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The Insight is made with two transmissions:
Note that while the Honda Insight and Toyota Prius both offer CVT transmissions that both provide stepless acceleration and a continuous range of motor speed to vehicle speed ratios, the Prius CVT (called 'ECVT' by Toyota) system is mechanically entirely different.
The CVT transmission used in the Insight is very similar to the CVT transmission that Honda has used in other vehicles, including the Civic HX in the United States, and the Honda Logo in Europe & Japan. CVT equipped Civic HX models have been sold in the U.S. since 1996. The Insight and 2001 Civic HX use a redesigned and significantly improved version of the CVT transmission.
* Note: Images provided here are based on the version of Honda's CVT transmission used in the '96-'00 generation Civics. By and large this information applies equally well to the CVT transmission used in the Insight, but there may be some minor differences in the new CVT transmission. Consult your service manual before doing any work related to the CVT transmission.
Overview of the CVT Transmission
Rather than having a fixed set of gear combinations, or "ratios", the CVT transmission allows an almost limitless number of engine speed to vehicle speed ratios. This provides significant benefits over a traditional automatic transmission, including:
Honda claims that their CVT transmission is the world's first mass-produced, high-power, stepless transmission. While such transmissions existed previously, they claim the CVT is "far superior in quality, endurance, power output [and] cost". They have also specifically designed the CVT to respond in the way that drivers are accustomed to other automatic tranmissions responding.
The CVT transmission consists of an oil-pressure variable input (aka "driving") and output (aka "driven") pulley, and a metal belt that connects the two. With an oil-system clutch on the "driven" side, the Multimatic acts as an automatic transmission. The power output from the engine goes through: Front/Back Switch Mechanism -> Driving Pulley -> Metal Belt -> Driven Pulley -> Clutch.
The two pulley widths, adjusted by oil pressure, react to the position of throttle, speed, and other conditions. For instance, when the accelerator is depressed, the driving pulley width increases. At the same time, the driven pulley width decreases - the two combining for a "lower gear" effect.
By making such adjustments, we have full control over the entire gear range previously available to automatic transmissions. From LOW to OVERDRIVE - and everything in-between. In addition, the metal belt is highly flexible, and easily accommodates the ever-changing width of the pulleys, and transfer power efficiently without any slippage.
This difficult task of adjusting oil pressure, and adjusting to variable driving conditions is handled completely by the ECU, and allows the transmission to extract the maximum performance out of an engine - making this a revolutionary automotive transmission.
The Unique Features of the Honda Multimatic The Honda Multimatic does not use a torque converter, but uses a newly designed multi-layered clutch. Additionally, to obtain smooth acceleration, various proprietary equipment were added in order to make a step-less transmission with high reliability and durability.
(1) Driven-Shaft-Placed Acceleration Clutch
The Honda Multimatic differs from previously existing step-less transmissions is that the acceleration clutch is placed on the driven shaft. The primary reason we took this route was to control torque at the closest possible place to the axle, allowing for smooth acceleration. In addition, we were able to apply a modest creep* which most automatic transmission users have grown accustomed to. This gives the standard advantages of an automatic when parking, as well as starting from a dead-stop on hills. (*creep - you know, how your car with AT will sneak/creep forward unless you apply the brakes)
Secondly, this allows for controlling the speed in all circumstances. In order to control speed, the pulley needs to be continually spinning. By placing the clutch on the driven pulley, the pulley can remain spinning even when the car is stopped. This means that in emergency situations or sudden deceleration, the transmission can quickly step down to LOW gear.
Lastly, this set-up allows for the transmission to be towed. When the engine is stopped, the input from the tires is locked out by the final gear and the driven pulley.
(2) Proprietary Oil Pressure Control System
The pulley width and speed control is handled by a high/low pressure regulator. The four-way valve releases oil pressure evenly to the pulleys. Additionally, the force that pinches the metal belt between the pulleys is also controlled by the lower pressure regulator. As a result, the two pulley pistons are of the same design - allowing for a more simple design, yet allowing high power output as needed.
(3) Slim Design
The Front/Reverse switching mechanism was placed on the driving shaft, while the acceleration clutch was placed on the driven shaft. Because of this opposing setup, the transmission is very compact, making it ideal for a FF layout. Additionally, the input shaft from the engine is inserted into the driving shaft, allowing for the number of bearings to be decreased - which ultimately means less power lost to friction.
