crank case pressure
 

I've got oil leaking from the front of the cam cover near where the rtv goes at the cams... again. That's the bad leak. It's also seeping around the entire cam cover and around the filler cap. It's been doing this for a while but the leak near the cams is bad enough to get on the tbelt. I'm running a turbo supra PCV valve which is still in good operating condition (just checked it). I've had my cam cover vent running through a catch can to the intake pre turbo and now the can is just venting. I hardly get any oil- maybe a tablespoon in 500 miles. Compression is still ~185 across the board - as it was before the turbo.

What I have noticed is that in 1000 miles my cam cover gasket is far harder than it was new as installed. I can only assume this is from the heat. So that might explain the seepage. But I suspect there's enough pressure going on to make the leaks far worst than w/o boost.

I'm wondering if anybody else sees any evidence of crankcase pressure like this. And has anybody taken other measures to improve the crankcase venting. It seems that just about all the other turbo cars out there get some kind of venting upgrade when the boost goes up or when they go from NA to boost. For example- a lot of the hondas get a big (AN12) hole right in the cam cover to a catch can that vents back to the OE pvc/vent system.

Looking at the mazda cam cover, it looks very restrictive in allow this venting with it's internal chambers for the pvc and vent. I've got a spare cam cover, so I'm seriously considering something invasive that will allow easy ejection of the gases from the crankcase like I've seen on the hondas. - rob

Correction: those hondas with the huge vent hoses almost always vta.

Just make 2 big holes like they do and put in some 1/2" hose barbs, and fashion up some sort of plate to block oil from directly entering the hole on the inside.

Maybe your PCV valve is shite. Vent that to atmosphere as well.

Run the turbo PCV system and the breather to turbo tube and you won't have the same problem. Put a 3/8" filter or a catch can between the breather and turbo, no oil in turbo, same with PCV. Crankcase will see negative pressure during vacuum and boost.

I was going to mention blowby as the problem, but saw you did a compression test. A couple sessions before piston 4 let go in an old engine, small amounts of oil leaked from the filler cap, more after each session. Then the 4th session of the day did it in, and things turned very smokey.

I can guarantee you that the crankcase will not see vacuum in boost with the breather replumbed. The lowest pressure you will ever see in a boosted car is by VTA with the breather. If you make is a closed system by plumbing into the intake pressure will increase with time.

Plumbing from the can to the intake pre turbo is damn near the same thing as vta. Most turbos don't have much of a intake length. I had mine run that way with a good 45* angle on it in the intake and then just stuck a filter on the can in place of the intake tube and there was no difference. The reality is that crank case pressure is just that- pressure. And it's way more pressure than most of these pcv/vent systems were designed to manage. It will find a way out, and is, but it just needs a bigger "pipe" to get out quicker.

I'll go ahead and set up the spare cam cover with some big ass barb ports on it and dump into a can and see what happens. If anybody sees any clever solutions to blocking oil passage through these ports, post them up.

are you certain it's not your cam seals....

rob, look at the diagram i posted in the last pcv thread....the one with the long title and response. i'd link but this "free" internet in my hotel is slower the 28kb.

I was pushing 13psi on track with the setup I mentioned and didn't notice issues with oil leaking from anywhere, and the clear filters I installed showed no oil other than slight misting.

I'll look again. It's possible, given how oil spreads about in the vicinity of spinning parts. And the cam seals are ancient, not to mention they sat dry for two years.

photos
 

I removed the vent chamber covers from the cam cover and took some pics. Looking at the overall picture, it looks like the pcv chamber sees way more action. Of course this might be from vacuum at high rpm. BUT it's half the size, has a much larger entry, far less baffles (2 vs. 6) and a much larger exit than the vent side. Also noticed that the vent chamber exit has a much smaller hole in the cam cover than what appears on the outside connection. It's almost half the size- about 3/16".

The small exit hole and numerous baffles must be a big restriction on pressure trying to exit while the pcv exit is block under boost. So at this point I'll plug the pcv bung on the intake manifold and then route the cam cover pcv port to the catch can (vta) to supplement the venting. Thoughts?

