Avanti

Is that a minnow in there?

Maxie2U

Steve Carter

PatternDayTrader

Yes it is.
I guess the only thing to add to the discussion would be that the only way you can keep crankcase oil mist out of the intake, is with a catch can. And, as an engine wears out, more and more crankcase oil mist will pass through the pcv system and therefore the intake manifold, unless a catch can is used. The only disadvantage is that you have to clean it from time to time.

ptalar

First time I heard that.

ptalar

Here are two "ask Tadge" threads where he answered on the subject. I get how the add on catch can by the owner can void the warranty based on Tadge's description of how a catch can system is suppose to work in GMs eyes and as installed on the Camaro. He seems to think this whole issue is a non-issue based on engineering data GM has collected for the Corvette. I think I am going to pass on an add on catch can.

https://www.corvetteforum.com/forums...on-valves.html

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

3 Z06ZR1

I would agree but it for sure it is needed on the Lt4 to keep oil out of the blower! Mighty Mouse can is the bomb!

spinkick

I run one because I prefer to burn air and fuel only. I'll recycle the stuff in the catch can with my oil change waste.

JerryU

Of interest, Tadge's comments (that were in an Ask Tadge post) do not discuss why they spent the time and money to improve the dry sump system for that "non existent coking issue" and also say nothing about improving the C7 wet sump PCV system although they say why they improved the Camaro wet sump system! .

The one sentence in that Tadge response I did not fully understand is this:

"Catch-can" systems that do not have a drain back path for separated oil run the risk of poor oil pressure performance over time as oil is removed from the lube system."

I can understand the issue, IF as GM must consider, someone does not empty the "catch can" periodically, the oil could build up and cause the PCV system to malfunction. Since many don't even check their oil level when GM recommends, a reasonable concern for them! However saying a catch can removing oil from the system (see even Tadge says the "stuff" we collect is oil) will create oil pressure problems because of lack of oil - is confusing! That makes no sense as we are ONLY removing what would be going into the intake manifold to be burned in the combustion chamber like PCV systems have done for years. We are NOT creating any extra vaccum to pull out more oil. Especially those of us with single outlet cans as it is just located after the PCV valve replacing the hose that goes to the intake manifold. Therefore without a "can" the same amount of oil is being sucked out of the crackcase, it just all goes into the manifold!

Getting to your point spinkick, a race engine would never digest crackcae "stuff" and mess up the carefully controlled air/fuel ratio delivered to the combustion chamber. Some use a venturi devise that pulls the crackcse "stuff" directly into the exhaust (not advised when using CATs or for EPA controlled cars!) Or as in my '56 Chevy V8 and up to the early 1960's we could use a "road draft tube" and dump the "stuff" in the air! (Not a good idea but what was done before the ealy 1960s!)

kennyjames21

He's claiming its a non-issue with the dry sump engine, but really his whole explanations sounds like BS - I'm thinking they added a catch can system to the camaro because this is an issue with these engines. And the claim that an aftermarket catch can will create oil pressure issues (because it doesn't return the oil back into the system like the GM one on the camaro) is horseshit too because without a catch can doesn't pretty much the same amount of oil get lost anyway getting caked onto the valves (either way there shouldn't be that much oil getting bypassed regardless in either situation)?

PatternDayTrader

I tend to think catch cans become more and more useful as the engine becomes more and more worn out.

ptalar

At the time of his response he was referring to the Camaro SS which has a wet sump system. The dry sump apparently was designed to act as a catch can in the Corvette is what he was alluding to. Yes, I agree there must be a problem with intake valve coking with the wet sump LT1 engine if they finally added a GM Production Catch Can system in the Camaro. Then the question becomes what about the base Stingray with the wet sump? Why didn't they add a production catch can to that LT1 engine? Tadge did not say it directly, but my perception was the base stingray is not going to see track use so they see no need to add a Production Catch Can System. I have a 2016 Z51 with dry sump so I am not going to add the catch can based on what Tadge said. Plus I am afraid it might compromise my smog inspection here in California.

JerryU

Having watched grandsons car get smog tested in Upland CA it would appear to be up to the station. This was a private fellow who went beyond what it could of to get it past. He let the engine run and then used an outside device to get the engine at the max idle rpm allowed.

