Oil Control In Rb's For Circuit Drag Or Drift

[GT-RZ]

I can't be sure but look at the intake side of the sump. I would guess that that is where the rear head fitting is plumbed into the sump. it's the same pic you posted before.

I have lots of pics of the m-speed engine bay somewhere. if you have time have a look at my japan photo diary. there are bound to be some in there (link in my sig). otherwise if I have time I will try and find some on my other pc.

I also can't see any connection between the rocker covers and the PCV. as sydneykid states it's not being used for that.

That would be great. I'll check your diary post too.

The pipe in view could be an oil drain but it seems too high as i would rather mount a drain at the lowest point.

If it was a drain there would still be another connection elsewhere. The pcv valve is needed in recirc simply so that when the engine is on boost it will close and not let any positive pressure in the crankcase, when idling it will open and allow natural vacuum to suck from the crankcase. The connction before the turbo intake (i think it sits in the cold air box, unsure - have to check) does it's job primarily when the engine is boosting as the other valve is closed and this one lets the turbo suck a vacuum from the crankcase via this line. upon idle it teams up with the other connection with the PCV valve attached to it which would be open.

If you have one line run directly to your cold air box or my preference (between turbo and pod) you do not technically need a PCV valve inline but it will not hurt anything and could help if natural vacuum was created within the crankcase.

m-speed due to the PCV valve being connected on the balance tube(above throttle bodies) clearly use both vacuum points. vacuum lines can be very small and m speed has chosen to adopt the rear in to a hardline across the firewall, nice idea. this will in-turn join with the line from the cold air box or alike.

Somtimes people can do more harm than good when messing with factory set-ups. venting to atmo is not too bad and the primary reason people do it is because they install a catch can and think re-circ is only for emissions, which is wrong.

Infact if that were true the factory connection to the intake vac line would not be there as not all gasses would be sucked back through the turbo. The primary reason is for good venting of the crankcase, just that under high loads the connections from the block to the head obiously are not sufficient and the head potentially becomes overun with oil and we get a mess or in re-circ excess vapour in the intake.

m-speed's extensive filtration system clearly aims to eliminate as much oil vapour as possible before allowing it to enter combustion.

Sorry quick edit: i never saw your last bit at the bottom. You cannot see any small connection from the PCV to the cam covers because unlke the factory setup where the two are linked without catch cans and additonal filters, M speed do have the additonal catch tank and filters. so the lines from the cam breathers must pass through the catch filters before re-entering via the vacuum lines.

Edited July 6, 2009 by GT-RZ

[Beer Baron]

argh!!! I know you mean well but argh! yes I know what a PCV valve is, where it goes, how it works and what it looks like and even what it smells like.

their rocker cover ventilation system does not incorporate it. it has two giant green pipes going to a catch tank system which as far as I know is vented to atmoshphere. there may be a hidden pipe conntect at one of the turbos inlets but i'm 90% sure it's not.

the other pipe going into the left side of the sump i'm talking about is from the drain/vent fitting on the back of the head. you kept asking where it went and I'm fairly sure that is it.

we are getting massively bogged down in minute detail now. it really doesn't matter....

[GT-RZ]

argh!!! I know you mean well but argh! yes I know what a PCV valve is, where it goes, how it

works and what it looks like and even what it smells like.

their rocker cover ventilation system does not incorporate it. it has two giant green pipes

going to a catch tank system which as far as I know is vented to atmoshphere. there may be a

hidden pipe conntect at one of the turbos inlets but i'm 90% sure it's not.

the other pipe going into the left side of the sump i'm talking about is from the drain/vent

fitting on the back of the head. you kept asking where it went and I'm fairly sure that is it.

we are getting massively bogged down in minute detail now. it really doesn't matter....

I'm looking through your diary atm. looked like fun.

Positive crankcase ventilation valves are only meant for one thing, what other use would it be. If you follow where it connects to the firewall, follow that hardpipe and it goes to the right hand side somewhere, on it's way to the intake.

There is certainly no filter in view sat on top of the catch can or the side. it would make perfect sense for a top class car to be using re-circ, it's the most efficient way to do it.

