Exactly, I have never seen a compelling reason to remove the factory DOD pump; it is the best factory pump ever put in the LS series engines. In fact the TSB from GM on the pan pressure relief valve is just as ridiculous, the DOD engines use oil because of the V4 mode; it has nothing to do with oil spray from the relief valve.
Proper DoD delete oil pump
- Thread starter 03GMCYukonXL
- Start date
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I'd be interested to hear how oil gets from the dod hardware to inside the cyl to burn?
Marky Dissod
Full Access Member
What are the two shortest oil paths to inside the cylinder?
I have a somewhat unique experience with this.
I actually had my former '12 Yukon XL ecm reprogrammed to INCREASE the engine half@$$ duty cycle,
over and above GM's original limits.
Including but not limited to being more eager to activate engine half@$$ mode, more often and more quickly.
At the time I was trying to get better MpGs by using engine half@$$ mode 'as much as possible'.
After a while, the engine started consuming oil.
In hindsight, he 'lazier' cylinders were glazed, something to do with carboned / coked piston rings.
Credit @B-train with that observation.
Marky Dissod
Full Access Member
1. From the oilpan past three piston rings. Short, but not easy - unless the piston rings are worn.
2. Over the top of heads, down the valve stems. Not short, not easy - unless the valve guides are worn out.
#1 happens more often, and sooner, than #2.
By leaving both valves closed under cylinder deactivation the disabled cylinders have trapped air which cushions the pistons and helps the engine feel smooth when in 4 cylinder mode.
The engine is designed to lubricate the cylinder from beneath and control the oil to a limited amount via the oil control rings and the expanding gasses on the power stroke.
With no power stroke the oil passes the oil control ring but is not burned (no power stroke) but does receive cool pressure from the trapped air in cylinder.
This causes coking of the oil control rings and huge mess in the combustion chamber, when the cylinder is reactivated it cannot completely burn that coking off. Over time this causes the oil control rings on the DOD cylinders to become loaded up and lose their ability to effectively control the cylinder lubrication; the result is increased oil consumption.
Possible theory I guess, but I think they only choke up the one cyl that the bypass valve sprays excess oil into to all the time? and the drivers side is always worse than the passenger side.
leading most to think it's the pvc system that is pretty awful, more so than the valves being closed. my catch can gets quite a bit of oil and it's new enough to have the upgraded valve cover and the deflector. valve cover is just a bad place to suck air from. the valley is much better spot.
I have had a compression gauge on a cyl with both rockers off (non ls) before and believe me. it does nothing.. gauge doesn't even flicker and the 2nd ring is always cut on a angle to scrap the wall down of anything the oil ring misses.
I feel like it's a horrible pvc system using oil and gunking up rings thru the intake portsmore than the afm. before my catch can I had my intake off and was amazed the amount of oil that drained from it. there's guys here with 200k on afm still working without issue. unless they have some magic oil, they would have coked up the rings a long time before that.
just my 2 cents on it. could be wrong..
Put a bore scope in the AFM cylinders and the non AFM cylinders and you will see the difference, insufficient PCV oil mist can cause this as well (why catch cans became a thing) but a catch can will cure that issue with the PCV entirely; the DOD system will coke up either way. And that oil psi bypass is below the windage tray, it is not creating an issue in any cylinder.
Also, the DOD system activates after the intake stroke on the cam base circle, this is done intentionally by GM to provide that air cushion; it is designed to do that. Just running a compression test on an engine with both valves disabled has no air to compress.
Also, the DOD system activates after the intake stroke on the cam base circle, this is done intentionally by GM to provide that air cushion; it is designed to do that. Just running a compression test on an engine with both valves disabled has no air to compress.
if there's air in the cyl, wouldn't that keep postive pressure, opposite of sucking oil up thru the rings?
I'll have to take your word for it. I have a nice bore scope but I'm not going to pull fresh plugs just to look at the cyl haha. honestly I think they would look fine thou, I ha oem plugs in mine when I got it at 135k of active afm, also the hybrids run in 4cyl mode much more often because of the electric assist. it doesn't need to switch to v8 to get moving. especially interstate cruise, it can handle the small elevation changes by battery not switching out of 4cyl. from the settings I see in hp tuners under dod, looks to be limited mostly by time to oil foaming. but anyways, point being all 8 plugs looked the same, no extra white crude on the afm cyl from burning extra oil.
the windage tray has a nice cut out right at the bypass valve.
to be fair, I alway thought the bypass valve sprayed oil straight up out of the hole on the top on the back cyl wall. but this Pic it looks like there's some holes around the bottom. so I don't know for sure. so eh? my truck has a crazy high oil pressure variable displacement pump. like 60 plus almost all the time. so I have a feeling it's bypassing constantly, especially with afm turned off. no sign of choked up rings or low compression to me.
I mean I get it, it's a junk system. but the details just feel off to me.
I'll have to take your word for it. I have a nice bore scope but I'm not going to pull fresh plugs just to look at the cyl haha. honestly I think they would look fine thou, I ha oem plugs in mine when I got it at 135k of active afm, also the hybrids run in 4cyl mode much more often because of the electric assist. it doesn't need to switch to v8 to get moving. especially interstate cruise, it can handle the small elevation changes by battery not switching out of 4cyl. from the settings I see in hp tuners under dod, looks to be limited mostly by time to oil foaming. but anyways, point being all 8 plugs looked the same, no extra white crude on the afm cyl from burning extra oil.
the windage tray has a nice cut out right at the bypass valve.
to be fair, I alway thought the bypass valve sprayed oil straight up out of the hole on the top on the back cyl wall. but this Pic it looks like there's some holes around the bottom. so I don't know for sure. so eh? my truck has a crazy high oil pressure variable displacement pump. like 60 plus almost all the time. so I have a feeling it's bypassing constantly, especially with afm turned off. no sign of choked up rings or low compression to me.
I mean I get it, it's a junk system. but the details just feel off to me.