However if you get someone who goes by the book r.e. CA laws you could not add what many C7 owners have called a crossover. Since all C7's have a crossover in the same place, these are devices that eliminate the secondary CATs. That is detectable and not allowed by CA Law! But a catch can would be less likely to be detected and would have NO affect on exhaust emissions.

If you have a newer Dry Sump you have the "significantly Improved PCV system" that uses no doubt internal engine baffles, more hoses from the valve covers to dry sump tank and whatever in the dry sump tank so as I have found your getting about half the extra "stuff" going into the intake from the crackcase through the PCV system. If you have an older dry sump system (for sure that was 2014 or 2015) than you don't have the advantage of the money and engineering time GM spent to reduce "the nonexistent coking issue!"

Your car and if you have any concerns don't add one but don't be like the Fox in Aesop Fables and just say the grapes were sour anyway!

ptalar

I have the newer dry sump system. I have a 2016 Z51.

Part of the CA inspection is a visual inspection of the engine to look for any add on mods or loose hoses and what not as well as a leaky gas filler cap.

I am not calling anything sour grapes. I have not heard of any C7 DI engine being repaired at owner cost or repaired under warranty for excessive valve coking causing performance issues on this forum. With almost 150K C7s on the road with cumulative mileage in the millions GM should have any red flags on valve coking by now. I am sure we would of heard about it. There must of been a trade off done on benefit vs cost and the DI engine has more benefit than warranty cost impact and I suspect they also assumed that more dry sump vettes would be sold thus reducing the need for a catch can. That combined with the fact that most of us don't track our cars made it a low cost risk to not add a production catch can.

JerryU

^^^
About half the C7's are Wet Sumps and at best the Dry Sump is NOT collecting all the excess "stuff." I'm collecting in my 2017 Grand Sport catch can about half the amount I had for 3 years in my 2014 with the same can -NOT zero. It still has the same PCV valve and hose as my 2014 Z51. Not sure if 2016 or 2017 was the change year in dry sump design for a Z51.

But if your not concerned about getting the last amount of power than I agree there have been no engine failures reported and I didn't expect any! The carbon build-up on the intake valves is more a performance issue and if you never put your foot to the floor or if you do not worry about a few horses being out to pasture you'll probably not see a difference.

Scoobydoobydoo

. All.depends on your dealer. Both of my local ones told me a catch can WILL void the wardanty

kennyjames21

Forget what they tell you now, because as anyone who has ever dealt with dealers trying to get warranty work done, if you have a major engine problem, they will look for any reason not to have to cover the repairs, and they can, and will, use a catch can as an excuse.

(this is for the guy who was told by the dealer that the catch can is ok...)

JerryU

Yep, if you have any concerns, don't add one. If anyone wants full details with Tadge post info etc this is a 19 page PDF with lots of pics and info abut "coking": http://netwelding.com/Catch_Can.pdf

Covers LT1's but if you have a Z06 or are Tracking, search for more info. Yep, I have an aFe low restriction air intake system with a oiled cotton filter that is "supposed to" void warranty (it worked fine on my 2014 Z51 for 3 years so removed it when I sold the Vette and it's now on my Grand Sport- just cleaned the filter!). But my experience in getting GM to replace a clutch pressure plate in a Chevy after 1 year and recently in my C6 Vette an AC condenser that the dealer said GM won't cover because "it could be caused by a rock" - makes me confident I could defend both! BUT it's a risk. (That doesn't include getting a failed dif in my 260Z paid for several months after the warranty was up! But that required a report to Datsun in Japan with a cover note in Japanese witted by one of our engineers! )

Foosh

So Jerry, are you confident enough in your powers of persuasion for your car to go to a dealer w/ a failed engine with the catch can in place, or would you remove it before the car takes a ride to the dealer on a flat bed?

JerryU

^^^

No, although that is so easy, took 10 minutes to removed from my 2014 C7. I keep the original 6 inch long hose, which is all that gets replaced. When I sell the Grand Sport will remove it as too many folks with concern about warranty etc. I'll use logic to prove there is no way it caused an issue. Good chance IMO, I'll win!

Can will no doubt not be needed in the C8 as my bet it will have port injection and DI to get rid of the "non issue" they spent lots of time and money solving half way!