My write up on a Catch Can for keeping oil out of the intake

Started by Super Villain, April 22, 2010, 02:41:51 AM

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Super Villain

Catch As CATCH CAN

The title is a phrase I have heard batted around more than once.  Often in the company of older people who were more learned and literate than I could ever hope to be.  As an adjective, it means using any available means or method.  Well as a gear head, that certainly sounds like hot rodding to me!  Only this time around this little bit of shade tree engineering actually involves a Catch Can.  Some of you may have heard the term Catch Can tossed around before and wondered why do we need a can and what the hell does it catch?!  To put it simply, a Catch Can separates oil from the crankcase gases flowing into your intake manifold and traps it until you dump it out.

To get into the details, we will first need to make a quick stop at Engines 101 and understand a bit about PCV.  It stands for Positive Crankcase Ventilation and this system's main purpose is to vent out the pressures that build up inside the engine as part of the normal combustion process.  This pressure can be so great that if it is not properly vented, gaskets and seals can get over-pressurized and blow out.  The gas pressures are made up of unburned fumes, oil vapors, blow-by, and other unpleasant leftovers.  They are re-routed back through the intake manifold and into the cylinders again for another chance to be combusted.  The other function of the PCV is to supply the crankcase with fresh air.

On a stock Gen 3 Viper, a hose from the air cleaner box is connected to the passenger side valve cover.  This hose supplies fresh, clean air to the crankcase.  It is in front of the throttle body so that the air supply is uninterrupted whether the throttle blades are open or closed.  On the driver side valve cover, a hose is connected to the intake manifold from underneath. This location is also behind the throttle body.  Vacuum from the intake manifold helps to pull in the vapors from the crankcase.  This is what helps to relieve the pressure build up and any unburned gases are cycled back through the intake to be combusted again.  On a stock Gen 4 Viper, the hose arrangement is opposite, but still does the same thing.  The air box hose connects to the driver side valve cover to supply fresh air to the crankcase.  While the hose on the passenger side valve cover is connected to the intake manifold.

Now that all sounds fine expect for one very critical flaw...the intake manifold hose that uses vacuum to pull in gases and relieve the pressures in the crankcase is also sucking in oil vapors.  Once these oil vapors get inside the intake manifold they pretty much make a mess as they start coating the insides with a film of oil.  This contaminates the air going into the combustion chamber (less fresh oxygen air molecules means less power) and over time this contamination also lowers the octane rating of your fuel.  Once your fuel octane starts dropping the engine will start to knock and ping.  When the computer sees this it will pull back on timing which will of course cost you even more power.

This is where the Catch Can comes into play.  It is installed in between the hose going into the intake manifold and the connection to the valve cover (passenger side on Gen 4s and driver side on the Gen 3).  The Catch Can serves as a oil separator by having the gases and oil vapors flow through it and then trapping the gunk so that only the air and fumes continue on into the intake manifold.

There are a number of Catch Can options on the market and at varying price points.  The designs range from a simple empty cylinder with an "in" hose fitting and an "out" hose fitting.  Others add a bit of steel wool inside as a barrier to help separate the oil from the gases.  Some have breathers while others have special baffles and chambers inside.  After much research, the one that seemed to have the best features and still be reasonably priced was the McKinney Raceworks Catch Can (web link: http://tinyurl.com/viper-catch-can ).  $133 is a decent price for this design.  

Balancing the great features with ease of install and simple regular maintenance while hitting the right price point is always a challenge, but the McKinney Raceworks Catch Can seems to have done it.  It is CNC milled from a solid 2.25" rod of 6061 Aluminum so it feels hefty and fitting under the hood of a Viper.  At 7 inches long and 2.25" diameter it is easy enough to find space for it to fit in the engine bay.  As a totally sealed design, it really allows the vacuum from the intake manifold to suck the air out of the crankcase.  They make several versions with the main differences being the size and arrangement of the fittings.  The 1/2 inch 90 degree fittings are the ones that will work best due to the Viper's low hood clearance.  