I think you are right with the images of the engine though. on the front of the engine image:

We have them two lines, the one on the right most likely is to connect to the head attachment as

the one on the left is shown attached on the engine bay shot:

And i just found a front shot of the bare block (had it before and never paid attention ):

There is the attachment that the hose will connect to from the rear of the head. With it's location it's most definently being primarily used as an additional windage vent, which is how i planned to use mine like posted earlier today! Finally i know

So that's cleared up on m speeds use, which i'm happy to follow. i'll continue through your diary for images lol.

Edited July 6, 2009 by GT-RZ

[Sydneykid]

The pcv valve is needed in recirc simply so that when the engine is on boost it will close and not let any positive pressure in the crankcase, when idling it will open and allow natural vacuum to suck from the crankcase.

The problem with the standard PCV valve is that they don't like a lot of boost, too much over 1 bar and they leak. You would need a decent aftermarket one way valve as there isn't a PCV vlave that is have seen which will handle lots of boost. The RB25's ones are plastic.

The connction before the turbo intake (i think it sits in the cold air box, unsure - have to check) does it's job primarily when the engine is boosting as the other valve is closed and this one lets the turbo suck a vacuum from the crankcase via this line. upon idle it teams up with the other connection with the PCV valve attached to it which would be open.

Where doe the separated oil go? Fill up the catch can, leaving the sump short on oil?

If you have one line run directly to your cold air box or my preference (between turbo and pod) you do not technically need a PCV valve inline but it will not hurt anything and could help if natural vacuum was created within the crankcase.

What happens when you have positive pressure inside the cold air box?

Cheers

Gary

[GT-RZ]

It looks to me like they are using the vacuum take off (on top of the throttle bodies) for the brake booster, which is what I do on the R32. It replaces the PCV valve, which isn't used anymore.

The alloy cylinder on the RHS strut tower looks to ba an oil/air separator, the air then flow from it into the large catch can near the RHS head light. Any oil collected in the separator could be returned to the sump via a fitting on the RHS of the block/ sump or by the dip stick tube.. Which is what I do on the R33.

Cheers

Gary

Never saw this post before. which puts forward a good point. What does connecting it to the brake booster improve?

Edited July 6, 2009 by GT-RZ

[GT-RZ]

The problem with the standard PCV valve is that they don't like a lot of boost, too much over 1 bar and they leak. You would need a decent aftermarket one way valve as there isn't a PCV vlave that is have seen which will handle lots of boost. The RB25's ones are plastic.

Part of the reason i was looking for an aftermarket one but then came across lots of modern nissan ones which may be better?

Where doe the separated oil go? Fill up the catch can, leaving the sump short on oil?

if there was enough blow-by oil to leave the sump short on oil i would be worried, to add to that the factory system would burn this oil, a catch can would collect it.

What happens when you have positive pressure inside the cold air box?

positive pressure inside the cold air box when. maybe if you had no BOV and you let the air return through this path it might be positive (factory does not have this problem). otherwise on idle there would be a vacuum and on boost there would be a vacuum. To add to that it's part of the reason i suggested an inline PCV valve (i don't run a bov which is why i added that)

Cheers

Gary

Edited July 6, 2009 by GT-RZ

[Sydneykid]

The problem with the standard PCV valve is that they don't like a lot of boost, too much over 1 bar and they leak. You would need a decent aftermarket one way valve as there isn't a PCV vlave that is have seen which will handle lots of boost. The RB25's ones are plastic.

Part of the reason i was looking for an aftermarket one but then came across lots of modern nissan ones which may be better?

Where doe the separated oil go? Fill up the catch can, leaving the sump short on oil?

if there was enough blow-by oil to leave the sump short on oil i would be worried, to add to that the factory system would burn this oil, a catch can would collect it.

What happens when you have positive pressure inside the cold air box?

positive pressure inside the cold air box when. maybe if you had no BOV and you let the air return through this path it might be positive (factory does not have this problem). otherwise on idle there would be a vacuum and on boost there would be a vacuum. To add to that it's part of the reason i suggested an inline PCV valve (i don't run a bov which is why i added that)

Cheers

Gary

Too simplistic, there are lots of times when there is positive pressure inside the cold air box when the car isn't idling. For example, what happens at 275 kph when I back off the throttle. not close it, just lift a little, for say the kink into the chase at Bathurst? Or the turn 1 at Oran Park? Or turn 1 at Eastern Creek? It still has boost so it can't vent via the one way valve and there is positive pressure inside the cold air box, so is it feeding positive pressure into the sump?

