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What catch can for Road Racing?

Old 01-11-2019, 09:21 AM
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Originally Posted by bammax View Post
The dirty side should be large to reduce velocity. The slower the air moves the less oil vapor it'll carry. Many catchcans are useless because the velocity is too high and the flow from inlet to outlet doesn't have enough material in between for the oil to grab onto.
That's what I was thinking, but one elaborate setup I saw was opposite of that with larger on clean and smaller on dirty side and that seemed counter intuitive, but he said it solved his oil consumption. Maybe there were other variables at work in that case.
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Old 01-11-2019, 12:14 PM
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Originally Posted by mikedamageinc View Post
That's what I was thinking, but one elaborate setup I saw was opposite of that with larger on clean and smaller on dirty side and that seemed counter intuitive, but he said it solved his oil consumption. Maybe there were other variables at work in that case.
Every setup is going to be a bit different. The velocity in the hoses, the flow path through the catchcan, the media inside the can, the number of times the air changes direction and even the temperature of the can and hoses will have an impact on how much oil vapor gets pulled from the air. Even exactly copying someone else may not be successful since the motors will have their differences and driving conditions won't be exactly the same. Also remember that everyone has a different idea of what's acceptable.

The best bet is to understand how the ventilation system works as well as you can and then start out with small upgrades and track the changes. Quite a few use a small air/oil separator designed for air compressors since they're cheap at harbor freight/lowes/home depot. It's a good starting point for people to see just how much oil their engine is dumping through the stock system. It gives a fairly precise baseline to start from before opening everything up and buying expensive parts.
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Old 01-11-2019, 05:22 PM
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Guess how much oil I get from this breather can when I open the drain. Zero! My engine oil stays in the engine! Guess how much oil makes its way into my intake manifold. You guessed it! ZERO And you know what? That's a good thing! Just saying
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Old 01-11-2019, 07:03 PM
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Originally Posted by 01CamaroSSTx View Post

Guess how much oil I get from this breather can when I open the drain. Zero! My engine oil stays in the engine! Guess how much oil makes its way into my intake manifold. You guessed it! ZERO And you know what? That's a good thing! Just saying
Of course not, you're not pulling any vacuum through it. It's strickly a breather can and you're not pushing any fresh air in your crankcase either.
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Old 01-12-2019, 11:13 AM
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Originally Posted by mikedamageinc View Post
Of course not, you're not pulling any vacuum through it. It's strickly a breather can and you're not pushing any fresh air in your crankcase either.
And I need fresh air in the crankcase for what reason?
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Old 01-12-2019, 01:33 PM
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01CamaroSSTx Because ring blowby will eventually get into the oil, contaminate it, degrade the oil. Supplying clean air, while evacuating the dirty air, keeps the bottom end cleaner. Remember how old cars used to need 3000 mile oil changes, but new cars go 10k miles. Part of that is better oil, but also PCV systems that keep it all cleaner to start. I'd bet an oil analysis on your next change would have a lot more stuff in it than a PCV car of equal mileage and driving use.
On your setup, it appears to be just a breather, so the crankcase pressure will sometimes push a little air out of that filter top, but not a lot. You don't get anything in the can because the airflow in your crankcase is stagnant compared to a PCV system car. I see you have a tube from your throttle body but not sure how or if it's connected to anything. So I can't tell 100% what's going on there.
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Old 01-12-2019, 02:24 PM
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Originally Posted by Chris Paveglio View Post
01CamaroSSTx Because ring blowby will eventually get into the oil, contaminate it, degrade the oil. Supplying clean air, while evacuating the dirty air, keeps the bottom end cleaner. Remember how old cars used to need 3000 mile oil changes, but new cars go 10k miles. Part of that is better oil, but also PCV systems that keep it all cleaner to start. I'd bet an oil analysis on your next change would have a lot more stuff in it than a PCV car of equal mileage and driving use.
On your setup, it appears to be just a breather, so the crankcase pressure will sometimes push a little air out of that filter top, but not a lot. You don't get anything in the can because the airflow in your crankcase is stagnant compared to a PCV system car. I see you have a tube from your throttle body but not sure how or if it's connected to anything. So I can't tell 100% what's going on there.
Yeah everything is capped off and the only things pulling vacuum are the A/C and brake booster. I went this direction to keep the blowby gases and moisture out of the intake manifold so it does not mix with the air/fuel mixture. This is not a daily driven vehicle but I run a full synthetic oil and change it every 2,000-3,000 miles It would not pass a visual inspection for emissions but can be easily remedied by simply swapping to factory valve covers and connecting the hoses back up like stock..
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Old 01-12-2019, 07:15 PM
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Originally Posted by 01CamaroSSTx View Post
Yeah everything is capped off and the only things pulling vacuum are the A/C and brake booster. I went this direction to keep the blowby gases and moisture out of the intake manifold so it does not mix with the air/fuel mixture. This is not a daily driven vehicle but I run a full synthetic oil and change it every 2,000-3,000 miles It would not pass a visual inspection for emissions but can be easily remedied by simply swapping to factory valve covers and connecting the hoses back up like stock..
You could have skipped the catch can and just put the filter on the vent tube. What do you mean your a/c is pulling vacuum?
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Old 01-12-2019, 07:36 PM
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There is also a very small line that plugs into the back of the intake manifold and I believe it has something to do with the air conditioner.
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Old 01-12-2019, 09:59 PM
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I've been thinking about this over the offseason as well. My car uses no oil on the street but consumes about a half quart per autocross. It's pretty obvious it's been pushing oil out of all of the seals at high RPM and ingesting a bunch through the intake as well. The PCV system was not even set up as well as factory on this car so that didn't help. I've settled on the changes below.

