Controlled breathing – Part II

baffle plates being made

With the recent fitting of the catch can to my Stagea, I feared the worst. I thought “how can a standard RB25 blow so much oil?!” So I took it to Dahtone and we preformed a compression test.

I was anxious to say the least, but the results came back consistent and not too far off the factory specs which is pretty damn good to me! So it just happens to be that my RB25 is pumping too much oil into the head, and cannot drain it back quick enough.

I didn’t want to go and pull apart a mint engine to fix this tedious issue that the RB is renowned for. So I did some research into the baffle design on RB25 cam covers.

RB25 cam cover baffle design stock

As you can see there isn’t much going on with the standard setup, there is a big opening towards the back of the cover and only a small piece of mesh to slow the flow of oil before exiting out the cam cover.

The ultimate goal was to slow the oil down, to a point where a minimal amount would be able vacate the cam cover.

enlarged baffle drain RB25
The first thing I noticed was how small the drain holes in the baffle plate were, I did some testing and under a medium flow of fluid, the drain would struggle to release it all and overflow.

I then opened the drain using a flat head screw driver, and tested again. The enlarged drains were more efficient and even handled a higher flow.

RB25 baffle plates 2

Next up I designed some metal plates to baffle the cam cover. I went for three in each , one was placed at the back to restrict and slow down the flow of oil entering the breather section.

RB25 baffle plates

The other two were welded in-between the standard mesh.  Basically I wanted to reduce the oil entering past the mesh, and escaping out of the breather holes. The idea of the baffles was to keep any oil that enters in the drainage section of the OEM baffle plate.

cam cover filled with foam

to finish it off, I filled the cam cover with fuel cell foam, to further slow the oil. It’s super dense where the drain holes are to emphasise this.

tapping RB25 cam cover

For those keen on adding their own baffling, just a word of warning. You will need to drill out the plates as they are spot welded on. You’ll also need to tap the holes so you can use bolts to secure the plates.

Painted RB25 cam cover

While the covers were off the Stagea, I gave them a coat of paint … black as always.

The recent practice night was the test to see if the extra baffles have helped keep oil within the engine. Although the track is a lot shorter than Wakefield, I was still on or near limiter for roughly 30 seconds at a time.

Anyway I checked the catch can, plumbing and the intake pipe after the event and there is no oil to be found!

 It’ll be interesting to see if it’s the same senario next time I go to Wakefield, but so far so good and I think this’ll do the trick.


6 Responses to “Controlled breathing – Part II”

  1. Ray April 2, 2013 at 10:21 pm #

    Hey Adam.
    Just curious, has the new baffling had any effect on crankcase pressure? This is a great idea anyway. Cudos on some great outside the box thinking.

    • Adam April 3, 2013 at 3:23 pm #

      Hey Ray,

      I did notice a slight increase in oil pressure actually (IIRC around 3-4psi). So I’d assume there is more pressure being built up. Though I haven’t blown out my dip stick or anything like that so it seems like it’s fine.

  2. Nathan July 28, 2013 at 11:41 am #

    Hi Adam,
    have you taken the car out much since? i just wanted to know if you are still having blow by issues. I have the same problem with my 30det.
    I was gonna get 26dett covers but if this works im all for it!

    • Adam July 30, 2013 at 10:38 am #

      Hey Nathan. I recently sold the car but I did take it to 3 or 4 events before it went to it’s new owner. This definitely fixed my blow by issue though. I say go for it!

  3. Steven March 24, 2015 at 3:08 pm #

    Hi mate. Great write up, this is exactly what keeps happening to my rb25. I’m about to do this mod to mine just wondering if you have the sizes of the little plates you welded in? I was wondering if just putting the fuel cell foam in without the plates and widening the returns will be enough??

    • Adam May 14, 2015 at 3:13 pm #

      Hi Steven,

      The plates were 1mm thick IIRC. If I were to do it again, I would probably leave the fuel cell foam out and just put the plates in. I’d assume that the oil would return a little quicker this way. I have a new R33 Skyline currently and all I have done is widen the returns. I have bounced it off the limiter all day long at a recent drift day and it didn’t have an issue with pouring oil into the catch can. There was a little bit but the dip stick was still on the full line at the end of the day.

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