What is VCM in Honda and Acura vehicles?
The two videos created by Honda and Acura explain the Variable Cylinder Management (VCM) system used in their V6 engines.The Honda video - https://youtu.be/tIZP0024stE
The Acura video - https://youtu.be/2yE5V7raQNM
The VCM system improves fuel economy by deactivating two or three cylinders while the vehicle is in motion. Since less fuel is burnt as compared to constantly running on all six cylinders, there is also an environmental benefit.
What are the potential issues related to VCM?
Vibrations occur when some cylinders are deactivated. In order to reduce the amount of vibration transmitted to the passenger cabin, Honda and Acura vehicles are equipped with components (e.g., specially designed engine mounts) that can dampen the vibration when the engine switches to running on three or four of its six cylinders. Besides, there are a number of measures that are employed to smooth the activation-deactivation of cylinders – see http://hondanews.com/releases/ab15a7c2-0797-4cc8-8b42-b0081743c563.While the VCM technology continuous to be improved, there are two potential issues. First, the vibration is a source of material fatigue that has a negative impact on the service life of affected components, particularly the engine mount.
Second, in some models, the piston rings of variable controlled cylinders (i.e., number 1 to 4) may rotate and align under certain conditions, causing engine oil to enter into the combustion chamber. Resulting effects include: excessive oil consumption, spark plug fouling, cylinder misfire, and the MIL (i.e., check engine light) would come on. When this happens the fault code could be any or a combination of P0301, P0302, P0303 and P0304 (and you should bring your vehicle to be checked for the root cause instead of, for example, replacing the spark plug to make the code disappear).
The second issue affected 1.59 million vehicles across a range of models.
- 2008-12 Accord
- 2008-13 Odyssey
- 2009-13 Pilot
- 2010-11 Accord Crosstour
- 2012 Crosstour
Honda announced a powertrain warranty extension as a result of a settlement of a class action lawsuit. More information can be found at: http://settlement-claims.com/enginemisfire/FrequentlyAskedQuestions.html
Subsequently, Honda has issued service bulletins in the US and Canadian markets to fix the resulted problem, for example:
https://techinfo.honda.com/rjanisis/pubs/web/A13-081.pdf
The engine problem due to piston ring alignment appears to be correctable, and by applying a software update the problem can be prevented from recurring.
Pros and cons about suppressing VCM – with two kinds of tools
Theoretically, suppressing VCM can obtain some benefits under the assumption that the related potential issues could be avoided. However, Honda did not provide an official way of disabling VCM (they choose to improve the VCM technology instead), and the cons of disabling it still exist.1. The VCM is part of a tight and complex drivetrain system. An intervention that is not part of the design may inadvertently interfere with operations beyond the intended purpose of disabling VCM and lead to undesired consequences.
2. The gas consumption will be higher when all cylinders are running all the time than having two or three of them deactivated in some situations, e.g., when the vehicle is decelerating. The fuel economy of you vehicle will be lower without VCM.
3. The VCM technology helps Honda to meet CAFE standards for vehicles, which are measured by the U.S. Environmental Protection Agency, as throughout the entire usage of a given vehicle, its greenhouse impact on the environment due to fuel consumption will be reduced by VCM. This benefit would be lost if VCM is disabled. (The US Congress specifies that CAFE standards must be set at the "maximum feasible level" - source: Wikipedia.)
In the case that the engine of a vehicle has already suffered a (partially) rotated piston ring but not yet to the extent of triggering any of the P0301-04 codes (i.e., cylinder misfire causing more than 2% imbalance detected on the shaft), disabling VCM may delay exposure of the problem. The extended Honda warranty has a time limit of eight years from the date a vehicle was sold, within which the high cost of replacing piston rings is covered by the manufacturer. To some, this may cause a dilemma as to whether or not to suppress the potential issue in the warranty period.