Cam cover with chamber covers flopped out:
http://i158.photobucket.com/albums/t...t/IMG_2055.jpg

Cam cover exit vent side:
http://i158.photobucket.com/albums/t...t/IMG_2056.jpg

PCV chamber entry:
http://i158.photobucket.com/albums/t...t/IMG_2061.jpg

Those are great pics. You def just gave me some good ideas.

Thanks

Those are the FE covers right?

Yes. Though I wouldn't be surprised to see similar designs on the B engines. Easy enough to try out on either, though nobody else seems to be seeing anything like this on the B. I should have a chance to try it out before the weekend.

I couldnt find those pics that i thought i took. perhaps i never took them. either way, it doesnt matter as yours are of the utmost quality anyway :-)

Further to discussing this with both Rob and Brian last night, i was thinking about what i might do for one when i get back.

Currently i just have the longer labyrinth with the short oem hose hanging in mid air doing nothing much at all, and the oem pcv setup to my manifold much like stock.

For a number of reasons i believe its beneficial to have the pcv valve in place and functioning in some place or other. the pcv gasses can be greasy and oily with no negative impact on anything much, so the small labyrinth is probably best left supplying that in the long term.

its apparent from Robs fine pics that the longer labyrinth and its associated escape route are rather small and restrictive. most likely totally fine for normal NA use, but if you double the power it would be reasonable to double the blowby and therefore with nothing else changed double the velocity of gas through that port under load. given a tripling of power, probably a similar tripling of flow would be needed to keep pressures oem low.

in order to achieve tripple the flow at the same near 100kpa pressure you would need approximately tripple the area to pass it. thats not going to happen through that stock rear port.

my proposed solution is this :
oem pcv as it stands
rear port enlarged as much as reasonably possible
inside of rocker at the front of the head ported where that gas enters the labyrinth to slow the flow sufficiently to allow the oil to fall out
some porting of the baffles in the big labyrinth to ease velocity in there.
and lastly :

having had a think about it and a good look at Robs pics and my own, it would appear that the only decent place to put an extra port on the fe3 cam cover is at the rear of the intake cam. they were nice enough to put a cast in wall across in front of it to keep the oil away, and because its adjacent to the end of the cam no oil will be being flung there are high revs.

an exhaust scavenging system installed on this new port, or just another catch can and VTA (vent to atmo) setup.

given these mods you end up with the following situation :

throttle closed at idle/trailing throttle :
pcv draws dirty (wet) gas out of the crank case and clean air enters the original feed that goes to the turbo intake or vta. either the check valve on the exhaust scavenger is closed and no flow occurs or it too is scavenging some gas and disposing of it.

effect : clean air entering the case on one side, and dirty air exiting where it doesnt matter
result : engine oil stays cleaner and more effective longer because moisture is scavenged out at idle and on trailing throttle

throttle open wide scenario one :
pcv closed due to pressure in the manifold being 100kpa or greater
exhaust scavenging pulls so much gas out that clean air flows in through vta/vtt (vent to turbo) and crank case is kept clean under throttle too.

throttle open wide scenario two :
pcv closed due to pressure in the manifold being 100kpa or greater
exhaust scavenging pulls in exact gas that is being blown by and nothing flows through vta/vtt

throttle open wide scenario three :
pcv closed due to pressure in the manifold being 100kpa or greater
exhaust scavenging pulls in a bunch of gas, but not enough to prevent pressure buildup or more flow.
VTT/VTA dumps excess to atmo or turbo inlet

in this way you end up with low pressure at all times and clean air flowing in to replace wet blow by whenever opportune.

its possible that the exhaust scavenger would always be enough, this could be tested with the vta/vtt blocked and a sensitive pressure guage installed in the cabin and watched while thrashing the car hard.

thats my take on it.

fred.

Sounds like a good solution to me. Am I wrong for thinking that the crankcase pressure goes far beyond double when you add (even moderate) boost? Don't know if the B cam covers have a similar wall cast in place, but that does look like the ideal spot for a new vent location.

I took the car out yesterday with this setup: ran the pcv valve in line on what was the vent line (more restrictive) and used the OE pcv port as the vent port to the vta catch can. Made several runs to ~5k at full throttle, and one run from low rpm to rev limit. There was no evidence of oil anywhere- not at the vta filter on the can, any gasket/seals nor the oil filler cap on the cam cover. I'll get to make some harder runs tomorrow.

rob, my memory was faded when i said "rbs get boxs welded on the top" half right :-)

they have boxs cast in from factory on the rb26 model :-) i couldnt find any serious plumbing pics of them, but the factory arrangement is fairly serious in the first place :

Attachment 215072

thats what i meant anyway.

fred.

