How to completely disable cylinder deactivation?

[N7turbo]

The problems that come from cylinder deactivation come from the design of the cylinder head and torque converter to accommodate it, not from the activation of the feature while driving. I doubt deactivating it will accomplish anything, but you're free to try and report back.

 

[Mulligan]

The problems that come from cylinder deactivation come from the design of the cylinder head and torque converter to accommodate it, not from the activation of the feature while driving.

That's probably right.

However, the temperature difference between active and deactivated cylinders likely adds stress to the head. That extra stress acting on the poorly designed (or poorly manufactured) cylinder head could be the straw that breaks the camel's back and results in a crack. If that's the case, disabling cylinder deactivation could reduce the likelihood of head failure.

Speculative, but not irrational.

I can't blame anyone for wanting to disable their cylinder deactivation on the chance there's something to the heat/stress hypothesis.

 

[walt]

But why? What is the benefit?

They were failing and causing a rattle that required head replacement if I recall.

 

[N7turbo]

The engine failure is a crack leading to an oil leak.

The transmission issue is wearing of the clutch material contaminating the fluid as previously mentioned in the thread.

 

[Mulligan]

They were failing and causing a rattle that required head replacement if I recall.

You're probably recalling a ticking problem that affected 2018 to 2021 (at least) models and was attributed to faulty hydraulic lash adjusters (HLA). There were some technical service bulletins about it, e.g., Bulletin 01-022/21 "TAPPING NOISE FROM ENGINE."

Repair recommendations started with "Hold the engine rpm between 2500-3000 for 5 min, then idle for 5 min. Repeat this 2 times." If that didn't work, the HLAs were to be replaced with a modified version. As far as I know, replacing the cylinder head wasn't discussed in the tech bulletins covering this problem.

It's not clear if the ticking HLA problem could happen if somehow cylinder deactivation was disabled.

 

[nickswhip24]

That's probably right.

However, the temperature difference between active and deactivated cylinders likely adds stress to the head. That extra stress acting on the poorly designed (or poorly manufactured) cylinder head could be the straw that breaks the camel's back and results in a crack. If that's the case, disabling cylinder deactivation could reduce the likelihood of head failure.

Speculative, but not irrational.

I can't blame anyone for wanting to disable their cylinder deactivation on the chance there's something to the heat/stress

A torque converter failing caused by CD?
Please tell...

 

[slusho]

CD is purely a CAFE thing. It’s not very impactful to individual owners in terms of fuel economy. Same thing with the “lifetime fluid” in the transmission. The EPA gives Mazda a CAFE credit for each vehicle with a sealed transmission.

 

[walt]

CD is purely a CAFE thing. It’s not very impactful to individual owners in terms of fuel economy. Same thing with the “lifetime fluid” in the transmission. The EPA gives Mazda a CAFE credit for each vehicle with a sealed transmission.

Why does a sealed trans count for a point? I have read that changing the fluid just once before 50k miles can double the life of trans if not otherwise abused. YMMV

 

[sinistriel@]

"Lifetime fluids" came about for a few reasons. 1st CAFE kickbacks because the vehicle is then expected to put less oil into the environment during its life cycle. 2nd the amount of OEM warranty claims dropped due to people being nervous of having fluid changed and having DIY/quick lubes doing the change incorrectly like the wrong fluid and incorrect levels causing failures during a warranty period.

 

[N7turbo]

CD is purely a CAFE thing. It’s not very impactful to individual owners in terms of fuel economy. Same thing with the “lifetime fluid” in the transmission. The EPA gives Mazda a CAFE credit for each vehicle with a sealed transmission.

If that is true, then the sealed transmission policy and the clutch design on the CD cars are opposed to each other. Sad.

 

[Shortafoot]

The thin motor oils are a result CAFE regs as well. EPA requires all makers to use the oil used in fuel mileage testing in the engines and to spec that oil in the owners manual. Remember, the engines are tested in a lab on a "bench" and not even a huge dyno/treadmill like the EPA used decades ago. The auto makers realized that since they had to test multiple engines, say 10, for fuel mileage, going to a thinner motor oil would allow them to eeckk out better MPG results. Example: Lets say with 10w-30 the 10 motors get an OVERALL AVERAGE OF 15.4 MPG on the city "loop". By going to a 5w-20 with less internal resistence, the overall average goes to 15.5 or 15.6 MPG. The EPA will let the auto maker "round up" and claim they get 15 MPG. You will see ZERO difference on in the real world. The thinner oils have nothing to do with durability but only to help chase hundredths or tenth's of MPG in the test lab. That is why the exact same engines in America will spec much thinner motor oils than the same engine in Europe, Asia or Australia.

 

[walt]

Meanwhile GM is losing new engines that are being recalled due to lighter weight oils. They dont quite admit it but the fix is heavier weight oil change out if the vehicle is still unsold on dealer lot. Many thousands of engines involved.

 

[Snake]

How to tell if your CX-5 has cylinder deactivation...

Look at the 8th letter in the VIN:

If it's an "L", it does not have cylinder deactivation.

If it's an "M", it has cylinder deactivation.

 

[RL911]

I have disabled it on my 2019 Honda pilot, but I’m not aware of being able to do it on a Mazda. I purchased an aftermarket device that does it. Hondas with CD are notirious for shudder at highway speeds when the cylinders deactivate, failed torque converters and uneven cylinder wear/buildup. I’ve had the device on for about 5 years now. I dont feel the shudder on the Mazda like I did on the Honda. Maybe because the Mazda is lighter, has less power and perhaps Mazda technology (motor/transmission mounts) is better at isolating it. There also aren’t widespread reports of transmission or tq issues like there are with Hondas.

Edit: just checked my vin, M is the 8th letter for my 18 sport and 19 touring so I have CD, don’t even notice it.

 

[Cooper1]

FWIW
I recently found the CD screen on my 21 (LOL).
I drove for a few days to see how effective it was. A few things I noted
1. I can not detect physically or audibly when it kicks in and out.
2. It only stays deactivated for a few seconds. The slightest grade in the road or touch
of the accelerator kicks it out.
I actually saw no reason why they would have this. Even on long steady highway stretches, it kicked out most of the time.