Dangerous cylinder deactivation trouble on 2018 CX-5 and 6 models

Avoidin Deer

Zoom Zoom, baby
Contributor
:
Central Virginia
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2019 CX-5 Reserve
The 2019 Mazda6 shows CD status live on the "economy screen". I watch it all the time. (And, its the "old" infotainment).

I have the CD recall done YESTERDAY, so far the CD did not activate at all for 33km - waiting for it to kick back in so I can evaluate the difference. I logged AS BUILT data before and after the update if anyone can decipher it, let me know.
Engine: 2.5L nonturbo 194 bhp (europe). 2019 model

Before: PXE4-188K2-B
After: PXE4-188K2-C

Bonus info: If you run the auto in manual mode, and select SPORT mode, the CD is backed off significantly.

Gee, you can either confirm or deny the "They disabled it" rumor for us.
 
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2014 mazda cx-5 touring FWD
I realize it would be expensive but maybe Mazda should nip this in the bud sooner than later with a direct mechanical fix and forget about CD and it's supposed fuel economy benefits.Relying on oil pressure to keep something in position seems like a marginal design.
 
I realize it would be expensive but maybe Mazda should nip this in the bud sooner than later with a direct mechanical fix and forget about CD and it's supposed fuel economy benefits.Relying on oil pressure to keep something in position seems like a marginal design.

Agreed! Seems to have been engineered way more elaborately than it had to...IMO. I believe our Honda Pilot (RIP) the ECU shut off fuel and spark to deactivate 3 cylinders but the mechanical action of the cam lobes and valves continued on...with lubrication from the sump of course.

I can see the merit in shutting down 3 of 6 (Honda V6) cylinders and 4 of 8 (GM truck V8) but shutting down half of a 4 cylinder seems like a little superfluous. IMHO and all that!

Our 2019 Touring has less than 500 miles. I hope the software patch is an effective fix!
 
The 2019 Mazda6 shows CD status live on the "economy screen"...
mazda6_2019_cd.jpg


Two or four cylinders will show in color when active. (the two marked ones are running in 2-cyl mode). Also, all four are disabled when coasting. Sorry about the weird danish language :)
 
Gee, you can either confirm or deny the "They disabled it" rumor for us.

Sorry, I need to drive more miles to draw any conclusions. The ECU was reset during update, so I think it needs a little time to re-learn stuff before beginning to CD. Also, I am quite sure they did not remove the feature. By the way, when cruising say 50-55 mph, the CD saves on my experience 20-30% fuel. It is very effective at this speed. (mind you, the M6 may be more aerodynamic than the CX-5, so the delta in fuel may be less on the CX-5)
 
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2018 CX-5 Sport
If the software truly fixes the current issue then CD shouldn't really be a concern. Mazda is all in, putting it on all their cars. They must be confident in their design. And hydraulic valves have been in existence for a long time, point being that over head cams had their valves held in place with oil pressure for decades. They made them this way so no manual valve lash adjustments are necessary.
 

yrwei52

2016 Mazda CX-5 GT AWD w/Tech Pkg
Contributor
:
Plano, Texas, USA
If the software truly fixes the current issue then CD shouldn't really be a concern. Mazda is all in, putting it on all their cars. They must be confident in their design. And hydraulic valves have been in existence for a long time, point being that over head cams had their valves held in place with oil pressure for decades. They made them this way so no manual valve lash adjustments are necessary.
On OHC valves stay at their position by cylinder head guide holes and springs, not by oil pressure. Some OHC's need rocker arms and all rocker arms mostly are held by a long shaft. With Mazda's design rocker arms are held by nothing but the oil pressure for hydraulic lifter, valve stem, and cam lobe. On those HLA's with cylinder deactivation, there's a lock pin to "lock" hydraulic lifter function so that it won't collapse while pushing the valve during non-CD mode, essentially loses the function of eliminating valve clearance adjustment.
 
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2019 CX-5 GT 184 2.2 twin turbodiesel auto - Sonic Silver
I was talking to one of my old motor industry colleagues and he was explaining why manufacturers are forced into constantly introducing tighter emission gear. Each stage of legislation (for us, currently Euro 6), they have various timed increments within each stage and the latest is to meet the target from key on to key off. Previously they had to meet at ever increasing levels and you will probably find that CD takes care of one of them. Might only be applicable in certain states of the US but meets in another country so you get it by default.
 