I'll bet the head is similar to the FE with a valley separating both sides - thus the tube for equalizing and releasing pressure on both sides. The B engines don't have a valley where the intake and exhaust are mostly isolated.

yeah, it is, there are 6 coils under that cover.

what that picture doesnt show is that off the outer side of each upright, comes a hose. the exhaust side one goes to the turbos/inlet, and the intake side one goes to a pcv setup of some sort i think.

this is how its done on a modded setup

http://www.upgrademotoring.com/car_p...ine_engine.jpg

not sure that i'd do it that way, but...

http://got-jdm.com/images/RB26RWD.jpg

you can see the valley and coils there

http://got-jdm.com/images/RB26DETT%20COMPLETE%20002.jpg

and the intake and turbo vents there

fred.

Hi,

I would add to the recommendation that it would be beneficial to find vacuum from somewhere for the crankcase. Exhaust side and even vacuum pumps are widely used in Drag Race engines and David Wizard showed the positive effects on power measured in dyno once vacuum was introduced into crankcase. It is pressure difference between the top and bottom of the piston, which makes it move.

hrk, still here and lurking

I've seen vacuum/scavange kits (Vibrant) that use a venturi like insert into a O2 sensor bung that supposedly gives you around 3" Hg on some setups. Uses 8AN line. I'd think you'd need a lot of exhaust velocity to make any significant gains, but who knows, seems easy to try compared to vacuum pumps for maybe some gains.

that would be cool, as i dont need my front o2 sensor....

I think the exhaust scavenging would be perfect for a track (road course) car where the run through the gears is perpetual. Ideally you'd want a combination of all these "passive" systems to optimize evacuation/release of the pressure/vapor. IMO - First step in the stock system would be to enlarge hoses/passes and remove restrictions (improve flow) like mod the baffles in the vent chambers.

Might be worth a try, not too expensive either
http://store.summitracing.com/egnsea...115+4294851516

hrk

http://i50.photobucket.com/albums/f3...4/21344ev2.jpg

just an idea for a breather box location. i dont like their plumbing... but the location is nice enough.

vacuum is definitely a good thing for at least two reasons.

fred.

Honda guys apparently love them some crankcase ventilation...
http://a593.ac-images.myspacecdn.com...ddbde99408.jpg

Check out this thread for more inspiration, the photo above has -12AN lines.
http://www.honda-tech.com/zerothread?id=1970101&page=19

:werd:
I plan to use the OE vent on the back and then create another behind the intake cam since there's an OE flange cast in the cam cover to shield the new vent hole from oil. I believe it's more critical for the FE to have vents on both sides since the "valley" is closed off from the cam cover (the B engines are open). And the only side to side connection is at the front.

Crank vacuum pumps:

http://www.gzmotorsports.com/vacuum-pumps.html


Their porn pics:

http://www.gzmotorsports.com/sample-installations.html


Nothing plug and play for Miatas, but probably their kit for EVOs is the closest in the engine size components choice:

http://www.gzmotorsports.com/4G63T-kit.html

Time for an update
 

Decided to tackle the cam cover since the rain put a stop to the boost control testing. The modded factory venting (pic below) worked reasonable for 10psi, but just a few runs near 17psi and I had some cam cover gasket leaks. With the new setup the pcv will return to the stock location and two vents at the rear will go to the can.

I managed to get two 3/8" NPT ports on each cam bank of the cam cover. I was amazed to see just how small the existing vent port at the back of the exhaust side was - about half the size of the actually opening - maybe 3/16". Pics show the difference - white circle highlights the actually interior passage. I used the step drill bits (if you don't have a set they're worth buying) to overbore the existing vent and to enlarge the pilot hole on the intake side. These should provide the venting I'm looking for (like the honda photo) - now on to the catch can. (Go kia power ;) )

http://i158.photobucket.com/albums/t...portoldnew.jpg
http://i158.photobucket.com/albums/t.../ventportI.jpg
http://i158.photobucket.com/albums/t...ntportsnew.jpg

current modded: OE ports swapped, better flowing pcv port goes to the can
http://i158.photobucket.com/albums/t...entVENTmod.jpg

Wow rob, nice!

