Low oil pressure after WOT

[pogman]

10 hours ago, MBS206 said:

Can you log battery voltage, and TPS, and put all four of those into a single image (even as split graphs)?

 

The oil pressure drops aren't following RPM as such.

I'm intrigued if you may have a ground loop between different sensors.

With the engine not running, log your sensors and for example cycle the throttle pedal. See if any sensor values flutter or move about. This won't be a perfect test either as the ECU won't be cycling all of its actuators like it would be while running.

What EMTRON do you have? Do you have a link to the wiring guide for that ECU?

i only have ecu voltage available but that certainly does drop as that still relies on the 27 year old wiring, although has an ls altenator that pump out 140 amps and wiring upgraded to suit that. i will test the sensors without it running soon thats a good one.

 

it an emtron kv8, i recently redid the engine side harness so i have my own wiring guide for it but i had the same issues when i used the plug and play kit that was adapted to suit my old vipec adapted harness

[pogman]

1 minute ago, Dose Pipe Sutututu said:

Definitely looks like an outlier, perhaps there may be some electrical issues like others have pointed out earlier.

My pressure drop I can replicate over and over again, which I'm blaming the relocation block for, however yours is mounted right up the block.

its certainly looking like a power issue now which im all for so i can test turn the limit off for the upcoming track day i was hoping to make ahahahah

[pogman]

9 hours ago, Kinkstaah said:

Get more oil pressure sensors. I have 3 purely because trust no-one.

It would be worth checking (if not already) if it happens on every shift. Like boring, 2-3 shifts at 60kph making 10kw with no obvious G-force on a shift with mega power. Does it still drop? Does it drop less?

What if you shift at 5000rpm or what have you with no load?

more sensors sounds very smart least you never doubt a single sensor. 

 

it has dropped about 10 psi at a 5k rpm low load shift but regains it in a normal way, not showing like a quick blip on the chart but more presenting as like a build up of pressure again. unlike the 8k rpm high load shift which shows a quick up and down spike on the oiul pressure graph.

[pogman]

9 hours ago, GTSBoy said:

Log voltage. I'm suspecting the alternator.

Or even maybe a bad earth somewhere.

ie, seeing as it is rev dependent, I am thinking it is alternator dependent.

Think ill be going hunting for bad earths and might just replace the alternator for shits n gigs as its an LS alternator but only about 5 years old with very minimal use in that 5 years.

[MBS206]

50 minutes ago, pogman said:

i only have ecu voltage available but that certainly does drop as that still relies on the 27 year old wiring, although has an ls altenator that pump out 140 amps and wiring upgraded to suit that. i will test the sensors without it running soon thats a good one.

 

it an emtron kv8, i recently redid the engine side harness so i have my own wiring guide for it but i had the same issues when i used the plug and play kit that was adapted to suit my old vipec adapted harness

Editting as I hit post to soon, and this will lock out otherwise.

Edited April 5 by MBS206

[MBS206]

The log you did with ECU voltage, can you log the other things too like rpm and oil pressure?

Need all that info together to compare easily

[pogman]

42 minutes ago, MBS206 said:

The log you did with ECU voltage, can you log the other things too like rpm and oil pressure?

Need all that info together to compare easily

i cant get them all in 1 screenshot unfortunately as i just dont know how to move things around tbh, but they are all from the same log and the line crosses at the same point for all of them

Edited April 5 by pogman

[Dose Pipe Sutututu]

That dirty voltage drop is the culprit I suspect 

[pogman]

3 hours ago, Dose Pipe Sutututu said:

That dirty voltage drop is the culprit I suspect 

I much prefer that to an actual oil pressure issue, never would of thought it would of been a volt drop issue but SAU brains win again. Guess ill be turning down the oil pressure limit for the track and hunting some grounds. Ill hopefully update this thread with some high oil pressure and solid ecu voltage logs. 

