Cylinder Deactivation Question

[MrViking]

I'm a new Mazda owner a 2022 CX-5 Premium. and so far I'm quite impressed.
I noticed that my cylinder deactivation monitor screen will go from 4 active to 2 active and then 0 active. In other words, all the cylinders in the graphic go dark. It ill happen if I take my foot off the gas That would indicate that none of the cylinders are active. But how is this possible? Does the transmission torque converter keep the engine spinning even though there's no combustion happening? As soon as I touch the gas pedal, all four cylinders light up again.
Thanks!

 

[RedBaron]

Lights indicate when cylinders are producing power (i.e. firing), nothing to do with if they're moving. All cylinders are always moving when you're driving.

If you are decelerating (engine braking) then all cylinders are 'turned off' and not firing. Hence no lights.

 

[MrViking]

Thanks for the reply. I understand that the cylinders continue to move and are continuing to be lubricated, etc. My question is, if none are firing, then the RPMs should immediately drop, technically to 0 but the RPMs are unaffected other than the normal drop from coasting. If none are firing, it should almost be like switching the engine off. So what's keeping the engine turning if none of the cylinders are firing? My guess is the coasting of the vehicle is keeping the engine spinning either from the torque converter or tranny lockup until the coasting is completed. I have noticed that when you get to certainly speed before stopping, all four come on again before coming to a stop.

 

[erhayes]

By GEORGE I think he has it.

 

[N7turbo]

I understand that the cylinders continue to move and are continuing to be lubricated, etc.

My question is, if none are firing, then the RPMs should immediately drop, technically to 0 but the RPMs are unaffected other than the normal drop from coasting. If none are firing, it should almost be like switching the engine off.

These are two contradictory statements...

But yes, your engine is mechanically coupled to the wheels by your drivetrain. Rolling down the road in any gear will turn your engine.

 

[MrViking]

I'm not getting what's contradictory.
What I meant by the two statements is what I was seeing (normal RPMs) and what I thought I should be seeing if all 4 cylinders were deactivated and it wasn't the drivetrain keeping the engine spinning like normal.

But now that it's been answered that the drivetrain is still keeping the engine spinning even if all 4 cylinders are deactivated, I understand. Thanks for the explanation.

 

[N7turbo]

Right. The only time that isn't true is in Neutral and Park. But even in neutral while rolling, the ECU will idle the engine.

Back in the day when manual transmissions were more common, people used to do rolling starts by popping the clutch.

 

[MrViking]

Done that a few times.

 

[nickswhip24]

hi mr. v-i get your question and was thinking the same thing...really tried to avoid getting the cylinder deactivation and now am doing everything i can to delete it-i see the monitor go from 4 to 2 then 0 and it annoys the crap out of me
i follow garage shop foreman on yt for great video content-he's awesome...if i get a solid fix i will post here

 

[Snake]

On those motors, when a deactivated cylinder has fuel cut off and closed valves, is the ignition spark also cut off?

Also, when the deactivation screen show zero cylinders running does that actually mean that the engine is running but only at idle OR, is it technically completely turned off and having to completely restart when power is needed again?

And finally, does the tach show idle speed or zero RPMS when the screen show zero cylinders running?

From what I am reading online about how Mazda's CD works is that it can turn two cylinder off, not all 4.

Kinda confusing...

 

[N7turbo]

On those motors, when a deactivated cylinder has fuel cut off and closed valves, is the ignition spark also cut off?

I can't say but I don't know why they would continue sparking.

Also, when the deactivation screen show zero cylinders running does that actually mean that the engine is running but only at idle OR, is it technically completely turned off and having to completely restart when power is needed again?

It's spinning under the power of the wheels. No fuel or spark, only an air pump.

And finally, does the tach show idle speed or zero RPMS when the screen show zero cylinders running?

Not sure about that.

From what I am reading online about how Mazda's CD works is that it can turn two cylinder off, not all 4.

Right, this is not cylinder deactivation. CD engages at cruise speeds under low load, on throttle.