Re: Conditions for cylinder deactivation?
(Score: 1, Normal)
Fishbulb wrote: Can a current owner give into any detail as to how the cylinder deactivation works?
Will it actually get down to 3 cyl holding a steady speed at 70mph, for example?
I'd like to get an idea of mileage at different speed ranges.
I think the mechanics of the actuation are actually simple, and yes, I see no problem with it using 3 cylinders at 70. At a steady state on flat roads, or downhill, you don't need a lot of HP to keep the vehicle moving.
I have been driving a 2013 RDX for the past week and I have to say the cylinder cut is the most seamless system i've experienced from Honda. All the other models I've driven (Odysseys, Pilot, Accord, Crosstour), I can sense the switchover even though it's very very subtle.
In the case of our '06 Odyssey, you are able to achieve 3-cyl operation up to about 82mph. Obviously that requires virtually no load on the engine so you need to be traveling on a dead level or slightly downhill grade with no headwinds or anything.
The RDX uses VCM-II so it has 3-, 4-, and 6-cylinder operation modes and as I recall the threshold where VCM ceases to operate is a higher speed on VCM-II. I believe there's a video I posted here on the site back when the '08 Accord's first came out where I tested it on the dyno. As I recall there may not have even been an upper threshold.
here is the boilerplate from the RDX press kit:
VARIABLE CYLINDER MANAGEMENTTM (VCM®) WITH iVTEC® In a first-ever application for an Acura engine, Variable Cylinder ManagementTM (VCM®) is applied to the 2013 RDX 3.5L V-6 engine to help improve the fuel efficiency. Known as VCM-II, it is the latest version of the system that allows the engine to run in one of three operating parameters— all six cylinders, four cylinders or three cylinders. The original version of VCM® (used on earlier Honda V-6 engines) only allowed for six- or three-cylinder operation.
With the VCM® system, during cold start-up or whenever high power is required (such as during acceleration) all six cylinders function as normal. However, during moderate throttle applications, the VCM® system allows the V-6 engine to operate on four cylinders to save fuel. During light throttle applications, VCM® switches the engine to three cylinder operation to maximize fuel economy. During VCM® activation, cylinders three and four are deactivated when running in four-cylinder mode. When in three- cylinder mode, cylinders one, two and three are deactivated.
Working in concert with the Intelligent Variable Valve Timing and Lift Electronic Control (iVTEC®) system, the Powertrain Control Module (PCM) electronically triggers the opening/closing of spool valves (integrated within the cylinder heads) that regulate valve lift. Based on commands from the PCM, valve lift occurs when the spool valves direct oil pressure to the rocker arms for specific cylinders. During Variable Cylinder ManagementTM activation, the spool valves reroute the oil which results in no valve opening for a particular cylinder.
With the VCM® system, for the cylinders not being used, both the intake and exhaust valves remain closed. In addition, the fuel injectors for the inactive cylinders are not fired during VCM® operation. However, during engine operation the spark plugs continue to fire for the inactive cylinders to minimize plug temperature loss as well as to prevent fouling that could occur as a result of incomplete combustion during cylinder re- activation.
During operation, VCM® monitors a wide variety of engine parameters including vehicle speed, engine speed (rpm), throttle position, engine load, transmission gear and other factors to determine the proper amount of cylinder activation required. To ensure smooth engine operation during the transition between cylinder activation/deactivation, VCM® adjusts items such as ignition timing, throttle position as well as determines if torque converter lock-up is required. As a result, the transition between six-, four-, or three- cylinder operation is virtually unnoticeable to the driver.