Are catch cans necessary? - CorvetteForum - Chevrolet Corvette Forum Discussion

Notices
C7 General Discussion General C7 Corvette Discussion not covered in Tech
Sponsored by:
Sponsored by:

Are catch cans necessary?

Reply

 
 
 
Old 08-09-2018, 10:18 AM
  #1  
boofus1
CF Senior Member
Thread Starter
 
boofus1's Avatar
 
Member Since: May 2010
Location: Franklin TN
Posts: 106
Thanked 9 Times in 8 Posts
Default Are catch cans necessary?

I keep hearing about catch cans on the C7's. Are these absolutely necessary? What harm can come if I don't install one?
boofus1 is offline  
Reply With Quote
Old 08-09-2018, 10:21 AM
  #2  
dfettero
CF Senior Member
 
Member Since: Jan 2016
Posts: 385
Thanked 54 Times in 41 Posts
Default None

Originally Posted by boofus1 View Post
I keep hearing about catch cans on the C7's. Are these absolutely necessary? What harm can come if I don't install one?
None - the car did not come with one.
dfettero is offline  
Reply With Quote
The Following 2 Users Say Thank You to dfettero For This Useful Post:
4thC4at60 (08-09-2018), boofus1 (08-09-2018)
Old 08-09-2018, 10:21 AM
  #3  
The HACK
CF Senior Member
 
The HACK's Avatar
 
Member Since: Apr 2018
Posts: 184
Thanked 90 Times in 52 Posts
Default

Take this for what itís worth.

https://www.corvetteforum.com/forums...te-engine.html

Thereís already an oil-air separator on the LT1.
The HACK is offline  
Reply With Quote
The Following User Says Thank You to The HACK For This Useful Post:
boofus1 (08-09-2018)
Old 08-09-2018, 10:52 AM
  #4  
JerryU
2017 GS, M7, 2.5LT
Support Corvetteforum!
 
JerryU's Avatar
 
Member Since: Sep 2007
Location: South Carolina
Posts: 10,716
Thanked 2,031 Times in 1,516 Posts
Default

Had one on my 2014 Z51 and was collecting ~1 oz of oil/1000 miles. That's one oz that did not pass over the very hot intake valves and cause "coking" - i.e. baked on oil on the back of the valves. Tadge says it's "Only Cosmetic." Perhaps not a significant power detractor but some of us are more OCD about the inside of the engine that the outside. I could care less about fingerprints that come off when I wash the car! Don't want to clean the backs on intake valves!

Also GM have spent a lot of time and engineering effort "improving" the PVC system in the new dry sumps as I have in my Grand Sport! Doubt they did that for "no problem!" I took the "single outlet can" from my 2014 Z51 and put it on my Grand Sport. I now collect only ~1/2 oz of oil that does not go past the hot intake valves.

Would I buy a can for the new Grand Sport? Don't know that I would. However IMO it can't hurt.

For those that fret about possible warranty issues etc don't do it. I don't-had no issues with my 2014 nor do I expect any with my Grand Sport. The argument of why GM (or other manufacturers) don't add one is not rational IMO! Folks don't check their tire pressures or oil level as recommended. Most would not check the "can" and empty the collected oil. If you don't empty the "can" periodically and dump the collected oil it could cause problems. Then were would the none-DIY owner dump it? In the drain? Don't think that would be recommenced by GM! I dump mine in the container I use when I change my oil. That gets dumped at that time in a recycle center.

TO EACH THEIR OWN!

Last edited by JerryU; 08-09-2018 at 10:55 AM.
JerryU is offline  
Reply With Quote
The Following User Says Thank You to JerryU For This Useful Post:
boofus1 (08-09-2018)
Old 08-09-2018, 11:10 AM
  #5  
VaydorVette1
CF Member
 
VaydorVette1's Avatar
 
Member Since: May 2017
Location: California
Posts: 87
Thanked 17 Times in 15 Posts
Default

Originally Posted by JerryU View Post
Had one on my 2014 Z51 and was collecting ~1 oz of oil/1000 miles. That's one oz that did not pass over the very hot intake valves and cause "coking" - i.e. baked on oil on the back of the valves. Tadge says it's "Only Cosmetic." Perhaps not a significant power detractor but some of us are more OCD about the inside of the engine that the outside. I could care less about fingerprints that come off when I wash the car! Don't want to clean the backs on intake valves!

