2009 Honda Pilot: Powertrain
4/15/2008 6:02:00 AM
The Honda Pilot is designed to provide a comfortable, confident and fun driving experience with plenty of power to match its capabilities as an eight-passenger SUV with off-road capabilities and up to 4,500-pound towing capabilities (4WD). For 2009, Honda engineers prioritized fuel efficiency for the all-new Pilot and applied the latest generation of the company's Variable Cylinder Management technology to all models. Low emissions, a broad torque curve and low maintenance were also key development targets.
The Pilot is powered by an advanced 3.5-liter 24-valve i-VTEC, V-6 engine mated to an electronically-controlled 5-speed automatic transmission. Peak engine output is 250 horsepower at 5700 rpm and 253 lb-ft. of torque at 4800 rpm. The "intelligent" Variable Valve Timing and Lift Electronic Control (i-VTEC®) valvetrain technology with Variable Cylinder Management (VCM) allows the V-6 engine to operate in six-cylinder mode for power and four- and three-cylinder modes for efficiency. The Pilot meets California's stringent Ultra Low Emissions Vehicle (ULEV-2) exhaust emissions standards. A fully-automatic Variable Torque Management 4-wheel drive system (VTM-4) is available on all models and delivers seamless "decision free" application of four-wheel drive when needed.
- 3.5-liter i-VTEC engine
- 250 horsepower at 5700 rpm, 253 lb-ft. of torque at 4800 rpm
- Variable Cylinder Management
- Honda-estimated EPA city/highway fuel economy* of 17/23 (2WD) and 16/22 (4WD)
- ULEV-2 emissions rating (CARB)
- VTM-4 four-wheel drive (available)
- 100K +/- Miles No Scheduled Tune-Ups**
- Regular unleaded gasoline
*Based on 2009 EPA mileage estimates, reflecting new EPA fuel economy methods beginning with 2008 models. Use for comparison purposes only. Do not compare to models before 2008. Actual mileage will vary.
**Does not apply to fluid and filter changes. Exact mileage is determined by actual driving conditions. Please see owner's manual for more details.
Powertrain Specifications: 2009 Pilot vs. 2008 Pilot
|2009 Pilot||2008 Pilot||Change from 2008|
|Engine Size (L)||3.5||3.5||Same|
|Engine Output (HP)||250 @ 5700||244 @ 5750||+6 @ -50 rpm|
|Engine Output (lb-ft.)||253 @ 4800||240 @ 4500||+13 @ +300 rpm|
|Valvetrain (4WD)||i-VTEC w/ VCM||VTEC||Added VCM|
|Valvetrain (2WD)||i-VTEC w/VCM||i-VTEC w/VCM (6/3)||Added 4cyl mode|
|Fuel Economy* (mpg city/hwy)||17/23 (2WD)16/22 (4WD)||16/22 (2WD)15/20 (4WD)||+1/+1+1/+2|
|100K +/- Miles No Scheduled Tune-Ups||Standard||Standard||Same|
|Tow Rating 2WD/4WD||3500 / 4500||3500 / 3500**||Same / +1,000**|
* Based on 2009 EPA mileage estimates, reflecting new EPA fuel economy methods beginning with 2008 models. Use for comparison purposes only. Do not compare to models before 2008. Actual mileage will vary.
** Applies to box trailer tow rating or boat towing. On 2003-2008 4WD models, a tow rating of 4,500 pounds for boats only was possible when properly equipped.
Key New Features
- Variable Cylinder Management with switching between 6-, 4- and 3-cylinder modes
- Cold air intake
- Magnesium intake manifold (4WD only)
- Active Control Engine Mount (ACM) and Active Noise Control (ANC) on 4WD models
The Pilot's engine is an advanced 3.5-liter, SOHC, 24-valve, 60-degree, V-6, aluminum-block-and-head design that is compact, lightweight and powerful. The i-VTEC valvetrain and high efficiency intake manifold optimize cylinder-filling efficiency across a wide range of engine speeds. Low-restriction intake and exhaust systems, a 10.5:1 compression ratio and roller-type rocker arms further aid efficiency and power delivery across a broad rpm range.
