Jump to content
SAU Community

Recommended Posts

Ok so I hear some people say that the RB benefits from positive crankcase ventilation and some say it does not?

So should you just let it breath 'oh naturale', or does it benefit from a bit of -ve pressure to suck out those fumes and blow by?

FYI I couldn't give a monkeys about emissions laws it is purely for the health of the engine.

Link to comment
https://www.sau.com.au/forums/topic/386750-lets-talk-pcv/
Share on other sites

Yeah man I'm in the same boat. I got a GTR, a little off topic but i want to set up a oil catch can so I don't know if i should block the pcv valve and run the catch can or let it breath and run a catch can OR block/ unblock the pcv and run no catch can. (stock set up)

I've been told people just block it to keep the revs down at idel and numerous things about a RB26 not creating alot of blow by to really worry about any problems. I guess the only reason why it breaths in the first place is just for emission laws.

But if you block it, all that pressure has gotta go somewhere... ie. through seals causing oil leaks. Out the dip stick..

Link to comment
https://www.sau.com.au/forums/topic/386750-lets-talk-pcv/#findComment-6168426
Share on other sites

I am making a venturi set up attached to my dip stick tube to remove pressure from my crank case. This is a stop gap plan until I can get the engine out to do the proper oil control - smaller oil restrictors and better drains etc. There is a theory that the "drain" some people put at the back of the head actually acts as a breather for the sump and that excessive pressure build up in the crankcase helps tp prevent the oil from draining from the head.

If it works I'll post up pics etc

Link to comment
https://www.sau.com.au/forums/topic/386750-lets-talk-pcv/#findComment-6168959
Share on other sites

Was told by a very experienced RB specialist to leave it plumbed in. His 700rwhp RB certainly doesn't have any problems with it...

Sure but does he run it through a catch can before it goes to the intake?

Link to comment
https://www.sau.com.au/forums/topic/386750-lets-talk-pcv/#findComment-6169560
Share on other sites

I am making a venturi set up attached to my dip stick tube to remove pressure from my crank case. This is a stop gap plan until I can get the engine out to do the proper oil control - smaller oil restrictors and better drains etc. There is a theory that the "drain" some people put at the back of the head actually acts as a breather for the sump and that excessive pressure build up in the crankcase helps tp prevent the oil from draining from the head.

If it works I'll post up pics etc

Doesn't the RB crankcase breath through the head with the stock set up? I thought that was the point of the breather system on the rocker covers. I understand that gases coming from the bottom end are competing against oil trying to flow back in the opposite direction, but otoh if you are producing a load of gas then surely you have a busted piston ring at the very least?

Link to comment
https://www.sau.com.au/forums/topic/386750-lets-talk-pcv/#findComment-6169570
Share on other sites

Here's a thought. You go from idle to WOT with the recirc system. It puts the head under a bit more -ve pressure compared to idling, the gases in the bottom end try and equalise pressure and so flow up into the head, but this is right when you are wanting to stop build up of oil in the head and that oil is trying to drain down against the flow of gas up caused by your extra -ve pressure? Surely better to leave the head just at atmospheric pressure and the system open?

Link to comment
https://www.sau.com.au/forums/topic/386750-lets-talk-pcv/#findComment-6169575
Share on other sites

closed throttle is when you have the most -ve pressure in standard form as its sucking through the intake manifold, once you go past 0 boost the pcv valve shuts and its sucked through the intake pipe (high flow but not much vacuum).

Link to comment
https://www.sau.com.au/forums/topic/386750-lets-talk-pcv/#findComment-6169806
Share on other sites

"

Doesn't the RB crankcase breath through the head with the stock set up? I thought that was the point of the breather system on the rocker covers. I understand that gases coming from the bottom end are competing against oil trying to flow back in the opposite direction, but otoh if you are producing a load of gas then surely you have a busted piston ring at the very least? "

No. I have read the 40 page oil control thread twice

http://www.skylinesaustralia.com/forums/topic/110680-oil-control-in-rbs-for-circuit-drag-or-drift/page__hl__sk+oil+control

and it is a problem suffered by others with a new or old engine. It only manifests itself with sustained high revs therefore really only on the track. I had it with my RB25DET and now again with the RB30DET (yes I should have learnt).

You are right about the breathers on the can covers but when the head fills with oil they just fill the catch can with oil (and blow it out elsehere as well). The problem is thought to be worse with RB30s.

There is always some blow by and especially at high boost and revs and the action of the crank is thought to make things worse.

So yes you need to keep your breathers and preferably run them through a catch can and then into the intake for a street car.

Link to comment
https://www.sau.com.au/forums/topic/386750-lets-talk-pcv/#findComment-6169854
Share on other sites

  • 2 weeks later...

Hi guys - for the second time (I should have learnt) I have installed a catch can and blocked the PVC valve. Both times I have. Loan the front crank seal. From now on I think I'll be leaving the PVC valve plumbed in.

It seems likely to me that the blown seal is from too much pressure with the valve removed. Any thoughts?

Link to comment
https://www.sau.com.au/forums/topic/386750-lets-talk-pcv/#findComment-6187716
Share on other sites

I ran a hose from the catch can to the intake pipe before the turbo - I gather this is not what you mean by atmo?

I seem to be the only person on SAU complaining about a blown seal, other people seem to have their dipstick blown out. Poor me.

Link to comment
https://www.sau.com.au/forums/topic/386750-lets-talk-pcv/#findComment-6187743
Share on other sites

Ok lets firstly dispell some myths..

All a "catch can" does is catch oil.. requirement for most racing categories (must hold a certain volume) so you don't spew fluids onto the track. Useless in a street car.

