2006 Mazda MX-5 Miata Secifications
Engines: Light, compact, highly responsive, powerful MZR engines with appropriately sporty intake and exhaust notes were developed to assure that the MX-5 is brisk, nimble, linear in response, and very fun to drive. Based on the acclaimed MZR engine series installed in other Mazda models, these engines are front-midship mounted on the MX-5 and adopt the latest technologies developed to boost power appropriately for a lightweight sports car while supporting environmental compatibility with greater fuel-economy and reduced emissions.
Powertrain lineup by market
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Key features of the MZR family are aluminum block and head construction with iron cylinder liners, chain-driven double-overhead camshafts, variable intake-valve timing, electronically controlled sequential-delivery port fuel injection, and coil-on-plug ignition.
The compression ratio is 10.8:1 and both engines also share an 83.1 mm (3.27 in) stroke. The bore in the 2.0-liter engine is 87.5 mm (3.44 in) versus 83.0 mm (3.27 in) in the 1.8-liter engine. The range of intake valve opening and closing variability is 30 (camshaft) degrees. The bucket tappets have low-maintenance shims for lash control. Piston skirts are coated with a molybdic anti-friction compound.
Overall engine length was trimmed by 69 mm (2.72 in) compared with the second-generation model by thoughtful location of external components. Tilting the engine 10 degrees to the right provides room for a large, low-restriction Variable Intake System (VIS) with two operating modes to enrich the torque curve. VIS is tuned with an emphasis on odd and half-order harmonics at high rpm to provide a lively, robust engine note. MZR engines destined for Europe have swirl-control valves located in the intake manifold near the cylinder head interface to improve cold drivability and to reduce low-rpm exhaust emissions. A four-into-one exhaust manifold is positioned on the low (right) side of the engine block. Compared to the previous MX-5 intake restriction is lower by 57-percent and exhaust restriction has been diminished by 40-percent.
Peak output of the 2.0-liter engine for North America is 170 hp at 6,700 rpm with a manual transmission.
At least ninety percent of peak torque is available from 2,500 rpm to the 6,700 rpm redline. (The fuel cut-off is at 7,000 rpm.) Response has been tuned by use of a flywheel lightened by 0.3 kg (0.7 lb), a large electronically controlled throttle, and very rigid drive shafts.
Engine specifications (Provisional data)
|
MZR 1.8 |
MZR 2.0 |
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| Transmission | 5-speed manual |
5-speed manual |
6-speed manual |
6-speed Activematic |
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| Displacement (cc) | 1,798 |
1,999 |
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Bore x stroke (mm) |
83.0 x 83.1 |
87.5 x 83.1 |
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Compression ratio |
10.8 |
10.8 |
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Max. output |
EU: 93kW (126PS)/ 6,500rpm |
NA: 170hp/6,700rpm |
NA: 166hp/6,700rpm |
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Max. torque |
EU: 167Nm/ 4,500rpm |
NA: 140lb-ft/5,000rpm |
NA:
140lb-ft/5,000
rpm |
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NA: North America , EU: Europe , JPN: Japan , AUS: Australia
Transmissions: The five-speed manual transmission is carried over from the second-generation MX-5 with key changes. To handle the additional torque, the inner structure of the transmission, the counter shaft, and third gear are stronger. Triple-cone synchronizers for first and second gears, double-cone synchros for third, and a carbon-type synchro for fourth reduce shift effort.
Gear ratios in the newly engineered six-speed manual transmission are purposely close to enhance the joy of sporty driving. Short, quick shift strokes have been achieved by use of triple-cone synchros on the first four gears. To reduce inertia, the third-fourth synchro is located on the counter shaft. For positive feel, the shift linkage is a single unit supported by low-friction bushings and guided by a steel plate.
As a convenience, reverse is located adjacent to first gear. Accidental engagement is prevented by the need to press down on the shift lever in order to select reverse gear.
A new Activematic automatic transmission adds a fresh dimension to the MX-5’s driving personality. Six ratios are provided with wide spacing in the interests of fuel efficiency. First gear is 31-percent lower than the second-generation MX-5 automatic to provide a very aggressive launch performance. Sixth gear is 21-percent higher for high mileage and quiet highway cruising. Steering wheel paddle shift is available in certain markets and models. Paddles mounted behind the steering wheel command upshifts while buttons positioned on the spokes are used for downshifts. Coordinating engine torque with the shift sequence results in smooth, seamless, and fast gear changes.
