Intake Cam Failures - Materials, Design, or both?

[Remorseless]

Thank you, sir. I will certainly give this a try. My JLR is not a daily driver, and situation is similar to yours but not kiddo-related. My only concern is dry-cranking the engine for 10 seconds or so. But I guess that's the idea; to get the oil moving to the important bits before the rpms skyrocket.

I had the same thought, but it's much lower RPM than a normal startup would be dry. And when you start it up after running the crank procedure it's SO much quieter than normal. In my 2.0 you could hear the timing chain tensioner ratchet into position after it finally got oil pressure on cold start. Not so after the cranking.

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[JeepinPete]

I tend to think the oil is a major contributor. Not the weight, but the formulation. As has been stated, flat tappet cams are age old tech, but they are not common these days. Oils used to have wear packages formulated for that kind of sliding friction, but with emissions and the need to not contaminate catalytic converters, many of those ingredients have been greatly reduced or eliminated.

I replace the right side intake cam at 70k miles. Three of the lobes were wiped IIRC. Researched oils looking for the highest zinc content and readily available. Best I could find was Mobil 1 ESP. Running 0W-30 ATM as my engine runs significantly quieter with heavier oil. Oil change is coming and will run 0W40 for the summer.

Sadly only time will tell if it was a defective part or something off in the engine itself.

 

[bmpcamry09]

Do you know what the conditions are for the VVL system going into high lift? Thought occurred to me that as much wear as was on the pictured cam from earlier would require probably significant time where the roller shoe or whatever you wanna call it is in contact with the cam. Wonder if it's in contact with the cam when it shouldn't be and that's when it's wearing. Stuck partially up or something, due to a peculiarity of the oiling system or even a software fault if the solenoid state is wrong or something.

VVL high lift on these only activates at low load, low RPM. Typically between 1700 and 3000 RPM with aircharge values under 400 MG. Load values less than about 30-40 in my testing. I believe it’s to supplement extra airflow for the EGR valve to do its thing. All my testing indicates that is its true purpose. It is not used at WOT at all. If you have ever driven a hemi or a GM V8 with V4/DoD mode, the activation points are actually very similar in regard to load and RPM for our VVL high lift.

I had a ton of people who didn’t believe me, so I made a couple YouTube videos talking about it, one was kind of a rant

 

[jeepingib]

High lift, but short duration correct? And the rollers are low lift, high duration in order to maximize the scavenging effect as much as possible at high RPM I would expect.

 

[roaniecowpony]

Do you know what the conditions are for the VVL system going into high lift? Thought occurred to me that as much wear as was on the pictured cam from earlier would require probably significant time where the roller shoe or whatever you wanna call it is in contact with the cam. Wonder if it's in contact with the cam when it shouldn't be and that's when it's wearing. Stuck partially up or something, due to a peculiarity of the oiling system or even a software fault if the solenoid state is wrong or something.

I think you're onto something. I think it has to do with the oil galley design, since it's the same lobe over and over. It would really help nail down the cause if we had real data on which lobes have failed and how many. But, I wouldn't be surprised if the pre-PUG had the same lobes chronically failing. The PCM and VVL solenoid just controls oil pressure to a network of galleys leading to the rocker arm.

 

[Remorseless]

VVL high lift on these only activates at low load, low RPM. Typically between 1700 and 3000 RPM with aircharge values under 400 MG. Load values less than about 30-40 in my testing. I believe it’s to supplement extra airflow for the EGR valve to do its thing. All my testing indicates that is its true purpose. It is not used at WOT at all. If you have ever driven a hemi or a GM V8 with V4/DoD mode, the activation points are actually very similar in regard to load and RPM for our VVL high lift.

I had a ton of people who didn’t believe me, so I made a couple YouTube videos talking about it, one was kind of a rant

So more air could defeat it or you could just live at WOT like a 16 year old, hmmm

 

[jeepingib]

As a visual reference for everyone. This is what I would expect from a cam failure with proper heat treatment, but lack of lubrication/overload condition.