No blow by, just a lot of oil pumped into the head that can't return to the sump making it's way out the cam cover breathers and into the catch can? Long left handcorners with high G forces such as Read Park to MacPhillamy at Bathurst? The oil is trapped on the RHS of the head by the G forces? Or up Mouintain Straight and through the Cutting, where the oil is forced to the rear of the cylinder head by the climb?

I don't know about yours, but my car spends lots of time not idling and not on full throttle, about half in fact. Plus it spends most of it's time with high G forces, lateral and/or longitudinal pushing the oil around? Add those influences into your thinking and I bet the answers are no longer the same.

Cheers

Gary

[GT-RZ]

Too simplistic, there are lots of times when there is positive pressure inside the cold air box when the car isn't idling. For example, what happens at 275 kph when I back off the throttle. not close it, just lift a little, for say the kink into the chase at Bathurst? Or the turn 1 at Oran Park? Or turn 1 at Eastern Creek? It still has boost so it can't vent via the one way valve and there is positive pressure inside the cold air box, so is it feeding positive pressure into the sump?

No blow by, just a lot of oil pumped into the head that can't return to the sump making it's way out the cam cover breathers and into the catch can? Long left handcorners with high G forces such as Read Park to MacPhillamy at Bathurst? The oil is trapped on the RHS of the head by the G forces? Or up Mouintain Straight and through the Cutting, where the oil is forced to the rear of the cylinder head by the climb?

I don't know about yours, but my car spends lots of time not idling and not on full throttle, about half in fact. Plus it spends most of it's time with high G forces, lateral and/or longitudinal pushing the oil around? Add those influences into your thinking and I bet the answers are no longer the same.

Cheers

Gary

Full throttle, full vacuum. Half throttle, half vacuum.

The Manifold PCV valve only operates at idle. it is only there because it is within a sealed atmosphere and thus is able to pull stronger vacuum. It is not needed.

The vacuum pipe that connects to the airbox also operates at idle, however this pipe operates when boosting also. Whenever the engine is running there is always vacuum within the airbox. As RPM increases the vacuum becomes stronger which is why it works so well (positively increasing blow-by pressure,positively increasing vacuum pressure).

Because the airbox is directly connected to the atmospheric pressure of 15psi any positively pressured air that was to come through the turbo would instantly become de-pressurised. Air does choose the path of lease resistance. Air would most definently flow through the airbox filter rather than attempt to pressurise the crankcase. Neither would air inertia be a problem as the vacuum pipe would be connected at a right angle to the mainstream of air. (hence why the factory pipe from the crankcase to the airbox does not have a PCV valve, not really required). But would have no trouble operating here as no large boost pressures would be present, would not hurt to fit one.

Considering our problems only happen at higher RPM the idling PCV valve is not really required which is why i suggesed earlier to connect it directly to between the turbo/filter.

So with a connection to ATMO you have a crankcase pressure of >15psi and with the vacuum attachment you will always be <15psi.

The lower the pressure in the crankcase the easier oil will return from the head, helping with them big corners. Aswell as the other advantages associated with less resisticance for the rotating assembly and pistons, ring seal etc.

[Beer Baron]

like gary said I don't think there is a PCV there. look at where the fitting is. it goes to the brake booster and has nothing to do with the catch tank system. there is no need to recirculate the breathers back into the inlet on a track car. all that does is feed that dirty air back into your system. it's simple. you just need a good tank to seperate the vapour from the oil, a tank to catch that oil and a filtered opening to allow that air to escape and under vacuum to filter the air coming back in. as for the sump breather that's a good idea too.

[GT-RZ]

Had a good look at some pictures and looks like i assumed the wrong way. i'v imposed the block on the engine to show the connection location better. Note that the two large lines are just hung there, i'v drawn where they connect to the engine bay.

Going by there setup the oil at the back of the head must be fairly heavy and not aerated so it is allowed to flow direct in to the sump well under surface oil level. Acting ONLY as a drain.

The attachment on the block however (image is deceiving, look at bare block. the attachment sits in the lowest point of the block).

