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As I recall, we "discussed this issue" for our 2014's and our later C7's you said you were think about deposits in the combustion chalmber NOT the backs of intake valves! DI has gas with cleaning additives that "squirt' into the combustion chalber so it's the back on the intake valves where the issue exists.
A published article in a well respected auto mag quoted several GM engineers who were discussing the LT. iJohn Rydzweski, Assistant Chief Engineer for Small Block V 8’s was one of the two engineers. “A little bit of oil on a port-injection engine can help lubricate valves, but because the Gen 5 V8’s (all C7’s as the LT1) are Direct Injected, there’s no fuel washing the back of the intake valve. That means oil in the PCV system can end up sticking to the back of the hot intake valves impeding airflow and eventually preventing the valves from seating properly.”
Tadge who is always very careful how he words things said this in a Forum Post, Quoting: "Granted, deposit formation on DI engine intake valves is greater than what is seen with PFI engines, but the Gen 5 engines are typical for SIDI engines, and in fact better than other DI engines we have benchmarked. So the bottom line is that we believe the carbon build up is only an internal cosmetic issue, not anything that will affect customers over the life of their cars.”
Yep for some of us, like folks who are OCD about fingerprints on their doors and hatch, prefer clean intake passages and valve backs. For some folks it doesn't exist because they can't see it!
BTW, I'm sure everyone believes every word Tadge says! Yep there is no standard trans in a C8 because there is no room for a 3rd pedal! Wasn't Tadge but a GM engineer who said removing the center air dam from the C7 Z51 was for rear brake cooling- NOT!
The LT1 engines reported on here with over 100K miles, and the valves inspected when they were in for other engine repairs were from 2014s, before the later MY "plumbing change" you love to cite. Those valves needed no attention as reported by the mechanics to their owners. Not a single LT1 has been reported here with a valve coking problem to my knowledge.
That's hardly a definitive study either, but it remains true that there is no EVIDENCE of a problem. There is plenty of evidence of problems with other DI engines, just not this one.
Evidence, Jerry, evidence. The LT1 engines reported on here with over 100K miles, and the valves inspected when they were in for other engine repairs were from 2014s, before the later MY plumbing change you love to cite. No a single LT1 has been reported here with a valve coking issue to my knowledge.
That's hardly a definitive study either, but it remains true that there is no EVIDENCE of a problem.
Yep GM spent a lot of engineering time and money improving the dry sump system in the 2014/2015 C7's because there was NO PRIOBLEM! I chuckle when some won't accept that there is an issue and it was worse in the 2014 you argued wasn't needed because Tadge said it was only cosmetic!
You probably installed a "Dog Door" opener on you C7 because you don't like looking at fingerprints! Suggest you could have just closed your eyes as you and others would prefer than think about baked on carbon on the backs for your intake valves. Some of us care more about that than fingerprints. To each their own!
Yep, the laws of physics must be different for GM!
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Hmm, I quoted a comment from a published article in a well respected auto mag attributed to John Rydzweski, GM Assistant Chief Engineer for Small Block V 8’s. He's seen more "coking" tests of the LT1 and LT2 engines than you or I: “A little bit of oil on a port-injection engine can help lubricate valves, but because the Gen 5 V8’s (all C7’s as the LT1) are Direct Injected, there’s no fuel washing the back of the intake valve. That means oil in the PCV system can end up sticking to the back of the hot intake valves impeding airflow and eventually preventing the valves from seating properly.”
Also GM significantly improved the PCV system in the 2016 and later PCV systems you refuse to acknowledge "proved" there was an issue with the early C7s! Yep better not perfect and I'm confidant GM did an even better job in the C8
Your "fatal flow" is you don't want to accept what is in front of your eyes or what you hear! You should consider doing as the other monkey and Speak No Subjective Opinions!
Just wow, I feel really bad for you Jerry, regarding your apparent inability to focus upon the discussion at hand. I completely understand the lack of data on the effectiveness of after-market catch cans in preventing DI valve contamination, as well as the lack of data on there being a problem in LT engines.
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As expected you will not consider what the GM Assist Chief Engineer said in a 2 day interview of the LT4 & LT1.
