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Discussion Starter #1
The problem:
If I gently (up to 50% throttle) rev the engine up to the rev limiter (8k rpm), the oil pressure normaly goes up to 6 to 7 bar, along with the revs.
If I floor the pedal, when the engine comes to real life, after the turbo lag (approx 4,300rpm or so), I suddenly lose between 1 and 2 bar of oil pressure when compared to the value I have at the same rpm on part throttle.

BUT, what is interesting is that it's not related to engine load at all. Actually, if I do this test in 4th gear (or even in 5th gear), the oil pressure doesn't really change from its normal value and gently stays above 5 bar.
But when at WOT on 2nd gear, the oil pressure drops below 4 bar at 6k rpm.

So basically, it's related to crank acceleration. It seems the oil pump can't suck enough oil in a little amount of time. Dunno if I make things clear...
Anyway, IMHO, it defo sounds like oil cavitation.

First question: should I worry?
Second question: would an oil grade change help in any way? (thicker or thinner)
Last question: I've seen pics of oil pumps and I wonder if it would be possible to change it without having to completely remove the engine?

And now for those who gonna help, some details:

First of all, my oil system setup:
- N1 oil pump
- Extended sump (Tomei IIRC)
- Oil cooler
- Mobil 0w40 oil at the moment
- std oil filter

Engine: nevermind the specs, here are the dyno results:



The oil pressure metering device I'm using: std gauge and Defi gauge. Both showing the same behaviour (even if std gauge is way less accurate).

Oil pressure @ idle:
- 6 to 7 bar when cold
- approx 2.2bar @ 80/90°C
- approx 1.9bar after about 30min on track

Thx for help!!!
 

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Discussion Starter #2
BTW: I never noticed this phenomenon before today when I entered a track day at Spa in Belgium...
Actually, I don't use the car very much and when I use it, I mostly enjoy some in gear launches on highways and not during a very long time...
 

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Discussion Starter #4
Why wouldn't I suffer from this problem when cornering?
RBs are not affected by lateral G forces?
 

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Mine was doing the same as this. It turned out that it was a faulty oil filter (nissan oil filter! that had just been installed)

I two thought it was the sump running dry/ baffle extended sump needed but when i realised it would do it in say 4th or 5th gear where there is no where near as much g-force i started looking at other reasons why it was doing it.

However i have now purchased an accusump to be double safe.
 

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oil filter is the last thing anyone thinks of, but it does have an effect. I switched from generic plain oil filters to K&N high flow oil filters. Made a difference.

I had the same symptoms, but that was before I added an extended sump and set up my Accusump.

Essentially, for whatever reason, under fast engine acceleration (not load-related), the oil pump is running out of oil and ends up sucking oil as fast as it's being returned to the sump. To get a better idea, take a straw and a drink. Then put the straw at the very edge of the drink, and suck. Flow becomes intermittent.

Oil pumps don't like sucking air; you can break your pump.

Quick fix - add another liter of oil, fill your dipstick past the max line up to the hump. Check oil level regularly.

Yes, you should worry. But it's not difficult to fix. It's good you put so much information, it makes it easier to diagnose.

To replace the oil pump, take out the engine. It's the easiest way. Ironically, if you were to do nothing else except change the oil pump to a Tomei, your pressure problem versus crank acceleration would only get worse. The symptoms indicate that the oil pump isn't being fed enough oil in the early gears.

Another way to look at this is that oil is being returned to the sump slower than the pump is pulling oil out. Hence, changing oil grade should have little to no effect on your problem. With 0W-40, what are the oil temperatures that you see? Maximum oil temp your car sees?

I can't imagine that your sump doesn't have a baffle, but if for some reason that was true that could explain some of the problem.

Another very rare problem could be perhaps some kind of blockage with the oil return galleries. But if that were true, it'd be the first time I've heard of it.

Anyways, fill the oil up to the hump on the dipstick. See what that does. When you change your oil, how many liters are you putting into the engine to refill it?
 

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Discussion Starter #7
Ok, so it seems I should begin with an oil and filter change. Kismetcapitan, where do you buy your K&N oil filters? (Has anyone tried the Nismo Veruspeed filters?)

Do you guys have pictures of your accusump fitment? Is that a hassle to fit? I thought I understood how it works, but I don't understand why it would help me as my oil pressure is far from dropping to zero. Have I missed a point (possible)?