Also GM have spent a lot of time and engineering effort "improving" the PVC system in the new dry sumps as I have in my Grand Sport! Doubt they did that for "no problem!" I took the "single outlet can" from my 2014 Z51 and put it on my Grand Sport. I now collect only ~1/2 oz of oil that does not go past the hot intake valves.

Would I buy a can for the new Grand Sport? Don't know that I would. However IMO it can't hurt.

For those that fret about possible warranty issues etc don't do it. I don't-had no issues with my 2014 nor do I expect any with my Grand Sport. The argument of why GM (or other manufacturers) don't add one is not rational IMO! Folks don't check their tire pressures or oil level as recommended. Most would not check the "can" and empty the collected oil. If you don't empty the "can" periodically and dump the collected oil it could cause problems. Then were would the none-DIY owner dump it? In the drain? Don't think that would be recommenced by GM! I dump mine in the container I use when I change my oil. That gets dumped at that time in a recycle center.

TO EACH THEIR OWN!
Good perspective on the issue. I think every car should have one.. but hadn't really thought about the masses that would fail to check and drain the can as needed.
Keeping the gunk off the top of the engine is nothing but a good thing.
VaydorVette1 is offline  
Reply With Quote
The Following 2 Users Say Thank You to VaydorVette1 For This Useful Post:
boofus1 (08-09-2018), JerryU (08-09-2018)
Old 08-09-2018, 11:13 AM
  #6  
Foosh
CF Senior Member
 
Foosh's Avatar
 
Member Since: Oct 2004
Location: Maryland/DC Metro
Posts: 13,987
Thanked 5,358 Times in 3,152 Posts
Default

Completely unnecessary. This has been debated ad nauseam, and no one can provide any credible evidence that they provide any meaningful benefit. They do make some people feel better, and if it serves that function, then I suppose there is that benefit.

Last edited by Foosh; 08-09-2018 at 11:17 AM.
Foosh is offline  
Reply With Quote
The Following 3 Users Say Thank You to Foosh For This Useful Post:
4thC4at60 (08-09-2018), boofus1 (08-09-2018), Glenmcp (08-10-2018)
Old 08-09-2018, 11:27 AM
  #7  
robert miller
CF Senior Member
 
robert miller's Avatar
 
Member Since: Jan 2007
Location: cookeville tennessee
Posts: 25,492
Thanked 964 Times in 876 Posts
Default ttt

You will have guys that say yes & then others that will say no. I do have one on car I say this if it catches any at all & if you put one onto your car it will do so. That is that much what ever that amount is that didn't get coked onto the valves & down into the intake. You can do it are not do it that is your choice.. Robert
robert miller is offline  
Reply With Quote
The Following 2 Users Say Thank You to robert miller For This Useful Post:
boofus1 (08-09-2018), JerryU (08-09-2018)
Old 08-09-2018, 11:40 AM
  #8  
Foosh
CF Senior Member
 
Foosh's Avatar
 
Member Since: Oct 2004
Location: Maryland/DC Metro
Posts: 13,987
Thanked 5,358 Times in 3,152 Posts
Default

There is no credible evidence that whatever you caught would otherwise get "coked onto the valves" and cause any more coking than pure gasoline combustion. Whatever tiny amount of oil that may enter the combustion chamber is round-off error compared to the amount of gasoline ignition, which causes valve coking too. Between 5-7K oil changes, most LT engines show almost no oil consumption.

Like I said, it does make some people feel better. Sugar pills make many people feel better too. As sure as the sun rises in the east every morning, someone here will soon post a picture of coked valves, but they can't demonstrate a catch can would have prevented it.

Last edited by Foosh; 08-09-2018 at 12:10 PM.
Foosh is offline  
Reply With Quote
The Following 3 Users Say Thank You to Foosh For This Useful Post:
4thC4at60 (08-09-2018), boofus1 (08-09-2018), Tom760 (08-09-2018)
Old 08-09-2018, 12:07 PM
  #9  
JerryU
2017 GS, M7, 2.5LT
Support Corvetteforum!
 
