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Vantastic Voyage

Toyota Sienna engineers crisscrossed the country to create a minivan that is designed for, built in and exclusive to the American market.


The Sienna has been praised by industry insiders
 and executives for its flexability, quality and price.

There’s a rumor going around the auto industry that when General Motors’ product guru Bob Lutz saw the new Toyota Sienna at the North American International Auto Show in January, he declared it the “vehicle of the show.” And it’s a fact that during that same week, the minivan’s versatility, quality and performance drew strong praise from analysts.

But with the show finished and upon closer inspection and a first drive, Sienna is proving to be more than just a showstopper. Its flexible interior, flawless engine, reasonable price and quality construction is a shot across the bow for segment leaders like DaimlerChrysler and Honda.

And for those who say it takes an American company to build a truly American minivan, they should know Toyota’s Newport Beach, Calif., styling studio helped design Sienna, Toyota Technical Center, Ann Arbor, Mich., helped engineer and develop it and Toyota Motor Manufacturing in Indiana is building it exclusively for the North American market.

Sienna is arguably the best minivan ever to grace the segment, which is weaker than it once was but still substantial and stable. “The popularity of SUVs in recent years has come at the expense of nearly every segment in the industry, minivan included,” says Don Esmond, senior vice president and general manager, Toyota Motor Sales, U.S.A. “Yet minivans hold a special place in the market. That has helped them hold their own against the higher image SUVs. Like no other vehicle, the minivan is all about family values.”

Minivans: The Real Family Car
Before Toyota began development work on Sienna’s all new platform, engine and body panels (only a few suspension parts are shared with the Camry), Chief Engineer, Yuji Yokoya wanted to understand everything there was to know about how the vehicle would be used. He went into his boss’ office and told him he needed to drive the entire North American continent and experience what U.S. drivers would be dealing with in their Sienna.

“My goal was to evaluate the strengths and weaknesses of the current Sienna,” says Yokoya, “and to evaluate early prototypes of the next generation Sienna.”

In driving those 53,000 miles, Yokoya had a laundry list of things that needed to be changed on the new vehicle; some were mere refinements, while others deserved immediate attention. For example, crosswind stability clearly needed to be improved, turning radius reduced and handling needed to be crisper and more confident. And on the image side, Yokoya declared Sienna would be defined by its convenience, flexibility and interior comfort. Backing up those attributes the minivan would also need a powerful engine, loads of safety features and a solid structure — all crucial things for a minivan. “The other thing that really hit home is what I call the kid factor,” Yokoya says. “It’s the kids who occupy the rear two-thirds of the vehicle. And it’s the kids who are the most critical and the most appreciative of their environment.” While Yokoya worked in Japan, John Jula, executive engineer and program manager, worked at Toyota Technical Center in Ann Arbor, Mich., to help get costs down but content up. Jula, who rode shotgun with Yokoya during his North America Sienna trek, says that while Toyota wanted the best-in-class minivan, it had to be affordable. The company needed to find new efficiencies while keeping quality, content and performance as high as possible. “The goal was not to slash costs,” Jula says. “The goal was to achieve greatness at a great price and that meant rethinking, refining refining the entire development and manufacturing process.”

Any cost savings taken out of development and manufacturing would be funneled back into a prioritized list of product and quality improvements, he says. One example Jula gives of both manufacturing cost savings yet improved vehicle quality is in the sliding door.

The previous generation Sienna provided power to the door via contact terminals mounted on the B-pillar and door. The new Sienna has continuous power provided by a flexible harness routed around the door opening.

“The new design of both the track assembly and the wiring harness is much more dependable, lower in NVH and more durable,” Jula says. “Not only are there significantly fewer parts, tooling complexity was simplified reducing the cost of both parts and tooling.”

Final assembly is also simpler, takes less time and requires fewer individual steps. All of this, he says, reduces manufacturing costs. Sienna’s quick 22-month development cycle helped keep costs in check as well.

Sienna’s interior is packed with places to store things like CDs, phones, PDAs and remote controls. The vehicle’s seats fold down for additional useage or eventual removal.

Software Saves Time and Money
With a goal of zero engineering changes, Toyota turned to its proprietary computer software, which allowed engineers to design, fabricate and assemble every component on the new Sienna before building any prototype part.

“Because parts were designed digitally, changes could be done quickly, at a fraction of the cost with much closer tolerance and higher quality,” says Jula.

The software, interestingly, is only available in Japanese, pushing American engineers in Michigan to learn the Japanese symbols for file, edit, etc., in order to be proficient in the program. Prototype parts were built only after extensive digital work, which, according to Toyota, reduced the number of parts built as well as prototype costs. Toyota also used digital assembly to illustrate each assembly task using programmed, animated workers. This process gave detailed and true-to-life information about ergonomics in the plant.