The Pilot has a die-cast lightweight aluminum alloy block with cast-in-place iron cylinder liners. Made with a centrifugal spin casting process, the thin-wall liners are high in strength and low in porosity. The block incorporates a deep-skirt design with four bolts per bearing cap for rigid crankshaft support and minimized noise and vibration. Both the block and caps are heat treated for greater strength.
Crankshaft, Connecting Rods and Pistons
A forged steel crankshaft is used for maximum strength, rigidity and durability with minimum weight. Instead of heavier nuts and bolts, connecting rod caps are secured in place with smaller, high-tensile-strength fasteners that screw directly into the connecting rod. Short-skirt, cast-aluminum, flat-top pistons are notched for valve clearance and fitted with full-floating piston pins.
Like other Honda V-6 powerplants, the Pilot V-6 cylinder heads are a SOHC design, with the cams driven by the crankshaft via an automatically tensioned toothed belt. Made of low-pressure cast, low-porosity aluminum, each cylinder head incorporates an integrated exhaust manifold to reduce parts count, improve flow and optimize the location of the close-coupled catalyst on each cylinder bank.
The cylinder head employs four-valve combustion chambers, the best approach to optimum performance with excellent fuel efficiency and very low emissions. Valves are clustered near the center of the bore to minimize combustion chamber volume and to provide ample squish area. A 10.5:1 compression ratio helps maximize thermal efficiency, power output and fuel efficiency. One centrally located camshaft per cylinder bank is driven by a fiberglass-reinforced toothed belt. Head gaskets are made of high-strength materials to contain combustion pressures.
Dual-Stage Intake Manifold
The Pilot uses a dual-stage intake manifold that is designed to deliver excellent airflow to the cylinders across the full range of engine operating speeds. On four-wheel-drive models, the two-piece manifold is extremely light due to its cast magnesium design. The intake manifold on two-wheel-drive Pilot models is constructed of aluminum using an identical design.
The induction system significantly boosts torque across the engine's full operating range. Internal passages and two butterfly valves within the intake manifold are operated by the powertrain control module to provide two distinct modes of operation by changing plenum volume and intake airflow routing.
At lower rpm these valves are closed to reduce the volume of the plenum and effectively increase the length of inlet passages for maximum resonance effect and to amplify pressure waves within each half of the intake manifold at lower rpm ranges. The amplified pressure waves significantly increase cylinder filling and torque production throughout the lower part of the engine's rpm band.
As the benefits of the resonance effect lessen with rising engine speed, the butterfly valves open at 4200 rpm to interconnect the two halves of the plenum, increasing its overall volume. An electric motor, commanded by the powertrain control module, controls the butterfly valves. The inertia of the mass of air rushing down each intake passage helps draw in more charge than each cylinder would normally ingest. The inertia effect greatly enhances cylinder filling and the torque produced by the engine at higher rpm.
i-VTEC with 3-stage Variable Cylinder Management™ (VCM™)
To help improve the fuel efficiency of the V-6 engine, the latest generation of Honda's VCM is used (similar to the Accord V-6). This is the first application of VCM on a Honda 4-wheel-drive model. (The previous generation of VCM used in the 2007 - 2008 Pilot switched between three- and six-cylinder operation and was used exclusively in two-wheel-drive models.) The Pilot's new VCM system can operate on three, four or all six cylinders, and is standard on all both two-wheel-drive and four-wheel-drive models.
During startup, acceleration or when climbing hills - any time high power output is required - the engine operates on all six cylinders. During moderate speed cruising and at low engine loads, the system operates just one bank of three cylinders. For moderate acceleration, higher-speed cruising and mild hills, the engine operates on four cylinders.
With three operating modes, the VCM system can finely tailor the working displacement of the engine to match the driving requirements from moment to moment. Since the system automatically closes both the intake and exhaust valves of the cylinders that are not used, pumping losses associated with intake and exhaust are eliminated and fuel economy increases. The VCM system combines maximum performance and maximum fuel economy - two characteristics that do not typically coexist in conventional engines.
