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Im just interested in the real problem. Obviously there isnt one with GMs version of DI on these engines.
Can you imagine what this forum would be like if there were ?
Every third thread would be about how someone took their car in for walnut shell service, but the service dept got half of a greasy fingerprint on the door handle, so now they want the car bought back or they are going to sue.
Agreed "excess coking" in general not a major issue with the LT1, either are fingerprints on a Vette as far as GM is concerned! But IMO you're drawing an erroneous conclusion from a few DOHC engines that perhaps used inferior valve stem oil seals! That could have been the issue with some terrible coking on some older BMW's. Yep in the "old days" they used cheap "Umbrella type seals" on Chevy V8s. There is still lots of oil in rocker arm pushrod engines! Have to lub the rocker tip to valve stem.
Honda and other DOHC DI engines who used fixed pressed in seals don't have excess "coking." Compared to those slip on cheap "Umbrella Seals" they are a PIA to replace! In fact the wife's 2014 and now 2018 Twin Turbo L6 engines in her BMW X5 SUV's are not reported to have issues with "excess" coking.. As I said, in most cases even if folks are putting on many miles but never putting their foot to the floor may never know there is an issue! The issue remains those of us colleting an once of oil (some more) every 1000 miles was one once less that did not have a chance to coke! As I have said several times, GM fixed that "Non-Problem" in later C7s with an improved PVC system where, with the same "can" I was colleting only 1/3 to 1/2 the oil I was with my 2014 Z51! They didn't do that for fun!
Agreed "excess coking" in general not a major issue with the LT1, either are fingerprints on a Vette as far as GM is concerned! But IMO you're drawing an erroneous conclusion from a few DOHC engines that perhaps used inferior valve stem oil seals! That could have been the issue with some terrible coking on some older BMW's. Yep in the "old days" they used cheap "Umbrella type seals" on Chevy V8s. There is still lots of oil in rocker arm pushrod engines! Have to lub the rocker tip to valve stem.
Honda and other DOHC DI engines who used fixed pressed in seals don't have excess "coking." Compared to those slip on cheap "Umbrella Seals" they are a PIA to replace! In fact the wife's 2014 and now 2018 Twin Turbo L6 engines in her BMW X5 SUV's are not reported to have issues with "excess" coking.. As I said, in most cases even if folks are putting on many miles but never putting their foot to the floor may never know there is an issue! The issue remains those of us colleting an once of oil (some more) every 1000 miles was one once less that did not have a chance to coke! As I have said several times, GM fixed that "Non-Problem" in later C7s with an improved PVC system where, with the same "can" I was colleting only 1/3 to 1/2 the oil I was with my 2014 Z51! They didn't do that for fun!
Are you now proving my point ?
I`m a little confused by your tactics right now Jerry.
Are you now proving my point ?
I`m a little confused by your tactics right now Jerry.
No tactic, just trying to put in facts on how things work. From the start I didn't say the LT1 had excess coking like some older reported early DIs. I still think it's an issue and for some may think it's cosmetic but for some of us would rather see the engine interior be as clean as possible!
I have PDF on the subject with lots more info, for those who just want to face that it is an issue, even perhaps minor, these are two statements in that doc:
The first from Tadge, the Corvette Chief Engineer answering a question re the Camaro that came with catch can, quoting: “The Corvette's dry sump tank looks relatively simple on the outside but the internals are really quite complex. The top third of the tank contains a PCV air/oil separation system. On the Corvette, PCV lines route from the valve covers to the air/oil separator on top of our dry sump tank. Oil from PCV air is separated and returned to the lube system through the oil tank. The PCV separation system on Camaro V8 performs a similar function except oil is returned to the engine oil pan from the PCV separator's drain back tube. The Camaro V8 PCV air/oil separator is more complex than a "catch-can" since it not only separates oil from PCV air it provides a drain back path for this oil to be reused by the lube system.
"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.
The bottom line is that both cars use optimized engineering solutions for their lube systems based on vehicle architectural considerations.” (NOTE HE DOES NOT ADDRESS WHY THE C7 WET SUMP DOES NOT US THE CAMRO SYSTEM AND IT DOES NOT HAVE A DRY SUMP TANK!)
The second was from a printed article: An article in the December 2014 car magazine quotes several GM engineers who were discussing the LT4 with the author Brandan Gillogly. John Rydzweski, Assistant Chief Engineer for Small Block V 8’s was one of the two engineers.
This is a quote by the author NOT one of the GM 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.”
I emailed Gillogy and asked about that statement. He responded and said it was discussed during his interview. This is not a simple problem that GM uniquely solved!
Having the history on the Corvette LT1, the issue is not major BUT IT"S NOT non existent!
Disappointed to see the #1 naysayer above didn't take that opportunity to explain how oil leaking past the valve seals and down the stems got all the way up into the port and all over the walls.
Never understood why people bother making posts just to point that out or why they think it matters. Forums are meant to be timeless depositories of knowledge. Perhaps the naysayer has been spending the last three years developing a theory about how oil travels upstream in the intake charge and spreads itself all over the manifold walls and is about to dazzle us all.
Meanwhile, 3 years on, perhaps there have been developments in the understanding of DI engines that other forum members can report on here in this revived thread.
I never understood responding to an old thread to chastise someone (which is what you did) not contribute to the thread with any new developments. But you do you.
I never understood responding to an old thread to chastise someone (which is what you did) not contribute to the thread with any new developments. But you do you.
I never understood responding to an old thread to chastise someone (which is what you did) not contribute to the thread with any new developments. But you do you.
I don't respond to these to chastise the poster , i do it as an FYI as most new members don't look at the date and that the orginal OP might have moved on
Never understood why people bother making posts just to point that out or why they think it matters. Forums are meant to be timeless depositories of knowledge. Perhaps the naysayer has been spending the last three years developing a theory about how oil travels upstream in the intake charge and spreads itself all over the manifold walls and is about to dazzle us all.
Meanwhile, 3 years on, perhaps there have been developments in the understanding of DI engines that other forum members can report on here in this revived thread.
wannabe hall monitors. They all want to be first to call out someone for reviving an old thread. I found it to be an interesting read.
Disappointed to see the #1 naysayer above didn't take that opportunity to explain how oil leaking past the valve seals and down the stems got all the way up into the port and all over the walls.