Yeah, those are small, i pulled one out of mine years ago, but I'd forgotten completely about that! if you aren't going to and don't mind I'd like to hijack these pics and add them to that thread on mx6.com.

Thats going to work MILES better for sure :-)

Well done.

Fred.

Also, good to see those leads being used :-) they even look good with the red.

yes, use at will, and it'll save me from having to cross post.

You think those leads will look good with a silver kia cam cover? :gay:

Exhaust side vent chamber plate is now modded and installed. Dramatically shortened, it still uses one cast fin from the cam cover and an opposing tack welded plate fin, plus the added fin/bend at the end of the plate.

http://i158.photobucket.com/albums/t.../sIMG_2262.jpg
http://i158.photobucket.com/albums/t.../sIMG_2264.jpg
http://i158.photobucket.com/albums/t.../sIMG_2263.jpg

well, you weren't shy with the tin snips were you! i had imagined you mean the opposite bend on the end, and much much longer overall. interesting.

Just trying to keep the oil out while maintaining a similar volume for pressure passage. It was less about length and more about getting two of those "fins" in for oil trapping. I think bending down would probably encourage the trapping of oil w/o any benefit of pressure relief. Tin snips did a good job for providing three drain back avenues for oil.

in boost is keeping the crankcase in vacuum beneficial?

Under boost there is no vacuum. But when you let off the throttle that vacuum is what pulls all the vapor from the crankcase. So boost blows it out via the vent(s) and the vacuum sucks it out via the pcv. Both are beneficial.

Yes if you have a suitable pump to try to keep up with the volume of flow, but it's not going to be easy :-)

look at the pumps linked above.
at the corvette forums some people use such pumps. if i remember correct BigGulp was/is using something like that too

I don't think a vacuum pump is necessary. The problem is managing the cc pressure occurring from boost blow-by. The oe vent system was not designed with that intent (obvious since it has a ~3/16" vent passage). So the addition of the two larger ports should manage the "new" pressure fine. This is essentially the same thing done to the honda engine pictured and what comes OE from nissan on the their turbo engines pictured above. I'm only using two 3/8" npt ports because my engine has a valley, separating the intake and exhaust sides. This way pressure from one side doesn't have "travel" to opposite side. In this case, I don't think there's such thing as too big or too much.

Rob, if you have a spare head, take a closer look at the middle and two ends, there is plenty of open area between the two that connect them. there can not be a pressure differential there really. i'm not sure how the rb one is laid out inside, but ours has good sized 1.5" x 1.5" channels in three places already. (not sure what i was thinking when i agreed with you about that on the last page, seemed like it was correct anyway :-) )

The other part of the vacuum pump is that it actually increases ring seal in the first place and reduces the blowby from the start. thats why its good. the increased seal A keeps things cleaner, B makes more power. its not necessary. but generally, its a very very good thing if you can afford/fit it.

i still havent got to writing what i think of your tin snipping in detail :-) i will though, i promise :-)

fred.

Some thread on electric vacuum pumps:

http://www.corral.net/forums/showthread.php?t=356004

and from that thread one guy's setup:

http://www.cardomain.com/ride/479951/3

I won't argue the effectiveness of a vacuum pump- there's a reason they exist and are used. And for having two vent ports, well, I doubt it's going to cause problems, and if it did, nothing a 3/8" npt plug couldn't fix. ;) Don't forget, this is a scrap cam cover.

Here is some more info - the pros and cons of vacuum pumps:

http://www.dragstuff.com/techarticles/vacuum-pumps.html

I was going to ask if you had pics of the whole thing, but i flicked back a page and found them. notice the lengths they go to on the pcv one? the thing you call the entry is i think an oil drain and there is an open port on the side above it. in that way any oil that came in from the side would fall straight out the bottom and any oil that found its way in the bottom would find its way back out again fairly quickly. If you consider the rotation direction of the cams, the exhaust side of each chamber is the side to put the slot/holes i think as it would be flung past them rather than into them. just like the pcv side.

Now instead you have those two flaps almost catching oil.