You also will not acknowledge your "It's Not Needed" words you said in 2014 and 2015 were wrong when GM spent a lot of Engineering time and effort improving the according to you was "Non Existent Issue" when they designed the >2016 Dry Sumps.
Even though I'm retired I do have a part time Internet Business and only have one computer at this desk- not 3 and one to play with the Forum. Can't justify the time anyway! I'm dealing with questions for a prospective customer! You do what you feel is important to you! Just WOW!
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Hmm, I quoted a comment from a published article in a well respected auto mag attributed to John Rydzweski, GM Assistant Chief Engineer for Small Block V 8’s. He's seen more "coking" tests of the LT1 and LT2 engines than you or I: “A little bit of oil on a port-injection engine can help lubricate valves, but because the Gen 5 V8’s (all C7’s as the LT1) are Direct Injected, there’s no fuel washing the back of the intake valve. That means oil in the PCV system can end up sticking to the back of the hot intake valves impeding airflow and eventually preventing the valves from seating properly.”
What you quoted above is in no way an acknowledgement that there was ever an intake valve coking problem in the production LT engines. The GM engineers would have been aware of a theoretical issue with DI engines, and also with problems which the early Audi (and some BMW) engines had. Can you provide any evidence that this has ever been a problem on the LT?
I still do not understand why catch cans get so much debate while embroidered headrests and chrome tail light rings get a free pass under the 'its his car let him do what he wants'.
While I am truly impressed at the complete difference between the LT1/4 dry sump and the LT2 ventilation strategy, there was STILL standing oil in the pcv return line less that 1k miles on the clock.
The bottom line is no matter what someone may say on the internet; Take a look inside your lines. If what you see bothers you, then you are in the market!
We have the most efficient separator on the market, and the only with integral pressure control. Satisfaction is guaranteed so you can see for yourself or just send it back. https://www.corvetteforum.com/forums...-shipping.html
Yes, we all know there is a little bit of oil collected if you mount a catch can. That is not the topic of discussion here. The question is does collecting that small amount of oil solve the DI valve coking problems seen on engines where it is a known problem? The LT engine isn't one of them.
What you quoted above is in no way an acknowledgement that there was ever an intake valve coking problem in the production LT engines. The GM engineers would have been aware of a theoretical issue with DI engines, and also with problems which the early Audi (and some BMW) engines had. Can you provide any evidence that this has ever been a problem on the LT?
I quoted a comment from a published article where the author was with the two GM engineer small block engineers for two days! Granted it was in 2014 with the first C7 PCV systems. It "may" be only cosmetic (assuming you believe Tadge statement as I'm sure you and others believe all his re cracked wide C7wheels!) but some of us care about keeping the backs of the intake vales as clean as possible.
Also GM spent a lot of engineering time an effort to improve the 2014/2015 PCV system, which is what I also had on my in my 2017 Grand Sport. Below is a pic of my Grand Sport much more complex system. I made the test to see how they eliminated one line going into the air intake from my 2014 which had 2. Wanted to be sure I did no harm before I added! Did they do that because there was their a need- not for fun! I measure 1/2 the captured "stuff" in my 2017 Grand Sport than in my 2014 Z51so yep they made it better.
Folks with a 2014 or 2015 can do as they wish- their choice!
New PVC System on M7 2017 Grand Sport is Much More Complex Than My 2014 Z51- GM made That Change for A Reason
Tried to Find Out Why They Were Able to Go from 2 lines Goung to Tha Air Intake in my 2014 Z51 to 1 in my 2017 Grand Sport To Be Sure When I Addd Was Dong No Harm.
In a few words, compared to Jerry's stock dissertation and cute cartoons, which have nothing to do with data from Corvettes: No one here (and certainly not me) has denied that there have been valve coking issues on a number of DI gasoline engines. I had the problem in an Audi, which needed a walnut shell cleaning. Thus I 100% understand it CAN be a problem.
The point, which always whiffs right by Jerry in dozens of threads here over several years, is that there is no available evidence of significant valve coking in LT1 engines in C7s. If those data exist, no one on CF has been able to find it. Thus, there no reason to suspect there will be a problem in LT2 engines.
