What PCV system are you running on big single?

[Tricky-Ricky]

If you are passing over 750 cubic feet of air every min through the engine, just how much is cranckcase blowby/oil mist ? would this really have any effect that is noticeable on octane?

Strikes me that 750 cubic feet of air is a large room full..

 

I agree, adding a dedicated pump seems a lot of faffing about, and expense to gain a theoretical 10BHP,

Since the oil that i am referring to mainly only accumulates in the low areas of the plenum/intakes when the engine is on idle,

as one breather is shut once on boost.

[jevansio]

I wouldn't add the pump to gain 10bhp, but if a couple of strategically placed vacuum feeds could do it I'd do it

[Tricky-Ricky]

I wouldn't add the pump to gain 10bhp, but if a couple of strategically placed vacuum feeds could do it I'd do it

 

Ahh right, thought you where considering the pump approach Jay,

If you're going to use an uprated PCV system then keeping all crankcase ventilation sources away from the combustion process is a positive step IMO, mainly for the reasons i mentioned previously, and if it can be done for the price of buying and fitting the exhaust valve then go for it:) my only concern would be what happens if they fail?

[jevansio]

Ahh right, thought you where considering the pump approach Jay,

If you're going to use an uprated PCV system then keeping all crankcase ventilation sources away from the combustion process is a positive step IMO, mainly for the reasons i mentioned previously, and if it can be done for the price of buying and fitting the exhaust valve then go for it:) my only concern would be what happens if they fail?

No, that's too much hassle, it was just to illustrate the lengths some people go to and the potential gains

 

I'm thinking of reproducing the stock setup with one going to the plenum with a check valve as stock, but the other going to the exhaust (rather than the inlet). Obviously the above would be using -10AN lines as my covers have -10AN fittings

 

I would want a vacuum reading in cabin incase of failure (I posted about setting my boost gauge up on a switch in another thread so I could "flick" onto crankcase pressure every now & again to check all is OK)

 

Obviously before all this I'm waiting on Dans results, if the truth of the matter is there are no performance gains then I won't do it

Edited August 3, 2010 by jevansio (see edit history)

[paul mac]

the stock pcv is not going to net you any performance gains its really there for emmisions, as soon as you hit positive boost the one way valve on the pcv closes, the only way you would get a performance gain is from attempting what Dan has done and introduce a vacuum at the top end, really interested to see those results Dan

[jevansio]

the stock pcv is not going to net you any performance gains its really there for emmisions, as soon as you hit positive boost the one way valve on the pcv closes, the only way you would get a performance gain is from attempting what Dan has done and introduce a vacuum at the top end, really interested to see those results Dan

The one way valve to the plenum close, but the other cam cover is connected to the inlet. The stock system is drawing a vacuum no matter what idle/cruise/wot.

 

I would hope to replicate the stock system but bigged up for single boost pressures, I already have the -10 feeds, all I need is some meaty check valves (Aeroquip actually do a -10AN fitting one although it is expesnive). If Dans tests prove a gain is to be had I will go all out & get one, if not it's staying as is

[dandan]

Uh oh - the pressure is on

[Nodalmighty]

Uh oh - the pressure is on

 

or OFF hopefully

[dandan]

I think I would revise my system slightly if for some reason the downpipe etc had to come off the car or I was doing it on another car.

 

My slash cut pipes are a long way down the midpipe and they are plumbed back to the engine bay with hardpipe (aluminium bent to shape the path up past the downpipe). Those two pipes are pretty long, probably around about 5ft each. The one way check valves are right next to the catch can and therefore along way from the heat source in the exhaust. This is great as it means the valves run cooler and I'm sure this is the reason they are lasting without issue.

 

However, I now think that I could shorten the length of the aluminium piping and possibly put the slash cuts into the start of the midpipe or maybe even in the downpipe with only a couple of feet of the aluminium piping to keep the valves away from the heat. The upside to this would be less pressure lost (or in this case gained) along the length of the aluminium pipe giving me a tiny bit more vacuum than I have now with these long pipe routes. However, that is a lot of ballache for potentially negligible gain.

 

Slash cut entry points can be seen in the kit pic; other pic shows the valves.

