Got a modified L series? please look in...

[Ian Patmore]

Quote:
Originally Posted by tel240z View Post
And you are joking about connecting the system to the exhaust arn't you

No, people do this... hose from crankcase to check valve (to prevent backfire destroying your engine casing) then to pipe welded at an angle into the exhaust system. The flow of exhaust gases creates a negative pressure on the end of the pipe which pulls PCV gases into the exhaust.

Been used in the drag racing scene for ages (USA). Tried system on mine, but pulled way too much for everyday use, going to try something else...as not fan of open system.

 

[SKiddell]

No, people do this... hose from crankcase to check valve (to prevent backfire destroying your engine casing)

Confused

If backfire destroys engine cases then something else is badly amiss like the owner forgot to install piston rings or it’s a heavily gassed or boosted engine.

Under most engine conditions backfires happen in the inlet manifold (whilst "afterfire" is in the exhaust)
Any pre or post ignition event in the chamber has to get past piston rings etc to even make it into the crank case.

Backfire and after fire are usually symptoms of air fuel ratio issues or other mechanical issues such as valve timing or induction system issues that cause partial combustion with the combustion event travelling back into the induction system (partially closed valves) or dumped into the hot exhaust where it is ignited

If someone is confusing detonation with backfire then no amount of "ventilation" in the world will save the engine from eventual destruction.


Re plumbing in the crankcase to the exhaust
As previously mentioned in Ian’s original thread, plumbing crankcase vent directly into exhaust on a conventional engine is flawed, during the overlap cycle significant exhaust vacuum can be developed (cam!!) due to the velocity of the exhaust gasses....this can pull way too much volume through carrying contaminants with it all to be burnt in the exhaust system.......imagine the mess on a track day during a heavy right hand corner and quite a few millilitres of oil going straight into the 900 degree exhaust.


In answer to Datsfun
Catch tank where the battery used to be (now behind drivers seat) for both the block and the (Kamerari ) custom rocker cover vents.

 

[morbias]

Well sorry Steve for calling it a backfire instead of an afterfire, I'm pretty sure the point was otherwise understood. Obviously you would need some serious blow-by problems to have a big risk of crankcase vapour ignition but if it wasn't a possibility then they wouldn't have fitted them with PCV valves in the first place?

As for stopping oil being sucked into the exhaust, couldn't you fit a restrictor in the line?

[EDIT] actually couldn't you just find a suitable PCV valve to use in place of the check valve? It would act as the check valve and limit flow under high vacuum conditions.

 

[Ian Patmore]

For me the catch tank needs to be lower down, as water and oil are affected by gravity, yes you get vapour, but filter to deal with that.

Morbias, think in another direction... as maybe another solution...

 

[richiep]

Thanks love the location! I was planning on mounting the catch tank on the more conventional (boring) locations around the strut towers etc

Ditto. A catch tank is on my tweak list for 2013 and I really like the unobtrusive solution you've used. I may have to copy you!

 

[morbias]

Morbias, think in another direction... as maybe another solution...

Well it seems like a good solution if it can be made to work, though to be honest I don't really see any major benefit over just having a catch can vented to atmosphere, except that the vapours are drawn out of the crankcase a bit more efficiently.

 

[Ian Patmore]

except that the vapours are drawn out of the crankcase a bit more efficiently.

The idea of having "suction" out of the crankcase is partly to clean up emissions, as in the OEM set-up, where the vapours are drawn back into the engine to be burnt. The other possible benefit is that the air under in the crankcase (therefore under the pistons) is drawn out. As the piston and piston ring goes up and down, its pushing against the air below. The thinking is as this happens, air from below the piston/ring pushes up between the ring and the block bore, making a lesser piston ring seal. In reducing the air under as the piston moves reduces the air being forced between the ring and the bore giving a better seal. Hopefully a better/cleaner burn.

There are plenty of Z engines running being "just vented" and work fine. For me, I err towards the OEM type system...esp. if it cleans up combustion and may improve engine running. The man down the pub may say otherwise, but hey, that's my take on it!

My understanding is it is a "must", probably due to greater pressures involved in a turbo application.