Oil level: on my dipstick, my oil level (engine hot) was approx 5mm above the max level (it's about 0.3 or 0.4L extra I think). Should have I overfilled a little bit more?

Baffle plate: I guess I have one as lateral G forces doesn't change my oil pressure, no matter how hard I'm cornering. (and trust me, this car is mental! Never seen so much lateral grip!!).

Changing the oil pump: so you don't think it could be cavitation due to crank acceleration? And that an oil pump change would cure the problem? I'd be happy if you're right, cause I don't have time to drop the engine on this car! (which seems to be a hassle BTW) Is the oil pick up directly bolted on the pump?

Max oil temp: yesterday on track, the needle was just below the middle of the gauge, so I would say 110/115°C. But the weather was kinda cold.

How many liters do I put when changing oil? Errrr...will tell you that within a few days! lol Actually I bought the car in April and the oil had just been changed. Now the oil is approx 3,000 miles old, I'll flush it for the first time.
 

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Problem like this is what wrecked my engine . Happened in 2nd gear at hard acceleration . Oil pressure droppped and sounded as if i had run a bearing . Got towed home by a mate . Next morning started car and the noise was there for a couple of seconds then went away . Was convinced but nissan head was knackered but changed head and theres stiil a slight rattle on cylinder6 which has been found to be a small end bearing . Think it was caused by the oil pressure drop . New motor busy being build which will handle alot more power but dont know what to do to prevent this from happening again .
 

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i have not fitted my accusump yet. I will be doing so next week. Toby has some pics on here of his fitted if you try a search.


The way the accusump works is that it will pump iol direct into the engine (not the sump) when a certain set pressure activates it. You can set this pressure yourself. I,e it could be set at 1bar and below or maybe 6bar and below.

I think most people set them at about 4bar? So when the engine does drop oil the accusump takes over. When the oil pressure pick up again from the oil pump the accusump will be refilling itself ready for the next drop in oil pressure.

These are simple to fit. Basically you need to connect one oil pipe.

Also you can set the accusump up to pre oil your engine before you even start the car. for instance you could put your key in the ignision and you will have 4bar of oil pressure running around the engine without the car being started!
 

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Discussion Starter #10
Nexen: have you found what has caused the problem? In my case, I don't think the problem is due to anything else than the oil circuit because tests proved that it's not related to revs nor load... But I wanna solve it before throwing a bearing or something else...
 

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Have you tried to rev your engine fast up to 7000rpm and watched the oilpressure?

If the oilpressure is ok when doing this, then it is because of the hard acceleration making the oil move around in the sump.

Asim
 

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well I only had standard oil pump so hoping n1 oil pump will solve it . reading this thread though seems to happen with n1 aswell . Was thinking of trying a higher velocity sump but googled the accusump earlier and looks like a good idea . Might just buy one while running motor in . Thats when its finished
 

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Have you tried to rev your engine fast up to 7000rpm and watched the oilpressure?

If the oilpressure is ok when doing this, then it is because of the hard acceleration making the oil move around in the sump.

Asim

when mine was playing up it was only doing it when it pleased and mainly after your giving it 3/4 throttle which would explain that it was oil surge in the sump and not picking up oil.

But like i say, mine turned out to be a faulty NISSAN filter. I only found out it was a faulty filter by chance and that was because i had another one lying around and i tapped an oil pressure gauge into the top of it.

The problem was solved when using the other oil filter. So i swapped back to the nissan filter (which was brand new at the time -5 miles) and the pressure drop was there again.

It makes me wonder how many people have fitted an extended sump etc presuming that it was lack of oil pick up? End of the day you would change the oil filter and oil while fitting a sump extension so you would of gotten red of the faulty item without knowing about it!

BUT! i have still purchased a accusump also to safe gaurd myself against oil surge/lack of pick up or what ever you want to call it. :thumbsup:
 

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Discussion Starter #14
Asim: as I said, when reved up on part throttle, no pb. When reved up on high gears, no pb. I only have the problem when reved at full throttle in low gears, when my 500+ engine is pulling the car f*cking hard. So yes, it's related to acceleration. But my main question is which one? Crank acceleration or car acceleration?

