catch can thought

[nicknorth11]

I have read TONS of threads about catch cans and their utility and detriments. The problem is that I have a lot of crankcase pressure and until I figure out the cause I need to alleviate it. I thought about getting a catch can and running the valve cover outlet (left side) to it and venting it with an air filter like others do, but since eliminating the vacuum source (intake pipe) is bad and should be avoided, I thought about coupling the two ideas.

I was thinking about using a "Y" at the valve cover and running one hose to the intake pipe for vacuum and one hose to the catch can with a breather filter. This will alleviate pressure, but will still draw vapors out of the valve cover.

 

[snox135]

Remove the air filter from the catch can. Then put a hose on that spot on the catch can and run it to the intake pipe.

 

[nicknorth11]

I don't see how that will help me with my crankcase pressure. I have A LOT of pressure building up. Much more than could fit into a catch can.

 

[turbosax2]

Check this thread out.
http://www.dsmtuners.com/forums/showthread.php?t=254437

 

[snox135]

The stock system is a better design for removing crankcase pressure. The catch can will remove oil before it gets into your turbo and ic. If you are running the stock MAS and run a y at the valve cover you could get unmetered air through the catch can under boost conditions. Do you still have the stock PCV hooked up to the intake? Have you checked if the PCV is leaking?

 

[nicknorth11]

I will check out that link above right now.

I don't mean to sound unappreciative, but I know how well the stock system works and it is insufficient for my c.c. pressure. The pcv is fine. I have dsmlink, so I can adjust for the unmetered air.

By the way, how much of an increase is to be expected when comparing dry/wet compression tests?

 

[Dream On]

I don't mean to sound unappreciative, but I know how well the stock system works and it is insufficient for my c.c. pressure. The pvc is fine. I have dsmlink, so I can adjust for the unmetered air.

How are you able to determine that it is insufficient? Are you blowing out the dipstick every time you go WOT or something?

 

[snox135]

If the stock system is not doing enough it sounds like you have a lot of blow by on your rings. I would do a leak down test.

 

[nicknorth11]

How are you able to determine that it is insufficient? Are you blowing out the dipstick every time you go WOT or something?

Questioning my basic statements doesn't help me. With that being said, yes, my dipstick blows out and when clamped down I blew the o-ring to my oil filter housing.

If the stock system is not doing enough it sounds like you have a lot of blow by on your rings. I would do a leak down test.

I know. If you read the bottom line of post #6 you will see that I have already had that thought. I don't know, however, the difference that is acceptable.

On a side note, this looks promissing: http://dsm.dejonpowerhouse.com/

*edit* I have read some threads on this product and it doesn't solve the problem.

 

[snox135]

I was not referring to doing a wet/dry test. A leak down test will tell you percentage of leak down.

 

[nicknorth11]

Is leak down test a measure of piston ring failure?

 

[snox135]

A leak down or "cylinder leakage" test is similar to a compression test in that it tells you how well your engine's cylinders are sealing. But instead of measuring pressure, it measures pressure loss.

A leak down test requires the removal of all the spark plugs. The crankshaft is then turned so that each piston is at top dead center (both valves closed) when each cylinder is tested. Most people start with cylinder number one and follow the engine's firing order.

A threaded coupling attached to a leakage gauge is screwed into a spark plug hole. Compressed air (80 to 90 psi) is then fed into the cylinder.

An engine in great condition should generally show only 5 to 10% leakage. An engine that's still in pretty good condition may show up to 20% leakage. But more than 30% leakage indicates trouble.

The neat thing about a leakage test (as opposed to a compression test) is that it's faster and easier to figure out where the pressure is going. If you hear air coming out of the tailpipe, it indicates a leaky exhaust valve. Air coming out of the throttle body or carburetor would point to a leaky intake valve. Air coming out of the breather vent or PCV valve fitting would tell you the rings and/or cylinders are worn. But this could also be a leaking head gasket, into a oil passage.

A leakage test can also be used in conjunction with a compression test to diagnose other kinds of problems.

A cylinder that has poor compression, but minimal leakage, usually has a valvetrain problem such as a worn cam lobe, broken valve spring, collapsed lifter, etc.

If all the cylinders have low compression, but show minimal leakage, the most likely cause is incorrect valve timing. The timing belt or chain may be off a notch or two.

 

[nicknorth11]

Great post. That is really useful. Thanks.