Catch Can run to Exhaust

[4x4le]

Originally Posted by Big Zee

you guys have totally lost me, blame it on the blonde hair I guess.

Wouldn't a S13.4 VC negate the need for a catch can altogether ? I am having one built and was going to run a breather setup to the middle port, the rear exhaust port to Crank Case, and the PVC to whatever it hooks up to.

its a step in the right direction, my valve cover is like doing the 13.4 cover but I still used a can that got very little oil in in afterwords. I never ever drained it and there were just a few drops. Im not going to run a can on this next engine just because I can run shorter hoses then, just running it to the venturi in the exhaust where it can cook.

[Frank_Jaeger]

Bumping this to add that in my research a lot of evidence (i.e. people using vacuum gauges) suggests the back pressure of the exhaust under boost prevents scavenging. I'm going to be running my catch can line preturbo.

[KAT-PWR]

Anecdotally my friend who is 100% performance oriented did a slash cut and said he had adverse effects, I will ask him what he encountered.

[jr_ss]

Originally Posted by Frank_Jaeger

Bumping this to add that in my research a lot of evidence (i.e. people using vacuum gauges) suggests the back pressure of the exhaust under boost prevents scavenging. I'm going to be running my catch can line preturbo.

Frank, what components were plumbed in this test? Was a Venturi utilized? If not, of course they weren't seeing any benefit. Venturi's use exhaust flow/velocity to pull the vacuum. If they did use a venturi, was the slash pointed in the correct direction?

I have not put a gauge on my exhaust line/CC to see an actual number, but I can tell you at idle I have decent vacuum on the system. I'll be glad to swing by and let you listen to the air release when the dip stick is pulled out at idle.

[Frank_Jaeger]

Originally Posted by jr_ss

Frank, what components were plumbed in this test? Was a Venturi utilized? If not, of course they weren't seeing any benefit. Venturi's use exhaust flow/velocity to pull the vacuum. If they did use a venturi, was the slash pointed in the correct direction?

I have not put a gauge on my exhaust line/CC to see an actual number, but I can tell you at idle I have decent vacuum on the system. I'll be glad to swing by and let you listen to the air release when the dip stick is pulled out at idle.

Most that I've read were using the summit kit. It has an angled bung with a slash cut tube. Before this is a check valve. I can't verify if they had it oriented properly though.

I might take you up on that. I'm rebuilding my SR right now and I'm wanting to get the best seal possible as I wear in the new rings. A few years ago I read about using the exhaust to pull vacuum and it seemed like the best method however checking again now it seems that it doesn't do so well under moderate / high loads.

[jr_ss]

Just shoot me a pm if you want to meet up.

Here is the correct orientation required for vacuum. If it's positioned the opposite way, it will not function properly. This isn't new tech by any means. Drag racers have been using this for decades.

[tunermt]

whether or not this set up will work for your car GREATLY depends on the exhaust on your car and for 90% of cars it will not work as the exhaust DOES get back pressure that is not over come by the vacuum created from these.

Its not that hard to set up and test your self though so if your considering it just give it a go and T in a MAP sensor or boost gauge and report back. *you'll see + *

[jr_ss]

Yes, backpressure is present, but the exhaust velocity is what causes vacuum on the catch can. Is that back pressure enough to force closed the check valve vs the suction pressure created by the Venturi? That would be the question to ask. Is the differential pressure across the check valve/Venturi enough to create flow? Dyno numbers have proven this works, I'm not sure why there is so much skepticism.

[Grenade180sx]

The only time ive seen this done, is when blowby is high and they get tired of dumping the catch cans, its just hiding the problem with rings. A properly plumbed catch can setup doesn't involve running anything to your exhaust.

[jr_ss]

Originally Posted by Grenade180sx

The only time ive seen this done, is when blowby is high and they get tired of dumping the catch cans, its just hiding the problem with rings. A properly plumbed catch can setup doesn't involve running anything to your exhaust.

It's no different than running in to the turbo suction, just like a factory setup...

[TheRealSy90]

You could have a catch can ran to the exhaust even lol.


Weird, I figured the orientation of that valve would have been the other way, with the opening facing down stream. Interesting.

[KAT-PWR]

Originally Posted by Grenade180sx

The only time ive seen this done, is when blowby is high and they get tired of dumping the catch cans, its just hiding the problem with rings. A properly plumbed catch can setup doesn't involve running anything to your exhaust.