It connects to under the oil/air separator, if that's what we think it is... I'm unsure because due to it's location, crank windage would be firing straight at this pipe... Maybe it acts primarily as a vent from the block and the oil/air is caught in the next large catch can and disposed off. However under low rpm any oil that may have accumulated in here could drain back in to the block, id really love to see inside that small oil/air separator.

As for the whole re-circ, i don't think anyone can prove either way. both have a positive effect but vacuum would still be the best option providing you can clean the air adequately...

this is how it can be setup, no reason why m-speed has not got the same out of view in them images straight to the cold air box they have.

I liked reading your post BB with your trip to japan, looked great fun. I think the GT500 cars may have taken a simplistic approach to oil problems?

Them little cam covers wouldn't have too much space for lazy oil?

Edited July 8, 2009 by GT-RZ

[Beer Baron]

the GT500 cars have dry sump so very different in what they need. they can control things very nicely with their set-up where as with wet sump and standard type pump you are always being reactive in whatever you do.

the pic you drew is definitely wrong though. the pipe going across the front of the cam covers goes from the thermostat housing, it's carrying coolant not oil. it's not connecting to the fitting on the sump.

[Sydneykid]

Whenever the engine is running there is always vacuum within the airbox.

No there isn't, not in my airbox anyway and I know because I log the pressure (and the temperature) to make sure I have enough cold air feed. Go back and reread what I posted "what happens at 275 kph when I back off the throttle. not close it, just lift a little, for say the kink into the chase at Bathurst?" I'll tell you what happens, there is positive pressure inside the airbox. Because the throttle is partially closed and so the engine isn't injesting as much air but the car is still doing 275 kph and the cold air feed is very efficient at 275 kph let me tell you. I designed it that way so that it reduces the lag (ambient air temp plus positive pressure) when I get back on the throttle, for the short straight to the actual chase.

There is positive pressure inside the airbox and the PCV valve is still closed, so the engine has nowhere to breath. It's in fact worse than that as the crankcase is copping the positive pressure from the airbox. That's why I run an open to atmosphere catch can, so the engine can breath no matter what the throttle position.

Cheers

Gary

[Adriano]

How much positive pressure are we talking?

[Sydneykid]

How much positive pressure are we talking?

Couple of psi, more than enough to push back against a good condition engine breathing.

Cheers

Gary

[GT-RZ]

the GT500 cars have dry sump so very different in what they need. they can control things very nicely with their set-up where as with wet sump and standard type pump you are always being reactive in whatever you do.

the pic you drew is definitely wrong though. the pipe going across the front of the cam covers goes from the thermostat housing, it's carrying coolant not oil. it's not connecting to the fitting on the sump.

I think you have confused my picture BB. the red dot is supposed to represent the oil return at the back of the head, that's why it's a broken line not solid.. i sort of guessed where it sits in in relation to the front (probably shouldn't have placed it on that line to avoid confusion)

I changed the image a bit:

No there isn't, not in my airbox anyway and I know because I log the pressure (and the temperature) to make sure I have enough cold air feed. Go back and reread what I posted "what happens at 275 kph when I back off the throttle. not close it, just lift a little, for say the kink into the chase at Bathurst?" I'll tell you what happens, there is positive pressure inside the airbox. Because the throttle is partially closed and so the engine isn't injesting as much air but the car is still doing 275 kph and the cold air feed is very efficient at 275 kph let me tell you. I designed it that way so that it reduces the lag (ambient air temp plus positive pressure) when I get back on the throttle, for the short straight to the actual chase.

There is positive pressure inside the airbox and the PCV valve is still closed, so the engine has nowhere to breath. It's in fact worse than that as the crankcase is copping the positive pressure from the airbox. That's why I run an open to atmosphere catch can, so the engine can breath no matter what the throttle position.

Cheers

Gary

So what your saying is that the intake pressure you are reading is far greater than that of your crankcase pressure? By pressure i'm referring to evenly distributed force (atmospheric pressure) As that's the only one that would affect our crankcase given that the vent would be situated @ 90* to the direction of airflow mass from the airbox intake. Where is your pressure gauge located relative to the direction of the engine intake and airbox intake?

If your gauge is located anywhere in the airflow masses direction you are simply reading a locailsed pressure from the velocity of airflow mass, which won't affect our crankcase vent too much.