At the moment, here is what I've planed to do: change oil and oil filter. (Matty, are u still using std Nissan filters?). And after this change, find a hill and see what happens when going up on part throttle (gravity helping to simulate car acceleration), and going down at full throttle in low gear (gravity helping to reduce oil going backways in my sump).

I'm also looking at accusump products (with 60psi valve)... ;)
 

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Asim: as I said, when reved up on part throttle, no pb. When reved up on high gears, no pb. I only have the problem when reved at full throttle in low gears, when my 500+ engine is pulling the car f*cking hard. So yes, it's related to acceleration. But my main question is which one? Crank acceleration or car acceleration?

At the moment, here is what I've planed to do: change oil and oil filter. (Matty, are u still using std Nissan filters?). And after this change, find a hill and see what happens when going up on part throttle (gravity helping to simulate car acceleration), and going down at full throttle in low gear (gravity helping to reduce oil going backways in my sump).

I'm also looking at accusump products (with 60psi valve)... ;)
Ok, i think im having trouble getting my point clear.

Have you tried to rev the engine fast while car is standing still. Just floor the pedal and watch the oilpressure gauge.
Suerly the revs will go up fast enough, or close to what is happening when you drive the car i 2nd gear.

If the oilpressure is ok, then it is not related to crank, but to the accelleration of the car.

Asim :)
 

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K&N oil filters can be bought on eBay, I bought a whole bunch, about two years worth. I was using Nismo Veruspeed filters, but the K&N just seems to flow better. Plus it's a lot bigger. If you do a search, I once posted the model number - the application is for Toyota but it fits onto Nissan just fine.

Also, did you try adding oil so it is around the middle of the hump in the dipstick, above the max line? It's a quick patch fix, but I've gotten into the habit of always going past the max line, even with 4 extra liters of oil in my extended sump as well as Accusump.
 

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ASIM i understand where you coming from....... and again in my case the car would only do this fault while moving that would indicate acceleration G-force. However it was not in my case and again it makes me wonder if it is the true reason in other peoples cases.


JOBI, i have stopped using the nissan filter after i found out that my problem was related the filter. I now use a filter from my local motor factors. People say that are not as good but end of the day at least my oil pressure now sits as it should do!

My mate used to work for a FRAM making oil filters and he has always said that there are many manufactores that they make filters for and there is no difference between the after market ones and the OEM ones apart from outside paint finish! He also makes oil filters for some top tuning names that sell for 3 x the price but are still the same thing. Im starting to belive him!


And yes, i have taken the car to a steep hill and launched it and drove it hard all the way into 3 numbers while passenegr watch's oil pressure gauge. There is no problem since.

However, im only running about 450 bhp. The power should be at 600+ after mapping hence i have the accusump also now.
 

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Discussion Starter #18
Have you tried to rev the engine fast while car is standing still. Just floor the pedal and watch the oilpressure gauge.
Suerly the revs will go up fast enough, or close to what is happening when you drive the car i 2nd gear.

If the oilpressure is ok, then it is not related to crank, but to the accelleration of the car.

Asim :)
Errr... I feel quite...err... lonely. :chairshot What you suggest ends up to the same result I'll have with the up and down hill test, except that it's way way easier to do!! :thumbsup: Will do that this week and keep you informed. Thx for this simple idea! ;)

Kismet: will do a serach for the K&N part number. Where have you ordered yours? Ebay?
 

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Errr... I feel quite...err... lonely. :chairshot What you suggest ends up to the same result I'll have with the up and down hill test, except that it's way way easier to do!! :thumbsup: Will do that this week and keep you informed. Thx for this simple idea! ;)

Kismet: will do a serach for the K&N part number. Where have you ordered yours? Ebay?
I have always used MAN W818/82. Cheap and you can get them from your local carpart store.

Asim
 

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Load on main bearings with big clearances can affect oil pressure. If I was chasing the problem I'd find a good operator with a variable load rolling road or hub dyno (not an inertia dyno) and run the car up under load to try and mimic RPM versus wheel speed change under hard acceleration on the road. This is a very different test to revving in neutral. If the oil pressure remains stable on the dyno look to oil surge, if it still changes look at the bearing clearances with a view to possibly running less clearance. Too much clearance can cause the main or big end bearings to act as an epicyclic pump and squeeze oil out as they rotate, and they can move a LOT of il to the detriment of oil pressure.
 
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