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Genchi-Genbutsu and Creating the Toyota 4Runner

With the proliferation of SUVs on the market right now, the folks at Toyota knew that there was a big challenge in developing the new 4Runner. So Toyota engineers applied a methodology that got them thinking about what really needed to get done.
#HP #Yamaha #Toyota


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From Millimeters to Kilometers

As anybody who has even been in the same room as a copy of The Machine That Changed the World knows, Japan-based vehicle manufacturers are masters at continuous improvement. These are typically the sorts of improvements that are incremental—millimeter by millimeter, they get better and better. Pretty soon they're centimeter sized improvements. And the aggregate then becomes meter sized. And pretty soon they are, comparatively speaking, kilometers ahead of their competitors. But this whole incremental thing is only part of what companies like Toyota do.

Because another clear strategy is to make thorough-going, fundamental improvements to their products, not just the kaizen baby steps. They create new versions of existing products. There may be some carryover, but by and large, these are large changes. In the case of the 4Runner SUV, the first one was introduced in 1985. The fourth-generation is being launched now. This mid-sized SUV is different right down to the chassis compared with the model that it replaces. The improvement has, yes, been continuous. But it's also been substantial.

Or, as the chief engineer for the 4Runner, Junichi Furuyama, puts it, "One of the benefits of this project was that our team was allowed to start from scratch."

Sure, there are incremental improvements. And then there are the starting-from-scratch projects like the 4Runner.


How Do You Know What To Do?

Furuyama on creating a better SUV (or a better anything else, for that matter):

"There is a phrase that is often used by vehicle development engineers at Toyota to explain the foundation of our engineering strategy. The phrase is genchi-genbutsu. As a direct translation, genchi means ‘local' or ‘on-site.' Genbutsu means ‘real thing' or ‘actual materials.'

"More loosely translated as a philosophy, it means: Go, see, and confirm.

"The phrase is a reminder that we cannot assume to know everything. And that it is counter-productive to assume that we do. More importantly—and especially for those of us who think we have all the answers—the phrase is a philosophical caveat."

So, in the case of the 4Runner, Toyota engineers based in Toyota City came to the U.S., the most important market for the 4Runner (Go). They worked with the people at the Toyota Technical Center in Ann Arbor and Toyota Motor Sales (Torrance, CA) in order determine how people use their vehicles and what the market is like (See). And they subsequently made modifications to their initial plans for what a 4Runner should be (Confirm).

Furuyama: "Where we began the development of the 4Runner was far from where we ended up. In fact, it was about the distance between Japan and the U.S."

Genchi-genbutsu can make a whole lot of difference. Not only is it about being there, but it is, perhaps more importantly, about being able to accept that there are differences that may cause you to have to rethink your original suppositions.


Once You've Figured All That Out

Once they know what they need to do, then the Toyota engineers set to it via the implementation of simultaneous engineering. Furuyama says, "All aspects of development are now brought into the project at the beginning—at the drawing stage." Of course the "drawing" is now being done on computer screens. There was the extensive use of digital engineering tools in developing all of the components. Furuyama notes that almost all of the parts that are used in the vehicle were not only digitally designed, but were tested and used in simulated assembly routines. Furuyama notes, "Through digital parts design, changes can be made quickly at a fraction of the cost of building prototype parts. It is also the main reason why we can now build fewer pre-production prototype vehicles."

In addition to which: "Streamlining the production process, making the vehicle easier to build, is the final piece of the development puzzle. The logic is simple. A vehicle that is easier, safer and more enjoyable to build will be higher in quality and ultimately less expensive to produce."

The 4Runners are built in two facilities in Japan: the Toyota Tahara plant and the Hino plant in Hamura.


Leveraging Additional Resources

One clever bit of engineering deployed on the 4Runner is actually a development of Yamaha. Toyota engineers have worked with Yamaha engineers on other occasions. For example, the all-aluminum 1.8-liter, 180-hp four-cylinder engine that's used in both the Celica GT-S and the Matrix XRS was developed by Yamaha. And the California walnut wood trim that's featured in the Lexus LS 430 is actually woodworking done by the people who craft the Yamaha pianos. The work between Toyota and Yamaha actually goes back to 1967, with the Toyota 2000 GT, which was equipped with a DOHC, 1988-cc, 150-hp engine that was developed by engineers from both Toyota and Yamaha.

In the case of the 4Runner, the development is not under the hood but actually on the chassis. It is called X-REAS; it's a diagonally linked shock absorber system. Essentially, the compression chamber of each shock is cross-linked to the one diagonal to it (e.g., front left to back right). There is a center control absorber in between each of the linked shocks. This central absorber has a free piston that pushes against a low-pressure nitrogen charge; there is an orifice below the piston that passes small motions across the vehicle from front to rear. . .all of which is to say that it is setup to:

  • Dampen overall suspension compression and extension motions
  • Dampen diagonal roll and pitch motions
  • Improve stability and handling
  • Reduce vehicle bottoming

While it is certainly not unprecedented for a vehicle manufacturer to mention a supplier has provided some clever technology, it is interesting that Toyota engineers cite the X-REAS at the same level as their own work. Which is certainly beneficial from the point of view of working with one's partners.


What, No Hydroforming?

