Catch Can Question

[timandsam]

Hi All,

I am thinking about running an oil catch can. I just wanted to know what you guys think about my plumbing idea? Here is a drawing that might help to visualize it…

There is one inlet barb and one outlet barb for the catch can.

For the inlet (to the catch can) I was thinking about putting in a T, then running a hose from the stock crankcase vent (under the intake). The other hose from the T would be hooked into the line coming out of the valve cover.

For the outlet (from the catch can) I was thinking about another T. One line to the underside of the upper intake (where the PCV goes to from factory) with a check valve. The other hose to the turbo inlet.

Just trying to figure out if this would work…




Thanks in advance,
Tim

[matthewkennedy]

You can also just vent to the atmosphere, so that you don't have to suck any blow-by/oil mess back into the intake. There isn't a huge non-EPA related reason to return to the intake.

Instead of the left half of your diagram, you can just use a breather filter, like this one: http://www.ebay.com/itm/9MM-ENGINE-OIL- ... 1615812288.

To answer your actual question, that setup should work just fine, if you decide to route back into the intake.

[John Brennan]

It would seem that the catch can would eliminate any oil going into the intake tract-- that's what it's for, after all. But I'm wondering, why bother with the upper intake line? As it produces boost pressure when accelerating, and hence the need for the check valve, wouldn't it be simpler to eliminate it and have all the suction provided by the turbo inlet, which after all is always supplying vacuum, especially when under load?

[John V]

One could look and see just how Ford themselves solved the problem which might yield some interesting ideas for a starting point...

Of course crank-case pressure and gravity and rubber hoses all have completely changed since then because of new technology, new designs and new materials, so perhaps the best thing to do is study discussion forums full of guy who have never seen what was done at the highest levels because its all changed, and forum guys are in any case so much more aware of everything than mere WTCC, ETCC, and WRC engineers...
because keyboard.
Would you like to see what Ford themselves did on these cars?

[timandsam]

@matthewkennedy - i was contemplating just using a breather, but I'm not sure how bad the fumes from the oil would be

@John B - I just assumed that the upper intake would supply better vacuum than the turbo inlet. I am probably wrong though. If the turbo inlet would supply sufficient vacuum, that would definitely simplify the plumbing.

@ John V - Care to elaborate on Ford's solution to the US spec PCV system?

[thesameguy]

You can also just vent to the atmosphere, so that you don't have to suck any blow-by/oil mess back into the intake. There isn't a huge non-EPA related reason to return to the intake.

But there really is. You want something to suck out blowby vapors and moisture from the crankcase, and just venting the crankcase and valve cover to the atmosphere does not accomplish that. You end up with byproducts and condensation hanging around in the crankcase, falling back into the sump. On a boosted car, which typically suffers from more blowby than a naturally aspirated car, PCV is pretty important.

Back in the old days, this stuff was evacuated with a road draft tube - a tube from the crankcase extended into draft air underneath the car. While not environmentally sound, it's still better for the engfine than just a breather sitting around in the engine bay. That does absolutely nothing except prevent pressurization from blowby. A lot of people confuse the lack of a formal PCV system (that is, relying on engine vacuum to suck crap out of the crankcase) with no vacuum acting on the crankcase at all. You really don't want nothing getting that crap out. Cars have pretty much always had some source of vacuum acting on the crankcase.

The post-throttle body intake should provide much better vacuum than pre-throttle body at all times, except under boost. The advantage of having both sources of vacuum is that when the post-turbo side of the intake is under boost, you still have some vacuum acting on the system. The check valve is obviously important on the post-throttle body side.

[John V]

@ John V - Care to elaborate on Ford's solution to the US spec PCV system?

No sorry the hopelessness of the people blabbering crap is too much.
I have posted drawings here and at the Mare-kooor Sprout a dozen times...
And there is a link in signature. Check there...
Meanwhile back to pontification...also known as blather...

[Chris_12]

bring up an old thread, but its more a generic catch can question. With venting to the atmosphere and having two inlets (crankcase and valve cover breather), will a tee connector to connect to a single inlet can cause issues? I bought this but it only has one inlet without realizing it. I would rather not buy another one if I don't need to.

https://www.summitracing.com/parts/sum-g1506/overview/

[jkxr4ti]

The T inline with the valvecover and crankcase will work.
Larger lines will be better here especially if your considering an open breather. I used one of those summit ones for about 3 months before the drain valve fell out the bottom. Not the best quality.