VCM deactivates specific cylinders by using the VTEC (Variable Valve-Timing and Lift Electronic Control) system to close the intake and exhaust valves while simultaneously the Powertrain Control Module cuts fuel to those cylinders. When operating on three cylinders, the rear cylinder bank is shut down. When running on four cylinders, the left and center cylinders of the front bank operate, and the right and center cylinders of the rear bank operate.
The spark plugs continue to fire in inactive cylinders to minimize plug temperature loss and prevent fouling induced from incomplete combustion during cylinder re-activation.
The system is electronically controlled, and uses special integrated spool valves that do double duty as rocker-shaft holders in the cylinder heads. Based on commands from the system's electronic control unit, the spool valves selectively direct oil pressure to the rocker arms for specific cylinders. This oil pressure in turn drives synchronizing pistons that connect and disconnect the rocker arms.
The VCM system monitors throttle position, vehicle speed, engine speed, automatic-transmission gear selection and other factors to determine the correct cylinder activation scheme for the operating conditions. In addition, the system determines whether engine oil pressure is suitable for VCM switching and whether catalytic-converter temperature will remain in the proper range. To smooth the transition between activating or deactivating cylinders, the system adjusts ignition timing, drive-by-wire throttle position and turns the torque converter lock-up on and off. As a result, the transition between three-, four-, and six-cylinder operation is unnoticeable to the driver.
Active Control Engine Mount (ACM) and Active Noise Control (ANC)
The ACM system is used to minimize the effects of engine vibration as the VCM system switches cylinders on and off. Sensors alert the Electronic Control Unit (ECU) to direct ACM actuators positioned at the front and rear of the engine to move to cancel engine vibration. Inside the interior of the Pilot, the ANC system works in cooperation with the ACM system to further reduce any sound relating to the function of the VCM system. (Please see the Interior tab for more information.)
Drive-By-Wire (DBW) Throttle System™
The drive-by-wire throttle system uses smart electronics instead of a conventional cable system to connect the throttle pedal to the throttle butterfly in the intake tract. Besides allowing engineers to program the relationship between throttle pedal movement and engine response, the system optimizes engine response to suit driving conditions. The system monitors throttle pedal position, throttle butterfly position, road speed, engine speed and engine vacuum. This information is used to define the throttle control sensitivity.
High-Mounted Fresh Air Intake
The Pilot has a high-mounted fresh air intake system that reduces air intake temperatures to help improve low-end torque while protecting against water intrusion into the engine. To supplement good off-road and towing capabilities, the fresh air intake is mounted just above the front bulkhead (underneath the front edge of the hood.)
Powertrain Control Unit
A 32-bit, 96MHz powertrain control unit (PCU) within the powertrain control module calculates injection timing and duration after assessing an array of sensor signals: crankshaft and camshaft position, throttle position, coolant temperature, intake manifold pressure and temperature, atmospheric pressure and exhaust-gas oxygen content. The PCU controls the Programmed Fuel Injection (PGM-FI), i-VTEC valvetrain, and dual-stage intake manifold and also communicates with processors that regulate the five-speed automatic transmission and the available Variable Torque Management 4-wheel-drive system.
Programmed Fuel Injection (PGM-FI)
The PGM-FI system continually adjusts the fuel delivery to yield the best combination of power, low fuel consumption and low emissions. Multiple sensors constantly monitor critical operating parameters, such as throttle position, intake air temperature, coolant temperature, ambient air pressure, intake airflow volume, intake manifold pressure, exhaust air-fuel ratio and the position of the crankshaft and cams.
The fuel injector nozzles produce ultra-small fuel droplets, which improves atomization and flame propagation inside the combustion chambers. The better atomization enhances combustion and reduces emissions. Fuel is cut to all cylinders during deceleration.
