Why is cylinder deactivation/variable displacement generally considered so bad for long-term reliability? What are examples of cars/engines that use it with minimal issues?
Posted by KSoMA@reddit | cars | View on Reddit | 137 comments
Asking after discussion with a friend. Many cases of modern reliability issues are blamed on variable displacement, such as the 6.4L HEMI. Is this actually a widespread issue, or is it a case of something that hasn't actually become a big deal, like arguably auto start-stop?
Uni_tasker@reddit
IIRC Mazda 2.5l has had cylinder deactivation since 2022 or 2023. Unknown how good it is for long term reliability but Mazda is frequently compared to Toyota and Honda for reliability nowadays.
KetchupOnThaMeatHo@reddit
I had a 18 mazda 6 that had it. I never noticed it. Im not 100% but I think they discontinued it after 21, not sure about the newer models. Those engines had more issues than they should have had also.
BerserkChristian@reddit
2022 still has it, no issues so far but not very old car yet
Lentriox@reddit
Our 2018 CX-5 with cylinder deactivation cracked a cylinder head at 68,000 miles.
BullableGull@reddit
Ironically they might've had their most reliable engine during the Ford ownership days lol
One_Evil_Monkey@reddit
If you want long term reliability... especially with GM's DoD crap... don't just disable it. DELETE IT.
Honestly, all of the cylinder deactivation/ variable displacement stuff on any vehicle is garbage and should be done away with for long term reliability. Because the more moving parts you have, the more failure points you have.
Noobasdfjkl@reddit
What is “GM’s DoD crap”?
One_Evil_Monkey@reddit
Umm...
General Motors
Displacement on Demand
Noobasdfjkl@reddit
Oh, ok. I’ve only ever heard it called AFM.
csimonson@reddit
I have sometimes wondered why manufacturers don't used a vtec style system for cylinder deactivation, via a rocker. Rather than using collapsible hydraulic lifters. Seems like that would be a much more robust system.
Noobasdfjkl@reddit
How would you apply a vtec style of cylinder deactivation to a pushrod valvetrain?
csimonson@reddit
Neo-VVL then a la Nissan
Barbarian_818@reddit
Well, for starters anything that increases mechanical complexity will tend to decrease reliability. More parts mean more things to break.
Second, thermal management in an engine is a greatly underappreciated aspect of automotive design. Cylinder deactivation means that the deactivated cylinders are going to cool off compared to the active ones. Every expands and contracts in response to temperature. Having one section of the engine block be cooler and hence in a shrunken state while another part is hot and expanded makes keeping things sealed with gaskets more difficult.
Third, it might fuck with lubrication. The most damaging part of an engines life is often those few minutes every morning starting up. All the oil is in the pan, cool and thick. It takes a tiny bit of time for the oil pump to develop pressure, but a few minutes before the oil is up to temp. Oil at temp has low viscosity, so it spreads into fine areas easily. The oil control rings in the pistons are specced to create the desired oil film thickness when the oil is at operating temperature. The oil in the cool inactive cylinders won't make that desired thin film. The difference should be trivial AFAIK. But even very minor things can have a huge impact when you're doing them thousands of times per minute.
_badwithcomputer@reddit
Older GM displacement on demand will shut off specific cylinders which could cause some cylinder hot spots and mismatched wear issues. Newer displacement on demand changes up the timing so that it rotates constantly which cylinders are not firing to try and minimize that effect.
MembershipNo2077@reddit
The engine heat is actually a huge one and not just because of metal expanding/contracting and oil, but because of how combustion occurs within a cylinder. Cylinders have an ideal temperature within them for complete combustion according to various factors, but having a cylinder which is "cool" compared to the others you may have incomplete combustion which leads to various unwanted things such as soot.
Obviously manufacturers have methods to attempt to mitigate this as well, but its just one more issue whenever you add complexity.
MaybeTheDoctor@reddit
Could they just design the engine management software to rotate through which cylinders are deactivated every few seconds.Making all cylinders take some work to keep it even.