But since we don't see that cracking of the surface hardening, that leads to spalling, I am questioning the hardness of the cams. Especially when the slipper on the followers seems to show much less wear.

 

[bmpcamry09]

High lift, but short duration correct? And the rollers are low lift, high duration in order to maximize the scavenging effect as much as possible at high RPM I would expect.

Correct. But Scavenging on these is controlled primarily with VVT on intake and exhaust on these.

Here is a breakdown of how VVT is tuned on these from the factory…….note that intake and exhaust cam references are opposite of each other.

At idle, intake cam is parked around 145 degrees (fully retarded) and exhaust cam is parked around 120 degrees (fully advanced).

On throttle tip in and light demand, intake cam stays nearly fully retarded, and then the exhaust cam goes nearly fully retarded (down to 74 degrees). This is to induce a natural EGR effect and have natural overlap for efficiency.

On stock tuning, while in these same EGR areas, VVL high lift can activate. For high lift, both intake and Exhaust cam go close to full advanced for max aircharge. The higher lift allows for less pressure loss in the intake. Unfortunately, this whole process is poorly executed and is why 2022 and newer GPEC5 models have a nasty stumble.

On tip in from part throttle rolling situations where you want more demand but not wide open throttle, VVL will go back to low lift mode, intake cam will advance up to 78-80 degrees (60 degrees of movement!) to increase airflow and cylinder pressure, and exhaust cam will retard back up to 100-120 to reduce overlap and increase cylinder pressure and torque.

At wide open throttle, intake goes almost fully advanced until about 3500 RPM then it starts to retard to allow scavenging from unburied exhaust gases. Exhaust stays mildly advanced until about the 4000 RPM mark, where it will retard to help with scavenging.

Hope this helps.

 

[roaniecowpony]

As a visual reference for everyone. This is what I would expect from a cam failure with proper heat treatment, but lack of lubrication/overload condition.

But since we don't see that cracking of the surface hardening, that leads to spalling, I am questioning the hardness of the cams. Especially when the slipper on the followers seems to show much less wear.

I agree, that's what we would see...if we stopped running the engine soon after this occurs.

Hardening is probably done without a traditional heat treat oven. More likely that induction hardening is used, because it's faster and cheaper.

 

[Gregj]

VVL high lift on these only activates at low load, low RPM. Typically between 1700 and 3000 RPM with aircharge values under 400 MG. Load values less than about 30-40 in my testing. I believe it’s to supplement extra airflow for the EGR valve to do its thing. All my testing indicates that is its true purpose. It is not used at WOT at all. If you have ever driven a hemi or a GM V8 with V4/DoD mode, the activation points are actually very similar in regard to load and RPM for our VVL high lift.

I had a ton of people who didn’t believe me, so I made a couple YouTube videos talking about it, one was kind of a rant

So it's on the high lobe during light cruise? That's a lot more time than one would think.
Grergj

 

[bmpcamry09]

So it's on the high lobe during light cruise? That's a lot more time than one would think.
Grergj

Light cruise and very light acceleration is the only time it’ll ever be in high lift. It almost “cycles” if that makes sense. Can be watched with a good scan tool or using OBdWiz. Very similar cycling to how V4/MDS cycles on the V8 engines.

 

[bmpcamry09]

Funny thing is, the 1st gen Pentastar had enough overlap between intake and exhaust with VVT that it already had a natural EGR effect and was very efficient and emissions friendly for what it was. Adding a EGR valve and VVL high lift to the PUG just complicated things.

 

[bmpcamry09]

So more air could defeat it or you could just live at WOT like a 16 year old, hmmm

You’re exactly correct. That’s why on the threads talking about the hesitation/stutter that people were reporting an improvement when driving hard and not getting the sensation when driving like an ass. It only rears its head when your putting around.

 

[Remorseless]

You’re exactly correct. That’s why on the threads talking about the hesitation/stutter that people were reporting an improvement when driving hard and not getting the sensation when driving like an ass. It only rears its head when your putting around.

Aight boys, Toyota rev limiter time

 

[roaniecowpony]

Some info on VVL from my manual

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