Direct Ignition and Detonation/Knock Control
The powertrain control module (PCM) monitors engine functions to determine the best spark timing. An engine-block mounted acoustic detonation/knock sensor "listens" to the engine, and based on this input, the PCM retards the ignition timing to prevent potentially damaging detonation. The Pilot has a coil unit for each cylinder that is positioned above each spark plug's access bore.
Regular Unleaded Fuel Operation
To keep operating costs at a minimum, all Pilots are designed to use relatively less-expensive regular unleaded fuel, thanks to compact 4-valve combustion chambers and precise fuel injection and spark control.
High-Flow Exhaust System with Dual Outlets
A low-restriction, high-output, exhaust system is crucial to efficient power and torque production. A completely new exhaust system on the Pilot accommodates its increased power output. Tubing diameter has been increased and new dual silencers are used. High-chromium stainless steel is used throughout the exhaust system for excellent durability.
High-Efficiency Catalytic Converters
Key contributors to the engine's excellent emissions performance are its high-efficiency catalytic converters. The engine has its exhaust manifolds cast directly into the aluminum alloy cylinder heads to reduce weight and position each primary catalytic converter as close as possible to the combustion chambers. A high-efficiency close-coupled converter mounts directly to the exhaust port of each cylinder head for extremely rapid converter activation after engine startup. A second converter is positioned shortly downstream, beneath the passenger compartment floor. Both converters use a new thin-wall design that increases internal reaction area and improves efficiency.
Maintenance Minder System and Tune-Up Intervals
The Pilot's standard Maintenance Minder system calculates the engine's tune-up schedule based on driving conditions (tracked by the ECU). When determining proper maintenance intervals, the system minimizes owner guesswork about whether the vehicle is being operated in standard or severe conditions. The Pilot's Maintenance Minder information appears in the odometer display, and indicates when to change the oil, oil filter (every other oil change), air cleaner, transmission fluid, spark plugs and coolant, as well as when to rotate the tires. A tune-up is not required until about 100,000 miles. (100K+/- Miles No Scheduled Tune-ups may vary with driving conditions. Does not apply to fluid and filter changes. Exact mileage is determined by actual driving conditions. The owner's manual contains full details). Long-life fluids have been applied for reduced maintenance costs and environmental impact (fluid disposal). As a result, engine coolant changes are needed about every 10 years or approximately 100,000 miles, and engine oil changes are required every year or around 7,500 miles under normal driving conditions. The maintenance minder system calculates the exact miles between service intervals.
5-speed Automatic Transmission with Grade Logic Control
The Pilot's 5-speed automatic transmission has several features engineered specifically to match its performance requirements, including extra-wide gear ratios for good low-end response and comfortable highway cruising; a computer-controlled lock-up torque converter; a rigid alloy case; and a 4-shaft design. Honda Grade Logic Control technology is designed to hold the vehicle in a lower gear when climbing or descending a steep grade for improved performance.
An advanced 5-speed automatic transmission with extra-wide gear ratios was adopted to meet the Pilot's performance and efficiency targets. A computer-controlled lock-up torque converter is provided to maximize fuel efficiency. Torque-converter lock-up and shift timing are both managed by a CPU working in cooperation with the engine's central processing unit. Gear and clutch materials, and the transaxle case, are all engineered to support towing, off-road driving and 4-wheel-drive use. One notable feature of this unit's design is extra-wide gear ratios. The difference in torque multiplication between first and fifth gears is nearly 5:1 (4.932) to balance low-speed pulling power with good fuel economy and the ability to cruise quietly at highway speeds.
An over-running clutch is provided for first gear to smooth upshift quality. An extra-capacity transmission fluid cooler is standard equipment to help maintain acceptable lubricant temperatures during heavy-load conditions.
A direct-control strategy is used to provide real-time pressure management of the transmission's clutches. Various control strategies are utilized allow for smooth coordination of engine and transmission operations. For example, the driveline shock that often accompanies gear changes is minimized by momentarily reducing engine torque during shifting.
