2009 Honda Pilot: Chassis
4/15/2008 6:04:00 AM
As a crossover SUV that mixes car sensibilities with the truck capabilities, the Pilot is designed to deliver a confident, secure and fun driving experience with outstanding isolation of undesirable noise, vibration and harshness (NVH) for exceptional comfort in all driving conditions. The fully-independent chassis design also provides the foundation for the Pilot's capabilities as a people and cargo hauler, as well as an off-road vehicle.
The Pilot provides an exceptionally-wide wheel track of 67.7 inches front and 67.5 inches rear for high levels of handling stability and interior space. Chassis components were designed to provide for well-controlled body motions with ride and handling characteristics that are balanced and secure. The use of fully isolated front and rear suspension subframes enhances the Pilot's outstanding NVH controls to provide a ride that is quiet and secure.
- MacPherson strut front suspension
- Multi-link rear suspension with trailing arms
- 4-wheel disc anti-lock braking system with electronic brake distribution and brake assist
- Vehicle Stability Assist (VSA) with Traction Control
- All-season P245/65R17 tires
- 21.0 gallon fuel tank capacity (+0.6 gallons)
- Larger diameter disc brakes (13.0 inches front, 13.1 inches rear)
Key Chassis Measurements
|2009 Pilot||2008 Pilot||Change from 2008|
|Track (Front/Rear, in.)||67.7 / 67.5||66.3 / 66.5||+1.4 / +1.0|
|Stabilizer Bar (Front / Rear, mm)||23.0 / 26.5 x 3.5t||23.0 (24.0 2WD) / 20.0||0.0 (+1.0 2WD) / +6.5|
|Brake Diameter (front / rear in.)||13.0 / 13.1||11.8 / 12.3||+1.2 / 0.8|
|Front Caliper Pistons||2||1||+1|
|Fuel Tank Capacity||21.0||20.4||+0.6|
- Enhanced suspension geometry
- Hydraulic lower suspension arm bushings
- Hill Start Assist
- Front brakes have 2-piston calipers (first application on a Honda)
Redesigned for 2009, the MacPherson strut front suspension with an aluminum lower control arm (new) provides a generous 7.3 inches of wheel travel (4.3-inches in compression, 3.0-inches in rebound). Separate load paths to the unit body are provided for the coil spring and the shock absorber to reduce road noise. A solid 23mm (0.9-inch) stabilizer bar is linked directly to the strut via ball-joint connections to reduce body roll during cornering maneuvers, a critical factor in minimizing the "head toss" tendency that is associated with many taller vehicles and SUVs. A new hydraulic bushing, often referred to as a hydrobushing, replaces one of the conventional rubber bushings on each of the geometrically-optimized lower control arms. The hydrobushing uses fluid to damp vibrations for improved resistance to shimmy and brake judder. Additionally, the L-shaped lower arm allows a very tight steering angle resulting in good low-speed maneuverability.
A welded-steel subframe secured to the unit body's longitudinal rails supports the Pilot's engine, transaxle, transfer case, steering gear and front suspension. The front of the subframe assembly is constructed of tubular steel for maximum stiffness with minimal weight penalties and uses four tuned rubber mounts to isolate the subframe from the main body structure. A stiffener located under each subframe attachment fastener helps stabilize the assembly, thereby sharpening handling and braking performance. A stiffener plate bolted across the subframe under the transfer case (if 4WD) greatly increases the assembly's rigidity. The subframe houses two Active Control Engine Mounts (ACM) that counteract the inherent vibration created by the Variable Cylinder Management (VCM) system, plus one lightweight urethane transmission mounts. (See the Powertrain section for more details on ACM). The mounts are strategically positioned to counteract noise and vibration while reducing the transmission of engine noise and vibration to the passenger compartment.
The Pilot's rear suspension is a compact, multi-link trailing arm layout for excellent ride and handling, minimum weight and optimum packaging. Wheel travel is a generous 4.9 inches in compression and 3.3-inches in rebound. The three links that position each rear wheel laterally run between the knuckle assembly and the subframe. A trailing arm also runs from the unit body to each rear knuckle. Coil springs seat on the lowermost lateral link and anchor against the unit body directly behind each axle shaft. Shock absorbers positioned ahead of the drive shafts run from a low point on each knuckle to a secure attachment point on the unit body. Steering knuckles are an "in-wheel" design to optimize suspension geometry and packaging efficiency. Bushing compliance provides a modest toe-in effect in response to substantial cornering and braking loads to enhance overall stability.