Debates in the owner community
As evident in a number of Internet forums, there is much discussion around VCM and a shared desire among some owners to be able to suppress VCM in their Honda and Acura vehicles. Here are a few examples:http://www.driveaccord.net/forums/86-9th-generation/358690-vcm-problems-corrected-generation-9-v6-ex-l-sedans.html
http://www.piloteers.org/forums/82-2012-2015-pilot/70905-vcm-tsb-jan-2015-pcm-update-driveshaft-replacement.html
http://www.piloteers.org/forums/114-2016-third-generation-pilot/114273-vcmuzzler-ii-2016-honda-pilot-needed.html
http://www.odyclub.com/forums/52-2005-2010-odyssey/152534-vcm-long-term-reliability.html
https://www.bogleheads.org/forum/viewtopic.php?t=135560
Despite reports based on personal experiences, I did not find any published study showing that the necessity of completely suppressing VCM has been systematically examined, and the risk involved in disabling VCM with a non-factory method has not been quantitatively assessed. Nevertheless, it is reasonable to expect that adverse effects, if any, as a result of disabling VCM would also appear in such forums.
The 'Solution'
When this post was written, Honda had not provided a solution to the owners who wish to disable VCM in their vehicles. Some have come up with their own methods, for example:http://www.odyclub.com/forums/52-2005-2010-odyssey/237369-disable-vcm-how-2005-2007-odyssey-s.html
http://www.odyclub.com/forums/52-2005-2010-odyssey/211425-diy-2008-2010-vcm-variable-cylinder-management-disable-procedure.html
http://www.piloteers.org/forums/82-2012-2015-pilot/70873-vcm-disable-new-better-way.html
Each of these may be applicable to only certain vehicle models, because the total number of affected vehicles exceeds 1.59 million and no one except the manufacturer can plausibly know the technical specifications of all those vehicles.
One of the widely known methods can be derived from published documents, such as Honda’s patent applications. There are several factors used to determine if the engine is in a permitted cylinder deactivation zone. These include "the temperature of the engine cooling water, the vehicle speed, the engine revolution rate, and the depression amount of the accelerator pedal. In each case, these factors are evaluated based on a single predetermined threshold. In other words, if each of these factors is determined to be above or below (depending on the factor) a predetermined threshold, the cylinder deactivation operation is prevented" - extracted from Honda Motor Company patent application EP2840247.
You may find more information on the VCM technology in these patent files:
Method for controlling cylinder deactivation – EP2840247, EP2527622
https://www.google.com/patents/EP2840247A1?cl=en
https://www.google.com/patents/EP2527622B1?cl=en
Control device for hybrid vehicle with cylinder deactivation – EP1316461
https://www.google.com/patents/EP1316461A2?cl=en
Engine cylinder deactivation to improve vehicle ... US6786191
http://pdfpiw.uspto.gov/.piw?PageNum=0&docid=06786191&IDKey=E318C6C4EF09
In line with the above, some methods of deactivating VCM have appeared (see one explanation in the public domain – http://www.odyclub.com/forums/52-2005-2010-odyssey/268778-vcmuzzler-ii-disabling-vcm-faq-s.html). The principle of the method can be summarised as follows.
- The vehicle's ECU (engine control unit) determines that VCM does not start function until the engine coolant temperature reaches above 167°F (75°C). The hypothesis is that if the coolant temperature reading can be kept below that threshold, no cylinder would be deactivated.
- The coolant temperature sensor functions in such a way that, in most automobiles, its internal resistance decreases as the coolant temperature rises (and vice versa).
Source: https://en.wikipedia.org/wiki/Engine_coolant_temperature_sensor
- Keeping the total resistance of the coolant sensor circuit above a certain value, which can be achieved by adding a resistor in a series circuit, would fool the ECU to believe that coolant temperature has not reached the required 167°F (75°C) for VCM to be activated.
1. VCM Muzzler on eBay
The VCMuzzler II has a unique design which allows you to conveniently switch to a second resistor if the 82 ohm one does not fit your vehicle.
2. VCMTuner
It uses a potentiometer to allow manual adjustment of the inline resistance added on top of the coolant temperature sensor.
3. A new product called S-VCM Controller recently appeared and prompted me to update this blog post by adding the section below.
The S-VCM Controller is considered to be in a different category than the other tools. First, it appears to be an electronic device with active control logics programmed into it. Second, it claims to address the limitation described hereafter.
Shortcoming of the “Resistor” method
Most variations fall under the category that can be called the "resistor" method.
