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As I said I will use engineering logic to prove it didn't cause whatever problem. I don't need to use tricks! If I thought there was any downside I would not have added a can to the Grand Sport. I spent time defining, best I could, all the new the lines on the Grand Sport dry sump. The most difficult is there were two lines going into the intake tube on the 2014 (and for sure the 2015 if not the 2016 as well.) One brought fresh filtered air into the crackcase. That is needed on any PCV system as if you pull out "stuff" it has to be replaced with filtered air (installed that on the 502/502 cid engine in my street rod from the inside of the Holley 850 air cleaner.) The 2014 also had a line going from the dry sump tank to the air intake tube to "Burp Air" pumped with the oil from the crackcase to the dry sump tank (they both were located at the Helmholtz appendage on the intake tube.)
The "new" dry sump only has one hose on the air intake tube. I used a pressure/vaccum gauge to find that the one hose brings fresh air into the dry sump tank, at least at idle. Does that line still bring burped air into the air intake tube under certain conditions? Perhaps not and that is done with one of several extra hoses aded from the tank to the engine.
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.
i respect Tadge and applaud him for his amazing work involved in designing the C7 and representing the brand. That said, Tadge also said there is no reliability problems with the torque converter or the A8 transmission.
i respect Tadge and applaud him for his amazing work involved in designing the C7 and representing the brand. That said, Tadge also said there is no reliability problems with the torque converter or the A8 transmission.
I suspect that a lot of guys who have these torque converter problems are thrashing their cars at the drag strip and/or track and/or street. The dealers have a device now that can catch the entire driving history of the car. I would be interested to know the driving history of some of these cars with torque converter problems. With real race cars hardware breaks all the time.
With that said I don't plan on running my own engineering test programs on DI performance vs dry sump vs catch can with wet sump over time. I have to trust what GM says. If GM were to offer an add on catch can kit with a built in drain back to the engine, like the Camaro, I would consider it as a sign that there is a problem that is not recallable (not a safety issue). A lot of guys calling for recalls on some of these issues forget that recalls are for safety issues. Coking, reliability issues, and so forth are not recall issues unless they impact safety.
When this thread dies - and it will as they all do - Maxie, Jerry and I will still happily empty our catch cans while Steve, Foosh and others will find no reason to install one. Point is, no side will convince the other. I empty my catch can in my DI vette and DI Tahoe and the oil I collect is a good enough reason to have a catch can.
Here are my 2 cents, there are 2 groups those that have purchased a catch can will stand firm by its claim that it works and will continue using it, emptying it and so on. There will be nothing that will convince them that it is not needed.
The 2nd group are those like me who have chosen not to purchase a catch can and will not get one or be convinced that they need one.
With the above statements I made I propose that we all leave this thread alone because no one here will ever change anyone's mind that its needed or not needed. will my post be the last post in on this thread?
Perhaps you miss the point why some of us post who have investigated the issue, provide info to show WHY we added one and think it is a help! It's NOT to attempt to convince some of the ~50 vocal minority who posted on this Tread! Would not waste my time disturbing all these electrons to convey the message to some who are convinced it's not needed, don't want to dump the "stuff" frequently or are afraid about warranty issues, etc.
If you look at the statistics of this Thread there are ~2800 folks who have visited. I spend the time to get info to some of those who have an open mind and are willing to consider the issues as they make their decision. Hope they are entertained with the info as well.
This is no different than most Threads, many more visiting who are interested in the subject than posting.
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! )
Good article. I read the pdf. The real issue as I understand the paper is not the loss of performance from coking of the intake valve. It is the loss of performance when you dilute the fuel air mixture with some engine oil while you are racing. That is the real reason for the catch can as far as racing teams and engine builders are concerned. For me, I don't race or track my car so getting the racers edge out of the engine is not a reason to put the catch can on. I am going to trust what Tadge has said that the dry sump acts as a catch can. If GM should put out a kit for my year car I will put one on as a sign that there is a problem.
