TIRE PRESSURE MONITORING SYSTEM
New for all 2004 MDX models is the application of a direct Tire Pressure Monitoring System (TPMS). Using a series of four sensors and four initiators (one for each tire) and a receiver to capture and relay information, the system alerts the driver when it detects that tire pressure in one or more tires drops significantly below the recommended pressure.
The sensor transmitter is located inside the wheel. Should the tires be rotated around the vehicle due to normal maintenance or be replaced entirely, the new tires are "auto-located" by the system. If the system detects that tire pressure is significantly low (32 psi is recommended), a low tire pressure indicator located in the meter containing the fuel level and temperature gauge will come on while a schematic of the vehicle located in the center meter housing the speedometer will indicate which tires are low.
BRAKING SYSTEM
MDX is equipped with state-of-the-art, four-wheel disc brakes and a four-channel Braking System. The brake system hardware is tuned for quick response, low effort, and short pedal travel. For optimum performance with widely varying loads - including the possibility of towing - the MDX features an innovative Electronic Brake Distribution system (EBD). At the rear, a select-low braking strategy is used to preserve 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 preserve the rear axle's lateral stability.
Extra-large brake rotors and calipers provide the capacity necessary for short stopping distances and excellent fade resistance - even with a heavy load in tow - and the precise pedal feel expected of an Acura. The vented front rotors are 11.8-inches in diameter and 1.1-inches thick. Solid drum-in-disc rear rotors are 12.3-inches in diameter and 0.43-inch thick. The MDX features dual-piston calipers on the front wheels for even more secure stopping. A drum-type parking brake mechanism is positioned within the inner portion of the rear rotor. Parking brakes are both set and released by stepping on a pedal, freeing space in the console area. The compact tandem-type vacuum booster consists of two 9-inch diameter booster chambers.
ANTI-LOCK BRAKING SYSTEM (ABS)
MDX brake components are large in capacity to help handle heavy loads - both those carried on board and those towed behind. Front-to-rear brake effort proportioning is electronically regulated. The 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, then reduced, to permit that wheel to regain traction before full braking resumes. A select-low strategy controls the braking effort at both rear wheels as soon as one nears lock up to safeguard lateral adhesion and to help avoid any tendency to spin or fishtail during hard braking.
VEHICLE STABILITY ASSIST (VSA)
For enhanced control during acceleration, cornering, and sudden collision-avoidance maneuvers, the MDX is equipped with a standard 4-channel Vehicle Stability Assist (VSA) system that works in conjunction with the VTM-4, drive-by-wire throttle and ABS systems. The VSA system enhances vehicle stability by applying brake force to each of the MDX's four disc brakes independently while also managing the throttle and ignition systems. An additional benefit is the limited-slip differential effect the system provides for the front wheels by applying braking force to a slipping wheel thereby redirecting driving force to the wheel with more traction.
Analyzing data that is constantly received from eight vehicle sensors monitoring speed, steering input and lateral G forces, the VSA system compares the driver's control inputs with the vehicle's actual response. If the actual response is outside a predicted response range - as can happen when cornering forces exceed the tires' performance capabilities - VSA automatically intervenes with an appropriate corrective action. In the case of oversteer, VSA applies braking to the outside front and rear wheels to counter the unintended yawing effect. If understeer is detected, VSA applies braking to the inside front and rear wheels and reduces engine power to help bring the car back onto the driver's intended course.
The VSA system in the MDX has been carefully calibrated to add handling stability and predictability without intruding on the process of spirited driving. Whenever the system is actively enhancing the vehicle's stability, an indicator light flashes on the instrument panel. In addition, VSA's stability enhancement and traction control can be turned off with a cockpit switch while still leaving the Anti-lock Braking System fully functional.
FUEL SYSTEM
The 19.2-gallon, saddle-shaped fuel tank is molded of high-density polyethylene for low weight, freedom from corrosion, and impact resistance. It's positioned immediately ahead of the rear wheels and over the propeller shaft to help guard against collision damage. Corners of the tank are rounded and the inside of the tank is baffled to diminish the likelihood of sloshing-fuel noise. The polyethylene filler pipe and fuel lines are light, not susceptible to corrosion, and resistant to 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.
MDX complies with all evaporative emissions, on-board diagnostics, and refueling vapor recovery requirements. The fuel vapor canister and filter are rubber mounted for noise isolation and protected against rock and debris damage by a deflection shield.
TOWING
The ability to haul pop-up campers, medium-sized boats, and recreational vehicle trailers is high on the priority list for many SUV owners. To understand this aspect of the MDX's makeup, MDX engineers polled focus groups and studied survey results that tapped 200,000 households. Their findings offered the insights needed to properly outfit the MDX to surpass the towing expectations of most customers. Engineers learned that roughly one third of the six-cylinder-powered-SUV owners expect to tow something at one time or another. In addition, 18-percent tow more than four times per year. Approximately 10 percent of the miles accumulated on six-cylinder SUVs are with a trailer in tow.
Another notable discovery was that many customers aren't particularly knowledgeable about towing technicalities. Terms like "gross axle weight" may be germane to the engineering process but such language can leave average customers in a state of bewilderment. This realization convinced engineers that customers' interests are best served by load ratings that are both realistic and easy to comprehend. Ultimately, the engineers concluded that a casual or weekend towing capability was most appropriate for MDX. Customer feedback helped set the towing limit at 4500 pounds for boats and 3500 pounds for other types of trailers. A heavier load is acceptable with boats because their pointed bow shapes impose less aerodynamic drag on the towing vehicle than a slab-faced, square-cornered trailer.
Industry practice is to boast a high maximum tow rating, even though some sacrifice of passengers and cargo may be necessary to suitably accommodate such a trailer load - in some cases limiting the vehicle to one passenger to accommodate the maximum specified towing capacity. The Acura MDX's 3500/4500-pound rating is calculated to include up to four passengers and their cargo.
To help ensure that customers will be able to move a maximum-rated load up a grade from rest (such as pulling a loaded boat trailer up a launch ramp), engineers sought out the most challenging entry roads and launch ramps in the country. Through testing, they verified that MDX proficiently handles the 17-degree (31-percent) grades on mountain roads approaching Lake Cumberland in southern Kentucky and the strenuous combination of 15-degree (27-percent) grades and 5280-foot elevation at Lake Tahoe. At sea level, MDX can move a 4500-pound boat and four passengers up an 18-degree (32-percent) slope. A note in the MDX owner's manual suggests reducing gross combined weight two-percent for every 1000 feet of elevation.
In support of safe towing, MDX's tow hitch and other hardware needed for the job are factory engineered for dealer installation. The dealer-installed trailer hitch is a Class III receiver-type design that bolts on with no drilling, cutting, or bumper-cover modifications. An external transmission cooler and a separate power-steering fluid cooler is also included along with a harness to provide electrical power to trailer lights plugs into a connector provided at the rear of the vehicle.