FluidPart4918@reddit
IIRC the Ford Coyote engine (5.0L) uses a mechanical hydraulic actuator that deactivate the valve train on the same four cylinders… FOREVER . That’s why I drive my F150 in sport mode all the time.
Screw the government and anyone else that tried to deactivate half the cylinders in my truck without my permission. Now, I burn much more gas even though I drive it like a grandpa. Add that to the list of unintended consequences.
MNAAAAA@reddit
Probably just going to stir the pot with this one, but...
Nobody took the car that you already owned and made cylinder deactivation mandatory; you made the purchase decision with this feature active (was going to write "knowingly," but you could have been uninformed at the time of purchase. Either way, you're responsible for knowing what you buy...)
FluidPart4918@reddit
Third V8 F150. Great looking truck (IMO) and best overall option last year. Despite the cylinder deactivation, auto start/stop and a wet belt driven oil pump.
Not stirring the pot, just pointing out that CAFE standards force manufacturers to over complicate engines, build in unnecessary failure points, all in efforts to chase super marginal fuel efficiency.
PrpleMnkyDshwsher@reddit
Or these companies could ya know, actually spend the time and money to engineer a decent solution that doesn't blow up every 80K or at the very least doesn't cost a mortgage payment to repair if it does?
One_Evil_Monkey@reddit
I'll stir the pot...
I agree with everything you said except "F-150, great looking truck, and best overall option."
Sorry, but Ford's are POS trucks. Granted, pretty much all new vehicles are, no matter who the maker is but Ford can go piss up a rope.
WetChickenLips@reddit
Ford bad. Updoots please
One_Evil_Monkey@reddit
Uh huh der her....
News flash, yes, Ford trucks are not that great. They actually rather suck TBH.
But as I said, ALL new vehicles aren't that great no matter who makes them.
JournalistExpress292@reddit
Emissions control is a good thing.
PrpleMnkyDshwsher@reddit
I'm so sick of this attitude in the car world. The government said you vehicle has to produce X amount of emissions THAT'S IT. They didn't mandate different ways the automakers tried to get there.
The Automakers were the ones who came up with these half-baked, annoying, unreliable, and catastrophically expensive to repair methods to get there, and decided to sell them to you anyways
You should be upset you were sold a half-assed product. The Government has nothing to do with it.
robstoon@reddit
That's on Ford, not the government. The government sets the standards. It's up to manufacturers to decide how to comply with them.
Same with the diesel owners whining about how their SCR systems keep breaking and blaming the government instead of the company that designed a garbage system. I'm sure the manufacturers are thankful for that.
hsxcstf@reddit
Damn you disabled a fuel economy feature in your truck and now you are pissed you get worse fuel economy.
Insert shocked pickachu meme.
FluidPart4918@reddit
Gas prices are temporary, engine damage is permanent.
errie_tholluxe@reddit
Didn't say he was pissed, just that it was consequences
intern_steve@reddit
I think there may be a misunderstanding of how deactivation occurs, here. The ecu can control the timing of the spark and injection events, but with cylinder deactivation, you need to stop the intake and exhaust valves from opening as well, which is an event controlled by a physical component, the cam shaft. The cam timing can be altered by a few degrees with some fancy gear with on the timing belt, but not shut down without some more special equipment on the valve lifter. If you don't keep the valves closed, the engine is functioning as an air pump, and it requires a surprising amount of energy to put as much air through the engine as it moves at operating RPM, meaning you won't see any efficiency gains, and might actually burn more fuel, depending on the specific scenario. The special lifters you need are the focus of the reliability discussion, and adding more of them is not a great recipe for improved reliability.
TLDR: deactivation is not only an electronic process, it is a mechanical one. The ecu can't just pick a cylinder at random, the engine is designed around this process from the start.
MembershipNo2077@reddit
Some do, some don't. They also change which cylinders fire when based on various factors.
attanasio666@reddit
I may be wrong but I thought they already did that.
