Quick Question

"Arch Duke Maxyenko, Shit Talk Extraordinaire" (arch-duke-maxyenko)
08/18/2014 at 16:05 • Filed to: None

Do cars with cylinder deactivation deactivate the same cylinders every time or do they alternate them? Because if they don't alternate cylinders, I could see a huge potential for uneven wear.

DISCUSSION (28)

deekster_caddy > Arch Duke Maxyenko, Shit Talk Extraordinaire
08/18/2014 at 16:09

I guess it could differ from manufacturer but I always understood them to rotate the deactivated cylinders.

Arch Duke Maxyenko, Shit Talk Extraordinaire > deekster_caddy
08/18/2014 at 16:09

Is there a logger in the software to make sure there is even distribution?

RamblinRover Luxury-Yacht > Arch Duke Maxyenko, Shit Talk Extraordinaire
08/18/2014 at 16:11

I can't see why a logger would be needed. Even if you only run the engine 5 minutes at a time, the deactivation cycles (if sequential) could at most be two extra taps on a cylinder compared to others, which is a tiny fraction of a percent difference.

HammerheadFistpunch > Arch Duke Maxyenko, Shit Talk Extraordinaire
08/18/2014 at 16:12

From what I understand, its the same cylinders that go cold everytime.

deekster_caddy > Arch Duke Maxyenko, Shit Talk Extraordinaire
08/18/2014 at 16:12

I don't know that specifically. If it did it would have to keep track somehow though! Who knows if it's a parameter you would even be able to access.

Hmm. According to this:

http://blogs.motortrend.com/1402_when_deac…

rotating the deactivated cyls isn't all that common. I thought it was a given.

Arch Duke Maxyenko, Shit Talk Extraordinaire > RamblinRover Luxury-Yacht
08/18/2014 at 16:15

Lets say that you're on a long highway drive cruising, (hours) this is when cylinder group 1 gets deactivated. Now, you reactivate them and then cruise for only a short time, deactivating cylinder group 2. And this cycle continues, for say, 50,000 miles, which will have more wear?

Arch Duke Maxyenko, Shit Talk Extraordinaire > HammerheadFistpunch
08/18/2014 at 16:16

That's what I'm thinking too. But I'm curious if anyone actually can confirm this.

As Du Volant > Arch Duke Maxyenko, Shit Talk Extraordinaire
08/18/2014 at 16:17

The Chrysler/Dodge/Jeep/Ram Hemi uses the same four every time.

Haven't heard of any issues related to it though. It's a hell of an engine. We get 200k+ mile trucks all the time that are worked hard and still run great.

The record, though, was the executive taxi Chrysler 300 with 375k on it. The engine still ran perfectly. The rest of the car though... yeah, it was an almost-400k mile Chrysler, you get the idea.

RamblinRover Luxury-Yacht > Arch Duke Maxyenko, Shit Talk Extraordinaire
08/18/2014 at 16:18

I was operating under the assumption that rotation while running was possible or even profitable - perhaps not. Even if it only knocks off groups every time it drops out of full run, it's probably not going to be that significant.

HammerheadFistpunch > Arch Duke Maxyenko, Shit Talk Extraordinaire
08/18/2014 at 16:18

I know with the cam in block phasers, its a hydraulically controlled pin that deactivates half the lobes, it seems to me like it would HAVE to be the same lobes everytime.

Arch Duke Maxyenko, Shit Talk Extraordinaire > As Du Volant
08/18/2014 at 16:20

Have you ever tore down one just to see its insides after use?

As Du Volant > Arch Duke Maxyenko, Shit Talk Extraordinaire
08/18/2014 at 16:23

I have not, but with plenty of high mileage ones going through our used car inspection process and having nearly perfectly balanced compression test readings I wouldn't think uneven wear is much a problem.

jariten1781 > Arch Duke Maxyenko, Shit Talk Extraordinaire
08/18/2014 at 16:24

It seems to me that the mechanism activating them would wear before the engine. They still act as an air spring the whole time they're deactivated and that only happens under pretty low load.

ly2v8-Brian > Arch Duke Maxyenko, Shit Talk Extraordinaire
08/18/2014 at 16:28

You would have less carbon, but no real uneven wear other than that. The parts are moving and receiving the lubrication they need regardless.

Arch Duke Maxyenko, Shit Talk Extraordinaire > jariten1781
08/18/2014 at 16:28

Yeah, but there is less firing in the deactivated cylinders which would be less carbon build up, right?