98 motor with centerbolt valve covers
late LS6 valley cover
Radium engineering dual cans with 3/8 lines

Rules don't allow me to modify the valve covers so they cannot be upsized, hence the 3/8. Instead of blocking off the vent tubes on the rear of the covers I am going to run a tube between the passenger and driver side covers. Then just use the front passenger side vent for the second can and then to the intake. The other can will be the standard valley cover to can to TB.
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Old 01-13-2019, 01:30 AM
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Any thoughts on this approach?

Draw fresh air from a fitting that's in between the air filter and throttle body.
Plumb that through a one-way valve, so this line can only be used to let air into the engine.
From the one-way filter, go into one or both heads.
Vent the case via the valley cover.
From the valley cover, go into a catch can.
From the catch-can outlet, go into the intake manifold (downstream of the throttle body).

At low throttle, the intake vacuum draws fresh air in through the air filter, through the case, through the catch can, and into the manifold.
At high throttle, the intake vacuum goes away, but the check valve ensures that crankcase gases will exit via the valley cover and catch can.

Someone here or on CF suggested the check valve a while back, and it sounds good on paper, so I plan to do this to my C5 at some point over the winter.
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Old 01-13-2019, 08:28 PM
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Originally Posted by Chris Paveglio View Post
01CamaroSSTx Because ring blowby will eventually get into the oil, contaminate it, degrade the oil. Supplying clean air, while evacuating the dirty air, keeps the bottom end cleaner. Remember how old cars used to need 3000 mile oil changes, but new cars go 10k miles. Part of that is better oil, but also PCV systems that keep it all cleaner to start. I'd bet an oil analysis on your next change would have a lot more stuff in it than a PCV car of equal mileage and driving use.
On your setup, it appears to be just a breather, so the crankcase pressure will sometimes push a little air out of that filter top, but not a lot. You don't get anything in the can because the airflow in your crankcase is stagnant compared to a PCV system car. I see you have a tube from your throttle body but not sure how or if it's connected to anything. So I can't tell 100% what's going on there.
On what planet do you live on where the crankcase ventilation system can (ever) possibly prevent ring blowby from reaching the bottom end of the engine. I'd like to live on that planet. You're clueless.
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Old 01-13-2019, 08:31 PM
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Originally Posted by landstuhltaylor View Post
I've been thinking about this over the offseason as well. My car uses no oil on the street but consumes about a half quart per autocross. It's pretty obvious it's been pushing oil out of all of the seals at high RPM and ingesting a bunch through the intake as well. The PCV system was not even set up as well as factory on this car so that didn't help. I've settled on the changes below.

98 motor with centerbolt valve covers
late LS6 valley cover
Radium engineering dual cans with 3/8 lines

Rules don't allow me to modify the valve covers so they cannot be upsized, hence the 3/8. Instead of blocking off the vent tubes on the rear of the covers I am going to run a tube between the passenger and driver side covers. Then just use the front passenger side vent for the second can and then to the intake. The other can will be the standard valley cover to can to TB.
98 motor + centerbolt valve cover does not compute unless you changed the heads, which would make sense - though by the letter of the rulebook would not be legal (you'd actually have to run a 99-02 engine, since you have to update/backdate major assemblies, and not just parts - Street Prepared 15.1C) and the valley cover wouldn't be in any case, not that anyone would really care.

You hit the nail on the head with the rpm comment. 3/8 line(s) cant keep up. You need at least 5/8 line, though 3/4 works better.
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Old 01-13-2019, 09:21 PM
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Originally Posted by DietCoke View Post
98 motor + centerbolt valve cover does not compute unless you changed the heads, which would make sense - though by the letter of the rulebook would not be legal (you'd actually have to run a 99-02 engine, since you have to update/backdate major assemblies, and not just parts - Street Prepared 15.1C) and the valley cover wouldn't be in any case, not that anyone would really care.

