Dropping Oil Pressure!

[femno]

Hi everyone, got a small problem.

On cruise, my oil pressure is usually around 800 KPa at bout 3grand, and now, when i boost it, not to the boards, jus high revs and about a bar, it gets to a point where it drops to 600 then 400 and I back off.

This is bad and it never did it before, usually always stayed at 800.

The oil is smack on H. When I free rev the engine, its stays at 800.

So I overfilled by 0.75L, and its not dropping anymore when boosting, but this is just a bandaid fix.

I dont believe there is anything wrong with the engine itself, ie bearings and oil pump etc, as the engine is 8000km old and built by the best.

I do have a set of tomei baffles in the sump. Is it possible the rubber flaps have failed? But if they have, would it cause this? Just thinking from factory there are no flaps or gates etc.

A crack in the oil pickup?

I know im probably going to have to pull the sump off, just trying to get some insight first.

Cheers,

Mat.

[blind_elk]

How old is the oil? What grade?

I doubt it's "a crack in the oil pickup", or anything else, because adding extra (new) oil has alleviated the problem.

[femno]

The oil is 500km old. Its the same oil ive been using in the engine since the rebuild, and havent had a problem until now. So I doubt the oil would have much to do with it?

There is full pressure during free revving (car stationary) as stated above. If there was a problem with the oil im using id have low pressure all the time? Correct me if im wrong. Im thinking more towards this being a starvation problem.

[W0rp3D]

I have notced my gauge seems to drop really low at times, i have put it down to the sensor or gauge not reading right, but if i was you i would take it back to who ever built the engine just to be sure, if they didnt use new sensors and oil pump on the rebuild then they deserve to have to pay for it now.

[blind_elk]

If it was oil starvation, then you would have NO pressure. As long as the pump can get oil, then it will create pressure.

Whose oil (brand)? What SAE spec?

[femno]

Its Ausfield Extreme Synthetic, i think its a 5w50. Like I said, ive had no problems until now. And it wasnt doing it immediately after the oil change if you were thinking a bad batch of oil or something.

The readings are off my defi guage which is also 8000kms old so no issue there.

I will be contacting the builder later this week when im not working till 530, thought id get some opinions before then.

Cheers for the help so far.

[RPMGTR]

Every modified GTR should be run with an extra litre in the std sump.

I thought this was common knowledge by now......

[James_03]

Every modified GTR should be run with an extra litre in the std sump.

I thought this was common knowledge by now......

This is the first I have read about it, but if that's true I need to go put another litre in mine. But how would that effect his oil pressure? or is the extra oil just for impurities from a recent build?

Edited October 6, 2008 by James_03

[femno]

Well I thought that overfilling was for modded and tracked GTRs without baffles of some sort...and I wouldnt have thought if you didnt that it would cause this problem but anyways, problem sorted I guess.

Cheers Ben.

[some_cs_student]

Every modified GTR should be run with an extra litre in the std sump.

I thought this was common knowledge by now......

But, does this apply to track only? And is it the same if you have an oil catch can? Wouldn't the extra oil just go into an oil catch can? (sorry, my mechanical knowledge is not the best)

[W0rp3D]

But, does this apply to track only? And is it the same if you have an oil catch can? Wouldn't the extra oil just go into an oil catch can? (sorry, my mechanical knowledge is not the best)

The problem with these and gtst's (worse on gtst's tho) is that there is not enough drainage from the head to the sump, add to that a big volume oil pump and constant high revs and before you know it all the oil is somewhere around the head, from what i have read there is no harm in putting and extra .5 ltr of oil in for daily use but for track use and extra 1 to 1.5 ltrs is best, i put an extra .5 ltr in my gtst and it does not have any blow by.

Whilst for normal driving it is not really needed it does not hurt to put some extra in for those "excitable" moments

Edited October 6, 2008 by W0rp3D