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Ottawa, Ontario
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17 Mazda 6 GT
The sooner Mazda decides to introduce the X engine to North America, the sooner they'll be able to put this CD mess behind them.
Maybe this will accelerate the timeline.
 

Avoidin Deer

Zoom Zoom, baby
Contributor
:
Central Virginia
:
2019 CX-5 Reserve
I was talking to one of my old motor industry colleagues and he was explaining why manufacturers are forced into constantly introducing tighter emission gear. Each stage of legislation (for us, currently Euro 6), they have various timed increments within each stage and the latest is to meet the target from key on to key off. Previously they had to meet at ever increasing levels and you will probably find that CD takes care of one of them. Might only be applicable in certain states of the US but meets in another country so you get it by default.

My understanding is that it was an effort to meet such creeping legislation that gave us Direct Inject.
 
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2018 CX-5 GT
...With Mazda's design rocker arms are held by nothing but the oil pressure for hydraulic lifter, valve stem, and cam lobe. On those HLA's with cylinder deactivation, there's a lock pin to "lock" hydraulic lifter function so that it won't collapse while pushing the valve during non-CD mode, essentially loses the function of eliminating valve clearance adjustment.

Oil pressure isn't what holds the lifter against the rocker. The large, axial-acting spring inside the HLA is what forces it into contact with the rocker.

The conventional function of a hydraulic lifter in regulating (setting to zero) the rocker-to-valve clearance is still present in the cylinder deactivating HLAs. That function works the same for them as in the other non-CD lifters. It's independent of the oil pressure regulated operation of the locking/unlocking of the lifter. The patent describes this.

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I still do not fully understand the principle of operation, i.e. oil pressure should not affect the occurrence of a failure, and the problem lies in the valve jam, or the wrong (weak) force in the spring? Or maybe the hla is pressed too hard and slack occurs, but the spring would compensate for it by the spring itself???

And what about the rocker arm form and dimensions, maybe a small inaccuracy causes the arm to fall.


Someone smarter than me must say.
 
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2018 CX-5 GT
I'm speculating, but the following makes sense to me.

The figure below is a revised (by me) version of a figure from the patent. I suspect that the oil pressure variations involved in operating the locking pins in the HLA have the unintended side effect of interfering with the free flow of oil back into the lower chamber of the HLA where the compressed spring is enclosed. For that spring to return to its extended condition, the volume of the space occupied by the spring must be rapidly filled with fluid (or air) as the spring attempts to enlarge the chamber enclosing it. If the chamber is slow to fill with fluid, the HLA will stay shortened longer than intended, allowing a gap to open between the rocker and the top of the HLA.

By way of analogy, picture this: Put a spring inside a syringe. Expel the air from the syringe by pushing the plunger with your thumb, compressing the spring. At the bottom of the stroke, put your finger over the end of the syringe (there's no needle on our hypothetical syringe!). Move your thumb away from the plunger. The plunger will remain at the bottom of the stroke, despite the force of the spring. Only when you remove your fingertip from the end of the syringe will the plunger move back up. I suspect something similar to this happens with the HLAs when deactivated cylinders are supposed to revert to active status.

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2018 AWD GT Premium Red/Black
I was talking to one of my old motor industry colleagues and he was explaining why manufacturers are forced into constantly introducing tighter emission gear. Each stage of legislation (for us, currently Euro 6), they have various timed increments within each stage and the latest is to meet the target from key on to key off. Previously they had to meet at ever increasing levels and you will probably find that CD takes care of one of them. Might only be applicable in certain states of the US but meets in another country so you get it by default.

It's also possible that their current implementation of Cylinder Deactivation is meant to go in conjunction with other changes to realize an overall more efficient system. The initial implementation in 2018 may include part of the solution to phase-in the changes so they don't have to prove out everything in one lump. That's one explanation that seems to make some sense of the fact that they included this in 2018 but it doesn't seem to make a difference in the mileage ratings.
 

yrwei52

2016 Mazda CX-5 GT AWD w/Tech Pkg
Contributor
:
Plano, Texas, USA
Thanks for posting all of those info for cylinder deactivation, Mulligan! Like Luke_M6, I need some time to absorb all of these. (confused)