You can tell a Finn but you can't tell him much > Arch Duke Maxyenko, Shit Talk Extraordinaire
08/18/2014 at 16:30

I don't think you'd see any significant difference in cylinder wear. The frictional loading will be the same regardless of whether or not there is a combustion event. The thermal loading probably wouldn't be all that different either. The block will conduct heat internally very well and the coolant will do a good job of distributing heat too. About the only things I can think of that will see a significant difference in wear will be the injectors and the spark plugs.

Formerly worked as a mechanical engineer at a Tier 1 piston manufacturer so I'm not totally talking out of my ass.

Arch Duke Maxyenko, Shit Talk Extraordinaire > You can tell a Finn but you can't tell him much
08/18/2014 at 16:32

I'm thinking valves, carbon buildup, and injectors and spark plugs.

Lumpy44, Proprietor Of Fine Gif > Arch Duke Maxyenko, Shit Talk Extraordinaire
08/18/2014 at 16:39

Did lots of research on this and as far as I can find its the same ones every time. There are lots of different systems that do this it seems too, some knock out the spark plug and still have the compression in order to keep vacuum, while others just close the valves. Honda's system that can go from 6 to 4 to 3 seems pretty cool actually.

Saab also had a system that would move the block further away in order to change the volume of the cylinder, and GM had a system that would let you use only one bank of the engine if you had ever lost coolant.

As far as wear goes I would think the cylinders that always ran would wear out just like normal and you would need to replace the whole system anyway, the catch being that you saved enough on fuel that a replacement would not as bad on the pocket book.

I think they should be able to alternate on/off pistons though.

You can tell a Finn but you can't tell him much > Arch Duke Maxyenko, Shit Talk Extraordinaire
08/18/2014 at 16:39

Valves will see less wear because they aren't being actuated, but the lifetime of valves now is pretty much infinite relative to engine life. No carbon build up on the cylinders that aren't firing, but carbon build up is pretty much a non-problem with fuel injection and such. The injectors and plugs would see noticeably less wear, but plugs would still be replaced at whatever the recommended mileage and injectors would either get serviced as a group for a cleaning or replaced individually as needed. Basically I can't think of any significant service changes with respect to cylinder related items between a cylinder deactivation engine and the same engine without cylinder deactivation.

The only extra wear items would be any actuators that actually perform the cylinder deactivation.

Arch Duke Maxyenko, Shit Talk Extraordinaire > You can tell a Finn but you can't tell him much
08/18/2014 at 16:42

Cool, thanks for the answer, my boss was asking me the other day about his Challenger and the cylinder deactivation.

jariten1781 > Arch Duke Maxyenko, Shit Talk Extraordinaire
08/18/2014 at 16:43

From what I understand the systems keep track of cylinder temperatures and flip them back on to maintain level temps. Since carbon buildup is usually a function of low temps I think they've probably got that covered. None of the cylinders should be running rich enough to cause buildup on a well managed injection system like they did back in the day.

Dun know though, I've never really looked into it too much.

Manuél Ferrari > You can tell a Finn but you can't tell him much
08/18/2014 at 18:08

You know your stuff.

What would you trust more for your own road car (especially if it no longer has warranty):

1. A modern mass produced turbo charged engine

2. A modern N/A engine with cylinder deactivation

For example do you think the Ford EcoBoost or Chevy EcoTec engine will be more reliable in the long run?

You can tell a Finn but you can't tell him much > Manuél Ferrari
08/18/2014 at 18:11

will answer tomorrow when I'm on my computer. I don't feel like typing this answer out on a phone.

Manuél Ferrari > You can tell a Finn but you can't tell him much
08/18/2014 at 18:18

I totally understand. Typing on phones sucks!

You can tell a Finn but you can't tell him much > Manuél Ferrari
08/19/2014 at 14:51

I'm not sure how good this answer will end up being. Because I suspect I'm going to ramble a bit. The short answer is that they both have their pluses and minuses, but I think in the long run an engine with cylinder deactivation (CD) * can* be more reliable. I also suspect this argument becomes pretty much academic because I see the life spans being remarkably similar.

The other thing to consider is what is your definition of reliable? Does reliable mean it won't fail, that if it does fail the engine can run indefinitely, or that if it does fail it is easy and affordable to repair? If reliable means absolutely no failure I suspect failure rates will be roughly equal. If reliable means fault tolerant (engine can run indefinitely) I think the edge goes to a CD system. If reliable means cheap and easy to repair I suspect both systems lose.