BODY RIGIDITY
As mentioned in Chapter 2, as a result of employing ultra-high strength and high strength steel sheet as well as advanced analytical technology, compared with the second-generation MX-5, bending rigidity has been improved by 22-percent and torsional rigidity by 47-percent. Additionally, the rear of the transmission is rigidly linked to the front of the differential housing by a Z-shaped power plant frame made of pressed aluminum. This assures that the driver’s throttle inputs are faithfully and promptly conveyed to the rear wheels, ensuring the maximum possible oneness between car and driver.
The high-mount backbone frame running along the top of center tunnel from the rear of the dash panel is joined fore and aft to the main frame in continuous closed section. This improves body stiffness and energy absorption during collisions without imposing significant weight penalties. Bolting lateral under-tunnel members directly to the seat anchor points enhances rider and horse oneness by minimizing seat flexibility and vibration.
STEERING AND SUSPENSION
DRIVING DYNAMICS Whether it’s called JInba Ittai, rider and horse, or
happy-face motoring, driving fun in a highly responsive open roadster is a
cross-cultural experience that is appreciated in every corner of the globe.
Mazda revived this simple pleasure with the launch of the original MX-5 in
1989. With the arrival of a third-generation roadster this year, Mazda
engineers seized the opportunity to continue the best features from two
previous models while adding new MX-5 dimensions to assure that
Mazda’s Zoom-Zoom spirit continues to thrive in the 21st century.
Takao Kijima’s development team identified five core requirements
for achieving of a fun-to-drive personality: • Lightness • Optimal weight distribution • A priority on handling • A consistently nimble, natural feel • Dynamic-feeling performance. The pursuit of the lightest possible weight and the advanced
technologies selected to achieve a third-generation MX-5 that, in spite of
being larger in nearly every dimension, is only about 10 kg (22 lb) heavier
in base weight than the car it replaces are covered in detail in Chapter 2.
This chapter will focus on the four other core requirements and the details
of the chassis and powertrain components engineered to achieve them. Optimal Weight Distribution To insure that the driver’s control requests are faithfully and
expeditiously fulfilled by the car, its weight should be balanced equitably
between the front and rear axles. The optimum sports car has the lowest
possible center of gravity (cg), the lowest possible moment of inertia in
the yaw plane [major masses located closely to a vertical axis through the
center of gravity], and half of the total weight of the vehicle and its
occupants carried by each axle. These principles guided the general layout and development of the MX-5.
In spite of the new car’s slightly larger size, higher level of
standard equipment, and its larger and more powerful engine, Kansei
Engineering has allowed Kijima’s team to achieve the aforementioned
core requirements such as the optimal 50:50 front/rear weight distribution.
To lower the yaw moment of inertia by two-percent with respect to the
second-generation MX-5, major masses have been moved closer to the center
of the car. For example, the engine is moved rearward by 135 mm (5.3 in),
facilitated by an HVAC unit that’s seven-percent smaller than before
and an extra 20 mm (0.79 in) of distance between the driver and passenger.
Moving the battery—now changed to a standard type for lower
maintenance costs—from the trunk to a new location ahead of the
engine diminishes its distance from the cg by 265 mm (10.4 in). The fuel
tank has been moved forward by 110 mm (4.3 in) and lowered by 120 mm (4.7
in) from its previous position in the trunk to a new under-floor location.
