Casper

The reason cars dont just vent the vapors off is because of emissions. It is cleaner to burn the oil vapor than venting to the atmosphere as is.

The crank case usually gets pressurized by the limited ammount of blowby getting past the rings during compression. I can not see the little bit of vacuum from the intake being enough to cause the vapor to draw out of the crank case unless the crankcase has an inlet vent (its like sucking on a straw with your finger over the end. It wont do much, but if you take your finger off slightly it will move the air inside the straw).

hamhead

First, a catch can is not going to make a big enough difference for you to run "a few more PSI." I can run 23PSI with a catch can or without a catch can on 110 octane race gas. The only reason why I run a catch can is that the tracks (and most tracks) require cars that run 12.99 and under to have them and it reduces my chance of engine knock slightly.

Second, on a naturally aspirated car, if your running match TB/IM, and its polished smooth and is relatively good for velocity, there is no way that the vapor is going to condense and settle on a smooth surface. Its going to run straight into the combustion chamber, get burned, and we're all fine and dandy.

LarryMcFly

Maybe not on a tib but on many cars, they use a catch can to boost a few more psi...more boost=more vapor= increase the effect of vapors on octane=increased chances of knock=unsafe.
You are probably right, if the IM/TB are polished, the vapor would probably not condense.....but still, you can't say that you are better off without one.

Casper

Okay, so vapor might not condense on theTB/ IM, but what about the valves? What about the pistons? What about the exhaust? These will all get carbon build up from burning the impurities from the oil. I think the benifits of running a catch can outweigh the results from not.

REDZMAN

^^^

That's why you use a can of Fuel Additive every 4 to 6 tanks like me.

Casper

^^^ or with the catch can, you can use the fuel additive about once every 12-15 tanks tongue.gif

REDZMAN

Hell no, you still get nasty stuff in your fuel.

Chemtool, best stuff ever.

hamhead

Firstly, I'm not boosting a Tiburon, I'm boosting a GSX. 4G63T ownage smile.gif. Secondly, I'm running times where it is a plausible addition from all the blowby I'm going to get. I would fill and spill over one of those home depot catch cans with one run.

Saying its going to be needed on a 10.3:1 naturally aspirated engine with basic bolt-ons is pointless. You'll get a few drops of blowby a week. 80% of that blowby on a stock engine is going to get into the combustion chamber and burned. Then another 15% might settle for a bit, then eventually get blown in there anyway. If your not going to tear down your engine once a year and clean the Intake stretch, with an hour or two of your time, and running injector cleaner, you shouldn't be modifying at all.

I'll play along with a catch can on any turbocharged Beta with stock IM/TB. Thats when you will need it, since you might be getting a little bit more blowby, and more of it will start getting gooky everywhere. If your running 5PSI-8PSI and your running port matched and polished Intake stretch, you won't need it as much. 10PSI and up, I would use it all the time.

LarryMcFly

I am running n/a and my can (bigger than the one used in the diy) is full every month or so. If you would see what comes out, you would understand. Even on a stock engine, you can't say that you are better without it.



If you have a clean and effective air filter, catch can, good quality fuel and aggressive driving, there is no need to clean up, it stays clean.

hamhead

You've got other problems that a catch can won't fix if your running through that much oil N/A unless you've raised compression or running some lumpy camshafts. From what I've heard, the problems with oil get worse as the engine mileage increases. I only had a little bit of oil (few drops) and some carbon at the end of the IM runners when I tore the car apart @ 8500 miles.

It doesn't "stay clean." Even with a catch can, your still going to encounter fuel that condenses after the injector and never makes it into the combustion chamber. Gas isn't perfectly pure either, you might get some crappy gas with little dirt particles in it that once again, collects near the entrance to the engine. Air filters aren't 100% effective either. There is plenty of carbon/oil buildup around the IM ports to warrant tearing it down and cleaning it up. If your running a catch can that still runs into the intake stream, oil vapor can easily pass through it and then get stuck as well. Theres a good ten minute cleaning yearly.