Low oil pressure

[jaffaz32]

I have done lots of searching, can't really find much that is relevant to my setup.

I have been reading that I should see:

10 psi at idle and 50 psi above 3,000rpm, this is based on a stock motor. No oil warning light on the dash.

I have an AEM 0-150 psi sensor and gauge that I believe is in line with the turbo oil feed coming off where the factory oil pressure sensor is.

My pressure is about the 40 psi mark above 3k.


things i have done that may be oil pressure related:

• My car is turbocharged.
• I have a SOS external oil cooler.
• Cylinder heads vent straight to the atmosphere, filters directly on heads. No catch tank or recirc.
• I have a very slight oil leak, i mean very slight. bottom of sump is damp, i check my oil every time i take it out and hardly ever need to top up, Next on the list to resolve.
• Pure Power billet oil filter, which they claim gives more oil pressure
• oil lines to oil cooler run near turbo, hotter oil = thinner oil. all braided, lines insulated and turbo ceramic coated. Pulled out the way as much as possible.
• oil itself. I was running 5w40 was told to change that out, i couldn't get 15w50 off the shelf so put in 10w60 as a short term fix. Now i may have gone from one extreme to the other possibly and gone from to thin to too thick. Just an idea. Brand, Gulf Competition 5w40, Mobil 1 motorsport 10w60

Before i go out and spent another £100 on oil and giving it a go, what other suggestions? any of the above would explain the lower oil pressure?

Temp wise, my temp sensor is mounted on the left of the sandwich plate when looking in the wheel arch, i'm not sure if that is the feed or return side, but it may be important because the sandwich plate feeds the oil cooler, so that sensor is either before or after cooled. It reads around 200 normal driving and raises up to about 225 after a hoon.

All AEM sensors and gauges.

I hope I don't have a more serious issue and it is resolved by replacing one of the above. I do have a SOS oil pump with gear sitting at home but that isn't a easy swap, engine out? Might help things also.

Climate, it's the UK. so no extreme heat or too cold. summer or winter.

May be of use to other members, I had no idea my oil pressure was low until the external gauge was plumbed in. The factory gauge looked ok. Might be worth others checking their oil temps and pressures with external gauges.

- - - Updated - - -

I have just got a reply from an local oil supplier

I can mail order in either Fuchs Pro S / Millers CFS in 10w50 or Valvoline VR1 Racing 5w-50 Premium

The oil supplier recommended to go with either one of the 10w50's.

If we think the 10w60 could be the cause of the oil pressure drop i could order any of the above.

 

[Mac Attack]

Taking into account all kinds of factors could easily account for differences between your sensor reading and others. I wouldn't worry about it.

So, you have a factory engine with factory bearings and clearances. I'm not familiar with the sandwich plate fittings and how you may have your supplemental oil cooler plumbed in, but I'm guessing you are reading temperatures post factory cooler but probably before the aftermarket cooler. Your temperatures look reasonable for that. I would personally stick with 10W30, or if you feel you must, the old 5W40 you used to run.

My $0.02.

Dave

 

[jaffaz32]

Taking into account all kinds of factors could easily account for differences between your sensor reading and others. I wouldn't worry about it.

So, you have a factory engine with factory bearings and clearances. I'm not familiar with the sandwich plate fittings and how you may have your supplemental oil cooler plumbed in, but I'm guessing you are reading temperatures post factory cooler but probably before the aftermarket cooler. Your temperatures look reasonable for that. I would personally stick with 10W30, or if you feel you must, the old 5W40 you used to run.

My $0.02.

Dave

Thanks for your reply.

Does the same rules apply because it's turbo charged? allot of people swear by 15w50 on turbo cars.

I have done allot of research. This post is very similar to what i'm seeing http://www.nsxprime.com/forum/showthread.php/124613-oil-pressure-with-15w50

Changed to a thicker oil and added a external oil cooler but his was a NA car.

I'm really lost what to do, 15w50 will be better suited for the extra heat from a turbo setup but the downside to that is loss in oil pressure by about 10psi. Although i've not tried the 15w50 yet, the 10psi is based on the 10w60. So with 10w30/5w40 the oil pressure will be better but might not be able to withstand the extra heat from the turbo system.

This really becomes a problem for me, because my ecu throws me in limp mode based on the oil pressure table. The ecu is doing exactly what it should be which is a good thing. Lots of protection. Perhaps the answer is trying a different oil from the 10w60 in the hope i gain a little pressure back but meeting in the middle with a oil that will withstand the heat yet offer a little more pressure than it does now?

Oil pressure safety is set to 40psi above 4k. Because i'm on the line it goes in to protection mode, so perhaps tweak down to 35psi if I'm to expect the lower oil pressure because all the variables.