Thanks, It's actually both. Having built the engine in my first car, a '41 Ford I stuffed a bored Olds engine in and saw those nice shinny well contoured intake valves AND then when I semi-retired I built a 502/502 Chevy crate engine from some 30 boxes and also saw those shinny, smooth, well contoured intake valve surfaces, the Tadge idea of "it's just cosmetic" does not make me feel good!
This is a pic from when we had port injection as in my C6 and prior Vettes and gasoline companies were saying even though gasoline was continually passing over the hot intake valves-that ws not enough! You needed extra cleaning additives (as are in Top Tier gas.) To bad with DI that Top Tier does nothing for the backs of the intake valves as it never touches them! With DI only two things pass over the hot intake valve backs- Air and PCV "stuff!" With a catch can I have less "stuff" that can cause what is called coking. It doesn't stop it all but it helps.
These gasoline ads were not BS. Even with gasoline continually passing over the back of the hot intake valves, without cleaning additives there was still some coking. With DI there is not even gasoline passing over the valves, nothing but air and PVC "stuff" (a lot of oil vapors and fine oil particles created by the spinning crack etc) passing over them. GM has no magic to prevent it. It's an issue with DI in general. Toyota has what I hope will be in the C8 engine when I get it, port injection operated periodically and DI for it's benefits. Just costs money!
Wow, I cannot believe all you guys rather have all that oil sucked into the intake and distributed on each and every intake valve and being part of your burn mixture after the intake valve opens and deposits the oil . Why have a fine oil spray/fog being ingested and burned in the combustion chamber when you can have clean fuel only??
Wow, I cannot believe all you guys rather have all that oil sucked into the intake and distributed on each and every intake valve and being part of your burn mixture after the intake valve opens and deposits the oil . Why have a fine oil spray/fog being ingested and burned in the combustion chamber when you can have clean fuel only??
Because it doesn't matter in anything besides a maximum effort race car.
Jerry, I appreciate your viewpoint, but ads for FI engines ( and believe you me, I use only Top Tier) aren't evidence for catch cans. I guess I must have missed something when the evidence of actual coking on LT engines was shown???
Thanks, It's actually both. Having built the engine in my first car, a '41 Ford I stuffed a bored Olds engine in and saw those nice shinny well contoured intake valves AND then when I semi-retired I built a 502/502 Chevy crate engine from some 30 boxes and also saw those shinny, smooth, well contoured intake valve surfaces, the Tadge idea of "it's just cosmetic" does not make me feel good!
This is a pic from when we had port injection as in my C6 and prior Vettes and gasoline companies were saying even though gasoline was continually passing over the hot intake valves-that ws not enough! You needed extra cleaning additives (as are in Top Tier gas.) To bad with DI that Top Tier does nothing for the backs of the intake valves as it never touches them! With DI only two things pass over the hot intake valve backs- Air and PCV "stuff!" With a catch can I have less "stuff" that can cause what is called coking. It doesn't stop it all but it helps.
These gasoline ads were not BS. Even with gasoline continually passing over the back of the hot intake valves, without cleaning additives there was still some coking. With DI there is not even gasoline passing over the valves, nothing but air and PVC "stuff" (a lot of oil vapors and fine oil particles created by the spinning crack etc) passing over them. GM has no magic to prevent it. It's an issue with DI in general. Toyota has what I hope will be in the C8 engine when I get it, port injection operated periodically and DI for it's benefits. Just costs money!
I understand the coking process and that gasoline additives clean the valves in port fuel injection engines and carbureated engines. I also understand the gas is not there to clean the intake valves in the GM Gen 5 DI engine. So I agree that there is some degree of coking that occurs, whether there is enough to be a problem over time is the question. With that said GM has tested the engine and I am going to go with GMs recommendation that the coking is minor (discoloration) and know that the dry sump ventilation system is acting as a catch can as Tadge informs us.
Jerry, I appreciate your viewpoint, but ads for FI engines ( and believe you me, I use only Top Tier) aren't evidence for catch cans. I guess I must have missed something when the evidence of actual coking on LT engines was shown???