MaybeTheDoctor@reddit
Then I don’t see why cylinders would be cool. I’m not an expert so …
SizeableFowl@reddit
So every combustion chamber is going to be surrounded by coolant, the cooling system will be slightly pressurized, but at operating temperature it should be around 230F (110C).
Now, combustion temperatures can vary wildly, gasoline for example will burn at a minimum of 495F (257C) but the flames inside your combustion chamber are pressurized and therefore greatly exceed these temperatures, often exceeding 2000F (1100C).
In a typical instance where cylinder deactivation might be activated we can assume the engine will be running at low RPM, probably around/below 2000 rpm. In a typical 4 cylinder engine, with a 4 stroke combustion cycle, this means that you will have 4 cylinder ignitions per every 2 revolutions, meaning you’ll have 4000 ignition events per minute without cylinder deactivation. Assuming your ecm deactivates 2 cylinders, you cut that in half to 2000 ignitions per every 2 revolutions, which is notable in itself before you realize that now instead of 2 revolutions occurring before every cylinder achieves ignition you now need to go 4 revolutions and double the time for the same amount of heat to be generated. Given how heat transfer works, doubling the time allowed for the same amount of heat extraction could absolutely cause issues with correctly calibrating the air to fuel ratio for complete burn of all of the fuel especially if the load isn’t perfectly steady state.
dumahim@reddit
GM's AFM didn't. It only operated on 4 of the 8 cylinders.
OptionXIII@reddit
Yes, that can be done. It's more expensive of course, as now every single cylinder needs the deactivation lifters.
The easy way is to just limit time it's disabled, restart combustion, then go back to disabled. The EPA frowns on timers in general as defeat devices, so manufacturers probably need to mathematically model cylinder temperatures instead.
Teanut@reddit
So the ECM couldn't say "don't inject fuel this cycle in cylinders 1, 3, 5?"
Kind of curious how Honda does it, I haven't noticed issues with my J35 (knock on wood.)
Bassracerx@reddit
They just need to abandon cylinder deactivation altogether. Either have no cylinder deactivation or downsize the engine. Most automakers are on the honor system for fuel economy ratings so the engineers install cylinder deactivation and round up 1 or 2 mpg.
StupidAuthentication@reddit
Also the lack of a combustion event in the deactivated cylinders means that oil dragged up the cylinder walls pool on top of the piston rings+cylinders rather than burning off as it would in normal operation, then when the cylinder reactivates that excess pooled oil burns all at once and causes a large amount of carbon buildup... Which then leads to sticking rings that cause oil consumption problems and potential cylinder wall scoring: see Honda J series piston ring recall for VSA engines circa 2008+
DL72-Alpha@reddit
OK, I have a 2014 Honda Odysee and I have seen a huge puff of smoke from time to time behind the van. The first time it happened I actually got off the highway and checked the engine and undercarriage.
I have also noticed that I go through a lot of oil. Considering it's age and more than 200k miles I put 20-50 in it now. Reduced my mileage by .6 but I feel better knowing the engine is better protected. It's not the spry young thing it was with tight tolerances anymore.
Forrest319@reddit
This is why you don't let your car idle to temp. Start driving it pretty much right away to minimize the time it takes to warm up.
AmNoSuperSand52@reddit
I thought that was generally recommended…
__nullptr_t@reddit
It's not necessary early on, but things tend to dry out faster after you put some miles on them and some extra lubricant definitely helps get things going.
Droopy1592@reddit
Constant supply of lube
oneinfamoususername@reddit
The only cylinder deactivation I know of is Chevy’s, and if I understand it right it essentially turns off half the engine when deactivation is on. What would happen instead if you keep the same firing order of the engine and just skipped 1 or 2 power strokes? It would keep the engine moving, I imagine still keep a lot if not most of the heat and it would still allow for oil to be moved inside the cylinder.