They always say its what's on the inside that counts and that is certainly what won me over on this one.  The "dirty" crankcase air enters in through one port and travels down a ½ inch tube inside the Catch Can.  As the vapors exit the tube they encounter a small gap between the exit tube and the funneled surface of the Catch Can's mid-section.  A lot of the oil particles will impact on the funnel surface of the mid-section and then drain down into the bottom trap chamber.  The radius turn into the next exit chamber is quite sharp so while the air can flow into it, the oil vapors will lose velocity making the turn and entering the larger space.  This will cause any leftover oil, that did not impact on the funnel surface, to drop out of suspension of the air stream.  They would then condense on the mid-section and drain down.  Now the fumes and vapors that made it into the exit chamber must pass through some packed steel wool which will act as a kind of filter media, further separating out any remaining oil vapors or gunk.  This all ends up draining back down into the bottom section.  And finally, a foam filter is the last barrier before the air is allowed to be re-introduced into the intake manifold.

The bottom section of the Catch Can is where all the oil that condenses on the funnel surface of the mid-section drains into.  The drain hole is a small port in the middle of the mid-section.  This also helps to act as a baffle to further prevent oil trapped in the bottom section from traveling back up into the upper chambers under hard cornering or braking.  And for ease of maintenance, the bottom section comes off with a twist and then you can just properly dispose of all the collected oil and particles.  Looking inside the "cup" one can't help, but think how all that oil and gunk would have ended up in the intake manifold.

Here is a basic parts and cost list for install into my 2006 Viper.  You may need to adjust a bit depending on your model year.  Total install time should be a little over an hour.

1 Catch Can - $133
3 feet of 1/2 inch hose - $4.47
1 foot of 5/8 inch hose - $1.59
1 T-Bolt steel hose clamp 2.06"–2.37", 3/4" width - $3.30
1 Worm drive hose clamp 2.25"  - $1.50
2 Brass barb hose fitting – female 1/2 inch - $7.94
2 Brass barb hose fitting – male 5/8 inch - $5.64

Total for main parts came to about $157.44.  You will also want to have some smaller hose clamps or zip ties available for tightening any hose ends, but any self-respecting petrol head should already have that in their garage right?  Okay...I won't look while you run to the parts store and stock up.

You could save a few bucks by using plastic barb hose fittings that already come in a 5/8" to 1/2" adaptor.  I was short on time and my OCD demanded that it be done before the next Viper Cruise, which incidentally was the next morning so overpriced brass fittings for me.  The connector coming off the intake manifold and the rubber connector off the driver side valve cover on my Gen 3 was 5/8".  The Catch Can fittings were 1/2" so this is were the fittings come in to size down the hose.  The 1 foot of 5/8" hose goes directly on to the plastic connector coming off the intake.  Then the 5/8" to 1/2" adaptor goes on allowing you to run 1/2" hose all the way to the "OUT" port of the Catch Can.  For the valve cover, you plug the 5/8" to 1/2" adaptor right into the rubber elbow.  Then you run 1/2" hose all that way back to the "IN" port of the Catch Can.

The T-bolt clamp is what you will use to clamp around the Catch Can.  I like the Murray clamps.  Sure you could use a worm drive clamp with the slots, but the T-bolt clamp looks a lot cleaner.  The worm drive hose clamp is what you will use to hold the T-bolt clamp and thus the Catch Can against the engine bay brace bar.  Be sure to get a good quality clamp of thick gauge.  I used the clamps made by Ideal.  Some of the cheaper brands will bend when you try wrenching down on them.  And for this you will be wrenching down good to get a tight grip.  Once the clamp is tight and there is little to no movement from the Catch Can, you may notice that the worm drive clamp is not flush against the brace bar.  Just get a block of wood and then hammer down on the clamp until it goes flush.

Take a look at the pictures for further details.

It doesn't matter if the car is stock, mildly modified, heavily modified, or supercharged.  All Vipers can benefit from a good Catch Can.  One note for supercharged Vipers...you will need a one-way check valve on the line going into the intake manifold so as to not push air back into the Catch Can under boost.  In short, sucking oil into the intake manifold is never a good thing.  It contaminates the air and lowers your fuel's octane rating.  The inevitable knocking and pinging will cause your timing to be pulled by the computer and the end result will be a loss of power.  So there I just saved you some horsepower!  Paypal donations and introductions to single, loose women will be greatly appreciated.  

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12 oz ice tea can for size reference.  I drank it later and recycled the can too!  After which to balance things out I drove my obnoxiously loud, heavily modified Viper in a very non-eco friendly manner.  

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The bottom section twists off to easily inspect the contents and then dispose of any oil collected.  To the left you can seen the bottom side of the mid-section.  Notice the drain hole in the center.  This design prevents the oil from splashing up during hard cornering or braking.

