Acura RDX Purpose-Built For The Urban Environment (Where Most SUVS Tend To Tread)

Article From: 6/2/2006 Automotive Design & Production, , Editor-in-Chief from Gardner Business Media, Inc.

Yes, it has all-wheel drive. Yes, it is an SUV. But when Acura planners and engineers looked at demographic data and saw that in many major cities young professionals are moving back downtown, they decided to address that trend with a completely new vehicle.

IT’S NOT WHAT SOME THINK. Gary Evert makes an observation about the Acura RDX that some people within earshot cannot believe: “It is not based on the CR-V platform.” As Large project leader (a.k.a., chief engineer) of the RDX, he knows more than a little something about what it is based on or not. “It is a new platform.” In fact, there is nothing else that uses the platform. Yet. But there is that question about the Honda CR-V and the RDX . . .

Acura RDX
104.3 in.
180.7 in.
73.6 in.
65.2 in.
Honda CR-V
103.3 in.
181.0 in.
70.2 in.
66.2 in.

While one might say that it is an inch here, an inch there, it does, indeed, make all the difference, for the RDX, which they’re describing as an “Entry Premium SUV,” is an entirely different vehicle than the CR-V. Not only is this a matter of considerably more style in the overall design, but as regards the high degree of technological content. Make no mistake. This is an Acura, not a Honda.

WHY IT’S NOT A CROSSOVER. Or Is It? Generally, the nomenclature “crossover” is applied to an SUV that is based on a car platform. Like a car platform, the RDX has a unitized body (all steel); it is not a body planted on frame rails (say like a Saab 9-7X). Similarly, the Lexus RX 350 has a unitized body, and its platform is that of the ES 330 (and Camry and Avalon).

But here’s the rub: As it is an all-new platform, it is based on, well, nothing other than itself. So depending on what the meaning of the word “crossover” is . . .

“NEW URBANISM.” It’s a term that Greg Thomas, Advanced Product Planning, Honda R&D, uses in trying to place the RDX in the environment that it is designed for. He simply notes that “cars get destroyed in cities,” so they set about to design something that would be suitable for the return to the cities that demographic research indicates is occurring, particularly for the people encompassed by Gen Y. Thomas, who has been with the RDX program since it was a concept (when the concept vehicle was unveiled at the North American International Auto Show in January, 2005, it was the “RD-X”), says that SUVs are generally “too family focused,” and that sport sedans (say, the TSX) are not necessarily family focused, but then there is that problem of the urban environment being tough on things like suspensions and down-low sheet metal. Another aspect of the urban environment that needs to be taken into account in the design of the vehicle is size, as parking is a premium, which explains the comparatively compact nature of the RDX (check the numbers above and realize that the other Acura SUV, the MDX, has a length of 188.7 in., a width of 77 in., and a height of 68.7 in., so it is a more sizable package). As the demographic includes those who are going to be able to afford something that is in at least the entry-luxury market (they’re thinking that the primary purchaser will be a 30-year-old male who is an architect or art director, someone who is knocking down $100K/annum), there needs to be a presence that Evert calls “valet cache.” As pickup and maneuverability are essential, this vehicle has a 2.3-liter turbocharged engine and a new version of Honda’s “Super Handling All-Wheel-Drive” (SH-AWD) system.

A TURBOCHARGED VTEC? Not only is the platform all new, but this is a new engine, as well, with the RDX being the first (and so far only) application. (Honda has a turbo diesel in European applications and a small turbocharged gasoline engine—660 cc—in its ZEST minicar.) Nobu Takahashi, who is with the Engineering Research Dept. at Honda R&D’s Tochigi R&D center, is the chief engineer for the new engine. While the architecture of the die cast aluminum alloy block is similar to that of the TSX engine—both are DOHC 16-valve, in-line fours—there are a number of changes that Takahashi and her team made to the engine, including different bore sizes, new pistons, and new connecting rods, to say nothing of modifications for the turbocharger. While the 2.4-liter TSX engine provides 205 hp @ 7,000 rpm, the 2.3-liter RDX engine produces 240 hp @ 6,000 rpm. Significantly, the engine produces 260 lb-ft of torque @ 4,500 rpm (vs. 164 lb-ft @ 4,500 rpm for the TSX), which is so much torque that Evert points out the five-speed transmission used is of a size that would ordinarily be fitted to a six-cylinder engine, not a four.

While many turbochargers control the flow of air within the turbocharger, for the RDX, the variable-flow turbo design is one that controls the airflow before entering the turbocharger. Takahashi explains that one of the benefits of this design is that it puts the pivot for the flow control valve outside the stream of hot exhaust gas, thereby improving the reliability and durability of the valve.

Speaking of variability, the turbo works with the i-VTEC system, which combines variable valve timing and lift electronic control with variable timing control, the latter on the intake camshaft. According to Takahashi, this helps provide power and torque and fuel efficiency (estimated to be 19 city/24 highway) and low emissions (CARB LEV II ULEV; EPA Tier-2 Bin-5).

And before leaving the powertrain, it is worth noting that the SH-AWD system is modified from the one that was introduced in the 2005 Acura RL. Fundamentally, the SH-AWD system provides what Evert calls “optimal torque distribution”; as much as 70% of the torque can be sent to the rear wheels and of that amount, because there are independent left and right electromagnetic clutches, up to 100% can be sent to either of those wheels. One of the differences between the two SH-AWD systems is that the RDX has a fixed acceleration ratio of 1.7%, which means that the rear differential rotates 1.7% faster than the front; in the RL, there is a accelerator gear that allows a variable acceleration ratio of up to 5.7%. The elimination of that gear helps contribute to a comparative 35% weight reduction for the RDX system.

BUILDING BETTER BODIES. The RDX is built with various grades of steel that contribute to high torsional rigidity, as well as to a safer structure. Overall, 39% of the body is high-strength steel, says Evert. One interesting feature are polygonal-shaped 780 HSS frame members located both in the front and the rear of the vehicle. One of their functions is to distribute load forces in the event of a collision. For the front rails, the forces go upward and rearward. For the rear rails, that are “wave shaped,” as well as having the polygonal cross section, the forces go forward and outward in the case of a rear collision.

MADE IN AMERICA. The RDX is being manufactured in the Honda of America Manufacturing Marysville Auto Plant in Ohio, along with the Honda Accord and the Acura TL. According to Bill Easdale, manufacturing project leader for the RDX, the Accord and TL are built together; now there will be the production of the TL and the RDX. To be sure, there are notable differences between the sedan and the SUV from a volumetric standpoint. But there are other differences, as well, such as the need to install elements for the SH-AWD system (e.g., transfer case, rear prop shaft, rear differential), or even the installation of the system for washing the rear window of the RDX. According to Easdale, who also worked on the launch of the Honda Element in the Honda East Liberty Auto Plant, where the Civic is built, there are specific zones where work is done for the RDX.

left: Not only is the grille form in keeping with the “athletic armor” styling theme, but there’s function there as well: cold air is ducted from there to a large air filter assembly, then to the turbo, which is located on the back side of the engine block. (The compressed intake air then flows through an air-to-air intercooler, then through the drive-by-wire throttle body, through a manifold, and into the cylinders.)

right: The RDX, according to William Walton, senior planner, Acura Product Planning, is designed for the entry premium SUV segment, where there is potential for huge growth: as much as 551% between 2006 and ’11 (from 60,422 to 393,279). One of the main competitors that the RDX was benchmarked against is the BMW X3.