One_Evil_Monkey@reddit
In order to do it the way GM's DoD system works.... you just manage to even more complicate an already annoyingly complicated system.
It works by using special lifters on certain cylinders. The ECM activates/decativates a solenoid that stops oil flow to those certain lifters to make them collapse, thereby making the valves not open/close.
That's where the failure problems come from, those specific lifters.
What you're proposing just ADDED MORE of those stupid specific lifters and just DOUBLED your chances of failure.
delebojr@reddit
The newer version of GM's system is dynamic so the disabled cylinders are always changing, thus no cylinder should have significantly more wear than any other.
mada447@reddit
I think cylinder deactivation is much more common than we realize. My 2.5 4 cylinder Mazda has it.
dumahim@reddit
You mean leave the valves operating normally and just cut fuel? Part of what makes cylinder deactivation efficient is the closed cylinder acts as an air spring. It drew in air, valves shut off, air gets compressed, but no fuel to ignite. The compressed air will still push down on the piston somewhat cancelling out the energy used to compress the air in the first place.
The fuel savings are so meager with this method as it is. Making it less efficient by just pumping air would probably make it not worth using at all.
reversethrust@reddit
Wait.. engine oil doesn’t get thicker as it heats up? Like 10W30 means that it’s 10 viscosity cold and when it warms it is at 30 (whatever the units are) and thus thicker..? Or did I understand this wrong?
robstoon@reddit
The trick is that the viscosity numbers are also relative to temperature, based on the behavior of single-grade oil. So 10W30 oil is like a 10W grade in the cold that only thins out to what a 30 grade oil would in the hot. But the viscosity still decreases with temperature.
Given that single grade oil is almost entirely obsolete, the whole oil viscosity system is really kind of outdated and probably would be done differently if we were starting over today..
roscopervis@reddit
Yes! It’s mostly opposite. The w number is the cold number, or the weight of oil (thickness) when it is the coldest you might expect it to operate in for your use case. The bigger number is the oil thickness when it is hottest. This is the protection when driving on track or as hard as possible.
The oil when cold is always thicker than when it is warm. The numbers relate to how thick they are in those operating conditions. So your idea that the higher numbers mean thicker is correct, but only compared to other oils in the cold or warm operating condition.
LazyLancer@reddit
Don’t they alternate which cylinders are enabled and which are not?
_galaga_@reddit
Saw a recent Getty's Garage vid on YT that mentioned this issue with respect to the Coyote V8. Early gens didn't have deactivation but the latest gen does and he pointed out the added complexity as a risk factor for reduced reliability. He's an engine mechanic by trade so take his word more than mine but it makes sense. The mechanism to enable deactivation involves adding a lot of new plumbing to the motor.
randeus@reddit
Thankfully, the Coyote in the Mustang doesn’t have it.
_galaga_@reddit
Just got an idea for an April 1st post for 2027...
randeus@reddit
I’m lost, what do you mean?
_galaga_@reddit
Oh, just imagining a fake announcement of cylinder deactivation coming to the Mustang for an April Fools joke. A funnier one is along the lines of, "Today General Motors announced a monthly subscription service for cylinder re-activation" yada yada. Implying you would have to keep paying money to get your V8 out of 4 cylinder mode.
dumahim@reddit
I don't know of a case where it's been reliable yet. Maybe it exists?
Had an LS4 in my Monte Carlo, started burning oil really early. Their supposed fix was a new oil pan gasket with a baffle to prevent excess oil from getting thrown up into the cylinders. Of course it did nothing. Kept burning oil. Fouled the plugs and by the time I sold it, had pretty good piston slap.
Now I have it in my Accord. Thankfully it's pretty easy to disable, which I did fairly early on.
trick_m0nkey@reddit
2021 F150 Coyote V8 (and probably also for the Mustang) introduced cylinder deactivation and it's been out long enough and there enough high milage examples for people to consider to be a very reliable engine option for the F150s. If you get one, you may have transmissions issues, but you'll have a solid engine at least.
