fooger03

iTrader: (2)

slash tube install pre-cat?

wildo

iTrader: (1)

Waaaaaaaay before the cat. Last time I saw the cat, I think it was at the back of a shelf in my basement.

Race car, no cat.

Slash-cut was after the secondary merge collector.

bryan_1

Likely a knucklehead question, but are there any data that demonstrate a catch can has a positive effect on either engine longevity or power? I can appreciate the common-sense "better that stuff be in a bottle than in my engine", but any numbers to back that up?

Savington

iTrader: (31)

You really want one of us to blow up a motor due to excessive oil consumption through the intake? Oil has a really, really low octane rating. Burning it is not a good thing.

What I would like to see is some leakdown numbers from those of you who are getting blowby.

bryan_1

Not exactly. There are ways to quantify whether or not a given action has an effect; controls, variables, and all that. With all the money put into R&D for engines, racing, etc., it would not be unreasonable that some entity would have demonstrated an advantage to a catch can. If they provide significant benefit, why don't manufacturers include them when the product is built?

Savington

iTrader: (31)

Mazda included a factory oil separator in the PCV system of the MSM.

bryan_1

Sweet.

I wonder why they aren't more common as an OEM part? I'd just be interested to see if there are any real numbers out there, like X% increase in engine life, or the like.

fooger03

iTrader: (2)

consumers don't care if an engine is detuned by a few HP in order to run 87 octane while burning crankcase vapors.

Consumers would throw a ******* **** fit if they had to empty a catch can every time they filled up the car.

nitrodann

Thankyou fooger.

Dann

Laur3ns

Catch can is the cheap way of doing oil separation. Not acceptable for OEM, but very useful for track cars. Read that god damn PDF someone posted here or in the other catch can thread.

bryan_1

Yes, I read the g** d*** PDF. It does explain the prinicple but does not address my original question. Given the volatility of the responses, this is apparently quite a sensitive subject. I'm not trying to stir the pot, just looking for info.

Laur3ns

Not sensitive, just the nature of this forum

bryan_1

fooger03

iTrader: (2)

i tried looking through google scholar, but by the time i got to page 2, the only articles i could find that looked like they might lead somewhere were $40. Then I realized that it wasn't important to me to find a published article on it. So I pointed my browser to youporn.com instead.

Faeflora

iTrader: (2)

Thanks for all the information!

I put my oil cap on the other day and saw up to 2psi of crankcase pressure on my gauge off the oil cap. That was at 20psi of boost. I never saw any vacuum though, even while staying in vacuum.

I'm going to test some more today if I have time.

Laur3ns

I have blowby (dip stick out in left turns) yet leakdown is confirmed to be far below 3%. Fixing dip stick keeps it in, but the breather hole needs enlarging + catch can.

Savington

iTrader: (31)

My first built motor ran the stock PCV setup and a breather - never had any blowby issues, no dipstick popping up, nothing. Never leaked it down, motor didn't last long enough.

Second motor was horrible from day 1. Big blowby, filling 1qt catch cans in 2 sessions, horrible ****. Altering the PCV/catch can setup helped a little, but I'd still have to empty the catch can 2x/day to prevent it from overflowing all over the place. Right before I pulled it apart to diagnose the bottom end rattle, it leaked down at 19/30/31/19 after about a year of running (exhaust valves and rings).

I'm assembling the next motor this week, and I went a little backwards on the wall clearances and ring gaps to try and limit the blowby. ~.0035" wall clearance, .018" top ring, .023" bottom ring. It's also going to get a OCD-style break-in on our chassis dyno.

Laur3ns

I think I have fairly large clearances as I have mild cold slap when really cold.
Did you run the breather cold side too? From the posts above it seems that one will puke the most.