Adding to that airbox design is not as simple as some would believe. If you were to have only one entrance then disregarding the engines intake you only have one exit, too. And rejected mass (ie not needed by engine) will recirculate back out the intake, effectively slowing down intake air velocity and decreasing the effective intake size. You will not increase the airbox atmotpheric pressure. Simply choke and slow down any incoming airmass velocity which is part of the idea of having a directed intake.

A vent situated after the engines intake (to wheel arch? your choice) would prove far more efficient as only fresh air would be directed to your engines intake and it would be utilising maximum airmass velocity and not being choked by recirculated air exiting your entry.

And like i said before, only an atmospheric pressure rise within the airbox would reduce any blowby vent's efficiency. If you can show that you have an evenly distributed pressure increase inside your airbox (which i doubt) then you may have a valid point.

But like a menioned earlier, i really don't think having atmo pressure (15psi) in the crankcase is a problem, vacuum is better but it's alll better than rising pressures.

[Sydneykid]

I think you have confused my picture BB. the red dot is supposed to represent the oil return at the back of the head, that's why it's a broken line not solid.. i sort of guessed where it sits in in relation to the front (probably shouldn't have placed it on that line to avoid confusion)

I changed the image a bit:

So what your saying is that the intake pressure you are reading is far greater than that of your crankcase pressure? By pressure i'm referring to evenly distributed force (atmospheric pressure) As that's the only one that would affect our crankcase given that the vent would be situated @ 90* to the direction of airflow mass from the airbox intake. Where is your pressure gauge located relative to the direction of the engine intake and airbox intake?

If your gauge is located anywhere in the airflow masses direction you are simply reading a locailsed pressure from the velocity of airflow mass, which won't affect our crankcase vent too much.

Adding to that airbox design is not as simple as some would believe. If you were to have only one entrance then disregarding the engines intake you only have one exit, too. And rejected mass (ie not needed by engine) will recirculate back out the intake, effectively slowing down intake air velocity and decreasing the effective intake size. You will not increase the airbox atmotpheric pressure. Simply choke and slow down any incoming airmass velocity which is part of the idea of having a directed intake.

A vent situated after the engines intake (to wheel arch? your choice) would prove far more efficient as only fresh air would be directed to your engines intake and it would be utilising maximum airmass velocity and not being choked by recirculated air exiting your entry.

And like i said before, only an atmospheric pressure rise within the airbox would reduce any blowby vent's efficiency. If you can show that you have an evenly distributed pressure increase inside your airbox (which i doubt) then you may have a valid point.

But like a menioned earlier, i really don't think having atmo pressure (15psi) in the crankcase is a problem, vacuum is better but it's alll better than rising pressures.

Let's get past the absolute pressure versus above/below atmospheric pressure (boost/vacuum) that most people talk about. When I say 2 psi positive that's above atmospheric, or if you prefer 16.7 psi absolute.

I have 3 air inlets to the sealed airbox, 2 ducted & 1 not. The pressure sensor is located behind the AFM in the airbox, hence shielded from direct airflow. The temp sensor is actually located on the POD filter element such that it actually measures the temperature of the air going in the engine.

I specifically designed the air inlet to ensure that it would provide 65 lbs per minuite of airflow into the airbox and hence the engine, at any speed over 160 kph. This means that at 275 kph (my example) the air inlets are providing more air than the engine can swallow. Hence there is a small positive pressure inside the airbox even when the throttle is fully open (0.5 to 1.0 psi). Once I close the throttle, back off for the kink in my example, the positive pressure inside the airbox increases (1 to 2 psi). Obviously, same airflow in + engine swallowing less = more pressure.

The 17 psi (absolute) is enough reason not to vent via the airbox, but on it's own the possibility of drowning the filter, AFM, turbo inlet, compressor etc in oil from a failed engine would stop me. Cleaning up a catch can is bad enough, an airbox with all that's inside it and flows from it would be a righ royal pain in the ass.