Riverrattpei@reddit
Mazda, Mercedes, and I think all of the VAG brands (including things like the Huracan and Aventador) have been using it for years with no issue
It seems to be just the America V8's that struggle with it
AsparagusDifficult89@reddit
My Audi A8 L with the 4.0T definitely had it, and so do all the other VW Group cars with that engine. I believe the later W12 (6.3-liter normally aspirated in the A8; 6.0-liter twin-turbo in the Bentleys) used it as well.
Midgetsdontfloat@reddit
The 5.7 and 6.4 Hemi motors have their issues, but it is entirely unrelated to the MDS system. It is almost entirely down to insufficient oiling at an idle, causing excessive cam/roller wear.
A 5.7 will happily lug along on 4 cylinders for hundreds of thousands of miles, just change the oil on time and don't let it idle long.
FACE_MACSHOOTY@reddit
Bringo, too many people conflate the MDS side causing the failure when its the roller side of the lifter. Idiots idle their trucks 8 hrs a day and dont understand why thats a problem.
rugbyfiend@reddit
Somewhat interestingly the Huaracan introduced it in 2016 only in the tamest mode, and you shut down one bank of cylinders and run an inline 5. Each bank has its own ECU to manage this.
dumahim@reddit
And Honda V6s.
AGRDR@reddit
My GLA has this tech (M282 engine), although it seems to run on 2 cylinders only under very specific conditions from what I've seen.
Outside temp under 25°C, the AC is not running like a freezer (lowest temp setting), and engine is running under 2.5k rpm (moving or stopped).
It doesn't run on 2 cylinders if the engine hasn't reached it's operating temp (oil and water temp, it has a gauge for both).
The thing is however, the oldest versions of these engines used in Mercs are from 2018, it's not exactly new but not old either. Mine is at about 35k miles which is nothing. Only real issue is carbon build up because it's direct injected only.
dumahim@reddit
Yeah, I think they all only operate under certain conditions. Interesting that yours will do it when you're stopped. I suppose that's a little better than the auto shutdown thing.
RespectableLurker555@reddit
My 2018 Mazda supposedly has cylinder deactivation in the 2.5 naturally aspirated 4-cylinder but it's only been 55k miles so hardly a strong data point.
reversethrust@reddit
Same. My old 2018 cx5 had about 196k km and zero issues.
smexypelican@reddit
Is this a V6 Accord? It doesn't seem like the 1.5T and 2L hybrid ones have VCM.
dumahim@reddit
Right, it's a V6 thing.
baconlord1337@reddit
I am a Honda tech. The J35Y6 hasn’t seen the VCM issues that the previous gen had with the piston rings rotating and perpetually burning oil. It’s in my opinion the best version of the J series. Starting to see these hitting 200k miles in the shop with no fouling of the spark plugs.
The DOHC Y8 uses a completely different VCM method of disengaging the rocker tips from the valve stem and uses hydraulic lash adjusters. Haven’t seen too many issues with that system yet but piston slap is starting to become an issue from following other Honda techs on social media. I haven’t seen it yet personally.
ahorrribledrummer@reddit
Just changed the plugs on my '18 Odyssey at 105k af ew months ago. They looked great, and all identical. I had considered muzzling before, but no intention of it now.
baconlord1337@reddit
The gens that had the oil fouling the VCM muzzler was a must. On the DI engines the muzzler causes it to run lean due to the ECM trying to heat up the engine. You get better fuel economy due to that, but more heat and wear.
Only non OEM mods I did to my passport was an idlestopper and PRL resonator delete. I think at this point auto stop start is harder on components than variable cylinder management. Increased starter, battery, and honestly engine wear too. You go from 0 oil pressure to starting the engine and instantly putting torque on those components without being fully lubricated.
PretendLength1710@reddit
yeah the 6.4 hemi is the poster child for this shit but it aint every engine. gm afm and coyote both show it can be fine if the hardware and tuning arent janky.