The net change in the MX-5’s cg height is a worthwhile 18 mm (0.71
in). Thanks to the JInba Ittai emphasis and Kansei Engineering
strides, the new MX-5 sets an enviable standard in terms of light weight,
cg height, and polar moment of inertia. A few sports cars do top it in
certain categories: some are lighter, some have lower cg and lower moment
of inertia, etc. But the development team believes that there is no
lightweight sports car with the MX-5’s combination of design virtues
capped by an affordable price. A Priority on Handling Clear and specific handling targets were established
to assure that this attribute rose to the top of the requirements list. A
particular emphasis was placed on achieving a brisk, nimble feel which
sometimes causes diminished stability and undesirable sensitivity to
external forces such as road irregularities and crosswinds. With this in
mind, the development team sought a balance wherein the rear of the car
maintains an unshakable grip with the road for maximum stability while the
front of the car is solely responsible for initiating directional changes
requested by the driver. To achieve highly consistent grip over various
road surfaces and during changes in braking or power delivery, the
development team selected highly linear control of the toe (steering) and
camber angles as well as the vertical forces applied to each tire. At the
rear of the car, a new multilink suspension system was selected because
this approach offered the most freedom in selecting the ideal geometry for
all wheel movements. To minimize the amount the rear of the car rises during braking, front
and rear suspension systems are configured to provide a strong anti-dive
effect. Suspension links are arranged to convert a portion of the braking
force fed into the body into a moment which counteracts the natural
tendency of the body to pitch slightly down in front, up in back.
Minimizing the dive movement also minimizes rear-wheel travel and unwanted
changes in toe and camber. The net improvement over the second-generation
MX-5 is a 38-percent reduction in dive during braking. A similar technique is used to control the body’s tendency to
squat during acceleration. Arranging the rear suspension links to provide
an anti-squat effect again minimizes rear-wheel travel and unwanted toe and
camber deviations. The net effect is 78-percent less squat than in the
second-generation MX-5 and a more stable feeling rear grip that’s
undisturbed by changes in throttle position or brake applications. To achieve a feeling of nimbleness and willingness to change direction
in response to steering inputs, the development team focused on achieving
maximum rigidity throughout the steering system. The diameter of the
steering rack was increased from 23 mm to 24 mm (0.91 in to 0.94 in) in the
interests of higher stiffness, the torsion bar that opens the
power-steering assist control valve is stiffer, and the pinion gear and
control valve have been integrated into one assembly. At the rear of the MX-5, the subframe that supports the differential
and suspension links is attached to the unibody at six points so lateral
forces result in minimal deflection. Together these measures help minimize
the lag between steering input and car reaction. Achieving a Consistently Nimble, Natural Feel Competitive sports cars achieve excellent performance without
necessarily providing a natural feeling of nimbleness in all driving
situations. To raise the MX-5 above that level of achievement, a special
group of test experts was assigned the task of applying Kansei Engineering
to quantify subjective aspects of handling, to analyze these aspects in
detail, and to find the means of providing a consistently nimble and
natural feel in all driving situations. As a first step, consistent performance character was defined as an
operating feel through the steering wheel, accelerator, brakes, and other
controls that is light and predictable in all driving situations. Also, all
running, turning, and stopping movements should convey a feeling of
nimbleness. To study these characteristics in fine detail, the team focused
on six specific situations wherein any driver could experience the new
MX-5’s signature nimble and natural handling: • Entering a main road from a parking lot • Turning at a road junction • Driving through urban or suburban traffic • Driving on winding roads • Joining freeway traffic • Passing on the freeway. The team quantified nimbleness by plotting steering response versus
steering effort for all MX-5 generations and various competitors in order
to select a target point for the third-generation edition. Another measure
documented and studied was the amount of change in the rate of acceleration
(∆G) after the throttle was opened. This same procedure was used to coordinate accelerator pedal, clutch,
steering, and shift efforts. In each case, a consistency line was plotted
and control variables adjusted to achieve a highly consistent feel
throughout each driving operation. Another important criterion for sporty driving is the lateral restraint
provided by the driver’s seat. By studying the pressure distribution
in the seat back and cushion, it was possible to improve the level of
lower-back holdduring cornering. This index was also plotted versus
steering gain (vehicle response speed to steering) and steering force as
part of the consistency effort. Dynamic-Feeling Performance A key part of the desired lively feel is how a push of the throttle
translates into forward acceleration. Initially there’s a surge
followed by gradual convergence toward a steady forward acceleration.