JerryU's Avatar
 
Member Since: Sep 2007
Location: South Carolina
Posts: 10,716
Thanked 2,031 Times in 1,516 Posts
Default

Just to set the science straight, no gasoline goes over the back of the hot intake valves in a DI engine! That is why, unlike port injection or a carb, gas with “cleaning additives” washed all of the PCV oil, oil mist and “combustion products stuff” from the backs of the hot intake valves before it had a chance to bake-“coke.” There are also small oil particles that form when exiting the crack and rod journals and hit the spinning crack contacting the very hot underside of the pistons and oxidizing.

All that “stuff” exits the PVC valve and small PCV hose from the crackcase to the intake manifold. It never sees any gasoline before it hits the back of the very hot intake valves. One can “wish” GM has a magic solution and not consider the effort placed to improve the PVC system on the new dry sumps to reduce the amount of oil leaving the crackcase and staying in the crackcase. Folks can also “hope” that Tadge’s statement that the coking that does develop is “only cosmetic.” Similar to accepting that the increased Grand Sport and Z06 wheel breakage is just normal and only due to folks hitting potholes. Be happy to post that Tadge Answer forum post as well, but it won’t make your bent wheels any better!

Bottom Line, never used a “catch can” on my ‘88, ‘93 or 2008 C6- with their port injection, didn’t need one. I added one on my 2014 C7 Z51 and removed when I sold it and installed on my Grand Sport.

We can each have an opinion, and do as we wish.

Last edited by JerryU; 08-09-2018 at 12:17 PM.
JerryU is offline  
Reply With Quote
The Following User Says Thank You to JerryU For This Useful Post:
boofus1 (08-09-2018)
Old 08-09-2018, 12:13 PM
  #10  
Foosh
CF Senior Member
 
Foosh's Avatar
 
Member Since: Oct 2004
Location: Maryland/DC Metro
Posts: 13,987
Thanked 5,358 Times in 3,152 Posts
Default

Yes, Jerry, but that's irrelevant to the argument. You repeat the same argument over and over, which is completely missing the point.

Gasoline combustion causes coking, and the amount of that is exponentially larger than the tiny amount of oil ever entering the intake chamber. There is no proof that it's primarily or even detectably caused by oil. That's purely shade-tree speculation by amateurs.

Last edited by Foosh; 08-09-2018 at 12:19 PM.
Foosh is offline  
Reply With Quote
The Following User Says Thank You to Foosh For This Useful Post:
4thC4at60 (08-09-2018)
Old 08-09-2018, 12:23 PM
  #11  
SilverGhost
CF Senior Member
 
SilverGhost's Avatar
 
Member Since: Nov 2005
Posts: 538
Thanked 176 Times in 102 Posts
Default

Catch cans are toxic to your GM warranty. Funny, GM telling c7 owners we'll be just fine with no worries about carbon build up on the back of the valves from direct injection not sending detergent gasoline to wash buildups off....then GM: 1) reducing the powertrain warranty on 2016 and later models to 60,000 miles from the previous 100,000 miles coverage (performance reduction from crudded valves allegedly starts showing up at 60,000 miles)....and 2) making a running change to the C7 motor by ADDING port injection in conjunction with the direct injection on the 6.2 liter used in the 2019 ZR1. So ZR1's get their valves washed by detergent gasoline, other C7's do not.
SilverGhost is online now  
Reply With Quote
The Following User Says Thank You to SilverGhost For This Useful Post:
boofus1 (08-09-2018)
Old 08-09-2018, 12:48 PM
  #12  
JerryU
2017 GS, M7, 2.5LT
Support Corvetteforum!
 
JerryU's Avatar
 
Member Since: Sep 2007
Location: South Carolina
Posts: 10,716
Thanked 2,031 Times in 1,516 Posts
Default

Originally Posted by Foosh View Post
Yes, Jerry, but that's irrelevant to the argument. You repeat the same argument over and over, which is completely missing the point.

Gasoline combustion causes coking, and the amount of that is exponentially larger than the tiny amount of oil ever entering the intake chamber. There is no proof that it's primarily or even detectably caused by oil. That's purely shade-tree speculation by amateurs.
Yep and you keep trying to confound the issue by bringing up gasoline that I know you understand does NOT touch the back of the intake valves where coking occurs! However some of the silent majority that view these threads might not. Just have to look at the BMW and Ferrari high performance engines that used DI well before GM. They had NO gasoline passing over the hot intake vales and BMW suggested walnut shell blasting to maintain performance at ~50,000 miles. Yep coking occurs from PCV "stuff" not gasoline with "cleaning additives.

