View Full Version : question on crankcase evac system
Taylorman
11-20-2002, 07:12 PM
Can someone tell me the purpose of attaching a crankcase evac system to the exhaust and then to the intake like it is on this engine. Nice looking motor I just cant figure out why he has it attached this way. http://free.***boat.net/gallery/Reader_Rides/Jet_Boats/Dsc00029.JPG http://free.***boat.net/gallery/Reader_Rides/Jet_Boats/Dsc00031.JPG
Cool taylorman, never seen it done like that, will get lifter valley, both banks, virtually scavenge entire motor. Don`t see a breather though. How does that work. Does it pull much oil?
It looks like the manifold opens into the lifter valley there so it would be the same as running a hose to your valve cover. He probably did'nt want to mess up the valve covers.
Raskal
11-20-2002, 07:57 PM
nice loking motor thou eek!
corlish
11-20-2002, 08:23 PM
Taylorman,
If your question is why is the system connected to the exhaust, the answer is that exhaust gasses rushing by (usually only in upper rpm-range) will pull a vacuum on the crankcase, which is always a good thing. Because this style of system only works well in the upper rpm range you will usually only see it on drag cars, boats, and etc.
If your question is why is the breather connected to the manifold and not the valve covers, my guess and it's only a guess is because he did not want to cut holes in those particular valve covers. If I am not mistaken they are not made anymore and are a pretty sought after item. At any rate his solution is innovative--kudos
Corey
I believe that it is taylors boat. But where is the air intake. You can`t evacuate without an intake?
corlish
11-20-2002, 08:50 PM
Hoss,
I am not sure that I follow...are you talking about a breather on one valve cover that allows fresh air to be drawn in and exit the opposite side?
The "pan-a-vac" systems that I have set up did not have a breather either, just an air/oil separator on each valve cover and hoses going to each header collector.
Corey
Duane HTP
11-21-2002, 06:03 AM
Pan/Vac systems don't use breathers. If they had breathers, there would be no vacumn.
Then why would a PCV need an air intake or breather to draw air in? I am very curious? The system in the pic looks very simple to build. What are the pros and cons to this particular sustem. Never seen nor heard of it before now. Do I just hole saw through my intake and cut a plate, seal it and attach? Will this only work with tunnel rams beacause of their height which allows higher mounting?
Blazerjet
11-21-2002, 06:50 AM
Hoss,
This is a Crankcase Evac system it is Desinged to Evac Crankase Pressure not Circulate. This boat Belongs to Tim over on the Banderlog board. He moved the Breathers to the Intake so he did not have to cut holes in the Valve covers that boat runs very hard, 18Ft Kona runs around 82 and has none of the olds oiling probs. You could only do this on a tunnel ram because that is the only intake that does not have an Exhaust crossover.
Taylorman
11-21-2002, 07:03 AM
Maybe I didn't make my question clear. Im wondering why he has the breather in the intake. The intake is sucking against the suction from the exhaust. Unless the breather goea all the way through the intake into the crancase, I dont see what he has accomplished. The purpose of the system is to created a suction in the crankcase, but if the breather is attached to the intake and in the flow of intake air then the exhaust and intake are sucking against one another.
wfodude
11-21-2002, 07:39 AM
that is not into the runners which is where the vac. is.It is into the underside where the crankcase is .and to all the geniuses...the motors set up like this WITHOUT a air inlet usually leak oil. such a vac.is created that the seals are opened allowing oil to escape
I understand no air intake. Then why run a pcv and breather? Why not just pcv and no breather? Or better yet 2 pcv`s? Iam being serious. I am wondering how it works. I understand that is creates a vacuum with no other air inlet. But how is it venting the crankcase without getting air? It seems to me that a vacuum is not neccessarily achieving a crankcase ventillation system.
Is a vent system possible with thru transom exhaust? I run a PCV but am wondering. Is there a benefit for seal and gasket life with the system in this thread. Again, I am asking because I`ve never seen this before.
Taylorman
11-21-2002, 10:08 AM
OK IM DUMB!!! wfodude, I was thinking that it was connected to the runners for air intake. Now I get it. Im sure many were calling me an idiot for that question. I guess it works the same way as if it were attached to the valve covers. This way it suck from under the intake vs under the valve cover creating the same effect.
572Daytona
11-21-2002, 07:37 PM
Oh no...not the dreaded PCV discussion again. :) Boating season must be over in Louisiana and it is only a matter of time before we start discusing tractor pulls again wink
572Daytona, I am trying to understand what the benifits if any are this system as oppossed toothe vent systems. I am not trying to flame anyone on this thread.
schiada96
11-21-2002, 07:49 PM
Now thats funny, is it a pcv or pvc??
Oldsquirt
11-21-2002, 07:52 PM
HOSS, the system above is not designed to "ventilate" the crankcase, like a pcv/breather setup would. It's purpose is to create a vacuum in the crankcase to aid in ring sealing, which increases HP. It is most typically used on drag racing engines. The next step up from one of these systems would be a vacuum pump(originally a modified smog air pump)to create the vacuum.
Ok, now we are getting somewhere. The smog pump has an air intake. So does the pcv system. So does the system (whatever it is called) whereby both "breathers run to either collector (I think).
Anyway, is this a better way to evacuate crankcase pressure? From the lifter valley that is.
1HOTGMCJET
11-21-2002, 08:15 PM
schiada96:
Now thats funny, is it a pcv or pvc??PCV - Positive Crankcase Ventilation
PVC - Poly Vinyl Chloride
(a material used for various plumbing fixtures, among other uses)
Does anyone care - well, probably not, but if Schiada was serious - there you go!
:D :D :D
schiada96
11-22-2002, 07:31 AM
1Hotgmc no I wasn't serious this pvc/pcv thing with hoss goes back along way. It was pretty lame a long time ago. Lot of bs about vaccume systems and lot of reasons why and why not to run a pcv set up. :rolleyes:
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