The point of the pic I used was NOT that it reflects what happens in a DI engine as it doesn't. It is to point out that even when we had port injection i.e. C6 and prior Vettes (3 or which I had and never added a catch can- no need) or a carburetor like my street rod, gasoline without "cleaning additives" can still cause the PCV "stuff" that enters the intake manifold to cause "coking." That is where gasoline with enough and the proper "cleaning additives" eliminates the issue as it continually washes over the backs of the hot intake valves. That is when Chevron (the folks who sell Techron in containers as well) patented and added it gasoline. Others paid them a royalty or developed their own "cleaning additive" package and meet the Top Tier requirements. (Actually all gasoline must contain these additives but at a lower level that required by Top Tier.)
In a DI engine where 100% of the gasoline is injected directly in the cylinder, just like a diesel, there is NO gasoline passing over the hot intake valves. Therefor Top Tier CANNOT help the backs of the intake valves from building up some level of deposit. It does have benefits of keeping the injectors clean and build-up in the combustion chamber. Toyota does have an engine that has port injection operated periodically and DI. That can wash the PCV "stuff" off before it can bake on. Hoping that will be used in the new C8 engine so I won't have to add a catch can! That is done on the ZR1 for power reasons.
I relate the issue as similar to folks who are OCD and close their Vette doors with a handkerchief because they can't tolerate fingerprints. That's NOT me. BUT this "old gear head" feels the same about the internal parts of the engine! Coking being "just cosmetic" per Tadge doesn't make me feel good. I can wash those fingerprints off when I wash the car- not coking! In fact this "old gear head" who modified and assembled and Olds engine when I was 17 and more recently the 502 cid engine in my street rod can "see" the corrosion of those street rod cylinder walls occurring when it's mostly parked in the garage between car shows that I change the oil every year with few miles. Yep just like fingerprints on the door for the OCD feel about the outside -I feel the same about the internal working parts of the engine!
I understand the coking process and that gasoline additives clean the valves in port fuel injection engines and carbureated engines. I also understand the gas is not there to clean the intake valves in the GM Gen 5 DI engine. So I agree that there is some degree of coking that occurs, whether there is enough to be a problem over time is the question. With that said GM has tested the engine and I am going to go with GMs recommendation that the coking is minor (discoloration) and know that the dry sump ventilation system is acting as a catch can as Tadge informs us.
Glad you are looking at all the facts. Agree GM "says" coking occurs but is cosmetic (not minor discoloration, heck my street rod valves will have minor discoloration!) They did "improve" the PCV system in that later dry sumps- for sure 2017 and later BUT it only cut the PCV "stuff" I collect and dump in half. It did NOT solve the issue. My "Catch Can" does not solve the issue, it just reduces it. But I'm still collecting and having to empty the can periodically so have less "stuff" passing over the hot intake valves in my 2017 LT1 dry sump than if it was not present.
As mentioned, I'm hoping that like Toyota, the engine in the C8 I intend to buy will have both port injection operated periodically and DI so there will be no need to install a "catch can."
I respect your opinion deciding you don't need one as a thoughtful and considering the issues. Some of the 3000 silent majority who have visited this Thread may decide differently.
Wow, I cannot believe all you guys rather have all that oil sucked into the intake and distributed on each and every intake valve and being part of your burn mixture after the intake valve opens and deposits the oil . Why have a fine oil spray/fog being ingested and burned in the combustion chamber when you can have clean fuel only??
Folks continually miss the fact that pure gasoline combustion causes coking too. There is no such thing as "clean fuel."
As I said above, the OP collected what appears to be maybe 3-4 oz. of oil in 6500 miles, meanwhile he burned 325 gallons of gasoline. I'd bet almost anything his valves would appear identical with or without the catch can. Collecting a little bit of oil is not evidence that one is getting a benefit, but it certainly does make a lot of people feel better. There is no persuasive evidence that oil is the primary cause of coking.
Catch cans have not proven to be beneficial in the GDI engines that have suffered from the problem (Audi, BMW, VW). It's a GDI design issue in those engines that a catch can cannot overcome. The LT design has not exhibited those sorts of problems.
Folks continually miss the fact that pure gasoline combustion causes coking too. There is no such thing as "clean fuel."