 

I will get a photo of the intake plumbing and valve at the weekend, I've got a few parts at the powdercoater now so there's no catch tank or intake pipe in the engine bay

Edited October 2, 2013 by dandan (see edit history)

[dandan]

You might think that idle is the time you’d get the least vacuum due to limited exhaust flow but I didn’t see that at all. With just the two exhaust vacuum sources I could get decent enough vacuum at idle to hold a playing card against an open hole on the catch can - no problem.

 

Something to bear in mind with something like this is the exhaust design seems to be very important. I have an oddball exhaust where I can switch between a triple silenced 3" system or a single silenced 4" system. The 4" is only about 3ft long and exits near to the diff area, the extra 3” section continues full length exiting at the back of the car.

 

Obviously the 4" route is far less restrictive - we had an instant boost rise to 1.8bar (rather than the 1.6bar the ecu was trying to hold) when we first set out to do the remapping to suit so it makes a big difference. Point being - this affects the breather system...

 

Before I added a vacuum feed to the turbo intake I could see positive pressure in my catch tank when running through the 3" system...this is bad. With the 4" short and unrestricted exit opened up I got no positive pressure at all irrespective of boost/rpm. (Both gave vacuum at idle as I mentioned before). If I had an exhaust as free flowing as my short 4" section I would have left it at that and stayed with just the slash cuts in the exhaust. However, as I drive round in "quiet mode" quite a lot I added a turbo intake feed to provide additional vacuum for those situations.

 

Basically don’t try tghis system if your exhaust is at all restrictive

Edited October 2, 2013 by dandan (see edit history)

[Chris Wilson]

I have two -12 lines, one per cam cover leading into an old 4 litre plastic oil container, with holes punched in it for ventilation. It sure ain't pretty, but it sure was cheap, and works fine. I adhere to the KISS principles This is on my RB26 Nissan engine, but the same would apply if I was doing a 2JZ.

[Nodalmighty]

I have two -12 lines, one per cam cover leading into an old 4 litre plastic oil container, with holes punched in it for ventilation. It sure ain't pretty, but it sure was cheap, and works fine. I adhere to the KISS principles This is on my RB26 Nissan engine, but the same would apply if I was doing a 2JZ.

 

I think mine was a fairy liquid bottle

[paul mac]

The one way valve to the plenum close, but the other cam cover is connected to the inlet. The stock system is drawing a vacuum no matter what idle/cruise/wot.

not disputing that for a minute mate but from the intake you wont get really usefull vacuum that could be classed as performance enhancing this is why drag cars run vacuum pumps

 

Uh oh - the pressure is on

sure is dude

[jevansio]

not disputing that for a minute mate but from the intake you wont get really usefull vacuum that could be classed as performance enhancing this is why drag cars run vacuum pumps

 

 

sure is dude

Ahh, I'm defo not running a pump, even if it is the only way to see a HP gain,

 

If I wanted to measure the pressure/vacuum in the crankcase what would be the easiest way, a mechanical boost gauge on a fitment which screws into the cam cover?

[Tricky-Ricky]

Ahh, I'm defo not running a pump, even if it is the only way to see a HP gain,

 

If I wanted to measure the pressure/vacuum in the crankcase what would be the easiest way, a mechanical boost gauge on a fitment which screws into the cam cover?

 

You will need a gauge that will register small but accurate vacuum and pressure, i used a bike carb balancing gauge when i did some testing on my old Supra, and sealed it to the dip stick tube (direct reading from the sump which will see the immediate effects of any pressure build up)

 

Which is probably why i get a bit augmentative over the subject:innocent: had a few arguments with US guys over it, and as a result of my tests, i have theories on the subject, but it depend on if anyone is interested enough in the subject, as to whether its a discussion or an argument;)

[jevansio]

You will need a gauge that will register small but accurate vacuum and pressure, i used a bike carb balancing gauge when i did some testing on my old Supra, and sealed it to the dip stick tube (direct reading from the sump which will see the immediate effects of any pressure build up)

 

Which is probably why i get a bit augmentative over the subject:innocent: had a few arguments with US guys over it, and as a result of my tests, i have theories on the subject, but it depend on if anyone is interested enough in the subject, as to whether its a discussion or an argument;)

Brill idea mate, I never thought of that.

 

Get em wacked up bud, it's the reason I started this thread to get info in one place on the subject

[paul mac]

If I wanted to measure the pressure/vacuum in the crankcase what would be the easiest way, a mechanical boost gauge on a fitment which screws into the cam cover?

