oil catch can

[jessejames]

What do you think of using a fuel filter as a catch can? I have attached a link. Do you think this is a good idea? I'm afraid the filter would clog and not let air to pass through. Any advice? Thanks

[josh817]

What do you think of using a fuel filter as a catch can? I have attached a link. Do you think this is a good idea? I'm afraid the filter would clog and not let air to pass through. Any advice? Thanks

You could just use an overflow bottle... Filters as crank/valve cover vents aren't any good. Dirties up the engine bay big time. Run it to a true tank so the liquids can separate from the vapors, have vapors get sucked into the intake. OR You can weld a bung onto your exhaust at an angle that points down range of the flow, so point it the pack of the car. The moving gasses of the exhausts should create a venturi and draw the vapor into the pipe and if you have it close enough to the header/turbo, it should burn, but its important to separate the liquid oil from the vapors, otherwise you may blow smoke!

[hoov100]

Something like this.

 

[josh817]

Thats a good idea but I think too small. You'd always find yourself draining. For the same cost I would rather get a cheap catch tank on ebay ($25).

 

Edited May 5, 2010 by josh817

[bjhines]

Just to rehash it's purpose...

The catch can is connected to the block and/or valve cover vents. These vents can spill oil under extreme high G cornering and high RPMs can cause oil to build up in areas it normally does not. So you are required to use the original venting system or use an approved catch can for spills. The catch can should contain a quart of oil without spillage. Most of the aftermarket oil catch cans are a quart capacity to suit most class rules.

 

There are a lot of tanks and cans built for other purposes that may not contain enough oil to prevent spillage. The factory systems often allow drainback to the engine oil pan to prevent oil buildup and eventual spillage. You can use any variation you like as long as the tech inspectors are confident you won't make a mess on track, and your system fits their rules.

 

You may want to consider a PCV system to pull slight vacuum on the crankcase. This would require some modifications to the catch can to allow proper operation of the PCV system. The main modification is to the breather filter on top of the catch can. This would need to be replaced with a check valve that opens to allow pressure to escape and closes to maintain vacuum when it is available.

 

 

...

[josh817]

Yah most racing clubs require a quart for overflow. I was advising the exhaust thing so you don't gunk up the intake over time. When I go to the track for this one club, there is a guy there who was using a big plastic pickle container. Every race which is 20 minutes long, he filled that thing up all the way until it was spilling out and we'd flag him for blowing smoke.... that container was like half a gallon... haha he had a lot of blow by from a worn engine.

[bjhines]

Engines that puke a lot of oil out of the vents have more than just blowby causing their problems. In a Chevy V8 there are many types of oil control modifications that can reduce this problem. There are also a lot of oil system mods that can make the problem worse.

 

In general; High RPM use will pump more oil than is needed to the valve train(top end of the motor). This oil can build up instead of draining back into the crankcase. You end up with valve covers full to the brim with oil(and none in the oil pan). The first time you slam on brakes and turn hard the oil comes puking out the vents. This is why you cannot run on most tracks without some sort of a catch can.

 

My BMW M3 has a catch can that has a drainback tube that drains back into the dipstick tube.

[nish]

Thats a good idea but I think too small. You'd always find yourself draining. For the same cost I would rather get a cheap catch tank on ebay ($25).

 

 

 

FYI, I bought this eBay can and it's worthless. There doesn't seem to be any separation of oil/air.

[ktm]

FYI, I bought this eBay can and it's worthless. There doesn't seem to be any separation of oil/air.

 

That's because it is not internally baffled. There are two types of can's being discussed here, one for overflow and the other for blow-by from the crankcase and valve cover. You need a can that is baffled for the latter.

 

Even the Greddy units are junk because they are not baffled.

[510six]

http://www.turbophile.com/technical/diy_catch_can.html

 

This is a pretty well setup catch can.

 

http://www.aircraftspruce.com/menus/ep/airoilseparators_homebuilders.html

 

or an aircraft style.

[Nigel]

That's because it is not internally baffled. There are two types of can's being discussed here, one for overflow and the other for blow-by from the crankcase and valve cover. You need a can that is baffled for the latter.

 

Even the Greddy units are junk because they are not baffled.

 

You don't need baffling. Just by virtue of the vapour traveling at high velocity in the small diameter tube from the crank case, into a larger chamber, and then having to do a 180 to get back out again, a lot of the oil will drop out of suspension. I have a similar cheap e-bay catch can in-line between the crank case vent and a PCV valve on the intake manifold. I forget exactly how much comes out (1/8 full?), but there's always something in it to drain when I check it every oil change. BTW, I wouldn't want to plumb it back into the oil pan, as it's not exactly clean oil.

 

Oh yeah, one other note: I just have a filter on the valve cover, but it's not a problem because the SDS EFI system uses a MAP sensor.

 

Nigel

'73 240ZT

 

 

Edited May 14, 2010 by Nigel

[Snailed]

BTW, I wouldn't want to plumb it back into the oil pan, as it's not exactly clean oil.

 

Why? The fact that it gets blown out of the cranckcase doesn't make it any more dirty than when it was lubricating your bearings a few seconds prior.

[Nigel]

Why? The fact that it gets blown out of the cranckcase doesn't make it any more dirty than when it was lubricating your bearings a few seconds prior.

 

The vapor that's floating around in the crankcase isn't just pure motor oil. It's a combination of oil, water vapour, and blow-by gases. Here's a picture of what I drained out of an oil/air separator I had on my Subaru Legacy Turbo...

 

I didn't do a chemical analysis of it, but it sure doesn't look like something I'd want to pour back in the crank case!

 

Nigel

[Snailed]

The vapor that's floating around in the crankcase isn't just pure motor oil. It's a combination of oil, water vapour, and blow-by gases. Here's a picture of what I drained out of an oil/air separator I had on my Subaru Legacy Turbo...

 

I didn't do a chemical analysis of it, but it sure doesn't look like something I'd want to pour back in the crank case!

 

Nigel

 

I guess you wouldn't. I'm aware of what the vapor is, I just don't agree that draining it back is a horrible idea in all cases. Some of the motors I'm used to dealing with (Hondas) generally puke out a lot of oil at high HP levels so a drainback is a must. On the lower powered ones (under ~500whp) it's always the regular gunk like you have there. Draining back water doesn't bother me as it evaporated out of the oil once it's up to temp. Partially and unburnt fuel however is no good but that should be kept in check with a good ring seal on more mild setups.