It is almost de rigueur, it seems, for truck manufacturers to boast that they're using hydroformed frame rails. Strangely enough, that's not the case on the 4Runner, even though it has an all-new chassis design. According to Paul Williamsen, Curriculum Development Manager, University of Toyota, "The longitudinal rails are made up of steel C-channel sections of varying gauges, patterns, and heat treatment that are welded together. The frame is then reinforced by being fully boxed with smaller a C-channel, except for the rear-most section aft of the rear suspension, which is open C-channel." Williamsen observes that this approach provides the required rigidity. Whereas there are eight welded cross members spanning the third-generation 4Runner, the new one has nine.

And no hydroforming.


Architectural Issues

It's usually a pretty safe bet that an SUV based on the body-on-frame architecture that is characteristic of a pickup truck is going to be less car-like and more truck-like. But let's face it: For some people, the purpose of having an SUV relates to being able to bang the stuffings out of it, something that a unibody-based vehicle just won't be able to deal with. In the mid-size SUV market, Toyota added the unibody Highlander as a compliment to the 4Runner. According to Don Esmond, senior vice president and general manager, Toyota Div., this two-SUV strategy in that segment (overall, the company has a five vehicle lineup, including the RAV4, Sequoia, and Land Cruiser, as well) works well because their research finds that people who get out of sedans and into an SUV go into a Highlander, but those who are replacing an SUV tend toward the more robust 4Runner.


And Now, Aluminum

Heretofore, there has been no all-aluminum engine in a Toyota light truck. Now there's a 4.0-liter V6 that provides 245 hp @ 5,200 rpm and 283 lb.-ft. of torque @ 3,400 rpm. This is a new engine for Toyota. Why aluminum? Williamsen says that the unit is about 130 lb. lighter than a comparable V8 engine—and has nearly the same output. Given that this 4Runner is bigger than its predecessor (its wheelbase is 109.8 in (up 4.5 in.); overall length is 187.8 in. (up 5.5 in.); overall width is 73.8 in.; and, sans roof rack, is 68.5 in. high) and is fitted with more content, there was an interest in keeping the weight down. This is also the first Toyota truck engine with the company's variable valve timing with intelligence (VVT-I).

There is also a V8. This is a 4.7-liter 32-valve, dual overhead cam unit that provides 235 hp @ 4,800 rpm and 320 lb.-ft. of torque @ 3,400 rpm. It is quite similar to the engines used in the Sequoia, Land Cruiser and Tundra. Although it has aluminum heads, it has an iron block.

Both engines have the ETCS-i system—that's a linkless electronic throttle control system with intelligence. Which is a throttle-by-wire system: there's no cable between the pedal and throttle. This is a third generation system, one that has had several installations in Lexus cars, as well as in the Toyota Avalon and MR-2. Not only does this cut down on NVH through the dash panel (more about dash panel NVH momentarily), but it also helps assure better performance and fuel economy by figuring out what the real intent is of that foot on the pedal.

There are two transmissions available for the 4Runner, a four-speed automatic for the V6 models and Toyota's first five-speed automatic transmission in a truck for the V8. There are new transfer cases for each type of engine, both of which are said to be the world's first application of a Torsen limited-slip center differential in a mid-size SUV.


Up or Down

One of the fundamentals of electronics, like ABS systems, is that processors are typically more responsive than people. Four-channel ABS is standard on all 4Runner models (something that is becoming atypical in the market.

Presumably, in the SUV market there are those who aren't ordinarily off-roaders but who, because they can, decide that they need to take their vehicles off the pavement. For those who are not familiar with hill climbing, one problem can be that as one's foot is lifted from the brake to start climbing the grade, there is a tendency for the vehicle to slip back or sideways, both of which can be troublesome. There is a standard Hill-start Assist Control (HAC), which controls the brakes so as to prevent the vehicle from rolling backwards for approximately five seconds. But then there is the matter of going down. So there is the DAC—Downhill Assist Control, which is standard on all 4WD models. In this case, one selects the feature on the console, puts the transfer case in L4, and takes all feet off of all pedals (which takes more than a small amount of faith, particularly on steep grades); just as in the case of a cruise control, once a pedal is depressed, the system kicks out. The system controls both the brakes and the throttle and maintains a speed of about 2 to 4 mph. (Speaking of speed: the 4Runner is said to be the world's first use of active, or solid-state, wheel speed sensors; these sensors are capable of sensing both speed and direction of rotation; they make use of magnetic resistance elastography, which fundamentally means that there are bi-pole magnets in each wheel bearing that are read by two Hall-effect sensors so that there is extreme accuracy in measurement.) The noise mentioned in the previous section comes from the ABS braking system, as the valves are opening and closing in a controlled frenzy. This system, incidentally, is like that in the BMW X5 and the Range Rover, both of which are somewhat more dear in price than the 4Runner.



Having had the opportunity to drive the 4Runner both on the highway and on a series of logging roads, it is very clear that the vehicle is solid and capable, comfortable and capacious (EPA interior volume is 145.3 ft3). Because this is a body-on-frame vehicle and not the increasingly popular unibody, it has a level of ruggedness that would otherwise be lacking. However, the engineers at Toyota—undoubtedly thanks to their genchi-genbutsu approach—have made this vehicle nearly as driver- and passenger-comfort oriented as anything in the car-based class. Which is no mean feat.