[MBS206]

6 hours ago, pogman said:

I much prefer that to an actual oil pressure issue, never would of thought it would of been a volt drop issue but SAU brains win again. Guess ill be turning down the oil pressure limit for the track and hunting some grounds. Ill hopefully update this thread with some high oil pressure and solid ecu voltage logs. 

Don't turn down the limit yet.

Put a mechanical pressure gauge on the car in the same spot and go and prove it.

[Dose Pipe Sutututu]

6 hours ago, pogman said:

never would of thought it would of been a volt drop issue but SAU brains win again

I dare say all of us active SAU retards (no Gen Zs reading this right?) are probably more knowledgeable than the entire globe on Skyline shit boxes.

[Dose Pipe Sutututu]

6 hours ago, pogman said:

Guess ill be turning down the oil pressure limit for the track and hunting some grounds.

Try swap your alternator, someone else recently had a similar electrical issues with their 150A alternator too, swapped it, all the voltage issues went away.

[pogman]

36 minutes ago, MBS206 said:

Don't turn down the limit yet.

Put a mechanical pressure gauge on the car in the same spot and go and prove it

That sounds way too sensible, I may need to dumb it down before I try it.

[pogman]

32 minutes ago, Dose Pipe Sutututu said:

I dare say all of us active SAU retards (no Gen Zs reading this right?) are probably more knowledgeable than the entire globe on Skyline shit boxes.

Unfortunately I'm a Gen Z (Don't hold it against me pls) but I'm also retarded so surely they cancel out?

But yes definitely agree where else can you find people helping and bullying each other for the past 20+ years with a sprinkle of "hottest girlfreinds or wives of sau" in there too for some downtime after all the learning.

[joshuaho96]

7 hours ago, pogman said:

I much prefer that to an actual oil pressure issue, never would of thought it would of been a volt drop issue but SAU brains win again. Guess ill be turning down the oil pressure limit for the track and hunting some grounds. Ill hopefully update this thread with some high oil pressure and solid ecu voltage logs. 

Easy way to verify is just use an old style mechanical gauge and go for a drive. Then you can be 100% confident if the gauge reads one thing but your sensor reads something else. Just be super careful to not pinch the hose or anything, you don't want a bunch of hot engine oil spraying all over or a leak that empties your sump.

Edited April 5 by joshuaho96

[GTSBoy]

Just leaving this here in anticipation of good outcome.

[Duncan]

That is a pretty poor reflection on a well regarded ECU...surely a clean 5v supply for the sensors regardless of ECU voltage is #1 requirement

[Dose Pipe Sutututu]

24 minutes ago, Duncan said:

That is a pretty poor reflection on a well regarded ECU...surely a clean 5v supply for the sensors regardless of ECU voltage is #1 requirement

Probably the voltage dropping towards 11.1V, below a potential minimum requirement for the voltage regulator circuit and/or the capacitors inside are undersized to maintain a constant voltage.

I'm no electrical engineer but that's at a high level guess.

[MBS206]

6 hours ago, Dose Pipe Sutututu said:

Probably the voltage dropping towards 11.1V, below a potential minimum requirement for the voltage regulator circuit and/or the capacitors inside are undersized to maintain a constant voltage.

I'm no electrical engineer but that's at a high level guess.

Modern reg stuff now, they'd have a wide input range which would push through a buck converter, it would need to be able to maintain voltage for cranking conditions (sub 9V at times). Likely runs something like an internal 6V rail, and then further voltage regulators depending on which circuit/area it is feeding. Modern voltage regs, like what I'm starting a new power supply design with at work, will let me run a 5V rail output, and as long as my input is equal to or greater than 5V, I have a 5V output.
Except I'm not pushing a 5V rail in our system as I don't need one, we're setting up for a 3.8V rail. Our new design will allow me 6 to 60VDC input, and everything else doesn't care, even when I start pushing a few Amp outputs.

