Genchi-Genbutsu and creating the Toyota 4Runner - On Cars

Automotive Design & Production, Oct, 2002 by Gary S. Vasilash

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).