Making that convergence as rapid and as tight as possible greatly improved
the MX-5’s sense of directness and liveliness. Increasing the
stiffness of driveline components and reducing yaw inertia of rpm are
obvious means of speeding this convergence. A computer-aided engineering
system was very helpful in modeling, testing, and analyzing this aspect of
driving. In practical terms, we shaved weight off of the flywheel, tuned
the electronic throttle, further bolstered propeller shaft stiffness and
optimized the engine mountings. The engine’s ability to continue producing a strong flow of
torque at very high rpm is another highly sought after sports car
attribute. Mazda engineers call this “extensibility.” The
requirement is a very flat torque curve with minimal wilt after the peak
value. In the MX-5 various tuning measures were applied to achieve this
important characteristic. How the engine sounds is arguably the most critical phase of the sports
car experience. Here a driving simulator was used to clarify the
relationship between acceleration rate and engine sound. The team’s
conclusion was that a harmonic, linear sound was most appropriate during
acceleration. (Tuning the engine’s note through all operating regimes
is discussed in full detail in Chapter 5’s Dynamic Craftsmanship
section.) Given the MX-5’s global reach, engineers spent ample hours in
faraway places tuning and testing prototypes. There were four week-long
trips to drive on US roads, a month spent evaluating winter performance in
both New Zealand and Sweden , three visits to two Japanese race tracks, and
nine trips to England and Europe . High-speed dynamics were studied on
German autobahns. Nearly two weeks were spent exploring the ragged edges of
the performance envelope on the 73-turn, 21 km (13 mi) Nurburgring
Nordschleife circuit where the new MX-5 bettered the second-generation
model’s lap time by 15 seconds.
BASE CURB WEIGHT
WEIGHT REDUCTION AS THE TOP
PRIORITY Mazda’s “Gram Strategy” - The Ultimate
Weight-Saving Imperative There’s a natural tendency for curb weight to rise when car
manufacturers respond to market demands for more comfort, greater occupant
protection, and better environmental responsibility. Realizing that this is
contrary to the JInba Ittai goal and that extra weight has a
dramatically negative influence on driving, cornering, and braking
performance, Mazda engineers made every gram count. (In the English
measurement system used in the US and elsewhere, one pound equals 454
grams.) Their “gram strategy” assessed weight in the smallest
possible increments. For example, simplifying the rear-view mirror’s
design trimmed 84 grams (0.19 lb). But applying this strategy throughout
every nook and cranny of the MX-5’s design proved to be a very
effective means of building a very light sports car that met all of its
market demands. Targets were set for the total vehicle’s weight—at 1,128 kg
or 2,487 lb for the base MX-5—and also for the weight of individual
parts and systems. All 16 Product Module Teams (PMTs) then set about
designing the components they were responsible for with their weight
targets firmly in mind. Major opportunities for saving weight by changing
the decklid from steel to aluminum and the engine block from iron to
aluminum were naturally accounted for in the initial targets. Only then, in
order to close the gap between each PMT’s weight target and the
weight of the components they were responsible for, was the gram strategy
employed. Mechanical prototypes were carefully scrutinized for every possible
weight savings opportunity. More than 100 PMT engineers also examined
three-dimensional models of the upper body and interior components in
search of excess weight. Later, when completed running prototypes became
available, they too were studied part-by-part, detail-by-detail for ways to
trim weight one gram at a time. Notebooks compiled list a total of 573 ideas representing a total of
43.589 kg (96 lb) that were considered as weight savings measures. Of
course many were rejected as unsuitable from strength, reliability, or
crash-performance standpoints. But a lot of ideas—like trimming metal
flanges, eliminating excess quantities of lubricant and shortening the
length of fasteners—were employed to achieve the MX-5’s
ambitious weight target. Well before the gram strategy was employed as a final measure to reach
the weight target, the basic unibody was designed using high-strength,
low-weight materials capable of delivering the desired rigidity and the
lowest practical weight. Three fundamental weight-saving policies were: to
use thin material in large cross-section structures within the wheelbase in
the interests of high rigidity; to use the minimal amount of sheet metal in
overhang areas; and to incorporate as much ultra-high-strength steel in the
thinnest possible gauge to meet crashworthiness goals. High-strength steel comprises 46-percent of the new MX-5’s body