Pilot Gear Ratio Comparison
|2009 Pilot||2008 Pilot|
Heavy-Duty Automatic Transmission Cooler and Heavy-Duty Power Steering Cooler
A heavy-duty automatic transmission fluid (ATF) cooler is standard equipment. An ATF cooler contributes to long-term reliability by keeping damaging heat out of the transmission. Often an option, most vehicles used for towing require a transmission cooler in order to properly utilize the maximum advertised towing capacity. The Pilot's standard ATF cooler is mounted in front of the engine's radiator. Also related to towing and heavy payloads, the Pilot features a heavy-duty power steering cooler to help dissipate power steering fluid heat build up that can occur when hauling heavy loads or towing.
Honda Grade Logic Control
For driving on hilly terrain, the Pilot's transmission is equipped with Honda Grade Logic Control that monitors throttle position, vehicle speed and acceleration to minimize gear hunting. A lower gear is held to provide better climbing ability on uphill grades and more engine braking on steeper downhill grades.
Variable Torque Management 4-wheel-drive (VTM-4)
Ensuring a high level of all-weather stability, traction and control is the Pilot's available VTM-4 (Variable Torque Management 4-Wheel Drive) system. Unlike conventional on-demand systems that work only when the wheels are slipping, VTM-4 proactively delivers torque to all four wheels during acceleration for excellent dry-road vehicle dynamics as well as outstanding control in wet, icy and snow conditions. A unique "lock" feature is provided to maximize traction for extremely low traction or "stuck" conditions. A compact transfer case is bolted directly to Pilot's front-mounted transaxle. A two-piece propeller shaft delivers torque from the transfer case to a rear axle drive unit. Two computer-controlled, electromagnetically-powered clutches engage as needed to provide torque to the rear wheels.
The Pilot's innovative VTM-4 four-wheel drive system was designed to deliver outstanding traction, stability and control in all weather conditions as well as good medium-duty off-road performance. It was also designed to minimize the weight and packaging penalties associated with conventional four-wheel drive systems.
The VTM-4 system is unique in its operation. Unlike some approaches that use an engagement strategy triggered by wheel slippage, VTM-4 anticipates the need for all-wheel drive and engages the rear wheels whenever the vehicle is accelerating. Additional torque is applied to the rear wheels when wheel slip is detected, up to an approximate maximum of 70 percent depending on conditions.
Another unique feature of the system is the VTM-4 Lock function. Activated by a button on the instrument panel, the VTM-4 Lock mode delivers maximum torque transfer to the rear wheels to aid extraction from extremely low traction or "stuck" conditions. The feature works only when the vehicle is in first, second or reverse gears, and automatically disengages at speeds above 18 miles per hour.
When cruising under normal conditions, the Pilot provides front-wheel drive power for improved efficiency. Torque is proactively distributed to the rear wheels when the vehicle is accelerating or wheel slip is detected. The level of torque delivery, front to rear, is determined by the amount of acceleration (rate of change in velocity) and wheel slip (difference in rotational speed) and is controlled by a dedicated CPU with sensors in the braking, engine and transmission systems.
To avoid the weight and bulk of a conventional transfer case, VTM-4's torque transfer unit is a compact cast-aluminum housing bolted directly to the transaxle. The transfer case is a single-speed, permanently engaged device without a low-range, reducing weight and space penalties while maintaining excellent on- and off-road capabilities.
Attached to the front wheel differential's ring gear is a helical gear that provides input torque to the transfer unit. A short horizontal shaft and a hypoid gear set within the case turn the drive ninety degrees, move it to the vehicle center line and lower its axis by approximately 3.75-inches.
VTM-4 Engagement Modes
There are three distinct modes of VTM-4 engagement:
(1)The first mode, called Acceleration Torque Control (ATC), works whenever the vehicle's throttle is depressed, even on dry pavement - a feature unique to the VTM-4 system. Sensors in the engine and transmission monitor vehicle speed and acceleration. The amount of torque applied, as directed by the system's ECU, is determined according to vehicle speed, the amount of acceleration and transmission status (gear setting). This benefits not only the Pilot's ability to gain traction from a standing start, before wheel slip occurs, but also its overall dynamic stability on both dry and low traction roads. Reducing the propulsive force carried by the front tires under acceleration reduced torque steer and cornering adhesion. Rear wheel torque rises smoothly from zero to a preset maximum in proportion to vehicle acceleration (both forward and reverse). During constant-speed driving, all power is driven to the front wheels for improved fuel efficiency.