- Single inline resistor – e.g., VCM Suppressor DIY
- Exchangeable resistors – e.g., VCMuzzler II
- Potentiometer based model (adjustable resistance) – e.g., VCMTuner
The impact of adding a resistor (e.g., 82 ohm) is that the displayed engine temperature is inaccurate especially when it needs to be. This is problematic. For example, when the coolant temperature reaches 250°F (121°C) the electrical resistance of the coolant temperature sensor is reduced to about 89 ohm; however, the added resistor will elevate the total resistance that is indicative of coolant temperature and cause the vehicle’s ECU to receive a false reading of under 210°F (99°C) based on a combined 171 ohm resistance (89 ohm coolant sensor resistance + the added 82 ohm resistor). When that happens, the temperature dial on the dashboard would look 'normal', which is in fact not true due to the intervention of the added resistor.
Illustrations: Different temperature gauge positions at an actual 250F (121C) coolant temperature
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To overcome this limitation of the resistor method, the suppression of temperature reading should be cancelled when the actual coolant temperature is above, say, 230°F (110°C). In this way, should the engine becomes too hot, the driver will be alerted of the actual coolant temperature on the dashboard (assuming that at this point, being alerted of the true engine temperature is more important than suppressing VCM). To achieve this, the device should be monitoring the actual coolant temperature, and apply or stop VCM suppressing accordingly, i.e., automatic 'ON/OFF'.
So far, only the S-VCM Controller has addressed the inherent disadvantage of the resistor-based tools such as VCMuzzler, VCMTuner as well as the DIY kit of my VCM Suppressor.
Need for Cost-effective Solutions
Since I made available the VCM Suppressor DIY Kit, many DIYers have taken advantage of it. Presently, with the help and request from many of them, I am working on an electronic version of the VCM Suppressor that can address the limitation of the "resistor-method" and deliver similar functions to the S-VCM Controller. My goal remains the same – that is to offer cost-effective options to those considering similar yet more economic solutions. I will update this blog as soon as the electronic VCM Suppressor becomes available.
Features of the VCM Suppressor DIY kit
- 2 connectors: one male and one female, with wires crimped (so you do not need a crimping tool to use the kit)
- Resistors rated at 82 ohm, 100 ohm, 120 ohm, 150 ohm and 68 ohm (most of the time, the 82 ohm resistor will suffice)
- Heat shrink tube, and split wire loom
An assembly guide has been posted on YouTube.
You may also consult this forum post (http://www.odyclub.com/forums/52-2005-2010-odyssey/268778-vcmuzzler-ii-disabling-vcm-faq-s.html) to help determine the most appropriate resistor for your specific case.
At the moment, you can get the DIY kit for $29 USD (or $59 if you want it pre-assembled) plus shipping, while I try to find parts suppliers that can bring the cost down. Some parts in the kit may be partially assembled.
Note:
1. The coolant temperature sensor of different vehicles may require different connectors. After placing an order, you will receive an email to provide the model and year of your vehicle so that the right connector will be sent to you. Shipping confirmation will also be sent to the email associated with your PayPal account.
2. As stated in above Pros and Cons, there are risks involved in using a method of disabling VCM that is not validated by the vehicle OEM. You are acknowledged to be responsible for taking the decision to use this kit.
Why I wrote this blog
I was one of the vehicle owners affected by the aforementioned Honda service bulletin. The repair cost was covered by Honda, about which I have no complaint. Although the problem of my car has been fixed, the experience prompted me to do some research on the subject and make an effort to address the discovered gap in DIY needs. The results are presented here to share with the community.In my garage, there are three Honda automobiles: a sedan, an SUV and a van. Generally speaking, I respect Honda as a company. My respect comes from an appreciation of the reliability of the vehicles I own and use on a daily basis, as well as from case studies of Honda's management practices as published by Prof. Henry Mintzberg and other scholars and research consultants (e.g., https://youtu.be/CV_OEZ49sSA).
I feel that the insufficiency or 'flaw' related to VCM was not necessarily due to negligence and perhaps could have only been discovered after a large number of road applications over a few years. This shows that there is always room for engineering improvement through the actual use of a technology at the population scale. I hope innovations around VCM will quickly mature, so that end-users do not have to hack for less-than-perfect ways around it.
Hope you find this post informative and/or useful in some way.
Have a good day!
Dave L. B. Eng, PhD
Montreal, Canada