The sandwich plate is where the oil filter screws to, it replaces the factory one and i believe it bypasses the factory oil cooler, although i may be wrong. there are two AN fitting coming off which feed to and from the cooler which is located towards the other side of the car at the back. I had to relocate it from where SOS instruction specify because this is where the turbo sits. I will need to work out if the sensor is post cooler.

To clarify, you wouldn't worry about 40psi oil pressure at 4K and above? I have no idea when it comes to pressure, what's dangerous and what's safe. Just want to make sure i'm not going to do any damage to the engine.

 

[Mac Attack]

First, I would forget about your oil pressure safety. You can set that however you want it. The "rule of thumb" most cars go by is at least 10 psi per 1k engine RPM, so that is probably what your tuner set the failsafe to.

Oil pressure should increase with engine RPM up until about 6k RPM when VTEC is actuated and the bypass valve (spring-loaded plunger) in the oil pump housing opens up and recircs the bypassed oil back to the oil pump inlet. You could have multiple failsafes: 10 psi at idle, 20 psi at 3k RPM, 30 psi at 4k RPM, 40 psi at 5k RPM, 50 psi at 6k to 8k RPM for example. This is PLENTY of margin to allow you to run the engine yet still be alerted to a major problem like loss of oil.

Oil is there to lubricate and cool the engine obviously. Neglecting cooling for the moment, the crankshaft and rods do not physically contact the engine bearings except when the engine is off or during startup. At all other times they ride on a "hydrodynamic wedge" of oil film that is squished in there from your oil pump to support those journals. That's what you have to protect and ensure. If your oil isn't at the viscosity the engineers assumed in their calculations of bearing size and clearances to the journals, then it can (simplistically) "squish" out the sides and not support the rotating loads. That's why it is critical to know if you have stock bearings, journals, clearances, the oil you use, and the temperatures you subject it to.

Given that you have a stock engine and the temps you are seeing, you should still be using 10W30 oil. Turbo or not, your EXISTING oil temps are saying that you don't need to increase viscosity. Now, if you start tracking the car or move to a really hot environment and still get on it on the streets, then maybe. But not now.

The only variable I don't know about are your oiling requirements for the turbo. What does your turbo manufacturer say to run?

 

[Operator]

READ http://www.nsxprime.com/forum/showthread.php/168189-External-oil-cooler-on-boosted-Nsx

DDozier idea is Best what i have seen so far ! AN10 oil cooler hose is TOO SMALL for NSX!

 

[Mac Attack]

jaffaz32:
40 psi measured at the stock sender location at ~3k RPM is OK.

Main causes for a lower oil pressure in your engine are:
- Wear on bearings/journals (unlikely)
- Worn oil pump (unlikely)
- Blocked oil pickup (unlikely)
- Additional restriction due to your oil filter (relatively unlikely from the Pure Power filter - if the propaganda is true it should be opposite)
- Restriction due to the SOS oil cooler (yes, a small restriction and decrease in pressure as measured in the head)
- New leakage path prior to the sender for oil supply to the turbo (yes, a small decrease)

Bottom line is that your setup appears healthy. If anything, I would go back to a 30wt or 40wt oil before going to a 60wt oil.

 

[jaffaz32]

Thanks guys.

It's a Garret GTX 35 series turbo with the oil restricter installed in to the turbo.

A little update. To clarify I have Mobil1 10w60 Motorsport installed as we have limited choice on shelf here. I'm waiting for some new millers CFS Nanodrive to arrive.

I changed a few sensors around at the weekend, moved the oil pressure sensors to where the factory dash sensor is located, I have low oil pressure there also. To do this i used the SOS block adaptor, i had to sacrifice the factory gauge to do so, replacing with a digital gauge.

Oil pressure was very low. At idle on a cold engine 20psi! good! when it warmed up, i went out for a drive, psi didn't seem to go much past 20psi through the rpm's, turned around after shortly going down the road and nursed it home, low rpm. Once home idle had dropped to around 10psi. when i say around it fluctuated either way a few psi. This is measuring at the factory pressure sensor location off the block and not the warning light location off the filter. Not sure how much difference this makes.

no oil warning light comes on the dash, it lights up when you start the car.

So when the oil is cool, it's ok. when it's at temp the pressure drops.

I have traced the oil leak to the front head, it's leaking between the head and the cover. So i'll replace these gaskets.

I have ordered a new oem style filter to rule that out.


What is the easiest way to bypass the SOS oil cooler for testing? I'm assuming I would do this at the sandwich plate? Plugging the ports perhaps? Not sure where you get -10an plugs from though. Can you simply plug it? not sure how the sandwich plate works, if the ports are in line or not.