Cheers

Gary

[Beer Baron]

ok, now the pic is better. and I agree that's the way it probably goes.

but again, hardly anyone with a race car returns their catch tank to the inlet pre turbo as no one wants that oily mist running through turbo, intercooler and engine if you can avoid it. sure the vacuum may be desirable but I can think of dozens and dozens and dozens of cars that i've seen/worked on/owned/driven that were setup without that with no problem. and as for routing the catch tank outlet to the airbox i've NEVER seen that done. no body would ever have their catch tank venting into the airbox before their air flow meters. it's always done between maf or pod and turbo inlet but again most, particularly in japan just vent the tank to atmosphere with a little filter so that is the rocker covers are under vacuum conditions they are not sucking back in unfiltered air. and nearly all disable/block/remove the PCV. I know I have and everything is fine.

[GT-RZ]

I agree with you on the oil mess. lets hope that never does happen!

Obviously airbox design is critical on how your vent will work. The factory design is one to be replicated as it has lots of thought put in to it, the intake flow of airmass practically misses the blow-by vent and can exit via another vent giving that stream of airflow and no build up off pressure.

Your design seems to operate how you planned it and given that, maybe the vent would not be ideal. The design of an airbox with a blow-by vent should be designed with that in mind. That is a flow of air should be maintained and the vent should not be in the path of direct airflow mass.

For those who run just a pod there would certainly be no issues with a positive pressure build up (like the pic of the 180sx above) But an airbox is the better option, for obvious reasons.

I think we are over complicating the matter anyway. A vacuum would be a nice thing to achieve but atmospheric pressure or 14.7psi within the crankcase is more than acceptable if it can be maintained. It really depends on how serious of a machine you are building. when every last HP counts a vacuum would help for many reasons.

My new setup will be done like m speed (like the picture, bearing in mind the red dot is not connecting to the line on the front....) i'm going to setup a gauge on the block and observe, after that will depend if i setup a vacuum system, be it re-circ utilising venturi effect in the intake or exhaust. I will definently be making an aribox so i'll have to decide before i do this!!

With all the extra breathers and drains in place the vacuum or atmo doesn't really matter, it would just be the cherry on the icing.

[GT-RZ]

ok, now the pic is better. and I agree that's the way it probably goes.

but again, hardly anyone with a race car returns their catch tank to the inlet pre turbo as no one wants that oily mist running through turbo, intercooler and engine if you can avoid it. sure the vacuum may be desirable but I can think of dozens and dozens and dozens of cars that i've seen/worked on/owned/driven that were setup without that with no problem. and as for routing the catch tank outlet to the airbox i've NEVER seen that done. no body would ever have their catch tank venting into the airbox before their air flow meters. it's always done between maf or pod and turbo inlet but again most, particularly in japan just vent the tank to atmosphere with a little filter so that is the rocker covers are under vacuum conditions they are not sucking back in unfiltered air. and nearly all disable/block/remove the PCV. I know I have and everything is fine.

Factory has there blow-by vent in the airbox, standard. But i do agree, i was only trying to come up with a simplistic way of achieving a vacuum. I like things to be simple - last thing i would want is an external vacuum pump. When it comes to it i probably won't bother at all and will just vent to atmo...

depends what the gauge pressure is in the crankcase when i set it up. I certainly don't want a mess in the intake but that would largely depend how good your filtering is, o well!

I would love to see a picture with a little filter on the m speed tank just to finish any possible use on there behalf, but seems that car is top secret--- i emailed them to no success.

[Swiper the Fox]

Factory has there blow-by vent in the airbox, standard. But i do agree, i was only trying to come up with a simplistic way of achieving a vacuum. I like things to be simple - last thing i would want is an external vacuum pump. When it comes to it i probably won't bother at all and will just vent to atmo...

depends what the gauge pressure is in the crankcase when i set it up. I certainly don't want a mess in the intake but that would largely depend how good your filtering is, o well!

I would love to see a picture with a little filter on the m speed tank just to finish any possible use on there behalf, but seems that car is top secret--- i emailed them to no success.

I dont advise plumbing the catch tank back to the inlet...even after the AFM's...on decel our circuit car at superlap (due to the poorly set-up system) sprayed oil out the inlet and shorted out the afm's. This happened on the 1st 'hot lap' into turn 1. If we didn't have our mate and Aussie production car champ. Luke Searle at the wheel the car may have ended up on its roof. The car cut out and had no engine power, power steering, ATTESSA etc

Edited July 10, 2009 by DiRTgarage