(4) Dual Flywheels
We removed the torque converter, and instead sandwiched two flywheels - resulting in a dual-mass flywheel. Also, the harmonic resonance frequency was lowered to that of below idle - allowing us to shut out the unwanted vibrations often caused by the twisting force generated by the engine during torque rate changes. At the same time, this allows for a more direct connection to the engine, resulting in less slip-loss - which ultimately leads to higher fuel economy.
(5) High-Performance Oil Pump
The Honda Multimatic requires a high-pressure oil pump in order to operate the pulleys at optimum settings. Therefore, a highly efficient, low-friction oil pump unit was installed as a separate unit. This not only enhances the reliability of the transmission, but greatly reduces power loss and enhances both driving performance and fuel economy.
(6) Newly Designed Metal Belt
The power transfer belt was newly developed by the Dutch company Van Doorne's Transmissie. With careful testing, we were able to take the best of both the belt and the engine to make a superb engine with high output and a wide selection of gear ratios. Additionally, the belt proved to be extremely silent, due to its many hundreds of elements and the use of highly durable, yet thin metals.
Full Electronic Control The transmission is under full electronic control in order to attain its goals of a smooth ride and excellent fuel economy. This is largely separated into 3 sections - Gear Ratio Control, Acceleration Control, and Side Pressure Control.
(1) Gear Ratio Control
Gear Ratio is controlled by a pre-set 3D map with car speed, throttle position, and ideal engine rpm as its 3 axis. The difference between current and ideal engine rpm on the chart is continuously fed back to the ECU. Using linear solenoids, the four-way valves controlling pulley width are activated.
In order to prove useful in all situations, there are three 3D maps the user can select from. In D(rive) mode, the upper power band is avoided, resulting in excellent fuel economy. In S(port) mode, the user can redline the engine.
(2) Acceleration Control
The acceleration clutch's power transfer amount is controlled via the clutch piston's oil pressure. Additionally, the amount of creep is also controlled here as well. The "smart" creep has two settings - one with the brakes on, and one with the brakes off. While the brake pedal is depressed, there is very little to no creep, while releasing the brake pedal will engage creep again. By dropping the creep level while the automobile is stopped, additional fuel efficiency is realized.
(3) Side Pressure Control
In addition to the standard step-less transmission's oil-pressure controlled layout, we considered the effects of torque on the pulleys and belt. By applying linear pressure, friction is lowered, and the oil pump does not have to work as hard. Both yield in high fuel efficiency and better endurance of the transmission.
From its unique design, the Honda Multimatic is superior to conventional automatic transmissions using torque converters.
By using the 3D map control pattern, the Multimatic has the ability to stay in the same power band if/when needed. An example of this is the ability to remain in the high-rpm power band from a standstill to high speed. Because of this, full-throttle acceleration is equivalent to that of a manual transmission. In addition, when traveling at high speeds, because of its ability to infinitely adjust gear ratios, the Multimatic has more passing ability than not only the manual transmission but the conventional automatic transmission using torque converters. With these advantages and the ability to still "shift" to "L" to use the engine brake, there is nothing but advantages.
(2) Low Fuel Consumption
Because the Multimatic allows the engine to remain in its most optimal power range, excellent fuel economy is obtained. Compared to conventional automatic transmissions using a torque converter, there is zero slip, which translates into efficiency. In addition, the low-friction design and the side pressure regulator both contribute to excellent fuel economy.
(3) Smooth Acceleration
Because the newly designed clutch is installed on the driven shaft, smooth acceleration is possible. With appropriate creep, starting on hills or parking in garages can be done with ease. The difference in "feel" between the Multimatic and a conventional automatic transmission using a torque converter is minimal.
(4) Shock-Free "Shifting"
With the infinitely adjustable gear ratios at its disposal, the nudging motion caused by shifting is no longer present. Drastic jolting during lower gear acceleration is no longer present as well, leading to a stress-free, smooth driving experience.
(5) 2 Modes of Driving
Normal city/freeway driving with "D," and high-rpm power from "S." With the 2 modes of driving, you can select your car's behavior depending on your objectives, or situation you are in. Such precise control is only possible with the Honda Multimatic.