In a street car running a plumbed back system, you need an "oil/air separator" which is kind of like a catch can but has strategic baffling to scrub the oil vapour from the air before it is returned to the intake stream.

You can run a "catch can" AND an "oil/air separator" and then plumb back to the intake. For a stock street car this is overkill, only a separator is needed to scrub those nasty oil vapours out. For a modded street car with bigger turbo, making reasonable power and gets beaten up on then the catch can and separator setup would be beneficial while remaining legal.

If you block the PCV valve then must also block the return to the intake pipe. Basically, vent cam covers to catch can and then vent to atmosphere (those little filters you see on top of catch cans). I also vent my dipstick to the catch can to help reduce oil stuck in the head.

Link to comment
https://www.sau.com.au/forums/topic/386750-lets-talk-pcv/#findComment-6187789
Share on other sites

Did you leave it plumbed to the intake?

If you block the PCV valve you HAVE to run atmo..

Is that so? I've see a few set ups with the PCV blocked but the two ports on the rocker covers routed back to the intake either by way of a catch can or not? What's the problem with taht?

Link to comment
https://www.sau.com.au/forums/topic/386750-lets-talk-pcv/#findComment-6188175
Share on other sites

Is that so? I've see a few set ups with the PCV blocked but the two ports on the rocker covers routed back to the intake either by way of a catch can or not? What's the problem with taht?

Your AFM wont be metering the air that is drawn in through the catch can vent - leaning the engine out.

Link to comment
https://www.sau.com.au/forums/topic/386750-lets-talk-pcv/#findComment-6188183
Share on other sites

Back to what i believe was part of the original question and what i would like to know, is it better to use bigger breather hoses to get more out faster than standard, i have mine plumbed up in the factory configuration but i use a line from the cam cover that does not have a restrictor in it like the factory line does, it then runs through a catch can filled with stainless steel wool as a filter and then back to the intake pipe, is this better/worse/no different to have the restrictor in the line?

Link to comment
https://www.sau.com.au/forums/topic/386750-lets-talk-pcv/#findComment-6188330
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Hi, is the HKS  Tower Bar still available ? negotiable ? 🤔
    • From there, it is really just test and assemble. Plug the adapter cables from the unit into the back of the screen, then the other side to the car harness. Don't forget all the other plugs too! Run the cables behind the unit and screw it back into place (4 screws) and you should now have 3 cables to run from the top screen to the android unit. I ran them along the DS of the other AV units in the gap between their backets and the console, and used some corrugated tubing on the sharp edges of the bracket so the wires were safe. Plug the centre console and lower screen in temporarily and turn the car to ACC, the AV should fire up as normal. Hold the back button for 3 sec and Android should appear on the top screen. You need to set the input to Aux for audio (more on that later). I put the unit under the AC duct in the centre console, with the wifi antenna on top of the AC duct near the shifter, the bluetooth antenna on the AC duct under the centre console The GPS unit on top of the DS to AC duct; they all seem to work OK there are are out of the way. Neat cable routing is a pain. For the drive recorder I mounted it near the rear view mirror and run the cable in the headlining, across the a pillar and then down the inside of the a pillar seal to the DS lower dash. From there it goes across and to one USB input for the unit. The second USB input is attached to the ECUtec OBD dongle and the 3rd goes to the USB bulkhead connected I added in the centre console. This is how the centre console looks "tidied" up Note I didn't install the provided speaker, didn't use the 2.5mm IPod in line or the piggyback loom for the Ipod or change any DIP switches; they seem to only be required if you need to use the Ipod input rather than the AUX input. That's it, install done, I'll follow up with a separate post on how the unit works, but in summary it retains all factory functions and inputs (so I still use my phone to the car for calls), reverse still works like factory etc.
    • Place the new daughterboard in the case and mount it using the 3 small black rivets provided, and reconnect the 3 factory ribbon cables to the new board Then, use the 3 piggyback cables from the daughterboard into the factory board on top (there are stand offs in the case to keep them apart. and remember to reconnect the antenna and rear cover fan wires. 1 screw to hold the motherboard in place. Before closing the case, make a hole in the sticker covering a hole in the case and run the cable for the android unit into the plug there. The video forgot this step, so did I, so will you probably. Then redo the 4 screws on back, 2 each top and bottom, 3 each side and put the 2 brackets back on.....all ready to go and not that tricky really.      
    • Onto the android unit. You need to remove the top screen because there is a daughterboard to put inside the case. Each side vent pops out from clips; start at the bottom and carefully remove upwards (use a trim remover tool to avoid breaking anything). Then the lower screen and controls come out, 4 screws, a couple of clips (including 3 flimsy ones at the top) and 3 plugs on the rear. Then the upper screen, 4 screws and a bunch of plugs and she is out. From there, remove the mounting brackets (2 screws each), 4 screws on the rear, 2 screws top and bottom and 3 screws holding in the small plates on each side. When you remove the back cover (tight fit), watch out for the power cable for the fan, I removed it so I could put the back aside. The mainboard is held in by 1 screw in the middle, 1 aerial at the top and 3 ribbon cables. If you've ever done any laptop stuff the ribbon cables are OK to work with, just pop up the retainer and they slide out. If you are not familiar just grab a 12 year old from an iphone factory, they will know how it works The case should now look like this:
    • Switching the console was tricky. First there were 6 screws to remove, and also the little adapter loom and its screws had to come out. Also don't forget to remove the 2 screws holding the central locking receiver. Then there are 4 clips on either side....these were very tight in this case and needed careful persuading with a long flat screw driver....some force required but not enough to break them...this was probably the fiddliest part of the whole job. In my case I needed both the wiring loom and the central locking receiver module to swap across to the new one. That was it for the console, so "assembly is the reverse of disassembly"
×
×
  • Create New...