(2) The second engagement mode occurs when wheel slip is detected. Differences in rotational speed between front and rear wheels are measured by sensors in the ABS system and monitored by the ECU. In response, the ECU commands an increase in torque delivery to the rear wheels. Torque application is adjusted according to the amount and the rate of change in wheel slip. As slip increases, more power is delivered to the rear wheels for improved traction.
(3) The third mode of engagement is VTM-4 Lock. Lock mode occurs when the driver shifts into first, second or reverse gears and depresses the VTM-Lock button on the instrument panel. When lock mode is selected at vehicle speeds below 18-mph, the system ECU commands a preset maximum amount of rear-drive torque to be delivered to the rear wheels for improved traction in very low-speed, low-traction, conditions. As control is regained and vehicle speed increases, the system gradually reduces rear axle torque until it is completely disengaged.
The maximum torque delivered to the rear wheels is sufficient to climb the steepest grade observed on any public road in America - 31-degrees (60 percent slope) - with a two-passenger load on board. The Pilot will also move from rest up a 28-degree (53 percent slope) dirt grade. On a split-friction grade (different amounts of traction at each wheel), VTM-4 automatically provides sufficient rear-wheel torque to help the vehicle climb something like a steep, low traction driveway.
The two-piece propeller shaft that carries torque from the transfer case to the rear-drive unit is made of high-strength steel tubing to permit a smaller diameter. Minimizing driveline dimensions improves both ground clearance and interior room. The cross yokes attached at each end by friction welding are forged steel for high strength and low weight. The center support bearing is rubber isolated to block the transmission of driveline noise from the interior of the vehicle. A low-friction plunger joint located near the center of the propeller shaft accommodates relative motion between front- and rear-mounted driveline components.
A tuned-mass damper inside the front portion of the propeller shaft cancels any bending tendency in response to powertrain vibrations. Equal-length, front-wheel half-shafts have a plunger joint at their inboard end and a ball-type universal joint at the wheel end. Rear half shafts are similar in design but use a double-offset joint at the inboard end and a ball joint at the outboard end. All universal joints are constant-velocity type.
Rear Axle Drive Unit
The Pilot's rear axle drive unit consists of a hypoid ring-and-pinion gear set supported by a cast-aluminum housing which switches torque from the propeller shaft's longitudinal orientation to the lateral orientation necessary to drive the rear wheels. A connection from the ring gear to each wheel's half-shaft is made by left- and right-side clutches. Each drive clutch consists of three elements: an electromagnetic coil, ball-cam device and set of 19 wet clutch plates which are similar in design to clutches used in an automatic transmission. Ten of the plates are splined (mechanically connected) to the ring gear while nine of the plates are splined to a half shaft.
When the VTM-4 system's electronic control unit (ECU) determines that torque should be distributed to the rear wheels, an electric current is sent to the two electromagnetic coils. The resulting magnetic field moves a rotating steel plate toward each fixed coil. Friction between that steel plate and an adjoining cam plate causes the cam plate to begin turning. As it does, three balls per clutch roll up curved ramps, creating an axial thrust against a clutch-engagement plate. This thrust force compresses the wet clutch plates, engaging the corresponding rear wheel.
Unlike mechanically actuated four-wheel drive systems, the VTM-4 system is infinitely variable. The amount of torque provided to the rear wheels is directly proportional to the electric current sent from the ECU and can be adjusted from zero to a preset maximum. This current constantly changes to deliver the optimum rear torque calculated by the ECU. An internal gear pump circulates VTM-4 fluid to cool and lubricate the clutches, bearings and gears within the rear drive unit. Use of high-strength, low-weight materials - such as die-cast aluminum for the housing - minimizes the bulk and weight of the hardware.