The Goal of Developing the Honda Multimatic
| Honda's Multimatic Technology Page
Originally Published 1995/07/05
No matter how well the engine performs, if that power is not
transmitted properly, you cannot expect desirable results. In that line of
thought, one of the key factors to total power output is the transmission.
So we ask - what is the ideal transmission?
Currently, the automotive society is seeing an increase of
automatic transmissions every year. As more automobiles with automatic
transmissions become available, less skill be required for one to operate a
vehicle. In other words, anyone will be able to enjoy driving and extract
the full potential of the vehicle without difficulty. Because of this, the
importance of the automatic transmission will only grow.
Keeping this in mind, Honda has been working on a proprietary,
step-less shifting mechanism. It is but the natural progression from first
making shifts smoother, to putting in more gears to make more gradual shifts --
all the way to making the shifts step-less. Compared to standard torque
converters, there is less power lost, and more of the engine's power is
The slight, yet uncomfortable "nudge" that is felt
when shifting will no longer exist. Acceleration will be smooth and
optimal. Fuel economy will increase as well. All of these advantages
can be reached with the use of a step-less transmission.
While using the basic concept of the CVT, Honda was able to
create the world's first mass-production, high-power, step-less
transmission. While other such units previously existed, the Multimatic
was far superior in quality, endurance, power output, cost, etc. Using
proprietary technology, we were able to create an automatic transmission that is
controllable and feels just like an automatic. The plan was to mate it to
the 3-stage VTEC engine, and extract the engine's excellent performance.
This was then done with the EK3 Civic, the 3-door Civic Ri and
VTi and the 4-door Civic Ferio Mi and Vi. The Ri/Mi uses the standard 105ps
SOHC D15B while the VTi/Vi uses the now famous 130ps 3-stage VTEC D15B.
The Basic Mechanism of the Honda Multimatic
The Honda Multimatic 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
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 will happily accommodate 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
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 E(conomy) mode, the upper power band is avoided,
resulting in excellent fuel economy. In D(rive) mode, driving performance
and fuel economy are evened out. Lastly, in S(port) mode, the user can
redline the engine. The exact redline numbers are as follows:
E - 4500rpm
D - 5700rpm
S - 6800rpm
In addition, the standard "L" gear gate; and the "S" mode are
available to use as engine brakes.
A note about the quoted red-line figures. They seem to
be for the regular 105ps SOHC D15B. For the 130ps 3-stage VTEC D15B used on the EK3 VTi
and Vi, the 'red-lines' for the 3-modes (based on actual usage of the real
thing) are 4500rpm, 6000rpm, and >7000rpm. Redline for the 3-stage D15B is
7200rpm and under sustained WOT, engine rpm will happily hit and sustain 7200rpm !
(for the VTEC sound fans, yes, this means you can maintain the 'VTEC song'
for as long as you like).
(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
Merits of the Honda Multimatic
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) 3 Modes of Driving
Normal city/freeway driving with "D," superior fuel economy with
"E," and high-rpm power from "S." With the 3 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
Note : There were mentions of a "2" gear gate
in the original article but I have never seen such a gate in the EK3s I have
seen (all original JDM imported used from Japan) so I have edited those
references out. However, I am not sure if this is available on the new
2001 ES/EU generation Civic.
A word about the comparison chart. In my opinion it
doesn't show the true advantage Multimatic has over the standard 4AT
transmission especially "on-the-move", ie acceleration from medium
speeds (~ 50kph). Going WOT in any mode (E, D, or S) will cause Multimatic
to use the highest possible engine rpm (>7000rpm for S) which delivers
the optimum gear ratio for the highest possible acceleration from then
onwards. This feature offers superior pick-up from 4AT and superior
flexibility over 5MT during driving.
Recently I also saw a Dynojet power chart for an
EK3 Civic Ferio Vi. The standard 4AT mated to the 130ps SOHC-VTEC D15B (1991-1995 EG4 and
EG8 Civic VTi) will dyno at around 92ps at the wheels. However the EK3's dyno
chart I saw touched 100ps at the wheels, stock-standard.