 

personally having dealt with a lot of vacuum at work i would

go for something like this http://www.coleparmer.co.uk/catalog/product_view.asp?sku=6893030&pfx= , a damped gauge is essential as otherwise it will buzz around and be unreadable, or if your really serious a 0-5v transducer hooked up to an ecu and datalogged

 

 

it depends on if anyone is interested enough in the subject, as to whether its a discussion or an argument;)

 

well me and Jevansio are and i suspect Dan is so thats at least 3 of us, would love to see any data that you have

[jevansio]

Cheers Paul, I had to buy a gauge anyway so one of those will be perfect, it was only a temporary measure so I don't care how heath robinson it looks

[Tricky-Ricky]

Brill idea mate, I never thought of that.

 

Get em wacked up bud, it's the reason I started this thread to get info in one place on the subject

 

 

EDIT, due to cock up on gauge calibration, now corrected in post

OK, i did put up the results in brief on another post where i had a discussion with Dude on the subject.

 

Anyway, my Supra specs at the time was basically BPU running 1.2 bar with the std PCV hooked up to a catch can, and plumbed back into the std turbo pipe,

 

I am also pretty sure i ran the same test once i converted to UK hybrid turbos running 1.4 bar as well, with the same results.

 

Now my engine was in top condition piston/ring and bore wise, accurate compression and leak-down tests conducted with very good results.

And my reasons for going to the trouble of conducting these tests was down to the FMS failing three times, before finding the cause was down to oil pump wear, however i wanted to prove my own theories to myself, as well as dispel some of the myths that i had read on the US forums.

 

So as i said i used the gauge sealed to the dip stick by a short length of hose, and poked out form under the bonnet and taped in place so it could be read from the car when in motion (did try a peak hold gauge as well but didn't trust it)

 

Anyway at no time was any positive pressure detected AFAICR the gauge went from +10kpc and vacuum down to 600 millimetres of mercury and from what i remember it hovered around 10-12 millimetres of mercury with the highest reading being 6 millimetres of mercury at full boost, which on a good engine i would expect, and it proves that the std PCV system was of an adequate design, and i would expect it to cope well with fairly well worn rings and bore on an older engine.

 

Now don't get me wrong, if you add a big turbo running higher boost pressure . and especially if the rings and bores are not in tip top condition i would not expect the std system not to cope as well, and maybe see a very slight positive crankcase pressure,

but i would add that i see no way that this would ever be enough t cause the FMS failure's that the US guys blamed it on.

 

Now if you then add -10 or 12 pipes to the breather system and still run as the STD PCV system with an engine intake generated vacuum source to the same big turbo engine, i would also conclude that it should in theory not see any positive crankcase pressure, unless as already mentioned it had a fair amount of wear present

 

Now these are just theories based on my small amount of testing, but hopefully interesting to those with a technical leaning:)

Edited August 21, 2010 by Tricky-Ricky (see edit history)

[Tricky-Ricky]

or if your really serious a 0-5v transducer hooked up to an ecu and datalogged

 

 

Funny you should mention that, as i nearly went that far, but couldn't justify the £90 price tag for the transducer that i probably wouldn't use again.

[jevansio]

Great info Ricky, I read -8 Hg was well enough to benefit from the effects of vacuum in the crankcase

 

I'm going to get some readings this weekend from my engine which vents both cam covers to atmos (ie no PCV system)

[Ian C]

Good info

 

I always was a fan of leaving the stock PCV system alone. Mine is plumbed with the same diameter hoses in the same fashion, no catch can. I reckon if you need to catch a lot of oil or you're trying to evacuate positive crankcase pressure, it's treating a symptom rather than fixing a problem.

[paul mac]

Funny you should mention that, as i nearly went that far, but couldn't justify the £90 price tag for the transducer that i probably wouldn't use again.

 

good info dude, out of interest what were the Yanks getting upset about as i see nothing contraversal, although that forum is like a bear pit sometimes they could pic a fight with themselves looking in the mirror

[jevansio]

good info dude, out of interest what were the Yanks getting upset about as i see nothing contraversal, although that forum is like a bear pit sometimes they could pic a fight with themselves looking in the mirror

That is soooo true

[Swampy442]

I have to admit Im not that up on crank case ventilation and did wonder why mine has the set up it does. This thread has been a good lesson, cheers all