Heavy_Gap_5047@reddit
The Hemi tick has nothing to do with the cylinder deactivation.
PretendLength1710@reddit
yeah that gets mixed up a lot and lifters catch the blame way too fast.
Da_Funk@reddit
Again, /r/cars user showing they don't know what they are babbling about.
PretendLength1710@reddit
nah bro cylinder deactivation still gets blamed for stuff it didnt even cause.
U-B-Ware@reddit
Is there any data or evidence that the 6.4 hemi's have this issue?
PretendLength1710@reddit
yeah man most of it is lifter and cam wear and mds just gets blamed.
PeregrinsFolly@reddit
In the case of GMs V8 engines, it's because it the lifters in them that control the cylinder deactivation have a higher chance of failure, leading to at least expensive lifter replacement, and can cause catastrophic engine failure, requiring full replacement. GM's been trying to get it right for years but still has issues to this day. It's by far the most common cause of engine failure on GMs V8 engines. They appear to have a new system in the works, but it'll be a few years until we know if it makes any significant difference. Their 4 and 6 cylinder engines don't appear to have as many issues with the system as the 8 cylinders do. The 6.6L gas engines do not have AFM/DFM intentionally for the purposes of longer engine life.
LeatherDan@reddit
My new 2021 V8 suffered a "lubrication failure" in the first 1500 miles, requiring a complete engine replacement. A year later it was back in for lifter rebuild.
Wish they could delete the system entirely, but they can't due to federal fuel economy and emissions standards.
One_Evil_Monkey@reddit
They have it but you can delete it. I don't mean disable with the dongle. I mean DELETE it. There are kits. About $700 and a weekend's worth of time if you know what you're doing.
Makes for a way more reliable engine.
Gregarious_Raconteur@reddit
I mean, they could delete the system, but they chose to go the route of cylinder deactivation instead of other forms of efficiency improvements.
A 4.8L v8 with a turbo would likely be more efficient and reliable than a 6.2 with AFM, and the hybrid tech that GM was using in the tahoes and escalades in the mid 2000's was pretty impressive.
Both were likely more expensive than AFM, though, and from a marketing perspective, smaller engines or hybrid tech probably wouldn't have sold as well as more displacement (some of the time)
fuckin-shorsey@reddit
I got the golden unicorn 6.2. It’s definitely had its issues, just never anywhere between the radiator and firewall. Hope its second half-million miles goes as well as the first.
Confident_Season1207@reddit
The 6.6 gas should be reserved to just work trucks and commercial delivery vans, so putting that system on there is pointless
highflyer10123@reddit
Depends on the generation and design. I know Hondas for example, oil builds up on the cylinders that are shut down causing problems long term. Further, it throws the engine balance off. Third the car is always slow to respond with full power because when you hit the accelerator it doesn’t kick in all the power right away.
CommissarCiaphisCain@reddit
Yeah I put the VCM bypass on not long after we got our Odyssey. Have also done it for friends’ Hondas with VCM.
WarpcoreUser@reddit
This thread is perfect timing. I just received my VCMTunerII. My 2020 Odyssey has 70K on it and burns zero oil. Did they fix the design in the 3rd generation of VCM or does it still cause issues in newer Honda V6s?
CrazyErniesUsedCars@reddit
My S-VCM just died the other day and I've been thinking about getting a vcmtuner
dumahim@reddit
If you get the tuner, be aware that buying one is a pain in the ass. He only opens the window to buy for a very small window of time. It's like buying tickets to a big concert. Gotta be online and ready to buy at the right time.
CrazyErniesUsedCars@reddit
got one ordered!
dumahim@reddit
Congrats!