As I said above, the OP collected what appears to be maybe 3-4 oz. of oil in 6500 miles, meanwhile he burned 325 gallons of gasoline. I'd bet almost anything his valves would appear identical with or without the catch can. Collecting a little bit of oil is not evidence that one is getting a benefit, but it certainly does make a lot of people feel better. There is no persuasive evidence that oil is the primary cause of coking.
Catch cans have not proven to be beneficial in the GDI engines that have suffered from the problem (Audi, BMW, VW). It's a GDI design issue in those engines that a catch can cannot overcome. The LT design has not exhibited those sorts of problems.
Folks continually miss the fact that pure gasoline combustion causes coking too. There is no such thing as "clean fuel."
As I said above, the OP collected what appears to be maybe 3-4 oz. of oil in 6500 miles, meanwhile he burned 325 gallons of gasoline. I'd bet almost anything his valves would appear identical with or without the catch can. Collecting a little bit of oil is not evidence that one is getting a benefit, but it certainly does make a lot of people feel better. There is no persuasive evidence that oil is the primary cause of coking.
Catch cans have not proven to be beneficial in the GDI engines that have suffered from the problem (Audi, BMW, VW). It's a GDI design issue in those engines that a catch can cannot overcome. The LT design has not exhibited those sorts of problems.
Really don't understand your argument. All that 325 gallons of fuel went directly into the combustion clamber! Never passed over the hot intake valves. We don't just "feel better" we're collecting a significant amount of what would otherwise go into the intake. What percentage, don't know but must be significant or I would be having to oil and I don't! No different that folks without it so what I collect, 2 1/2 ounces in 5000 miles with my new "improved but not fixed dry sump" is 2 1/2 ounces that could not bake on the hot intake valves.
Yep your 325 gallons that went directly into the combustion chamber if Top Tier gas was used at least has a good chance of being cleaned up before significant combustion chamber deposits develop. If you're going to argue it's blow-by have an 80 page PDF on piston rings and how they stop probably 99.9% of the combustion "stuff" if anyone wants they can send a PM and I'll attached the PDF! It's well written and not an SAE tech paper that may be hard to understand! It's written by a ring company.
Really don't understand your argument. All that 325 gallons of fuel went directly into the combustion clamber! Never passed over the hot intake valves. We don't just "feel better" we're collecting a significant amount of what would otherwise go into the intake. What percentage, don't know but must be significant or I would be having to oil and I don't! No different that folks without it so what I collect, 2 1/2 ounces in 5000 miles with my new "improved but not fixed dry sump" is 2 1/2 ounces that could not bake on the hot intake valves.
Yep your 325 gallons that went directly into the combustion chamber if Top Tier gas was used at least has a good change of being cleaned up before significant combustion chamber deposits develop. If you're going to argue it's blow-by have an 80 page PDF on piston rings and how they stop probably 99.9% of the combustion "stuff" if anyone wants, PM and I'll attached the PDF! It's well written and not an SAE tech article that may be hard to understand! It's written by a ring company.
I didn't understand either, because like you said, the fuel never enters the intake port.
The "no persuasive evidence that oil is the primary cause of coking" needs further explanation as well, if it is to be believed.
Im sure he will explain everything though …
LOL, gasoline goes directly into the combustion chamber and explodes, causing combustion by-products which the valves most certainly come in contact with in the process of opening and closing. Really, Jerry?
09-19-2018, 04:25 PM
As I said I will use engineering logic to prove it didn't cause whatever problem. I don't need to use tricks! If I thought there was any downside I would not have added a can to the Grand Sport. I spent time defining, best I could, all the new the lines on the Grand Sport dry sump. The most difficult is there were two lines going into the intake tube on the 2014 (and for sure the 2015 if not the 2016 as well.) One brought fresh filtered air into the crackcase. That is needed on any PCV system as if you pull out "stuff" it has to be replaced with filtered air (installed that on the 502/502 cid engine in my street rod from the inside of the Holley 850 air cleaner.) The 2014 also had a line going from the dry sump tank to the air intake tube to "Burp Air" pumped with the oil from the crackcase to the dry sump tank (they both were located at the Helmholtz appendage on the intake tube.)
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