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Maxie, proof works many different ways. In this case, there is no evidence of a coking problem on the LT engines, thus it would be hard to prove a catch can has any functional or significant benefit. That fact alone tilts the evidence strongly toward no benefit. No one can show any evidence of a coking-related performance problem on LT engines, and if there were you'd then have to prove that a catch can successfully mitigated the problem. You can't prove a null hypothesis, you can only reject or fail to reject it.
In the Audi, BMW, VW DI engines that suffered performance degradation as a result of valve coking, it showed up relatively early, and catch cans were not a solution. I had an '07 Audi RS4 4.2 DI V8 that needed a walnut shell cleaning at 20K miles. We're just not seeing an issue in the 6-7 years LT engines have been in use. One member who posted in this thread has well over 80K miles on her car, and we've seen quite a few over 100K miles with no issues. Obviously, GM has done extensive long-term testing, and they're not seeing a problem either. The Chief Engineer has stated such on this forum.
We've seen just about every imaginable problem on C7s reported on this forum, but engines suffering from valve coking hasn't been one of them.
No comment, other than amount of oil pales in comparison to the combustion by-products produced by the 325 gallons of gasoline (assuming 20 avg. mpg) you burned during the same period.
I always have to laugh at the ignorance that clever marketing campaigns breed. But it also makes me feel sorry for those that are preyed upon due to their ignorance. Its a vicious cycle all in the name of making money. The ones that make me laugh the most are the Zero Ohm plug wires and the DEI catalytic converter heat shields. Although this catch can nonsense on stock motors is a close third.
Is this a design defect for the Direct Injection Engine? That is, not having a catch can device as factory production stock? GM says you might get some discoloration on the valves but does not impact performance. I am debating putting one on my C7. I wonder if it impacts smog testing?
Is this a design defect for the Direct Injection Engine? That is, not having a catch can device as factory production stock? GM says you might get some discoloration on the valves but does not impact performance. I am debating putting one on my C7. I wonder if it impacts smog testing?
Good luck getting good answers to this question here. It's like a religion to some who say you need one to prevent coking on the intake valves, even though nobody has ever posted a photo of such from a C7 engine. Catch cans and CAI systems have cult-like followers who are never interested in facts or objective evidence.
Valve coking comes from the extremely small amount of oil that gets past the valve guides. Everyone knows, the valves move up and down, and there is a vacuum in the intake port, therefore its impossible for valve guides and associated seals to seal perfectly. The only way it could is if the valve was seized in the guide.
Good luck getting good answers to this question here. It's like a religion to some who say you need one to prevent coking on the intake valves, even though nobody has ever posted a photo of such from a C7 engine. Catch cans and CAI systems have cult-like followers who are never interested in facts or objective evidence.
Hard to believe after all this time, no one has pulled the heads and taken a look (maybe for some other reason but still....)
Hard to believe after all this time, no one has pulled the heads and taken a look (maybe for some other reason but still....)
Wouldn't have to pull the heads, just the intake, to use a scope to inspect the upstream side of the intake valves. There have been photos posted here by catch can advocates where that was done, showing coking, but when asked they admit the photo wasn't from a C7. Go figure.
Good luck getting good answers to this question here. It's like a religion to some who say you need one to prevent coking on the intake valves, even though nobody has ever posted a photo of such from a C7 engine. Catch cans and CAI systems have cult-like followers who are never interested in facts or objective evidence.
And yet you never provide any facts yourself just your opinion nor are you interested (and often ignore) objective evidence.
And yet you never provide any facts yourself just your opinion nor are you interested (and often ignore) objective evidence.
Huh? Provide facts of what, exactly? I have yet to see objective evidence of coking on C7 intake valves, and objective evidence that a catch can would have prevented it. If you have that objective evidence, feel free to post it.
09-16-2018, 09:24 PM
Look what I found in the catch can