 

[Operator]

You cant "By pass" it ..take it OUT . Put new OEM style oil filter ..now you shoud have 85-90+ psi oil pressure when engine is cold , when warmed up 140-170F over 3000 rpm 75 psi (10-60 oil)
Measured att oem location
You dont need external oil cooler if you dont go track days ...even then take 2-3 laps ..let it cool and monitor oil temps .

 

[jaffaz32]

Thanks,

when you say Oem location, which one? The dash gauge location? Or the warning light location off the filter?

the dash gauge one I'm getting the low reading from.

ive took out the oil cooler completely. Replaced with Oem style filter.

Started up my oil pressure seemed allot better initially, then after a drive it was back to being low.

my magnetic sump plug didn't show much, so that seemed ok.

im waiting for my oil to settle to double check the level after a drive, loop warm it's just under max though.

it doesn't make any sense that I initially have good pressure then once it's been running 10 min or it settles to a low point.

one daft thing I did do was, I misplaced my oil pressure gauge so borrowed a friends, my sensor is rated at 150psi, his gauge was 100 psi, same brand. So I've swapped over now as I found it.

even still, I still have low pressure because I have an aem stainless sensor additionally to the brass one. Again measuring on the block where the factory dash hooks up next to the coolant tank. Maybe readings here are allot lower? As my oil light never triggers.

 

[Operator]

OEM location >dash gauge sender location . 20 psi ...it cant be or your engine is dead very soon ! ...re-check your pressure gauge ! Use only good quality mecanical gauge fom hydraulic
hardware shop.

 

[Mac Attack]

I'm glad to hear you started stripping all of the stuff off your car related to the oil system and going back to stock temporarily.

Pumps, in general, have different capabilities for flow and pressure. These two things are what's mostly important for pumps (neglecting efficiency and other factors). Pump flow capability is meaningless without pressure capability, and vice-versa. A positive-displacement-type pump like the NSX oil pump can be assumed to put out a fixed flow no matter what the pressure is downstream at a given pump speed (engine RPM). As engine speed increases, pump speed increases, and you have more oil flow through your engine (simplistically neglecting the oil pump housing bypass for now). So, let's consider a constant engine speed and look at the effects oil weight and temperature play on your oil pressure readings.

We want to know the status of an important part of our engine - if our oil pump is working or not. It can be argued that it is easier to measure oil pressure than flow to determine if oil is getting where it needs to. So, where do you measure oil pressure? You don't measure it in your oil pan since there is no pressure there (well, except perhaps from piston blow-by). You need to measure pressure somewhere between the pump discharge and the top of the heads where it opens up and drains down to your oil pan. Ideally, you place the sensor just before the last most restrictive orifice before it drains to the sump. Like where the engineers placed the oil pump gauge on the front head. That way, you know if there is a problem with blockage or leakage throughout all of the engine and not at just the pump discharge. The dashboard light for the pump discharge is to let you know of catastrophic failure of the pump or a loss of all oil.

So for the dashboard gauge that is measuring pressure up in the head before it drains down to the oil pan, at a constant pump speed, a 10W60 oil at 250F will read a higher oil pressure than a 10W30 oil at 250F because it is "thicker," and the pump has to do more work to push that thicker oil through all of those small engine passageways.

Similar thing when you start the car cold. The oil is "thick," and as it heats up it "thins" out due to it's decrease in viscosity as a function of increasing temperature. That's why you have "good" oil pressure when cold but after 10 minutes it drops back down. The drop in pressure is perfectly normal.



Since you have removed the sandwich adapter (with SOS cooler) and the PurePower filter, hook up a mechanical gauge to the dashlight oil pressure sender on the oil filter pedestal like page 8-5 of the Service Manual instructs. Compare it to the SM readings. This will at least tell you if you oil pump pickup in the pan is OK (not blocked with crud) and your oil pump itself is OK. You should be using 10W30 for this like specified on page 8-4 of the SM.

Let us know how that test goes first. If it doesn't pass the minimum SM values, then that is the reason why you may have low pressure as measured in the head. The oil pickup may be blocked, the oil pickup may be cracked and sucking air, the oil pickup o-ring where it mates to the oil pump may have disintegrated, you oil pump housing/rotors may be worn, or your oil pump relief valve (page 8-6 of the SM) may be stuck open and bypassing oil from your engine internals.

That should be your first test!

Dave

 

[jaffaz32]

Thanks for your help, i had a read and purchased a mechanical gauge as advised.

I didn't flush the oil though as i'm not able to do it where it's currently sitting, which would involve risking driving it but... after todays result it may had been wasted money.

