ASH8

Mazda's Skyactiv-G Cylinder Deactivation is coming to the USA (and others) in the new 2018 Mazda 6, it is ONLY available in the 2.5L (non Turbo) and has successfully been sold in Europe last year in the 2.5L CX-5 (KF).

Basically when cruising at certain RPM the ECU shuts down fuel delivery to Cylinders 1 and 4 turning it into a 2 cylinder engine, triggered hydraulic lash adjusters keep off Cylinder Valves closed.

Got to hand it to Mazda...the old Bangers are far from dead...

hornbm

iTrader: (1)

They might as well call it a 2019 model at this point. Its already February, and still no pricing or build tools available. I wonder what the holdup is.

UnknownJinX

Be careful with cylinder deactivation.

I used to have a 2008 Honda Accord Coupe V6 5AT. That car has a cylinder deactivation mechanism(Honda calls it VCM) and can turn it into a V4 or I3 depending on the load and speed.

It all sounds good until some owners reported their engine using a lot of oil, misfiring, and spark plug fouling. Some of them took legal actions. Honda America actually had to make a settlement for this fiasco and extended engine warranty.


I read that the problem is caused by the deactivated cylinders losing pressure to hold the oil rings if deactivated long enough. I think Dodge's take fixed this issue by having a combustion event in the deactivated cylinder once in a while just to increase the pressure.

Hopefully Mazda don't mess up like Honda did. I'd either wait and see what happens or buy a manual(which usually doesn't come with cylinder deactivation mechanism).

ASH8

/\, yes this did cross my mind, what happens to 1 and 4 when all vales are shut, pistons are still moving, what happens to the pressure inside each closed cylinder (1 and 4) where does it go, does it blow by back into sump (oil pan) for ventilation.?, what does that do to piston rings long term?

I am pretty sure the activation criteria is pretty strict, as in Only certain RPM and at certain throttle percentage, speed, load, etc.

2.5l Deactivation has been working in Europe KF CX-5 for well over a year, have not seen any TSB' with issues......yet.

UnknownJinX

For reference, here are the spark plugs from my Honda Accord V6. The first 2 are from cylinder 5 and 6, which don't get deactivated at all. As you can see, they are pretty clean(car had 82k miles/131k km or so when I pulled them). The last and the dirtiest one is from cylinder 3, which gets deactivated the most, in both V4 and I3 mode.



Theoretically, the pressure should hold, but in real operation, there is no perfect seal, and you will lose pressure if the cylinder is deactivated for long enough.

My Accord actually had a little indicator in the gauge cluster to show when the VCM kicks in, so the driver is aware when the deactivation is on.

Like I mentioned, Dodge had the deactivated cylinders activate once in a while to hold the pressure, and Honda themself also has fixed the VCM, as the newer J35Y engines with VCM2 don't have issues yet. Don't know how Honda has fixed it, though.

hichamaziz

Be careful with cylinder deactivation.