Oil Filling Catch Can

[ClumpyDog]

Hi,

I recently purchased a '94 GTS-t, RB25 running 1.2bar boost. I bought the car this way, so I don't know the nitty gritty of everything it has, but it has a oil catch can, which is the point of this question.

Under normal driving, the can doesn't fill up at all, it doesnt use any oil, and is generally well behaved.

Soon after I bought the car I took it down to Calder for the street drags, to see how it would do, as you do.

Unfortunately, over 7 runs, the car had managed to dump over a litre of oil into the catch can, filling and overflowing it, not to mention coming close to causing the engine to starve for oil.

Now- I assume running 1.2 bar of boost has something to do with it, but I am sure even with that there is something not right with the car dumping that much oil in such a short time. I am reluctant to take the car on to the track the way it is, as it really is going to put the car under much more stress than the drag strip ever would, and going around corners with oil low isn't a good idea.

Is this common, and is there a good way of preventing this?

Thanks,

Alan

[paulr33]

what turbo?

sounds like oil seal is shagged on the turbo

its leaking oil into the intake piping

turn the boost down until you find out whats wrong, see if it goes away

[ClumpyDog]

Thanks for the reply.

What turbo? That's a very good question. Short answer is I don't know. Its a Garrett, but I know that helps as much as saying the car is a Nissan.

When I had the intake piping off I couldn't see anything that identified it other than Garrett. It isn't particularly big though. The problem with buying a car someone else modified.

If the problem is completely non-existent except under extended high boost, would that still be likely to be oil seal? It gets regular boost, just not for 1/4 mile at a time.

I can see that it doesnt occur under low boost or short bursts.

[paulr33]

yeah if its under high boost the oil seal on it could be shagged

drop the boost and see if it goes away, if it does, it could be ok and will remain to be ok, the more boost, the faster the shaft speed, which could explain why its leaking oil under excess stress

[ClumpyDog]

Cool, thanks for your advice.

If you could excuse my ignorance for a sec, I am not sure how the turbo could be causing it. Maybe I am explaining the set up wrong or something. I am not too technically minded. I would have thought if the turbo was leaking oil into the intake I would have been burning a lot of it- this was not the case.

There is a pipe connecting the top of the rocker cover to the catch can- it does not seem to be connected to the intake in any way, and the only oil or air the catch can should be seeing is coming from under the rocker cover on the head.

I thought it was being caused by excessive blow by under high boost, or by too much oil getting into the head, and not being able to get out fast enough, so it pumps it out of the ventilation into the catch can. This is what I was hoping to rectify.

Of course, if this is just ignorance talking feel free to correct me.

Edited September 4, 2006 by ClumpyDog

[Craved]

I thought it was being caused by excessive blow by under high boost, or by too much oil getting into the head, and not being able to get out fast enough, so it pumps it out of the ventilation into the catch can. This is what I was hoping to rectify.

Of course, if this is just ignorance talking feel free to correct me.

this is also a possible cause... so reducing the boost level will help

get a compression test done to see , you might have worn rings or perhaps worse, excessive crank case pressure can cause the xtra blow by.

only way to reduce oil in the head if thats the cause is to restrict the amount oil going into the head.

check the forced induction FAQ's in the sticky section

[ClumpyDog]

Brilliant, I found the relevant posts now. I did search the FAQ's first, but I must have missed it. Exactly what I was after. The posts seem to describe what is happening, and it makes more sense now.

Winding back the boost for the track seems to be the cheapest/easiest option not involving head removal. Nice to know!

Thanks!

Alan

[Faid]

id say ur rings are starting to fail, jsut as said in a earlier post, your getting blow by. you know the coulor of oil when its goes in the engine, is the colour in the catch can the same as that or is it a dark cola like colour. if its dark it has reacted with som exhaust gasses like NO2 and caused it to blacken. it happens all the time with the machinery i work on. have your rings checked before some fatal shit happens to ur engine

[turbo87]

Do you have an auto or manual,

As the car stays at high revs for a decent period of time at the track it sounds likely your oil pump is simply overfilling the rocker covers with oil and therefore its overflowing into the catch can,

To overcome this you'll need to pull the head off and fit oil restrictors to some of the oil feeds

[sky30]

Turbo oil seal has nothing to do with you filling up the catch can, more to do with too much oil in the head with lots of blowby pushing it out the rocker breather.

put in some oil restrictors, and external oil return.

[ClumpyDog]

Do you have an auto or manual,

As the car stays at high revs for a decent period of time at the track it sounds likely your oil pump is simply overfilling the rocker covers with oil and therefore its overflowing into the catch can,

To overcome this you'll need to pull the head off and fit oil restrictors to some of the oil feeds

Thanks, I think that is what is happening. The car is a manual, and at the drags it was reaching 7500-8000rpm regularly. The sheer volume of oil seems to indicate it was pushing oil directly into the can using the built up blow by pressure. If it was excessive blow by due to rings, I still couldnt see it pushing that much oil by itself. The colour of the oil was pretty normal, a little dark, but that could have been 'old' oil in the can, because I hadn't emptied it before I got the car, so there may have been old oil in it as well.

If it was a product of too many revs cauding too much oil being pumped into the head, I am not sure that winding back the boost pressure would help all that much- the oil pump pumps the same at 7500rpm no matter what the boost pressure. The solution may be to keep the revs lower until a more permanent solution can be implemented.

[Craved]

more boost would cause more crank case pressure if worn rings... hence more pressure thats helping said oil out of the head into your catch can

get a comp test done to see how your rings are going.

[ClumpyDog]

more boost would cause more crank case pressure if worn rings... hence more pressure thats helping said oil out of the head into your catch can

get a comp test done to see how your rings are going.

Will do. Best to be safe.

Thanks.

[RB SANDY]

Is there a post on comp test's and how it is done also what should all the psi's be and the leak down time on a rb25 also do you take out all the plugs

or just the one you are doing.

Edited September 5, 2006 by RB SANDY