This is true, but on the ragged edge of tuning any oil vapor will decrease your effective octane rating, you won't see that happen with an exhaust ran evacuation point

[Kingtal0n]

IMO you shouldn't be on the ragged edge unless the car has sponsors, free engines, and is a serious race car. And Those cars will get vacuum pump, dry sump.

Probably need something with more resolution that a map sensor or boost gauge for PCV related activities. A gauge/sensor which renders 32"~ of H2O (WATER) on a data-logger would be ideal.

[RocketOgre]

While I do get that using some neat little effects of fluid dynamics it is conceivable that you could create a lower pressure in the exhaust line than exists in the crankcase. I do not understand why anyone would consider it for more than a split second when you have a constant source of vacuum while the engine is running at the intake. I mean maybe in a crazy all motor ITB build that doesn't always pull vaccum, but FFS just get a quality catch can with good filtration and you are done. Plumb the drain hole at the bottom into the dipstick tube, or turbo return line, and you don't even have to check/drain the thing. Not that most people on here need anything more than the factory one that came on SRs.

[godrifttoday]

I have a ka24de-t and on the stock pcv box location I simply welded a 10an fitting and ran a hose to my downpipe with a check valve. It's a moroso unit cost about 30 dollars , you must get the pipe that has a cut out , to weld it to your downpipe

[jr_ss]

Originally Posted by RocketOgre

While I do get that using some neat little effects of fluid dynamics it is conceivable that you could create a lower pressure in the exhaust line than exists in the crankcase. I do not understand why anyone would consider it for more than a split second when you have a constant source of vacuum while the engine is running at the intake. I mean maybe in a crazy all motor ITB build that doesn't always pull vaccum, but FFS just get a quality catch can with good filtration and you are done. Plumb the drain hole at the bottom into the dipstick tube, or turbo return line, and you don't even have to check/drain the thing. Not that most people on here need anything more than the factory one that came on SRs.

As stated above, when you're making decent power(500+ crank) on our tiny motors, maintaining octane ratings is paramount. Since that can be directly effected by oil vapor getting ingested by the motor, it is important to minimize or eliminate it entering the motor period. Regardless of ones opinion 500hp is pretty serious power from a small displacement motor. Cylinder pressures are pretty high and any error in fueling, timing or a combination of other factors can damage the motor pretty quickly. Granted, tuning to the "ragged" edge would be for one purpose, making the most power without regard to motor life. I prefer my tune conservative so I don't have to test fuel at every fill up for octane ratings to ensure I'm not going to pop my motor.

Yes, suction at the turbo is a good constant source, but not everyone has an intake pipe, let alone a filter mounted to their turbo. I plumbed mine to the exhaust because I didn't want the contaminated oil vapor sucked into the turbo and essentially puked into the intercooler, plumbing, sensors, and eventually motor. What you're sucking out of the motor is nasty shit and it will gum things up over time.

[jr_ss]

I emptied my catch can today. It hasnt been done in awhile and this was the result. Green tint/hue is from the Brad Penn motor oil I use. I'd say my exhaust evac is working just fine...

[Kingtal0n]

if I were running an exhaust driven PCV system without monitoring, I would incorporate a check-valve breather, such that during boost the system would default to open atmospheric (no pcv action) if there were any pressure, since I would also be using a quiet exhaust system (probably high back pressure). Back to normal driving and the exhaust driven system does the crankcase vacuum as if it were on the intake manifold, this way oil would never see the intake valves no matter what and any positive pressure that the exhaust driven setup couldn't deal with would exit via check valve (because I weren't monitoring it to know for sure). There is a guy on LS-1 tech "Mighty Mouse" promoting a similar setup, and after considering it, I agree this is a fair compromise on a high performance engine without crankcase monitoring refinement.

Oil may be collecting during normal driving, and none during WOT. Without a gauge on the crankcase, there is no way to monitor what is really happening. Also, oil vapor (as single, gas state molecules) might work its way into a tube and collect there (hydrophobic interactions) without any help from pcv systems (could be at any pressure around atmospheric).

[jr_ss]

While I'll agree that it could be from normal driving, back pressure is present while the car is running, only in varying amounts. With that said, so is exhaust velocity.