Until I see the "magic solution" GM is using versus BMW, Ferrari etc that express concern about coking I don't believe one is "foolish" to add and also don't believe it is harmful for someone who empties it periodically and dumps the collected "stuff" as is required. Does it catch everything -NO! Is it cheap insurance-YEP, IMO!

As I said, for those afraid of the warranty issue-don't add one! But don't think that solves the problem!

My guess is the new C8 engines will have one of the solutions used by Toyota, an engine with both DI and port injection. Even the ZR1 has that but primarily for the extra power. Expect it can be designed to work periodically to wash the PVC "stuff" off before it bakes on the back of the intake valves. Another solution is to get the EPA to agree we could dump the "stuff" on the ground as we did prior to the 1960s! Had one on my 1956 Chevy V8 and my prior 1950 Ford V8! Not a good idea!

TO EACH THEIR OWN!
JerryU is offline  
Reply With Quote
Old 08-09-2018, 12:55 PM
  #13  
Foosh
CF Senior Member
 
Foosh's Avatar
 
Member Since: Oct 2004
Location: Maryland/DC Metro
Posts: 13,987
Thanked 5,358 Times in 3,152 Posts
Default

Jerry,

To amplify my above points a little further, the backs of DI engine valves in the LT engine are exposed to the combustion by-products of 44,800 ounces of gasoline in a 7K mile period between oil changes (assuming 20mpg combined). And yes, we all know the backs of the valves are not getting washed as they would be in port injection systems. By contrast, in my two LT engines, the oil level has remained essentially the same between changes with no detectable oil consumption, so let's assume a worst-case scenario that 4-6 ounces of oil is entering the combustion chamber during that period. That's probably a significant over-estimate.

So let's see, the backs of those valves are exposed to 44,800 oz. of exploding gasoline by-products without getting washed, and maybe 4-6 oz. of exploding oil by-products, and you're really going to conclude that adding a catch can is going to prevent valve coking?

Last edited by Foosh; 08-09-2018 at 01:18 PM.
Foosh is offline  
Reply With Quote
Old 08-09-2018, 12:55 PM
  #14  
PatternDayTrader
CF Senior Member
 
PatternDayTrader's Avatar
 
Member Since: Oct 2008
Location: Lansing MI and Houston TX
Posts: 4,753
Thanked 459 Times in 383 Posts
Default

Originally Posted by JerryU View Post
Yep and you keep trying to confound the issue by bringing up gasoline that I know you understand does NOT touch the back of the intake valves where coking occurs! However some of the silent majority that view these threads might not. Just have to look at the BMW and Ferrari high performance engines that used DI well before GM. They had NO gasoline passing over the hot intake vales and BMW suggested walnut shell blasting to maintain performance at ~50,000 miles. Yep coking occurs from PCV "stuff" not gasoline with "cleaning additives.

Until I see the "magic solution" GM is using versus BMW, Ferrari etc that express concern about coking I don't believe one is "foolish" to add and also don't believe it is harmful for someone who empties it periodically and dumps the collected "stuff" as is required. Does it catch everything -NO! Is it cheap insurance-YEP, IMO!

As I said, for those afraid of the warranty issue-don't add one! But don't think that solves the problem!

My guess is the new C8 engines will have one of the solutions used by Toyota, an engine with both DI and port injection. Even the ZR1 has that but primarily for the extra power. Expect it can be designed to work periodically to wash the PVC "stuff" off before it bakes on the back of the intake valves. Another solution is to get the EPA to agree we could dump the "stuff" on the ground as we did prior to the 1960s! Had one on my 1956 Chevy V8 and my prior 1950 Ford V8! Not a good idea!

TO EACH THEIR OWN!
If coking comes from pcv oil then why doesn't the intake port get coked up ?
PatternDayTrader is online now  
Reply With Quote
Old 08-09-2018, 01:06 PM
  #15  
dvilin
CF Senior Member
 
dvilin's Avatar
 
Member Since: Nov 2007
Location: Rochester New York
Posts: 38,097
Thanked 2,558 Times in 1,853 Posts
Default

Absolutely not needed.
dvilin is offline  
Reply With Quote
Old 08-09-2018, 01:13 PM
  #16  
JerryU
2017 GS, M7, 2.5LT
Support Corvetteforum!
 