For 2009, the rear knuckles are made from aluminum and are 54 percent lighter compared to the previous steel units, helping to reduce unsprung weight for improved response. Optimized trailing-arm mounting points have been moved up higher to increase mechanical compliance for ride and comfort improvements. Coil springs, dampers and an anti-roll bar are tuned for the best combination of ride and handling. Rear subframe mounts and lateral control link bushing rates were adjusted to create a discrete level of lateral force steer at the rear axle. Since the Variable Torque Management® 4-wheel drive system constantly varies drive torque at the rear axle, the longitudinal and lateral force steer properties were carefully developed for optimum response, stability and consistency.
The rear subframe, which supports most of the rear suspension and the rear axle drive unit, is made of high-strength steel for high stiffness and minimal weight. The shape of the rear subframe is equally important - it must accommodate the drivetrain components for the available VTM-4 four-wheel drive system and the multi-link rear suspension, and still allow for the versatility of the third-row seat and flat cargo floor. For excellent ride and handling characteristics, the subframe attaches to the unit body at four widely spaced, rubber-isolated, mounting points. Rear-suspension components, especially the springs and shock absorbers, are as compact as possible to facilitate a wide, flat, load floor and to leave room for both a spare tire and a full-size fuel tank. The rear axle drive unit is mounted to the subframe by means of rubber isolators to block road and powertrain noise and vibration from the passenger compartment. .
Steering and Turning Diameter
The Pilot's rack-and-pinion steering system is tuned for quick, linear, car-like response and sensitive feel - and the torque-sensing power steering assist is high for parking maneuvers and low at highway speeds. For towing, standard equipment includes a heavy-duty power steering fluid cooler. The system uses heat-resistant rubber mount bushings, high-pressure die cast aluminum gear housings, a low friction material rack guide for good on-center feel and a damper valve to reduce steering wheel vibration. The Pilot features a tight turning diameter of 38.6 feet for excellent low-speed maneuverability.
Wheels and Tires
A 65-series tire was selected to provide optimum comfort for all passengers. Tires are P245/65/R17 105T radials mounted on 17 x 7.5-inch wheels. The Pilot LX is equipped with styled steel wheels, while Pilot EX, EX-L and Touring models feature cast alloy wheels with a bright machined look. The Pilot Touring has an exclusive wheel design for a more upscale appearance. Seventeen and 18-inch chrome finish alloy wheels are available as a dealer-installed accessory on all models.
The compact spare is carried under the rear load floor and can be lowered by turning a hidden hex-head bolt with the provided lug-nut wrench. The hex-head bolt is located under a cover conveniently located in the rear hatch trim area. This arrangement guarantees the security of the spare and keeps it readily accessible without disturbing luggage or cargo carried onboard. Room is provided to stow a flat or a full-size spare in the compact spare's location.
Consistent with its use as a people and cargo hauler and as a towing platform, the 4-wheel disc brakes on the 2009 Pilot are the largest brake system ever featured on a production Honda vehicle. The brake system is engineered to provide high levels of braking capability. The ventilated front brake rotors are 13.0-inches in diameter with a thickness of 1.1-inches, while the solid rear rotors are 13.1-inch diameter units with a thickness of 0.43-inches. Dual-piston cast iron brake calipers are used in front and single-piston cast iron calipers are fit in back. A single stage vacuum booster consists of one 10.5-inch diameter booster chamber.
The Pilot features large capacity brake components. Consisting of four-wheel disc brakes and four-channel anti-lock brakes, the Pilot's brakes are tuned for stable and linear braking forces. For optimum performance with widely varying loads, Pilot has Electronic Brake Distribution system (EBD) technology. EBD monitors braking force and adjusts front-to-rear brake effort to achieve maximum braking performance and stability. At the rear, a select-low braking strategy is used to help maintain directional stability in slippery driving. In the event one rear wheel verges on lock-up, triggering a pressure modulation at that wheel, brake pressure is also diminished at the adjoining wheel to help preserve the rear axle's lateral stability. The parking brake is set by stepping on a pedal located on the left side of the driver's foot well, freeing space in the center console area. The release is located on the lower left side of the instrument panel.
