CA18DET Breather issues and Catch Can

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troopiec
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Car: S13

CA18DET Breather issues and Catch Can

Post by troopiec »

Howsit guys, well those that seen it already know ive decided to install a catch tank after years of driving with open breathers, never had an issue but got tired of the fumes and the occasionall oil spillage when redlining the car, so i already made a thread on an overseas forum so il just repost it here:

Here is my setup and my issue:

- 76mm straight through exhaust
- walbro 255lph fuel pump
- garrett s14 t28 turbo at 1bar boost
- custom topmount manifold i built myself
- 38mm external wastegate
- turbonoz stage 2 eeprom chip
- front mount intercooler with 50mm hot side boost pipe and 63mm cold side boost pipe
- hks replica ssqv dumpvalve
- AAC and idle valves removed and blanked off
- motor internals stock standard never opened motor up in 6 years since ive had it

Last dyno was 169kw and 303nm at the rear wheels

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Anyways heres the story. Ive been running my setup above reliably for about 2 years and my breathers were always left open and PCV valve blanked off as i didnt want dirty oily vapours in my clean boost pipes and intake etc. The car drove perfect without any issues this way however when i used to drive the car very hard redline or spinning etc the exhaust breather would spit oil onto exhaust manifold and smoke and i constantly had crankcase fumes smelling in the passenger compartment so i decided to fix it properly, so i did my research and read on all the appropriate forums on correct catch can setups and did comparisons etc. I am a qualified mechanic and im well aware of how the PCV system is supposed to work so i installed things as per factory except with the addition of a catch tank to try reduce oil getting into turbo intake and boost pipes etc. However after the full install i came into the problem where my dipstick was blowing out and oil was spraying out, and i have never had the dipstick pop out ever before the catch can install. Oil level correct aswell. I will post pics of the setup now and how the breather system was effected in each example:

Original Setup derived from factory design with catch tank added, so PCV valve will scavenge crankcase pressure on idle and cruising and then on boost the pcv would close and turbo would scavenge crankcase through catch tank and not suck as much oil:

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this was done with catch tank unbaffled but fully sealed, test drove it down the highway and gave it 7000rpm boost a few times, pull off to check and i find dipstick popped up and sprayed oil on manifold, catch tank had about 50ml oil in it and turbo did suck a bit up but not much. So since i took the PCV valve out like 3 years ago before this i figured ok the pcv probably just leaked boost into crankcase and popped dipstick. So i blanked off PCV valve again and T'd the breathers together, heres Setup 2:

Setup 2 with PCV blanked off again and breathers pieced together and turbo alone scavenging:

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Test Drove car again down the highway as before 7000rpm a few times, pulled off, again same story dipstick popped out and oil sprayed, this just doesnt make sense to me, yes im well aware that my rings etc may be worn and i have excessive blow by, but the car pulls like a train and it never used to pop dipstick when the breathers were open, and besides even with very bad blowby the vacuum from the turbo should be sucking up all the pressure even if my rings were completely stuffed. So i tried one more thing to make sure its just the catch can setup, so heres setup 3:

Setup 3 with breathers T'd onto catch can and catch can simply venting to atmosphere, no vacuum on catch can and turbo inlet pipe piece blanked off

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Test drove vehicle like this again down highway nice and hard on a warm day, 7000rpm a few times, pulled off and checked engine bay, dip stick still seated nicely and no oil spraying anywhere, catch can had about 120ml oil in it now but thats including the previous 50- 60ml that was aquired during previous test runs.

So my question is what am i doing wrong, what can i do to improve my situation without a rebuild? the motor is pulling strong and not smoking, im not going to overhaul it for a small breather issue, noted also theres no sludge in motor i do an oil service every now and then as little as 3000km intervals, motor is gold inside. Possible just a badly designed catch tank? But really dont want to splash out on an overly expensive catch tank, i did try baffle and filter my catch tank above and it reduced oil getting into turbo but dipstick still popped on with vacuum from turbo.

Mmust i just live with a vented catch tank and have to smell the fumes.

Any input would be great, sorry for the long post!
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Nissan_Fanatic
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Re: CA18DET Breather issues and Catch Can

Post by Nissan_Fanatic »

My guess is the block breather from the block the the back of the intake tappet cover is blocked by gunked up blow by. Try clean that and try setup 1 again.

Also, is this a 8 or 4 port motor?

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troopiec
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Joined: Mon Dec 26, 2011 11:00 pm
Car: S13

Re: CA18DET Breather issues and Catch Can

Post by troopiec »

Cool thanks Nissan_fanatic, I was yet to check that breather out, a few guys on the international forums also told me to check that, so that's next on the list to check, I know it was clear when I took the intake off for polishing a while back but alot has been done since then, it's an 8 port but I removed all the butterflies and rods completely and welded the runners up to seal off the holes etc,

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