I guess my only concern would be that now the entry is right above the cam getting oil fired at it at high speed whereas before it was in that dead area between the cams and with IIRC a little cover stamped/spotted in.

I'm still wondering just how restrictive that chamber was in its full form and if there was a way of opening up the inlet end and maybe shortening all of the "walls" without cutting it down so much and leaving the open end in the between cam dead area.

I was expecting that you would just free up the chambers but leave the walls partially there. and open out the end in that middle area. Having seen yours and your nice pics i think i'll cut some notches into the edges off the ally at the pulley end and on the exhaust side at that end. that way you still get all the filtering of the long chamber and walls but less restriction.

after you pulled the fitting out, did you do a blow/suck ghetto flow test through the chamber to see if it was already free enough or not?

Either way, the worst that can happen is that your catch can gets more work to do. If it was plumbed to the turbo or intake like stock it would matter, but not how you have it setup.

Fred.

Bending up was an effort to shield oil as the oe finds on the plate do. Keeping the OE channel at the center V and V on the edges was for drain back. As is the OE hole in the rear at the "well". I figured that when the oil gets to the actual port, it still has to make a right angle and go up to get to the hose. And this is w/o the aid of pressure as before.

thanks for the pumps info
the bolt pattern of their pulleys might match the miata water pump pulley

Re: exhaust venturis to create vacuum, by using the O2 bung. With a street exhaust this point will show positive backpressure due to muffler and cat restriction. You will end up blowing exhaust into the crankcase.

Re: measuring effectiveness: Measure the crankcase pressure at the dipstick by fitting a rubber hose over the dipstick tube, and using a reducer to a 3/16" vacuum hose going to a boost gauge. BTDT; I found that the breather hole on the exhaust side is indeed restrictive - was getting 2 psi! I simply tee'd a hose from the dipstick tube to the vent line from the cam cover that goes to my "y8s hardware store special" PVC catch can. This greatly reduced oil weeping from my cam cover, and my turbo bearings too.

One the fe3 or the bp?

for the B - good info Jason, thanks. I can't remember exactly what the B cam cover and vent system is composed of. I remember finding a restricter inline somewhere...

From memory, pretty much exactly the same fitting as on the fe3. Interesting figures. How much boost, how many rpm and how much power with that 2psi?

This is on my '00 miata, at around 240hp, 10 psi, 6000ish RPM.

Hi, I have a major problem with either blow by or crankcase pressure. I'm not sure how many of you are familiar with "rappadan" old drift miata. But I have it now. I got it with a blown head gasket and the pistons smacked the head. I put in a 1.6 long nose, it was a short nose. At first oil was pooring out the exhaust mani (turbo off) I had the head rebuilt and also the turbo, put a mls head gasket on it. It's no where near as bad as it was but a very little oil in the exhaust still. It's not bad at cruising speed, just under a load. It's blowing the dip stick out also. I've tried catch cans. new pcv. I'm lost, the car runs great, no problem. Just smokes any ideas? Is there a vent port on the block? There isn't any oil coming out any where else, just the exhaust mani, And blowing out the dip stick.

Matt

Hi, I have a major problem with either blow by or crankcase pressure. I'm not sure how many of you are familiar with "rappadan" old drift miata. But I have it now. I got it with a blown head gasket and the pistons smacked the head. I put in a 1.6 long nose, it was a short nose. At first oil was pooring out the exhaust mani (turbo off) I had the head rebuilt and also the turbo, put a mls head gasket on it. It's no where near as bad as it was but a very little oil in the exhaust still. It's not bad at cruising speed, just under a load. It's blowing the dip stick out also. I've tried catch cans. new pcv.I'm lost, the car runs great, no problem. Just smokes any ideas? Is there a vent port on the block? There isn't any oil coming out any where else, just the exhaust mani, And blowing out the dip stick.

Did you use a PCV valve from a turbo car like a 323gtx or a Mazdaspeed Miata?

Have you done a compression test? What numbers did you get?

EDIT: Thank you for searching related topics. I don't mind the resurrection.

No I have been using the stock pcv. I didn't know I needed a turbo pcv, but ill do that. I drive a rig so I won't be home for another two weeks or so. Is there a particular pcv valve I should use? No I haven't done a compression test. I'll do that also.