In reality for a stock engine that you drive off the lot new and take care of you will likely have no problems with the engine. Chances are the car will fall apart long before the engine does. If you do have major engine problems they will probably be of the head gasket variety which can happen to either type of engine.

The slight edge I'm giving to CD systems is because their failure mode is probably not catastrophic unlike a turbo failure. I suspect CD systems are designed to be failsafe in that they will fail in a mode that allows the engine to keep running fine at full displacement. So probably when they fail you simply have a full displacement engine that loses its ability to shut down cylinders so your highway mileage will suffer slightly. Based on that failure mode there wouldn't be a need to get the CD system repaired immediately if it does fail. The downside to a CD system comes in the repair side of it. I'm not familiar with how they are actuated, but I suspect that it involves digging into the engine heads. Best case you would have to pull a guard off of the front of the engine, worst case you actually have to open up the heads.

When a turbo fails it tends to be catastrophic. Turbos are big expensive pieces of machinery so that is a strike against them. On the other hand they are external to the engine which theoretically makes them easier to work on or replace, so they have that going for them. Having said that, the metallurgy and design capabilities have advanced tremendously in recent years. Turbos are similar to diesels in that they got a really bad rap in the 80's. Since then technology and production capability has moved on but perception has not. The probability of a stock modern turbo engine actually failing is pretty low. More likely the problems will be with support systems. Turbos have a ton of plumbing associated with them. There are oil lines, coolant lines, vacuum lines and the actual piping moving air and exhaust between the turbo and the engine. The most likely failure with a turbo is going to be a vacuum leak in the system. That can be a PITA to find, but is an easy and usually cheap fix.

My take on the more reliable system is that a CD system is probably more reliable in that its failure mode will allow the engine to operate normally. To say cylinder deactivation is way more reliable than a turbo is like arguing whether a Chevy V8 or a Ford V8 is more reliable. In reality there is no significant difference between the two engine types when it comes to reliability.

After all of that I will point out that my personal vehicles are a 2007 STi and a 2011 F-150 Ecoboost.

Manuél Ferrari > You can tell a Finn but you can't tell him much
08/19/2014 at 15:15

Very good info, thank you!

I guess when I of the definition of "reliable" the answer would be kind of a combination of the engine running for a lot of miles (for example 150K+) before needing any serious work done and also being relatively affordable to repair if something does break and require repair.

What has always scared of about turbos is all the extra parts and plumbing that comes with them. But I do realize that turbos have come a long way since the 70s and 80s. I should get over my fear of them.

That's a real interesting point you brought up on the failure modes. I had never even considered what happens if a CD system fails. That would be pretty nifty if the engine can continue to operate, albeit with more fuel consumption.

I read that some manufactures are starting to combine the two technologies, so they are not mutually exclusive anymore. I believe Audi developed an engine that is both twin turbo charged and also uses cylinder deactivation.

You can tell a Finn but you can't tell him much > Manuél Ferrari
08/19/2014 at 15:56

So far I've got 56,xxx on the STi and 30ish on the truck. Throw in a decent amount of towing with the truck and I've seen no issues at all with it. Granted it is a long way from 30,000 miles to 150,000, but I don't really see any issues coming up with either engine, though it is possible.

I don't know that "high tech" features really mean an engine is more likely to fail. One of the big problems that I got dragged into was an engine that had ridiculous warranty claims. People were having engines seize before they got their new cars home from the dealer. The engine in question was a run of the mill, naturally aspirated inline 4 that had been around for years and wasn't particularly powerful. I wasn't closely involved because our plant didn't produce any of the parts for it so I don't know how it was resolved.

There are so many parts in an engine and they tend to be designed by a lot of people and produced at many different plants. Sometimes tolerances stack up and conspire against an engine. Sometimes the design engineers didn't do a good enough job considering manufacturing methods. Sometimes manufacturers don't do a good job designing their production system. At the end of the day the engineering that goes into an engine has a lot bigger job in determining how reliable it is than whether or not it has a turbo or overhead cams or any other feature.

Manuél Ferrari > You can tell a Finn but you can't tell him much
08/28/2014 at 19:36

That makes sense. Good engineering and quality production of components is the most important thing.

In the old days a good engine design would last for decades. But now engines have to be redesigned much sooner due to regulations and competition.