JerryU's Avatar
 
Member Since: Sep 2007
Location: South Carolina
Posts: 10,716
Thanked 2,031 Times in 1,516 Posts
Default

Originally Posted by PatternDayTrader View Post
If coking comes from pcv oil then why doesn't the intake port get coked up ?
Because the intake valves on a high performance engine operate at >1000F! Stuff bakes on quickly! I'm sure the intake runners don't look perfectly shinny as GM designed them for max power. Then again, most Vette owner's don't use Max power than what's some "coking!" In fact if you never put your foot on the floor-don't bother to add a catch can. In fact unlike some posters who are adamite they "know" one is not needed," I don't care if folks add one or not! Just trying to say why I do. Also if driving a "grocery getter" the valves don't operate as hot and DI is less of an issue.

Some of us have built engines, my latest is the 502 crate motor in my Street Rod. When I was 16 built a bored out Olds for my first car, a '41 Ford coupe. In the interim saw NASCAR engines and heads disassembled at Level Cross NC when we were a sponsor for Richard Petty!

This is what my 502 cid engine CNC port matched intake passages looked like in my garage in assembly! The gas from that 850 Holley "double pumper" keeps them looking relatively new!

Your car your choice!






Last edited by JerryU; 08-09-2018 at 01:23 PM.
JerryU is offline  
Reply With Quote
Old 08-09-2018, 01:17 PM
  #17  
PatternDayTrader
CF Senior Member
 
PatternDayTrader's Avatar
 
Member Since: Oct 2008
Location: Lansing MI and Houston TX
Posts: 4,753
Thanked 459 Times in 383 Posts
Default

Lol .. ok Jerry.
PatternDayTrader is online now  
Reply With Quote
Old 08-09-2018, 01:19 PM
  #18  
Foosh
CF Senior Member
 
Foosh's Avatar
 
Member Since: Oct 2004
Location: Maryland/DC Metro
Posts: 13,987
Thanked 5,358 Times in 3,152 Posts
Default

LOL, ok Jerry.

The combustion by-products of gasoline, and lots of it, are MOST CERTAINLY touching the backs of the valves. You are the one either missing or purposely confounding the issue.

Last edited by Foosh; 08-09-2018 at 01:23 PM.
Foosh is offline  
Reply With Quote
Old 08-09-2018, 01:23 PM
  #19  
Rebel Yell
CF Senior Member
 
Rebel Yell's Avatar
 
Member Since: Jan 2006
Location: Down south in Dixie
Posts: 5,086
Thanked 1,520 Times in 1,084 Posts
Default

boofus, I had to laugh. Not at you, but at the question. It's like asking, should I get "black or chrome wheels", "manual or automatic", or "does the jeans make my butt look big". The best suggestion I have is if you want one for the peace of mind then by all means yes, you should get one. We're just going to confuse you with the answers we give.
Rebel Yell is offline  
Reply With Quote
Old 08-09-2018, 03:45 PM
  #20  
JerryU
2017 GS, M7, 2.5LT
Support Corvetteforum!
 
JerryU's Avatar
 
Member Since: Sep 2007
Location: South Carolina
Posts: 10,716
Thanked 2,031 Times in 1,516 Posts
Default

Originally Posted by Foosh View Post
LOL, ok Jerry.

The combustion by-products of gasoline, and lots of it, are MOST CERTAINLY touching the backs of the valves. You are the one either missing or purposely confounding the issue.
It's like the old Duck question! The stuff I and many other's collect looks like oil, feels like oil and smells like oil! Let's hope what is in the crackcase isn't that much blowby as it is oil mist, burnt oil particle from the oil leaving the bearings in the crack main and journal bearings and hitting the bottom of the very hot pistons as well as fine "oil" particles.

The LT1 also has oil squirters that spray oil on the cylinder walls under certain conditions. Sure there is some water and other combustion gases, which is why I call it "stuff." All I and those that add a "can" know is we're catching some of that "stuff" and dumping it! It's stuff that does not have a chance of causing coking!
JerryU is offline  
Reply With Quote

Thread Tools
Search this Thread
Sponsored Ads
Vendor Directory

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: