Catch Can Setup/crankcase Ventilation

[No Crust Racing]

At a recent track day my CA filled the 1L catch can twice, I'd done an oil change the night before so it might have been a touch over full but certainly not 2Ls

I've read quite a lot about CAs having inadequate breathing through the head at high revs and with boost turned up but there seems to be a lot of conjecture as to how best to resolve it.

From what I've seen a common approach is to T both breather hoses together and feed into catch can, have catch can output to intake as per usual, block off pcv and in some cases vent the catch can so it can breath properly and also plumb the catch back into the sump or turbo oil return so it can drain back to the sump easily.

What have other track drive CA owners done?

I considered that the rings might be cactus but a cold and dry comp test with throttle open gave me a max of 160 in cyl 1 and then 150-155 for the remaining 3 so seems healthy enough as I'd suspect a hot test or a wet test to have figures closer to 170 which is decent for an original engine.

Car is running GT2560 on 17psi also and doesn't seem to be making any more power than it did with the 25G on 14psi (it was running a remap previously and made 164rwkw and now has a new remap + the supporting mod of injectors, Z32, and fuel pump to suit but doesn't feel any more powerful). Could my pressure issue be chocking it somehow? (I do need to check base timing again so that could be an issue but I doubt it's stopping it making ANY more power, I say no more power because back straight speed at Winton was no different than with the old setup and it just doesn't feel any more powerful).

It has also developed a half moon seal leak at the back of the rocker, which I also suspect is from pressure build up as the seal is only 2yrs old. That said though, the rockers shouldn't be so heavily pressurised unless it had some kind of compression leak I'd have thought?

So in short.

- What's a good setup to avoid the catch filling so quickly?

- Thoughts on why no power increase?

Cheers

[KiwiRS4T]

Read some or all of this although it doesn't mention CA anywhere I think.

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

I only know about RB30s but for you I would suggest immediately running two breather hoses into the catch can not one.

My problem was solved with severely restricting oil feeds to the head and fitting a large (20mm ID) breather to the sump (as high as possible on the inlet side).

I don't have any CA experience though.

Re power - has your ecu been rechipped or do you have something tunable? If you are thinking of checking base timing I would suggest you need a good tuner.

[No Crust Racing]

Yeah I've had a read about RB oil control but CAs apparently don;t require the head restrictors etc just better breathing but I'm unsure on exactly how to provide that.

ECU had a Remap in it, and has had a new EPROM with a new tune go in - this is dependent on certain base timing though which I still need to confirm once I borrow my mates timing light.

[Dale FZ1]

a common approach is to T both breather hoses together and feed into catch can, have catch can output to intake as per usual, block off pcv and in some cases vent the catch can so it can breath properly and also plumb the catch back into the sump or turbo oil return so it can drain back to the sump easily.

First step, consider changing the spec of your oil. Are you using a full synthetic? Also what weight?

If there was an engine build being planned, you'd have to say that checking the size of the oil returns and enlarging them would be a good step.

Otherwise, look at mods to the cam covers. Remove the baffle plates, add more screens under them, and then reinstall the plates. Look to knock down the heavy oil vapours before the air passes out into the catch can.

If you're a dedicated track runner, vent the catch can to atmo with two 1 - 1.25" breathers. And if possible delete the PCV, and use that takeoff plus the other two breathers so you have a total of 3 large-ish diameter feeds to your catch can. The idea here is to drop the velocity of the air passing out of your engine and venting to atmo. Expect a few oily smells.

I know there are different views on the drain-back to sump idea, but it can work. Install a PCV in that line to stop the sump pressurising the catch can, but allows the drain to function when crankcase pressure drops.

Whatever you do, work on improving it. Those CA sumps don't hold a lot of oil and you don't want to pump it dry.

[r33_racer]

You should do a leak down test and see just how well the rings are sealing.

I reckon your issue is blow by in which case the pressure build up in the crankcase and whole engine is whats forcing oil/air out into your catch can. You need a decent size catch can with some baffling in it and a crankcase vent from inlet side straight to your catch can and have ample sized breathers on it, say 2 x 32mm filters. Dont feed the catch can back into your intake and as said above make sure you have 1 hose for each cam cover.

Have the valve stem seals & guides been replaced at any stage? If they are heavily worn & still 20+ years old its possible some intake/exhaust gas is leaking there and helping to pressurise the engine also. Thats a bit of a stretch in terms of likliness but you never know.

[No Crust Racing]

First step, consider changing the spec of your oil. Are you using a full synthetic? Also what weight?

If there was an engine build being planned, you'd have to say that checking the size of the oil returns and enlarging them would be a good step.

Otherwise, look at mods to the cam covers. Remove the baffle plates, add more screens under them, and then reinstall the plates. Look to knock down the heavy oil vapours before the air passes out into the catch can.

If you're a dedicated track runner, vent the catch can to atmo with two 1 - 1.25" breathers. And if possible delete the PCV, and use that takeoff plus the other two breathers so you have a total of 3 large-ish diameter feeds to your catch can. The idea here is to drop the velocity of the air passing out of your engine and venting to atmo. Expect a few oily smells.

I know there are different views on the drain-back to sump idea, but it can work. Install a PCV in that line to stop the sump pressurising the catch can, but allows the drain to function when crankcase pressure drops.

Whatever you do, work on improving it. Those CA sumps don't hold a lot of oil and you don't want to pump it dry.

Semi Syn 10-40, nice and cheap, only stays in the engine for 500ks at a time.

No engine build planned as dry and cold comp test came back at 150-155, new they are 175 warm/wet so I'd susupect that if I did a warm/wet test it would easily be over 160, good enough for a 23yr old engine.

I've been getting some good advice on mods to make to allow it to breath and stop the oil leaving the rockers, yours included so thanks.

Correct les than 4L stock, mine holds a little more as it's got a remote relocator and an oil cooler on it.

You should do a leak down test and see just how well the rings are sealing.

I reckon your issue is blow by in which case the pressure build up in the crankcase and whole engine is whats forcing oil/air out into your catch can. You need a decent size catch can with some baffling in it and a crankcase vent from inlet side straight to your catch can and have ample sized breathers on it, say 2 x 32mm filters. Dont feed the catch can back into your intake and as said above make sure you have 1 hose for each cam cover.

Have the valve stem seals & guides been replaced at any stage? If they are heavily worn & still 20+ years old its possible some intake/exhaust gas is leaking there and helping to pressurise the engine also. Thats a bit of a stretch in terms of likliness but you never know.

Hopefully not, comp test came back pretty good.

Catch is 1L and has a home made baffle in it, which seems to work well as I don't get much oil leaving the can towards the intake.

Engine is factory, so no new valve stem seals or guides, but as comp test came back good, I'm inclined to beleive they are still sealing relatively well.

More reading shows CAs suffer similar to RB26s in that once the oil is up in the rockers it has a harder time returning. There' a "balance tube" under the inlet manifold I learned of recently which looks way to small and apparently clogs up, I'm going to pull that and check it too.

As for my power issues, my guess is still timing/tune related and I'll be checking cam and base timing this weekend hopefully.

[R31Nismoid]

CAs apparently don;t require the head restrictors etc just better breathing but I'm unsure on exactly how to provide that.

More reading shows CAs suffer similar to RB26s in that once the oil is up in the rockers it has a harder time returning.

You do realise the reason for the oil getting up there in the first place is the issue? Hence the restrictors. Not just RB26's either, RB25 heads suffer the same thing etc.

Englarging the returns/drains is only one piece of the puzzle

Semi Syn 10-40, nice and cheap, only stays in the engine for 500ks at a time.

Why do you change so often? If there is nothing actually wrong with the oil - changing all the time is just costing you money. I'd be surprised if you got it tested and after 500kms there was any degradation at all. Meaning you could use it for another 500km easily

Then changing every 1,000km (or even 2,0000) and perhaps use a better oil that might aid in alleviating and protect better as well - Just an idea

And as the others have said, have you actually done a leak down test?

Sounds like just comp tests you've done... Which won't neccesarily tell you the full story.

[No Crust Racing]

Every other CA I've seen that's solved the issue has done so by increasing the amount and diameter of points from which the rockers can breath, the head restrictor trick doesn't seem to have been adopted in CA land. My query in that regard is how best to setup the lines to/from where etc.

I'm only using Shell Helix Semi Synthetic and it only costs me about $35-$40 to do an oil change in the car, cheap insurance when the only time the car is driven is when it's being hammered, no oil analysis has been done on it. I could probably use a thicker oil to alleviate some of the symptoms though.

I don't have access to a Leak Down tester and when the basic comp figures are good that tells me that the chambers are being sealed pretty well. Yes a leak down test will allow me to hear if any air is escaping in the rockers, intake tract or exhaust specifically but as the comp figures are already decent, I'd think that's not the case.

What I would like to know though is if the sealing is good under WOT at full boost (as in are valves returning and seating properly) and I don't think a leak down test tells that does it? I thought that was more evident on a Dyno

[R31Nismoid]

The old "cheap insurance" argument is a bit silly really. It's not insurance if there is nothing wrong with the oil.

I'd seriously go and get it tested next time and just see where it's at. I'd be surprised if it's any different 500km of 1500km. Meaning you are adding time/cost/effort for no reason and putting in slighly thicker/better oil could certainly help. I'd give it a go if I was you man

[No Crust Racing]

Nowhere here to get it done, what do you Melb guys do? Send it in to someone?

Can move to thicker oil without too much hassle but finding a reasonably priced option is the thing, I'm not sure I can get away with using 20-50 so thinking it should be more like 10-50 or 10-60 both of which are dearer than what I use now. That said, if I'm not changing it as often it might balance out.

[r33_racer]

A leak down test will tell you if air is bypassing rings or valves and help you pinpoint where. Compression test cant really do that properly.

A leak down tester isnt really that expensive to buy either. You can find them for $100 or less these days and they are straight forward to use, you just need compressed air.

[bubba]

Dan, see if there is a Cat dealer in your state, here in WA we use Westrac for oil testing.

My opinion on breathers is thus (if you don't care about being legal), block PCV valve, block return to inlet, vent cam covers to catch can, vent sump (from intake side, I'm currently using the dipstick) to the catch can, vent catch can to atmo with decent sized opening/filter.

That is for my twincam 30's though and I restrict the oil feeds to the head, size depending on oil pump used.

[No Crust Racing]

Have any of you guys seen/used this?

http://www.moroso.com/catalog/categorydisplay.asp?catcode=13023

[bubba]

Have any of you guys seen/used this?

http://www.moroso.com/catalog/categorydisplay.asp?catcode=13023

*NOTE: Cannot be be used on cars w/ mufflers

Have seen the concept talked about and used in some supra applications in the US.

[No Crust Racing]

I noticed the note on that, a guy on NS is using one in his CA with success he reckons, he's what I'd call a reputable source. Curious if anyone else has seen/used it.

Edited March 15, 2012 by ActionDan