You hit the nail on the head with the rpm comment. 3/8 line(s) cant keep up. You need at least 5/8 line, though 3/4 works better.
Brainfart, meant the perimeter bolt. They have different fittings on them that make that possible. Is there any value running the bigger lines if I need to neck it down at every fitting on the motor and intake? I'm sure there is some, just not sure it will be enough with how short the runs will be.

And the head change would be totally legal. Everything in the long block is exactly the same down to the part numbers in a 99 and 2000 motor other than the heads so it's a very easy swap. Almost did it to update to the later castings that flow a bit better but decided I didn't want to mess with the heads as at that point it would just become a full rebuild. Valley cover definitely is not legal to the letter but you would have to be a massive **** to protest that. Worst case it's not a big job to put the original one back on.
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Old 01-14-2019, 09:16 AM
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Originally Posted by landstuhltaylor View Post
Then just use the front passenger side vent for the second can and then to the intake. The other can will be the standard valley cover to can to TB.
That sounds backwards unless it works better? Usually TB to valve cover, valley cover (to can if applicable) to intake.

Originally Posted by NSFW View Post
Any thoughts on this approach?

Draw fresh air from a fitting that's in between the air filter and throttle body.
Plumb that through a one-way valve, so this line can only be used to let air into the engine.
From the one-way filter, go into one or both heads.
Vent the case via the valley cover.
From the valley cover, go into a catch can.
From the catch-can outlet, go into the intake manifold (downstream of the throttle body).

At low throttle, the intake vacuum draws fresh air in through the air filter, through the case, through the catch can, and into the manifold.
At high throttle, the intake vacuum goes away, but the check valve ensures that crankcase gases will exit via the valley cover and catch can.

Someone here or on CF suggested the check valve a while back, and it sounds good on paper, so I plan to do this to my C5 at some point over the winter.
That's pretty much the standard setup, with the addition of the check valve which some people run, some don't. I've had reverse flow depending on the setup but not any more.


So how is anyone running 5/8 or 3/4 lines on a factory style routing? Easy to add oversize fittings from intake tube to valve cover, but from valley cover to intake would take major surgery to make it work. Maybe start with blank LS1 valley cover then use the EGR hole on a LS1 intake?
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Old 01-14-2019, 12:50 PM
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Originally Posted by mikedamageinc
So how is anyone running 5/8 or 3/4 lines on a factory style routing? Easy to add oversize fittings from intake tube to valve cover, but from valley cover to intake would take major surgery to make it work. Maybe start with blank LS1 valley cover then use the EGR hole on a LS1 intake?
Use the original ls1 setup. Replace the rear valve cover grommets with larger id versions and use larger fittings. Then run the larger lines along with the appropriate size T and send it to the front like factory. At the pcv valve switch to something with a larger port size (you can also fine tune opening and closing points while you're at it) and plumb the pcv outlet to the catch can. Then you drop back to factory line size from catch can outlet to intake since by that point the system has basically done its job. If you do it right nobody would know you did anything but add a catch can. The valley cover pcv setup would be a nightmare to size up.
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Old 01-14-2019, 01:50 PM
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Originally Posted by DietCoke View Post
On what planet do you live on where the crankcase ventilation system can (ever) possibly prevent ring blowby from reaching the bottom end of the engine. I'd like to live on that planet. You're clueless.
Straw man.
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Old 01-14-2019, 06:16 PM
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Originally Posted by mikedamageinc View Post
That sounds backwards unless it works better? Usually TB to valve cover, valley cover (to can if applicable) to intake.
Maybe it is, I've got my hands in to many pots right now. As long as the hardware is correct I'll verify the routing before actually installing it.
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Old 01-14-2019, 07:49 PM
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Originally Posted by DietCoke View Post
On what planet do you live on where the crankcase ventilation system can (ever) possibly prevent ring blowby from reaching the bottom end of the engine. I'd like to live on that planet. You're clueless.
I didn't say it **prevented** it.
You could be a little more polite about it.
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Old 01-14-2019, 08:15 PM
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Chris,

You stated that an oil analysis on your next change would have a lot more stuff in it than a PCV car of equal mileage and driving use. I question this but the only way to know for sure would be for me to send the oils in for analysis. I'm just not sure I'm willing to introduce the blowby gases back into my intake manifold. I suppose I could go down on performance for a little while in order to find out just for peace of mind. I also believe that PCV has very minimal if any improvement on ring seal as so many people seem to think that PCV does just that. Now racers have been using vacuum pumps for years but this is due to the low tension rings they run in their racing engines. Long story short PCV was designed as a way to control emissions "PERIOD"
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