CrazyErniesUsedCars@reddit
Yep I got a reminder for Monday at 9am haha
TenderfootGungi@reddit
This is why the VCM is blocked on all of my Honda's.
highflyer10123@reddit
I’ve done that and it’s 100% better. And the mpg isn’t that much different.
cheeseIsNaturesFudge@reddit
Hm, I'm imagining a system for the 300c that iirc had cylinder deactivation. Wouldn't it be neat to skip a firing for each cylinder sequentially every other time that it should fire in such a way to maintain balance but ultimately still fire half as often, it'd at least prevent the oil issue.
gdnws@reddit
The most recent version of GM's v8 cylinder deactivation, called dynamic fuel management(dfm) instead of active fuel management(afm) could operate like that. I don't know if it did but it was capable of deactivating any cylinder instead of always deactivating the same ones like the earlier version or like the Chrysler hemi systems. It was at least technically capable of wear balancing the cylinders.
Heavy_Gap_5047@reddit
The Hemi issue is not as wide spread as the internet would have you believe. But more important the Hemi tick has nothing to do with the MDS system.
MuffinRacing@reddit
Had a 2019 Ram without MDS and it ticked bad. Can confirm, MDS had nothing to do with it
gdnws@reddit
It is also important to remember that the MDS hemis have been around for over 20 years now and they put them in absolutely everything. I do think this is a case of more talk of broken parts than actual broken parts.
PorTroyal_Smith@reddit
Last point to this, afaik an exact cause hasn't been determined, but engine idle time seems to be the best indicator for future hemi tick engines (not exhaust manifold, just the lifter failures). The hemi was used extensively in work trucks and cop cars, vehicles that idle for hundreds of hours while also being worked very hard.
gdnws@reddit
From what I've seen, no exact cause has been conclusively determined but the most popular hypothesis is that there is inadequate oiling to the cam and lifter rollers at idle. Some solutions I've seen are either to limit idling or increase engine idle speed or install either a Hellcat or Melling oil pump that delivers a higher volume of oil. One way or another, there are a lot of them out there that get driven hard and they don't seem to care. Off the top of my head I can't think of my head I can't think of an engine in recent memory that has served in both in passenger car and and 1500 series pickup trucks as well as 2500+ series trucks apart from the gen 3 hemi. Last one might have been the vortec 6L GM ones I think.
nekmatu@reddit
It destroys hemi engines long term. I can’t think of an engine that doesn’t have long term problems because of it.
robstoon@reddit
Because the valve train problems on the Hemis have nothing to do with the cylinder deactivation.
nekmatu@reddit
That’s weird because there is a class action lawsuit specifically calling out MDS and the valve train issue.
chameleon_olive@reddit
That lawsuit has been going on for the better part of a decade with no payout. The Hemi has issues, but MDS is statistically not the cause of them
ProtonTommy15@reddit
It's the variable valve timing lifters that are the problem. They are a horrible junk design. They fail way too soon. All the other issues are secondary. Especially those of you who think that heat is the issue. 40+ years in auto repair and I have never seen such a horrible design. The basic premise was good the execution HORRIBLE.!
RiftHunter4@reddit
As far as I know, the American brands are the only ones where this has ever been a concern. Never hear much from Toyota or Honda about it.
robstoon@reddit
Honda has had some significant issues with the VCM on some of the V6 engines.
sashagof@reddit
The Mercedes M113 engine found in the W220 S-Class (S500) had cylinder deactivation but is one of the most reliable engines from the early 2000s. Many can go 300k miles with regular maintenance. Other stuff on that car will fail way before the engine.
AsparagusDifficult89@reddit
I knew the M113 (N/A) and M113K (supercharged) were fantastic engines. I did not know they had cylinder deactivation. But that makes sense.
In general, the W220 is actually a pretty solid car. There were issues with the early 7AT, but those have been solved, and the non-ABC ones that use AIRMATIC struts are cheap and easy to service.
CaliDude75@reddit
From what I’ve seen, it’s a bigger issue in pushrod than OHC engines. Overhead cam engines typically use a sliding pin mechanism, whereas with pushrod engines, it’s a collapsible lifter.
V48runner@reddit
Thankfully there are lots of great aftermarket solutions to some engines that defeat this easily.
