Review: Disabling Honda's V6 Variable Cylinder Management (VCM)

"Ash78, voting early and often" (ash78)
04/01/2019 at 12:14 • Filed to: None

For over a hundred years, !!!error: Indecipherable SUB-paragraph formatting!!! has been used (with !!!error: Indecipherable SUB-paragraph formatting!!! ) to improve fuel economy and give drivers “the best of both worlds” for efficiency and power.

Welp, I guess it’s time to rebadge the engine.

Enter Honda’s !!!error: Indecipherable SUB-paragraph formatting!!! (VCM), which started appearing on its 3.5L iVTEC V6 engines as early as 2005 in the US market. The idea behind VCM is simple: Once the engine is at normal operating temperatures, under light loads the engine is allowed to run on 3-4 cylinders. Once the demands are increased, the 2-3 inactive cylinders will seamlessly kick back in, yo.

While the idea is simple, the execution is not. The fourth-generation Odyssey (ours is a 2015) has FIVE electronically controlled engine mounts to dampen the vibration during cylinder deactivation and 3-4-6 transition phases. Further, long-term use of VCM has been acknowledged by Honda ( !!!error: Indecipherable SUB-paragraph formatting!!! ) to contribute to excessive oil consumption and premature failure of those expensive engine mounts — often requiring entire engine replacements.

Why would they go to such lengths? By most estimates, to gain approximately 1-2mpg on the highway; virtually nil in the city.

As a result of these failures and lawsuits, a handful of enterprising Honda forum members and technicians developed a few similar workarounds: Adding slight resistance to the coolant temp sensor (ECT sensor) would prevent the ECU from knowing that the engine is warmed up, thus preventing the use of VCM. The results are that the vehicle runs on all six cylinders at all times. While this may sound like an ecologically thoughtless act, the cost-benefit for most drivers is clearly in favor of preventing engine trouble, not saving a miniscule amount of emissions. Let’s pause and point out that an Odyssey with 4 people inside, on the highway, is still getting over 100mpg per person. Fully loaded, 200+ mpgpp.

After considering it for a couple years, I finally went with the $80 !!!error: Indecipherable SUB-paragraph formatting!!! , which includes a manually adjustable resistor for seasonal and local climate-based tweaking. It was a 5-minute plug-and-play solution under the hood, simply adding a “middleman” to the ECT wiring. The instructions left a lot to be desired, but were adequate enough.

It’s actually simpler than it looks here; just one t-shaped connector.

But how does it drive now?

In short: Beautifully.

The worst cruise control I’ve ever used is now one of the best. Since the car is no longer resisting the urge to keep VCM activated, the previous fluctuations of 3-4 mph (up and down) are now less than 1mph. The car remains at the speed where you want it.

Constant, subtle vibrations while moving between the three cylinder settings are completely eliminated, both on the highway and in light suburban driving.

Throttle lag (which was constant when under a light load) is now nonexistent.

A car I generally considered !!!error: Indecipherable SUB-paragraph formatting!!! is now...mostly tolerable!

All of this adds up to a more enjoyable experience, as well as less stress and better courtesy to other drivers when using cruise control. I couldn’t have asked for more from such a simple solution. At the moment, I’m still tweaking my settings during fluctuating spring weather to strike the right balance between a CEL and allowing VCM to engage, but that’s just minor adjustment. For most users, leaving it at a single setting will be fine.

And you’re probably wondering about my fuel economy penalty. So far, after nearly 1,000 miles of all types of driving, I’ve seen no meaningful hit. Our recent 500-mile road trip around Alabama and Georgia showed 25mpg, which is perfectly in line with our historical norm (90% highway/10% local driving with some A/C usage).

Highly recommended.

DISCUSSION (11)

Honeybunchesofgoats > Ash78, voting early and often
04/01/2019 at 13:20

Having VTEC always kicked in seems pretty dangerous, if not reckless, unless you’re just towing your Odyssey to and from the track.

and 100 more > Honeybunchesofgoats
04/01/2019 at 13:32

But that’s not what this does.

AMGtech - now with more recalls! > Ash78, voting early and often
04/01/2019 at 13:51

I read this waiting for the April fool's joke.

Daily Drives a Dragon - One Last Lap > Ash78, voting early and often
04/01/2019 at 13:55

A family member recently just had this problem on a Pilot. Rings were bad on half the motor. And it started misfiring because of oil on the plugs.

Ash78, voting early and often > AMGtech - now with more recalls!
04/01/2019 at 13:58

The joke started in 2005 and is somehow still going. Honda has a weird sense of humor ;)

RiceRocketeer Extraordinaire > Ash78, voting early and often
04/01/2019 at 14:02

stuff like this and their recent 1.5T issues makes me wonder if Honda has simply forgotten how to make engines altogether

Ash78, voting early and often > RiceRocketeer Extraordinaire
04/01/2019 at 14:27

I would say this engine is the most reliable I’ve owned in the first 50k miles (knock on wood). Doesn’t burn or leak a drop of anything under the hood, and the Blackstone analyses I’ve done — with almost all urban & suburban driving — are now recommending a 10,500 change interval. Honda definitely knows how to build engines when they try. It’s the tweaking of engines (mainly for economy) where they’re screwing up.

I truly believe that cars from the current era will all start showing these kinds of expensive problems over time, since we’re collectively just asking an ICE to do too much. Just look at the coking/carbon issues with so many direct injection engines all around. Or Dieselgate, which was indirectly born from chasing efficiency at all costs.

dogisbadob > Ash78, voting early and often
04/01/2019 at 14:55

They should get a 10 mpg penalty from their CAFE ratings for this shit

The good news is that they didn ’t use it when connected to a manual transmission, or on the first -gen Ridgeline

dogisbadob > RiceRocketeer Extraordinaire
04/01/2019 at 14:58

Yup! Honda doesn’t have enough experience with turbos, especially considering how quickly the 1.5T took over their lineup. That 1.5T is only the second turbo ever sold in the US (the first was the first-gen RDX from 10 years ago). And even internationally, Honda has used turbos very sparingly.

It’s so bad that ***China *** had to order a stop-sale on them! A country not known for superior engineering, and even they t hink it’s a piece of shit that’s not even worth copying.

fixmyv6 > Ash78, voting early and often
01/17/2020 at 10:58

I drive a 2008 Accord and starting having engine hesitation / spark plug issues at 60,000 miles. It was amazing how ruined some of them were due to the VCM system and the ECO mode. Instead of having to deal with constant spark plug maintenance and dealing with the annoying engine shudder and having an engine eat oil, I developed a fully automatic, compact VCM disabling device.

Compatible with many year Odyssey’s, Pilots, Accords, etc.... I likely have a solution for your problem. Unlike other units on the market, I have a passive option that requires no tuning or adjustment and automatically activates when your engine reaches temperature.

Check it out at www.AST-ApertureTech.com, and let me know if you have any questions. ast.aperturetech@gmail.com

longtimelurkingtdiguy > Ash78, voting early and often
10/24/2020 at 22:38

So, a year and a half later, are you still happy with the results? Any issues with the van? I'm just curious as I've thought about buying a Ridgeline at times.