Anti-Lock Braking System (ABS) with Electronic Brake Distribution (EBD) and Brake Assist
The Pilot's Anti-Lock Braking system (ABS) has four sensing and activating channels to detect a wheel on the verge of lock up. In the event this occurs, brake pressure is held and then reduced to permit that wheel to regain traction before full braking resumes. The front suspension geometry has a very small scrub radius to help maintain dynamic stability even when one front wheel is braking harder than the other because of uneven traction conditions. (See the safety section for more information.)
Vehicle Stability Assist with Traction Control
Vehicle Stability Assist™ (VSA®), also known as electronic stability control, is included as standard equipment. By continually monitoring the vehicle's operating parameters (such as road speed, throttle position, steering wheel position along with acceleration, braking and cornering loads), VSA anticipates the vehicle approaching oversteer or understeer. To help correct either of these situations, VSA first acts to transfer torque bias to the axle with the most traction. This preventative measure significantly reduces the number of brake and throttle interventions. The response is so quick that the instability may be corrected even before the driver knows it is occurring. Traction Control is integrated into the VSA, and it helps the vehicle accelerate smoothly on slippery surfaces. (See the safety section for more information.)
Honda took thorough measures to ensure that people with medium duty off-road needs would be satisfied with the Pilot. The vehicle meets design criteria, which was based on research at different off-road areas across the country.
This research was the foundation for specific minimum performance criteria for the new Pilot, including travel through standing water nearly 19-inches deep, off-road friendly approach and departure angles (27.8 degrees front and 24.5 degrees rear, respectively), rocks, off road and paved grades up to 60 degrees. Components located underneath the vehicle are tucked away to avoid damage in off-highway driving and the fuel tank's evaporative canister is protected by a high-strength steel guard.
The available VTM-4 system with computer-controlled traction capabilities helps the Pilot meet typical off-road challenges without the need for low-range gears. (See powertrain section for full description.) The system is designed for "decision free" operation meaning that the driver does not need to actively choose when to engage four-wheel-drive. The system is always active and ready to proportion rear wheel torque as needed. For stuck situations in mud or snow, a driver-selected 4WD "lock" mode locks the two rear wheels together at speeds up to 18mph. Consistent with typical SUVs, the front approach, break-over and rear departure angles enable the Pilot to meet the medium duty off road needs of its target buyers.
Hill Start Assist
New for 2009, Hill Start Assist helps to prevent the vehicle from rolling backwards when the driver switches from the brake pedal to the accelerator pedal while the vehicle is stopped on a hill. Hill Start Assist automatically activates when the road incline exceeds a 10 degree threshold and the vehicle is fully stopped in any forward or reverse gear. The system uses a longitudinal G-sensor along with a wheel speed sensor and steering angle sensor to control the hydraulic brake modulator. While activated, the brakes are released when the driver depresses the throttle to make the vehicle move.
Tire Pressure Monitoring System
An onboard Tire Pressure Monitoring System (TPMS) warns the driver if the air pressure decreases significantly in any tire. The system helps reduce the chance of damaging a tire or losing control of the vehicle due to low air pressure. This is important because a slow leak, such as one that might be caused by a nail or road debris, might not be easily detectable but could cause loss of grip and potentially a blowout.
TPMS uses a sensor mounted on each wheel that continually monitors tire pressure and sends a coded signal to the TPMS electronic control unit (ECU). The process begins with a signal initiator located inboard of each tire on the chassis. The initiator sends a unique signal for each TPMS sensor. Then the TPMS sensor sends tire pressure data to the TPMS ECU, which compares the values for each tire's pressure against an acceptable range of pressures. When a tire's pressure drops significantly below the proper level, an alert will appear on the information display screen.
On the Pilot Touring model, the system can display the air pressure in all four tires simultaneously via the Multi-Information Display (MID). At the driver's preference, the MID can continually show the air pressure in all four tires. Regardless of whether the driver chooses to monitor the pressures, a warning will still occur if a tire drops significantly below specification.
The 21.0gallon, saddle-shaped fuel tank is molded of high-density polyethylene for low weight, freedom from corrosion and impact resistance. It is positioned ahead of the rear wheels and over the propeller shaft to help guard against collision damage. The shape of the tank is designed to diminish the likelihood of sloshing-fuel noise. The polyethylene filler pipe and fuel lines are lightweight, and resistant to corrosion and fuel vapor losses. A high-efficiency fuel pump is housed inside the fuel tank. The fuel-filter is a lifetime design that never needs replacement.