And instead of using prototype tooling the company used pull-ahead tooling and in many cases the automaker completely eliminated prototype tooling.

“Finally, we used an advance rapid-prototype machine to form numerous prototype parts,” Jula says. “The machine is capable of building plastic parts directly from CAD data.”

One Engine, Unlimited Flexibility
Sienna comes in four trim levels, but all share a new 3.3L V-6 engine with variable valve timing with intelligence (VVT-i) and variable induction (ACIS). The new powerplant delivers 230 hp at 5,600 rpm and 242 ft.-lbs. of torque at 3,600 rpm.

The new aluminum-block 60-degree engine is based on an earlier 1MZ-FE 3.0L Sienna/Camry engine. It has a larger cylinder bore, which has been increased from 3.44 inches to 3.62 inches, and has driveby- wire throttle.

Toyota also developed an all-new 5-speed automatic transmission for the Sienna. The transmission has intelligence (ECT-i), which improves shift quality, throttle response and downhill shift logic for better engine braking while helping with fuel economy, says Toyota. It is operated with a dash-board mounted gate shifter.

Both the engine and transmission are built at Toyota Motor Manufacturing’s West Virginia plant.

Inside the Sienna, the interior was designed to be extremely versatile and flexible. The key to its flexibility being its seating. The vehicle is available with either a seven or eight passenger seating configuration.

There are 17 ways to configure the seats with either center or side walkthrough to the third row. Seven passenger seating is standard on all trim levels, with captain’s chairs in the second row that can positioned so there is an aisle in the middle or “indexed” laterally for a partial bench on the left side, says Paul Williamsen, curriculum manager, University of Toyota.

For the eight passenger seating, which is available on the CE and LE models, there is a third seat in the middle row. It can be a full bench or what Toyota calls a front and center’ seat that can be positioned in a forward position for easy access to an infant seat.

“The second row of seats tumbles forward,” Williamsen says. “They can be easily removed through the large door that is over 96 inches long and over 50 inches in width.” Standard on all models are the split and stow seats in the third row. The 60/40 split foldable seats easily recess into the floor, with one hand while the individual sides are stowable. This makes for a flat load floor as the spare tire is mounted below the floor in front of the second row, right side seat.

The Sienna also has a removable center console that latches onto floor-mounted brackets between either the front or second rows. It can be moved between the two rows. Standard on the XLE and Limited, the console has a large center compartment and a small top storage compartment. It also has a memo pad, four cup holders and a rear pullout tray with an extra-large cup holder.

Safety is Critical
Toyota understands that minivans carry families and that means safety is paramount. Besides its traditional front and side airbags, Sienna is also the only minivan on the market that is available with a full third-row side curtain airbag. Sensors in both the B- and D-pillars trigger the side curtain airbag that protects against injuries in side impacts.

Standard on Sienna models equipped with a navigation system is a rear view monitoring system with a video camera mounted in the back door. Linked with reverse, it allows the drivers to see in wide-angle the path behind their car. Separately, park assist uses sonar and two front sensors and four rear sensors to identify if there is something in the vehicle’s way. An audible beep and flashing icon alert the driver in both forward and reverse.

Toyota has equipped all versions of the vehicle with ABS, with brake assist and electronic brakeforce distribution. For higher end models and those with all-wheel-drive, brake assist is via the ABS actuator when vehicle stability control (VSC) and traction control (TRAC) are used. This technology uses a sensor on the master cylinder to detect a pressure rise rate indicative of panic braking. It is measured and controlled by the ABS and VSC computer. If the driver does not continue to apply sufficient peal pressure for a panic stop, additional pressure is applied to the calipers by the VSC pressure pump.

For models that do not have VSC and TRAC, a new mechanical brake assist is used. This system uses a conventional vacuum power brake booster but has a special valve and spring on the pedal rod. When a panic brake is detected, the vacuum booster increases the amount of power to the brake assist system.

All Siennas come with a 3.3L V-6 engine with variable valve timing with intelligence, and variable induction.
Stronger Means Safer
Sienna’s use of tailored blank construction in the front frame rails increases differential thickness for improved longitudinal crush performance, Williamsen says. A reinforced connection of the B-pillar to the roof rail improves side impact performance, while body reinforcements throughout the vehicle result in energy absorption and dispersion. Beneath the front and rear door skin, Sienna also uses energy absorbing foam.

Says Williamsen, “Sienna’s high carbon, heat treated steel skin allows us to get more dent resistance with less thickness. It also allows us to get better control over crushability. So it helps us a lot with side impact performance.”