One other item to consider with the open pvc is the fumes back into the cabin. The XR has no cabin filter so it's pretty noticeable under some conditions. For this reason I'll be recirculating it similar to your first picture. If I were you I would look for a can with larger diameter inlet lines and better construction.

[andyofcolumbusmerkur]

Would you like to see what Ford themselves did on these cars?

They designed a computer controlled system involving multiple processors and some little electric motors designed to make it until the extended warranty is over? Just a guess.

[Chris_12]

The T inline with the valvecover and crankcase will work.
Larger lines will be better here especially if your considering an open breather. I used one of those summit ones for about 3 months before the drain valve fell out the bottom. Not the best quality.

One other item to consider with the open pvc is the fumes back into the cabin. The XR has no cabin filter so it's pretty noticeable under some conditions. For this reason I'll be recirculating it similar to your first picture. If I were you I would look for a can with larger diameter inlet lines and better construction.

Ok thanks. The valve on the bottom did the same for me. It's for my 89 racecar. New to me, so I'm trying to keep it as is for now. Fumes aren't bad. No inner fenders =more ventilation

[andyofcolumbusmerkur]

just trying to figure out if this would work…




Thanks in advance,
Tim

Would the upper intake line pull air around the T fitting, from the turbo inlet? Since the vacuum would be higher there? With very little being evacuated from the engine?

[thesameguy]

Personally I would not run a turbocharged car (or really any car, but especially a turbocharged one) run without actual PCV. That is, a vacuum pulling on the crank case. With only a breather - leaving atmospheric pressure in the crank case - moisture and contaminants like carbon and fuel will not be extracted from the sump and the pistons are actually thrashing air around down there. You need that vacuum acting on the crank case to properly extract things you don't want and to keep your oil healthy and your sump free from sludge. This is especially important on turbocharged cars, where blowby is typically more intense than on naturally aspirated cars. You may even pick up a fraction of a horsepower by keeping splashing from air movement to a minimum.

Most factory PCV systems just recycle PCV air into the intake, and that's not great since oil in the intake can clog things up and might increase knock propensity so an aftermarket catch can (or some other functional air oil separator) isn't a bad idea. But keep the can under intake vacuum so active crank case scavenging can work. A catch can with the atmosphere on one side is effectively functionless.

I know sometimes people empty their catch cans and are upset to see it full of oil... but would you rather see your catch can full of oil, or know your oil pump is circulating carbon particles and fuel around? Would you rather some oil loss from PCV, or to rely on contaminated oil to keep your engine healthy? I know my answers.

[thesameguy]

Would the upper intake line pull air around the T fitting, from the turbo inlet? Since the vacuum would be higher there? With very little being evacuated from the engine?

Yeah, I don't think that's a functional design.

You need to pull air from the sump and you need to pull air from the head but you also need a fresh air supply to create air movement. I think it was discussed elsewhere, but I believe the function of the XR's stock setup is intended to address all three. Under light throttle - full intake vacuum - air is pulled from the turbo inlet pipe, through the head, into the sump, and out the crank case breather & PCV valve into the high-vacuum intake manifold. Under boost, the operation *kind of* switches direction, as the highest vacuum is now in the turbo intake pipe (because the manifold is pressurized) so air is pulled from the sump, to the head, out the oil separator, and to the low side of the turbo. This is how every old turbo car I've ever worked on works. If you use that diagram, you eliminate the fresh air supply which will dramatically reduce the PCV's effectiveness since the top and bottom end of the engine will be working against each other.

One thing I don't understand about the XR's PCV system is why they used a "conventional" PCV valve instead of a check valve. Well, I'm assuming the PCV valve is conventional - that is three position, with "restricted," open and closed. Maybe for the same reason as you would on any car, but since the air supply for the PCV is always metered I don't know why it needs that restricted position. Maybe I don't know what I'm talking about.

[DAReese]

http://www.42draftdesigns.com/oil-catch ... atch-cans/

Definitely not cheap, but a well-made product.