 

[morbias]

I agree that an optimal evacuation of vapour is better, but the original system wasn't ideal imo. At least with a catch can the oil vapour exits the engine permanently, rather than being sucked back into the balance tube. I've read about the vacuum giving better ring seal, but how much of a massive vacuum must be pulled to really have an effect on the rings, and surely that amount of vacuum would also pull oil out of your crankcase? I wouldn't have thought the standard setup would pull anywhere near enough vacuum to really do anything other than vent vapour properly.

 

[tmr]

The idea of having "suction" out of the crankcase is partly to clean up emissions, as in the OEM set-up, where the vapours are drawn back into the engine to be burnt. The other possible benefit is that the air under in the crankcase (therefore under the pistons) is drawn out. As the piston and piston ring goes up and down, its pushing against the air below. The thinking is as this happens, air from below the piston/ring pushes up between the ring and the block bore, making a lesser piston ring seal. In reducing the air under as the piston moves reduces the air being forced between the ring and the bore giving a better seal. Hopefully a better/cleaner burn.

 

[tmr]

For every piston going down there is one going up, crankcase compression is purely from gases escaping past the piston rings.Don't also forget if for competition use there are regulations re size and construction.

 

[Rob Gaskin]

Why do folks want to make everything so complex?

As I said earlier if your engine is in good nick very little fuming occurs.

The important thing is to retain the crankcase breather tube and vent it to something. The only problems I've witnessed have occurred when the metal tube has been removed because of exhaust manifold clearance problems.

On a 'performance' engine surely it's better to just breath cold air?

If you are worried about the environment then you shouldn't run one of these old cars.

 

[SeanDezart]

Exhaust manifold clearance problems ? Surely any manifold will have been made to fit ?

On a 'performance' engine and most probably running on a track, even if it isn't an abiding rule, self-responsability should push one not to vent out onto the track. On an homologated competitionc ar - it's obligatory.

I don't know your MOT rules but here, a car would fail under 'emissions' and I don't mean exhaust - ANY car fluids 'leaking' and therefore not within a closed circuit will be noted.

A bit like one of you running around with a runny nose, incontinence and prostate problems - maybe not against the law but undesirable in company all the same.......

Stop faffing and go buy a cheapo catch-tank off ebay and run both breathers to it !

 

[Rob Gaskin]

Exhaust manifold clearance problems ? Surely any manifold will have been made to fit ?

Not always Sean. I have seen the breather removed to give clearance, especially if the 'header' is for use on a car running triples.

My GDS manifold wouldn't fit with the breather on so I took it to Graham (of GDS) and he altered it for me.

Sean nobody is suggesting running without a catch-tank.

 

[morbias]

Nobody is talking about the environment either

 

[Rob Gaskin]

Nobody is talking about the environment either

I was referring to Ian's comment:

The idea of having "suction" out of the crankcase is partly to clean up emissions, as in the OEM set-up, where the vapours are drawn back into the engine to be burnt.

 

[SeanDezart]

Not always Sean. I have seen the breather removed to give clearance, especially if the 'header' is for use on a car running triples.

My GDS manifold wouldn't fit with the breather on so I took it to Graham (of GDS) and he altered it for me.

Sean nobody is suggesting running without a catch-tank.

Rob, I don't see why a header for triples use or the same header with twin SUs should be any different - whatever. First post talks of K and Ns - having run with them, they look pretty but then, a catch-tank looks pro unless the pipework comes off your old washing machine.

 

[Mr.G]

Quick note.

Thanks Zbloke, I've ordered one of these and it arrived next day. Nice well made piece which will suit my application.

I'm just using it to run from the crankcase breather into the catch can and then to my PCV. I'll mount it same place as Z bloke did - great idea and the existing bolt holes in the block are ideal. I am going to run a transparent hose from the can to the PCV - this will allow me to keep an eye on how clean the air is coming out of the can. There is no fancy gauze or funneling effect in the catch can as some have so will be wise to keep an eye on how effective it is. But for the price it's well worth it and must be better then not using one at all.

For the valve cover breather I am going straight to my air filter, thus creating a closed loop system like the original. Future plans will be to clean the air here too but not too bothered right now.

 

[zbloke]

There is no fancy gauze or funneling effect in the catch can as some have so will be wise to keep an eye on how effective it is

Unless its been removed there is a gauze filter, and baffle plate, below the crankcase breather stub in the block