There is also no available evidence that catch cans solve the problemin DI engines with a history of valve coking issues.
Aren't all of the Audis (and BMWs, and Subarus) reporting the problem turbo? I wonder if some additional oil is being introduced by the turbo leaking and that is causing the issue. Just thinking out loud here. I know once my son-in-law removed a bunch of emissions things off of his 2016 WRX (including I think part of the PVC system) we instantly noticed blue smoke and even some oil spitting out of the tailpipes. Putting the PVC system back in didn't solve the problem fully, I'm fairly convinced in his case his turbo has a slight leak. Wonder if it could be similar with the Audi/BMWs.
I quoted a comment from a published article where the author was with the two GM engineer small block engineers for two days! Granted it was in 2014 with the first C7 PCV systems. It "may" be only cosmetic (assuming you believe Tadge statement as I'm sure you and others believe all his re cracked wide C7wheels!) but some of us care about keeping the backs of the intake vales as clean as possible.
Also GM spent a lot of engineering time an effort to improve the 2014/2015 PCV system, which is what I also had on my in my 2017 Grand Sport. Below is a pic of my Grand Sport much more complex system. I made the test to see how they eliminated one line going into the air intake from my 2014 which had 2. Wanted to be sure I did no harm before I added! Did they do that because there was their a need- not for fun! I measure 1/2 the captured "stuff" in my 2017 Grand Sport than in my 2014 Z51so yep they made it better.
Folks with a 2014 or 2015 can do as they wish- their choice!
New PVC System on M7 2017 Grand Sport is Much More Complex Than My 2014 Z51- GM made That Change for A Reason
Tried to Find Out Why They Were Able to Go from 2 lines Goung to Tha Air Intake in my 2014 Z51 to 1 in my 2017 Grand Sport To Be Sure When I Addd Was Dong No Harm.
Blah blah blah.
Please tell us more times (with your usual pictures and diagrams) about your Oldsmobile build, your street rod, or how you need to accelerate fast out of your subdivision.
I will ask again for any evidence that LT direct injection engines have an intake valve buildup problem.
Please tell us more times (with your usual pictures and diagrams) about your Oldsmobile build, your street rod, or how you need to accelerate fast out of your subdivision.
Yep, glad someone's keeping up with my early build of an engine bought when I was 16 all in parts for $10 and my more recent assembly of the 8.2 Liter Chevy BB engine from 30 boxes in a wood crate!
Bet you haven't seen my video with clips of Richard Petty and myself that was run during a NASCAR Race in Charlotte! Or my going 160 mph into turn 3 at the Charlotte Motor Speedway at a private invitation from Richard for sponsors to the petty Driving Experience! Have many other anecdotes from the many visits to their shop in Level Cross!
There are some clips of Richard in a video I made about welding race cars:
Unbelievable how someone can show off a mod he installed on his car and guys can turn the thread into a PISSING match about if the mod is needed or not. Nice work guys.
Yes, we all know there is a little bit of oil collected if you mount a catch can. That is not the topic of discussion here. The question is does collecting that small amount of oil solve the DI valve coking problems seen on engines where it is a known problem? The LT engine isn't one of them.
If you have evidence, please show it here.
The evidence is deductive reasoning. GM (and every other automaker) has been chasing pcv efficiency since its introduction. Why are they doing this if it does not matter? Why is the ventilation system on c8 almost completely different than c7, which is also very different than c6, if these little bits of oil do not matter?
It matters because valve deposits are real, are accelerated by oil consumption, and further fuel efficiency, oil life, engine life, emissions, and power production are negatively impacted by oil consumption.
Less oil consumption = better across all of these metrics, therefore less oil consumption = better across engines in general (like ours).
If you care about that or not is up to the end user. "Acceptable oil consumption" will always be an opinion, just like embroidered headrests and chrome tail light rings.
Yep there is no standard trans in a C8 because there is no room for a 3rd pedal! Wasn't Tadge but a GM engineer who said removing the center air dam from the C7 Z51 was for rear brake cooling- NOT! 