So... Here we go, i put the mechanical gauge on the oil filter sensor location. Started the car initial psi about 40 ish but... I followed instruction as per manual waited until the car was up to temp and the fans had come on. I then took my reading, about 10 psi. I then held the revs at 3000rpm and got about 35psi. Yikes!!

I tried a couple of times, same readings.

The other day, my brother said do you remember that sound, when cruising on the highway we heard this sound because my car has aftermarket everything it makes a few sounds here and there. At the time it sounded weird, all gauges looked ok but went away, comes back now and then.

Because of that sound i stuck my head to the block, the usual slight tappy sound but there was a clunky sound. clunk, CLUNK, clunkclunk. Very slight but didn't sound healthy and could hear it only on the front head not the back. So i placed a hand on both heads, i could feel the same vibration on both but the front i could also feel when it clunked. That sound could of been that clunky sound but louder at highway rpm.

Out of curiosity, i still had the pure power filter wrapped in rag from when it was removed, took it apart. Interestingly it had magnets, i could see a build up around these magnets, looked like metal flakes but when removing with a small screw driver it looked more like thick gunky oil you would see in a CV joint. I looked inside the case and there it was.... metal flakes, very small, Not that many but enough to be seen without looking too hard.

Correct me if i'm wrong, but the sound and what i saw i am thinking there is damage there? When i compression checked my motor earlier this year, 5 pistons were only a few psi of each other, 1 was about 10 out but still within tolerance but only just. Although i'm completely skint and recovering from the install of the Aem ems I think i need to face the facts and rebuild the motor.

About 2 years ago, i almost built a motor, i bought a spare 9.2:1 90.5mm SOS pistons, head studs, MLS gaskets, timing belt, SOS oil pump, i have lots of gaskets not sure what i have or need, going to cross reference part numbers needed for a rebuild once i can find the parts list. I'm considering selling the Pistons/head gaskets and sleeving the block so i can build a stage 2 engine instead of stage 1. It should be a stronger motor and give the extra scope if i decide to run more boost than the stage 1 would allow.

What are your thoughts?

 

[Mac Attack]

Seems like the engine has degraded since your first post.

So, with Mobil1 10W60 oil you have ~35psi at ~3k RPM instead of the factory minimum 50psi using 10W30 at the oil filter pedestal? That's definitely not good. Your first post had about 40psi at 3k RPM as measured in the heads after all of the pressure drop through the rest of the engine internals. It has gotten worse since your first post unfortunately.

50 and 60-weight oils are WAY too viscous for the low oil temps you are seeing (225F max before or after cooler - doesn't matter). If you rebuild your motor with stock bearing clearances, run 30wt or 40wt maximum.

The clunking doesn't sound good and can be any number of reasons. Metal flakes (aluminum?) aren't good either. It's hard to say anything without opening up the engine. Compression only tells you the health of your piston rings and valves.

Sorry to hear about this.

 

[jaffaz32]

Yeap, the only difference was the gauge i used, previously was using a digital sensor, the second readings were with an mechanical gauge as you advised.

I'm going to try and not get too involved with the build process, i'm going to supply them with the parts and as much information as possible. I will ask them to build it to the spec of the SOS stage 2. I hope to learn a little more along the way and i'll ask them what clearances they built it to so I know what oil going forward.

Yeah, i thought to myself could the clunking still be down to the thickness of oil, but if that is the case then surely it would be felt in both heads not just the one. I'm not sure what the material the metal was in the filter, i can post some videos i took. You can hear the noise and see the flakes.

It totally sucks as i had spent all my savings on the turbo kit, then i needed proper engine management now a new engine, joys.

thanks again.

- - - Updated - - -

Here are the videos.

Oil filter:
<iframe width="420" height="315" src="https://www.youtube.com/embed/SAYGYoJ_8EI" frameborder="0" allowfullscreen=""></iframe>

Clunking (best heard with stereo):
<iframe width="420" height="315" src="https://www.youtube.com/embed/t71tGwk_UJ4" frameborder="0" allowfullscreen=""></iframe>

Oil pressure when cold:
<iframe width="560" height="315" src="https://www.youtube.com/embed/Y4Y2HrO7GW0" frameborder="0" allowfullscreen=""></iframe>

Oil pressure when up to temp @3k (from 2min27 up to 2min27 was my attempts at holding steady throttle):
<iframe width="560" height="315" src="https://www.youtube.com/embed/d6mGn26KuwY" frameborder="0" allowfullscreen=""></iframe>

 

[Mac Attack]

I would try to get your car in to see Kaz.

He may be able to save you a lot of money before going off and doing a full rebuild.

The knocking sound in the head may be a wiped camshaft journal that is also causing reduced oil pressure. Kaz is an expert with these and can steer you in the right direction.