I bought S-VCM for my 3.5 in my Honda and it took 10 minutes to install, and I never have to worry about it again.
BMWbill@reddit
The Skyactive G 4-cylinder motor has this in my daughter’s Mazda CX-30. Mazda engineers claim they had studied disassembled motors all with over 100k miles, comparing the non-cylinder deactivated motors with ones with cylinder deactivation and they saw no differences.
Hnry_Dvd_Thr_Awy@reddit
Damn this is a good question. The main one that comes mind is GMs 2.7L but that may be sampling bias and the fact that they just aren’t that old yet.
halotechnology@reddit
L3B 2.7 is actually a much better AFM than older engines or V8 and easier to service. It doesn't includes lifters at all.
I just wish it was offered for the Camaro I would have picked it ip
Sarah_hussain09@reddit
I don't get how AFM can be all that useful on a 4 popper...
halotechnology@reddit
It's a big engine with a larger displacement for a L4.
But idk to be honest
Hnry_Dvd_Thr_Awy@reddit
I’m considering a used 2.7 CT4 for the same reason.
gdnws@reddit
It has been around since 2019 and I seem to recall hearing about afm problems fairly frequently on the v8s by the time they were a similar age. There might be some amount of sampling bias, I did a cursory search for 2019 and up chevy trucks and the majority of them were v8s, but also that the system that the 2.7 uses is actually more reliable since it is really just a cam profile switching system which a number of manufacturers have used for about 20 years now with good success.
H-TSi@reddit
I despise it on the 1.5 TSI. I have no problems if it a system one can turn off.
YozaSkywalker@reddit
In my mind, you're removing a force from the reciprocating mass that was always supposed to be present. Without it, you could introduce uneven wear, lubrication and vibration to the engine it wouldn't have without it.
leebe_friik@reddit
1.5 TSI that much of VW and other VAG vehicles get outside of NA for the past 8 years seems to be doing quite alright with its cylinder deactivation.
Briggs281707@reddit
I think the VW 1.5 TSI doesn't have any real issues with the cylinder deactivation, although a 4 cylinder engine running on 2 is real funky
rnc_turbo@reddit
Wait until you hear there are 3 cylinder engines that run on 2!
deadlydesign@reddit
Agreed. It never seems to be issue, even with the older 1.4tsi that had it.
RicoLoveless@reddit
Anyone able to tell me if the current gen coyote on 2026 f150 is a grenade waiting or is this just a thing to consider when purchasing?
Riverrattpei@reddit
If you're that worried about it just get the 2.7, it's Fords best engine
It also drives a better than the 5.0
withoutapaddle@reddit
Everything I've heard about the F-150 the last 10 years or so (including my 2020) is that you don't have to worry too much about which engine you went with because the 10r80 tranny will destroy itself first regardless!
Tiny-Art7074@reddit
The Lamborghini Hurracan would shut of one bank of cylinders without much long term reliability issues. I know of rental cars with 70k miles on them that burn more oil that what you would want, but no other issues and at that mileage, its common for super cars to burn oil let alone rental examples.
green91791@reddit
Part of the issue issue that cheap parts are used to save weight.
funkmachine7@reddit
It's complex as you have to control the fuel each cylinder so they run minimally, ideally they will become 6/8/10 stroke cylinders and revert to 4 stroke on demand based on engine load. By just running some cylinders as air pumps for 2 cycles you get better heat management, cool air goes in sucks up heat and in forced out on the exhaust stoke.
It also needs a active power stroke often enough to give a consistent power output, so it's far more at home on multi cylinder engines like V8 or I6 where the power stroke overlap.
With a modern pile of parts, sensors, flexible valve control and an ECU that easy but expensive in parts.
Simply turning off a cylinder permanently risks oil blow by from cold oil rings failing to seal.
Vvette45@reddit
F150 5.0L I have not seen any proof of it having issues due to cylinder deactivation and I believe they have been using it since 2021
Diogenes256@reddit
It’s the lifters. Chevy too.