 

Realistically, the voltage drop off could be caused by a few things though, one could be literally the alternator is dieing, and hence charge power is dropping, which also means on a straight hard pull you're starting to send the battery flat... (Not that likely from a single couple of gear pull if the battery was fully charged). However, having earth issues, like stray earths not connected, or someone having put a ground loop in, will see the ECU appear to end up with lower voltage "input", mainly because the "ground" is no longer equivalent to battery negative. If they're comparing the input voltage using sensory ground for example, and sensor ground is what is in that ground loop, than the sensor output voltage will actually start to be reduced, when compared to battery ground...

Yeah, ground wiring design can start to be a bitch... Also voltage going weird from inductive loads not being managed properly is another real bitch...

Hence, why I asked above about how everything was wired in. If OP knows, and can post all of the actual connections from the ECU pin out, as well as what wires are joined where in the loom, which grounds from the ECU have ground points and where they are etc. Would help to see if there is a ground issue. The part I'd start with though, is putting a mechanical oil pressure gauge on to confirm the theory. Otherwise the next track day when the threshold is lowered could result in another of @Duncan favourite types of jokes... Knock knocks... Pretty sure this is what @GTSBoy is also self high fiving... 
Is all great that we have a decent theory... But they need to prove it before relying on it...

 

[pogman]

3 hours ago, MBS206 said:

Modern reg stuff now, they'd have a wide input range which would push through a buck converter, it would need to be able to maintain voltage for cranking conditions (sub 9V at times). Likely runs something like an internal 6V rail, and then further voltage regulators depending on which circuit/area it is feeding. Modern voltage regs, like what I'm starting a new power supply design with at work, will let me run a 5V rail output, and as long as my input is equal to or greater than 5V, I have a 5V output.
Except I'm not pushing a 5V rail in our system as I don't need one, we're setting up for a 3.8V rail. Our new design will allow me 6 to 60VDC input, and everything else doesn't care, even when I start pushing a few Amp outputs.

 

Realistically, the voltage drop off could be caused by a few things though, one could be literally the alternator is dieing, and hence charge power is dropping, which also means on a straight hard pull you're starting to send the battery flat... (Not that likely from a single couple of gear pull if the battery was fully charged). However, having earth issues, like stray earths not connected, or someone having put a ground loop in, will see the ECU appear to end up with lower voltage "input", mainly because the "ground" is no longer equivalent to battery negative. If they're comparing the input voltage using sensory ground for example, and sensor ground is what is in that ground loop, than the sensor output voltage will actually start to be reduced, when compared to battery ground...

Yeah, ground wiring design can start to be a bitch... Also voltage going weird from inductive loads not being managed properly is another real bitch...

Hence, why I asked above about how everything was wired in. If OP knows, and can post all of the actual connections from the ECU pin out, as well as what wires are joined where in the loom, which grounds from the ECU have ground points and where they are etc. Would help to see if there is a ground issue. The part I'd start with though, is putting a mechanical oil pressure gauge on to confirm the theory. Otherwise the next track day when the threshold is lowered could result in another of @Duncan favourite types of jokes... Knock knocks... Pretty sure this is what @GTSBoy is also self high fiving... 
Is all great that we have a decent theory... But they need to prove it before relying on it...

 

All of the ECU grounds are to the chassis, the IGN grounds are to the cylinder head and i believe all the OEM body harness are left in original locations, im trying to work out if i can tell if the sensor voltage itself is losing any power to it from the very low ECU voltage. But yeah a manual pressure gauge will help in picking which path to actually chase.

Also please dont bully my wiring plan i never designed it to be universally understood hopefully it still can make sense to you, im a wiring virgin. 

1 thing i have just noticed the pressure sensor in question relays both pressure and temperature, the temperature reading holds nice and steady despite the low ecu voltage but the pressure reading is the one that jumps around alot so maybe it is really a pressure issue?

wiring plan.xlsx

Edited April 6 by pogman