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All 3 main sections apart.  The mid-section is held in by two screws.  The o-rings help to form a nice air-tight seal.  The funnel surface of the mid-section directs oil to all drain down the center.  You can also see inside of the top section.  Note the 1/2" tube that brings in the "dirty" air and the steel wool that the air must pass through before exiting the "clean" port.

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Steel wool removed and now you can see the final foam filter.

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Foam filter removed and you can see the "clean" exit port and a better shot of the inlet tube.

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I couldn't resist and had to "church" it up a bit before the install.  Some polishing with Mother's Metal Polish and a Viper logo does wonders! ;)

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Installed!

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The Catch Can was installed the night before our Dukes Poker Run and was clean as a whistle.  Right after I got home I twisted off the cap and this is what I found.  That's a lot of oil and gunk!

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Now granted I did drive her pretty hard that day and I do have a big cam, heads, 11:1 compression etc. so you may not be pulling as much oil as I do under load, but daaaamn thats a lot of oil after just one day.  I'll have to check this thing at least 1 to 2 times a month.  For track days I will need to check her each day.

Happy Motoring!

"What is best in life?"...."To crush your enemies, see them driven before you, and to hear the lamentations of their women!" - Conan

NK BREKR

Great write up Anhtuan!  Now when can I bring the Blue Meanie by for the install  <11

ViperX

Anhtuan,

Great job with the write up and pics.

Love that last series of pics with the oil in the catch can.

I remember working on a catch can for my GTS with Dave C.  He was a bit skeptical at first of just how much oil these engines put into the intake manifold.  After I ran my GTS for a while with the catch can on, I showed him the contents of the can one day and he was amazed.  He then installed a catch can on his car and found the same results that you did.

Thereafter, he religiously "dumped" his catch can every month.

The good news is, you kept that crap out of your engine.

The bad news for most of us is, you'll be making even more power!

Dan

redtanrt10


Anhtuan,

Well done!!  Thanks so much for taking all the time on the description!!

Mike

PCH VIPER

Great write up Anhtuan !

Apparantly it was so good that everyone ran out and ordered the catch can and I hear they are Out of Stock .
www.kouchicentral.com  for more viper pictures

Super Villain

Thanks guys!  It always takes me longer than I think to write this stuff up, but seeing how much you guys enjoy the info and the read makes it worth it.

And thanks to YOU Dan for helping me confirm the routing path and other catch canny info ;) !  Next dyno day here I come!

If we get a few people interested we could probably do some kind of an install party.

They're out of stock already?  Wow...I hope they make more soon and fast!  The results of the last two pics really speak for themselves.
"What is best in life?"...."To crush your enemies, see them driven before you, and to hear the lamentations of their women!" - Conan

Banzai Ben

Very nice Anhtuan. I think I better get one now.
Thanks for the write up.
Ben
2013 SRT Viper, Race Yellow
2003 Viper Comp Coupe, GTS Blue
2005 SRT-10 Ram, Yellow Fever
2018 Hellcat Challenger, Indigo Blue

DEDLY4U

Anhtuan,

This is a great write up and the pictures are a great help.  I ordered the can today from McKinney and i will give you a shout when it comes in.  Thaks again.

Mike 

%y %o %u  %d %a  %m %a %n %!

ViperX

Hey Mike,

You will need a one way check valve with this set up (due to your supercharger) that will stand up to at least 10lbs of pressure.  Mesa hose or Torino Racing Products may be able to help locally.  You could also check with Summit Racing or Jegs online.

Dan

DEDLY4U

Thanks for the heads up Dan, I didn't even give it a thought.  Mike

DEDLY4U

Dan,

I noticed there are several types of check valves.  Where exactly is it installed and can you give me some idea as to what type and size I should be looking for?

Mike

ViperX

Hey Mike,

You would install it in the line the comes out from under the intake manifold, which is pressurized under boost but should provide vacuum when not under boost.  I'm not sure of the size.  You'd have to check Anhtuan's write up.  Likely it will be -8 (1/2 inch) or -10 (5/8 inch).

Dan

Specialty Performance Team

Mike,
You currently have a billet check valve installed in your system, another is not needed.

Dan

DEDLY4U


ViperX

Thanks Dan,

Good to know you're looking out for us.

When I first had my black car supercharged, the installer (who will remain nameless) didn't install a check valve!

Dan