structure by weight. Twelve percent of the unibody is made of
ultra-high-strength steel which has nearly three times the yield strength
of ordinary steel. The net savings attributable to this approach is
approximately 10 kg (22 lb). The complete body-in-white weighs 247.5 kg
(546 lb) which is 1.6 kg (3.5 lb) less than the previous MX-5 in spite of
major reinforcements added to improve crashworthiness and dimensional
increases necessary to accommodate larger-stature occupants. Use of aluminum for the hood, deck lid, power plant frame, front
suspension control arms, rear hub carriers, rear brake calipers, and rear
suspension spring seats trimmed additional grams. Furthermore, the new
engine’s intake manifold and cam shaft cover are molded of
lightweight composite-plastic materials. The block of the previous
1.8-liter engine was cast-iron while the new 2.0-liter engine has an
aluminum block with thin cast-iron cylinder liners. With accessories added,
the net weight savings attributable to the engine alone is a substantial
19.1 kg (42.1 lb). Mounting the power steering pump and the air-conditioning compressor
directly to the engine block eliminated separate brackets weighing 3.2 kg
(7 lb). Using a hollow tube instead of a solid rod for the front anti-roll
bar trimmed another 2.4 kg (5 lb). Use of aluminum pipe and optimization of
fixed structures in the steering system achieved another 0.6 kg weight
saving. High-strength steel has also been specified for seat backs and cushion
side frames yielding a net savings of 4.8 kg (10.6 lb). The gram strategy also met success in brake and steering systems. In final form, the new MX-5 is larger, more powerful, more capable,
more comfortable, and more useful. It offers several new features and
greatly improved occupant protection from collision injury. Yet, thanks to
Kansei Engineering and Mazda’s gram strategy, the MX-5’s base
curb weight is only increased by approximately 10 kg (22 lb). While saving weight is a top priority for achieving JInba
Ittai, because a lower weight improves every aspect of performance
including fuel efficiency. Other concerns were the stiffness of the unibody
structure, the height of the car’s center of gravity, 50:50 weight
distribution, and the MX-5’s moment of inertia about a vertical (yaw)
axis. (A lower yaw moment of inertia quickens the vehicle’s
responsiveness to the driver’s steering commands.) Each of these
parameters strongly influences the final design’s overall
fun-to-drive characteristics. A stiff body structure is an essential ingredient in the feeling of
oneness between the car and its driver. Thanks to shrewd analysis and the
application of advanced materials, the new unibody is 22-percent stiffer in
bending and 47-percent stiffer in torsion compared to the previous MX-5.
Moving the engine rearward by 135 mm (5.3 in) was a major step towards
balancing front-to-rear weight distribution and reducing the yaw moment of
inertia. Both the battery and the fuel tank were shifted forward to new
locations closer to the center of gravity. The fuel tank was also lowered
substantially. Slanting the top of the radiator forward also helped lower
the center of gravity. The MX-5’s total yaw inertia is reduced by a
significant two-percent. With two occupants on board, each axle carries approximately 50-percent
of the load (50:50 weight distribution). (Fully loaded with fuel and
luggage, the rear wheels carry slightly more weight than the front wheels.
At curb weight—no driver, no luggage, full fuel tank—there is a
slight weight bias in favor of the front wheels.) World’s First Friction Stir Spot Welding between Steel and
Aluminum One example of advanced technology employed to save weight is spot
friction welding used to join steel stud plates to the MX-5’s
aluminum decklid panels. It is normally difficult to join aluminum and steel by welding. To
overcome this problem Mazda developed new welding technology that employs a
special high-speed spinning tool. As the blade edge of the welding tool
spins and comes into contact with the aluminum, the heat generated by
plastic deformation of the aluminum softens the steel sheet directly
beneath. Continuously applied pressure removes the zinc plating from the
surface of the steel sheet, bringing the aluminum and steel sheet into
direct contact and joining them. The zinc serves to prevent bimetallic
corrosion that normally occurs at this point. Thanks to this spot friction
welding technique, the large current used in resistance spot welding is not
required, and each weld is completed in a few seconds. Mazda engineers have
applied for 20 patents to cover this innovative technology and expect to
use it extensively in the future to achieve worthwhile weight savings in
other vehicles.
2006 Mazda MX-5 Chassis Details
2006 Mazda MX-5 Exterior/Interior Details
2006 Mazda MX-5 Safety, Security Environmental Details
2006 Mazda MX-5 Special Features
2006 Mazda MX-5 Specifications