N55 Oil Pressure issue while braking!

[PacmanTF1]

Hi N55 friends

today i tried a bit how the pressure is behaving in cornering and braking.
When i brake like an emergency braking, the pressure drops to 17.7 psi! And guess what, when the engine is turned off, the pressure is arround 14.5, which is the ambient pressure.

What is going on? Do you expirience something similar?

 

[RuskiRacer]

How many miles on the motor

 

[SlowE93]

What is oil pressure at idle ?
What is it while cruising ?

 

[PacmanTF1]

Arround 125000 Miles, pressure at Idle ca. 36 PSI (hot) cruising depends on the revs, for instance 3000rpm arround 50isch PSI

 

[RuskiRacer]

You may wanna look into a new oil pump along with rod bearing replacement. My buddy has a n55 motor he built himself and his oil pressure is around 60-70 cruising and like 50 at idle.

 

[PacmanTF1]

50 at idle is not what bmw is aiming for... cant be technically.

My point is when hard and straight braking drops the pressure extremely, my question is if this is normal on others as well...

 

[RuskiRacer]

Much lower pressure than any n55 I've driven or worked on

 

[SlowE93]

May be a silly question but...have you checked oil level ? If low it can cause starvation under hard braking or cornering.

 

[RuskiRacer]

Another good question to ask is what oil and viscosity are you running ?

 

[PacmanTF1]

Oil level is already half a liter more, new 5w40.

 

[PacmanTF1]

Much lower pressure than any n55 I've driven or worked on

It really can’t be 3,5 bar at idle, that’s by far to much. It is 1,5 bar plus ambient = 2,5 bar total

 

[RuskiRacer]

It really can’t be 3,5 bar at idle, that’s by far to much. It is 1,5 bar plus ambient = 2,5 bar total

I don't know what to tell you lol thats the pressure. Its a fully rebuilt bottom end. Oil pressure is not an issue on his car it makes probably to much

 

[PacmanTF1]

Understand, probably a pump remap…

In my case all is stock.

 

[RuskiRacer]

Understand, probably a pump remap…

In my case all is stock.

Have you tried a Blackstone oil analysis yet ?

 

[wheela]

Here is the stock oil pressure map for my n55. I believe these values are in mbar.

 

[wheela]

It really can’t be 3,5 bar at idle, that’s by far to much. It is 1,5 bar plus ambient = 2,5 bar total

If i'm interpreting my oil pressure table right, stock pressure at idle appears to be 2.75 bar (about 40 psi), so depending on tune 50 psi at idle doesn't seem unreasonable. This aligns with what i've read on forums that idle oil pressure is around 40psi, and around 80psi under load.

In reading rod bearing threads, anecdotally the case seems to be that hard left hand turns (think tracking the car with sticky tires) can cause the oil inlet in the sump to starve. I'm not familiar with the layout in the oil pan, but perhaps really hard breaking can do the same.

 

[wheela]

For that 14.5 psi reading with the engine off, it hadn't occurred to me that those pressures may be absolute vs. gauge pressures. But I guess that makes sense since the crank case should be under partial vacuum. Are you confident it's reading absolute vs. gauge pressure? I have no idea either way, but it would be a pretty big coincidence if it was reading gauge pressure, and just happened to be off in a way where the gauge pressure reading matched ambient absolute pressure.

 

[RuskiRacer]

Wheela has a very good point where the oil pickup tube is located on the n55 hard left hand turns or hard left hand braking are pretty hard for these n5x motors

 

[PacmanTF1]

So yes, my Idle pressure is arround that 40 psi, correct an what BMW is telling me. But when i turn the car off, it is still showing the ambient pressure. Weird for me... At the end this is not my issue.

My issue ist that under heavy breaking the pressure ist nearly zero for a tenth or so...

And yes, N55 Oilpickup is a bad desing. BUT, my one is the X-Drive Oilpan which is looking even worse for my taste, everything is fully open.

 

[PacmanTF1]

Here is the stock oil pressure map for my n55. I believe these values are in mbar.

your graph is exactly what my pump is doing under normal circumstances, thank you very much for that.