Direct injection on 2018 Cadillac CT6

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#16
I understand the flaw with the GDI design. And I can see that an "oil catch can" in the PCV system might reduce buildup on intake valves. Other manufacturers have put similar devices in crankcase ventilation systems to reduce oil consumption way back to carburration days.
 
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#17
Thanks Dan for the input!! Do you have any recommendations of what type and where I can purchase a good quality oil catch can??
 

nickb2

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#18
OK, I am sorry of sorts, but as a day wrench grease monkey, I hear this sort of complaint every day, and my hands are tied.

So in essence, I vomited my frustrations on your thread. While you took the time to say what I wrote/said/did wrong, I certainly took the time to see my faults. And, I am at fault. I was totally unjustified. If I could erase, I would, but admins here know, I am easily replaceable.

Only way I know how to apologize for that is to say, hope you fix it.

So here is me being semblance of ok.

 

billr

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#20
Hmm... I have been avoiding this thread because I have no experience with GDI (Gasoline Direct Injection, as differentiated from Diesel injection?). And, the need/use of "catch cans" on the PCV system can get quite controversial, with little chance of agreement.

However, I'm bored this morning so here goes:

1) OP, have you tried a temporary catch can on that line to see how much of a problem it is? It is fairly easy to do. I have an engine that gets considerable amount of oil in the intake, but when I tried a (temp) catch can, there was nothing in it.

2) Oil in that area can, and often does, come from valve guides. Build-up of crud "under" the valves was a problem long before PCV was added.

3) Is GDI especially sensitive to oil in the intake; and why? The absence of fuel going past intake valves to "wash" them doesn't seem critical to me. In fact, I wonder if a GDI engine shouldn't be even cleaner since the fuel isn't "cooking" on the hot valves.
 

billr

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#23
If you want to keep it simple, just "remote" the PCV valve with a piece of clear plastic tubing, maybe with a low loop to provide a "sump". Put the tubing between the valve and wherever it presently connects to the crankcase. Vacuum should be very low there, so collapsing of tubing is no problem.
 
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#24
Last time I drove a Caddy was in 2010 and compared it with a Cruze, only difference was about 200 more HP you can't even use and one more inch of floor space in the rear seat. Oh, and $35,000.00 more.

Hyundai has direct injection, for one thing, can lean out AF ratio, but this generates ozone, so the EPA has strict limits on the amount of leaning you can do to get better fuel economy, 14.7 is the preferred ratio, maybe up this to around 14.9

I looked up the cost of a single injector, was around 800 bucks, labor is extra, not sure about the Caddy. Tend to look at repair parts before purchasing a vehicle.

Was very disappointed with GM warranty back in 2011, went to five different dealers with the same complaint, said a woman would have to come up from Milwaukee to approve it, 250 miles, she never showed up. GM said screw you, I said screw you, not ever buying a GM vehicle again unless they changed.
 

grcauto

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#25
I think the wide band sensors today can go out quite a bit further than stoichiometric. I believe most will control fuel at 18:1 or even a little higher than that. The only thing as for smog was Nox and the variable cams take care of that without needing EGR.
 

billr

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#26
I'm not sure how it pertains to the OP's questions, but yes, WB sensors are commonly used in the 10-20 AFR range. One thing to keep in mind, though, is that a rich misfire will show as very lean (20:1)
 

nickb2

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#29
20:1 is quite rare, but the newer version of vvt are actually seeing these numbers, but the efficacy of the system suffers for lack of high end heat. I love this site, cuz sometimes, a wondered out of this way thread becomes very interesting.

I will try to keep posted on other stuff, going for adas system two weeks from now. That is going to be a great debate.

I am most happy bill and others are still around here to circumvent original thinking. Because now, you HAVE to think outside the box when an algorithm go astray.
 

nickb2

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#30
A friend of mine/co worker just bought a new gm pick up. He went fishing and said he had never seen MPG's like that before. It cuts cylinders, much like the old caddy design of the 70's, but now on a algorithm. And if you have a live data capable thing that is quicker tan what we had in the day, trims start to get interesting.

On a good note, my shop foreman came to see me at my bay, asked if the transducer I was asking about. That means the boss is really maybe interested in developing. Cut down time easy.

So going back to gdi system, you can actually see the engine in real time as the gdi gets carboned up. It will show on vacuum. ;)