5V signal, I would use that.
02-02-2017, 09:20 AM
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