But the tradeoff is that it takes a lot more energy to stamp it into shape. “If you go from mild steel to high strength steel, which you might have been able to do on a 30 ton press, you now have to do on a 60 ton press because of this higher strength,” he says. It also helps keep weight down, something Toyota is deeply driven to do.

“As a company we are absolutely committed to beating the CAFE number every year,” Williamsen says. “We’ve never paid a penalty. That’s tough when you look at how many Lexus vehicles we’re putting on the road and the content on them. We’re real serious about weight.”

Peace and Quiet
Toyota is also serious about noise. Besides all the traditional ways to cut noise including hard and soft foam, dash panel silencers and rear wheel-house sandwich panel, Toyota developed two new ways to help reduce noise inside the car.

With traditional carpet, the hard, rubber backing does not absorb sound like the rest of the carpet. So Toyota developed a new process to allow the carpet to take in much more noise.

“After the carpet is made we run it through special machine called a needle punch and pokes holes in the carpet to let certain sounds — certain low frequencies in the cabin — go through the carpet and the felt underneath the carpet can dampen the noise,” Williamsen says. “The needle punch carpet contributes to the quiet ride.”

Toyota also selectively applies damping asphalt to the body shell using robotics. The robot applies the material only where it is needed, saving time, cost and weight compared to asphalt sheets.

Simplified Assembly
The Sienna is built at Toyota’s plant in Princeton, Ind., alongside the Sequoia.

“The most impactful thing in production is simply the concept that we are building the unibody Sienna and the body-on-frame Sequoia on the same exact line,” says Williamsen.

There might be a Sequoia frame and body drop and then the next thing that comes in is a Sienna powerplant on a subframe with MacPherson struts sticking out. It’s mind blowing to have that kind of flexibility car by car.” There is no setup, no changeover, not a moment of pause on the line. Toyota’s flexible tooling transitions from one vehicle to another imperceptibly.

To help cut costs and manufacturing complexity, Toyota also developed modules and moved them off the assembly line and in one case outside the plant — a simple adjustment that reaps huge dividends according to Jula. Key off-line modules on the new Sienna include the instrument panel, door panel and the largest of the group, the headliner.

“Visualize for a moment how large the headliner in the Sienna must be,” says Jula. It’s huge, it’s cumbersome and it’s really difficult to install.”

It’s even more complex since it includes side-curtain airbags, a roof mounted DVD system, multi-zone climate control air ducts and all the wiring harnesses. And as the complexity of all these things increases, so does the chance of poor fit-and-finish and ultimately increased NVH.

“The answer, we found, was modular assembly,” Jula says.

So, Toyota moved the headliner and all of its components off the assembly line.

Instead, Johnson Controls now assembles the headliner offsite at a facility less than 10 miles away. Instead of assembling the unit in stages and a small space, the headliner is laid on a bench. Individual component installation is now easier. The more precise method also allows for longer time for the adhesives to set while improving final fit-and-finish.

This resulted in less time for assembly and lower costs and in reduced worker fatigue and injuries.

“Bottom line,” says Jula, “the consumer gets a better headliner for less money.”

Both the instrument panel and inner door panel are assembled off the main line but still inside the plant.

“We don’t put anything (online) in the door except the window glass and the motor,” says Williamsen. “Everything goes into the door panel and then it goes into the vehicle.”

Minivans: Long Future Ahead
Most industry observers agree the minivan segment just isn’t what it used to be. During the last two years, sales have fallen as buyers turn to SUVs and crossover vehicles. But analysts say the segment will remain steady this year and may see a little growth during the coming years thanks to new products like the Sienna, Nissan Quest and Mercury Monterey.

Toyota expects to sell about 130,000 to 150,000 units a year of the Sienna. That compares to 81,000 sold during 2002. Families continue to be the main minivan buyers while “50 years-old and up emptynesters with an active lifestyle” are the ones buying more and more minivans.

“Looking at the minivan segment as a whole, the top ‘occupation’ listed among current minivan owners is retired at 25 percent,” says Esmond.

The LE version of the Sienna will be the biggest seller with about 68 percent of sales while the XLE will be No. 2 with about 25 percent of sales. The entry-level CE and top-of-the- line Limited will each make up about 5 percent of sales.

“When Sienna arrives in showrooms this month, it will absolutely redefine the American minivan concept,” Esmond says, “and give new credibility to the term ‘best-in-class.”

Toyota used high-strength steel on many exterior and key interior panels shown here in red.

The Sienna is the only minivan available with a full three-row side curtain air bag.

Low NVH was crucial on the Sienna so Toyota used dash panel silencers on the minivan.

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Thu. March 30th, 2023

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