Honda Civic -- Powertrain & Transmissions
9/15/2000 7:21:44 PM
The Civic has always been known as a fun, yet sensible car. For the 2001 model year, the engineers wanted to inject more performance into the mix, while also making the engine run smoother and quieter.
Engine Performance Objectives
Specific developmental objectives included improving torque characteristics so this engine would pull stronger from a stop. At the same time, Honda engineers wanted to develop an engine that would be even more fuel-efficient and clean burning than its already class leading predecessor.
Every 2001 Civic features a 1.7-liter ULEV engine, that boasts improved performance and a 5 to 10 percent improvement in fuel economy, providing tangible improvements for drivers and the environment.
- The engine displacement is 6 percent larger than the engine in previous Civic models (up from 1.6-liter).
- Torque output at 4,000 rpm is increased from 6 -- 13 percent (depending on model), which helps improve performance and fuel efficiency.
- All 2001 Civic engines will be certified ULEV (Ultra Low Emission Vehicle), making it the first ULEV engine to be distributed in all 50 states.
- The outward dimensions of the engine are more compact -- it is 7 percent smaller and 8 percent lighter than its predecessor, contributing to the improvement in fuel economy.
- Service intervals have been extended. Oil changes have been extended from 7,500 miles to 10,000 miles or every 12 months, whichever comes first. In addition, recommended tune-ups have been extended from 75,000 miles to 100,000 miles.
Bottom line, the Civic's new engine lineup delivers crisp performance, rapid acceleration, quiet operation, better fuel economy and is cleaner, across the board.
Engine Performance Comparisons
Engine Combustion Technology
Engineers determined that various changes in the area of engine combustion would help improve power output while reducing exhaust emissions. Those changes included:
Swirl Intake Ports
- The design of the intake port balances both vertical and horizontal vortexes inside the cylinder -- that improves the air fuel mixture "swirl" in the cylinder as it enters the engine. This optimizes even fuel dissemination for cleaner, more efficient combustion.
Improved Fuel Injector Design
A new 4-port injector design is more efficient than the previous single-port "pintle type" fuel injector used on the 2000 Civic.
- This new design delivers more efficient atomization of the gasoline. In turn, this reduces the amount of hydrocarbons in the exhaust for a cleaner burning engine with lower emissions.
Combustion Chamber Profile
- The new design of the combustion chamber allows the engine to optimize all of the other changes -- in other words, it has the optimum squish shape for faster combustion.
A common consumer misconception is that if an engine is more fuel efficient, it must also be cleaner burning. But achieving higher fuel economy is often at odds with lowering emissions. As a result, creating an engine that is both economical and clean burning is a significant challenge.
Reducing Emissions Right From the Start
A gasoline-powered vehicle typically produces the most pollutants when the engine is first started. This occurs for a number of reasons -- first, the engine is "cold" when first started, and it takes awhile for all of the components to reach the ideal operating temperature and for oil to circulate throughout the engine. Second, devices such as the catalytic converter need to reach a pre-set temperature before they start removing pollutants from the exhaust.
Therefore, one of the major accomplishments of the 2001 Civic is to employ engine control management which reduces emissions sooner and uses the latest improved catalytic converter technology, thus reducing hydrocarbons by 40 percent, resulting in all 2001 Civics achieving ULEV status.
- This system employs a new high-density catalytic converter (900 cell vs. 300 cell on the 2000 Civic). This design has three times the surface area, which allows it to be more efficient in reducing emissions. This design is similar to the one used in the 2000 SULEV Accord.
- Ignition timing is retarded after the engine is started -- this helps promote the rapid warming of the catalytic converter when the engine is cold.
Civic HX -- Improved Fuel Economy and Lean Burn
The Civic HX, Civic's mileage leader with two spots on the EPA's Top 10 fuel efficiency list (5-speed and CVT models), presented the ultimate challenge of producing maximum fuel economy and low exhaust emissions. So to maintain low emission levels on the Civic HX, Honda engineers developed a new catalyst and added an underfloor NOx catalyst. The result is that hydrocarbons are decreased by 63 percent and NOx emissions are reduced by 26 percent, allowing the 2001 Civic HX to also reach ULEV status.
- The 2001 Civic HX has a stamped exhaust manifold teamed with a 600-cell catalytic converter, for a quicker warm-up and more effective exhaust cleansing, replacing the cast-iron exhaust manifold with a 400-cell catalytic converter on the 2000 HX.
Civic GX CNG Engine -- 'World's Cleanest'
This Civic model is designed to operate on compressed natural gas (CNG). For 2001, it features a two-part fuel regulator as well as an automatic Continuously Variable Transmission (CVT). This combination provides a target driving range for the 2001 Civic GX of about 200 miles (at 3000 PSI first fill).
- The compression ratio in the CNG engine is 12.5:1 compared to 10:1 in the gasoline powered engines.
- The CNG engine uses exclusive intake and exhaust valves to handle the higher compression ratio and gaseous fuel.
- The CNG engine has special connecting rods that are stronger than in the gasoline engines in order to be able to handle the extra force generated by higher compression ratio.
Noise and Vibration Countermeasures
One potential byproduct of a high-performance, 4-cylinder engine is noise and vibration. Honda's engineers mitigated those effects by reducing engine noise around the exhaust opening, reducing piston knocking, and minimizing timing belt noise. This was accomplished by integrating the following technologies:
- The engine now features an equal-length intake manifold -- this eliminates the air sucking noise that occurs in induction systems with different length intake runners, and the engineers shortened the intake manifold runners helping to improve mid-range torque.
- The walls of the cylinder block were made more rigid by adding additional internal bracing.
- The engine mount brackets are larger and stronger and as a result, more rigid.
The pistons are not completely round, they have a new asymmetrical oval design. These pistons maintain a tighter tolerance on the exhaust side so they seal better, reduce engine noise and friction. Other piston refinements include:
- The skirt on the pistons in the 2001 Civic engines have what is called a "micro-dimple" treatment. To the eye, the pistons appear smooth -- but under a microscope, you can see the tiny dimples that are an integral part of the design. These dimples help "hold" oil on the side skirts to improve lubrication and reduce friction by two percent.
- The top piston ring has been shot peened to further reduce friction. This process creates a similar surface as the new pistons -- in other words, these piston rings can "hold" the oil, which in turn reduces friction by another two percent.
More Rigid Crankshaft
A more rigid crankshaft translates into reduced noise and vibration.
- The connecting rod bearings also have a new "textured" surface to better hold oil for consistent lubrication, lower friction and a smoother running engine.
Timing Belt Automatic Tensioner
Adding an automatic tensioner to the timing belt assembly dramatically reduces noise at idle and throughout the rpm range.
- The shape of the timing belt teeth have been changed to further reduce noise.
- The timing belt on the 2001 Civic is narrower than on previous models. This also contributes to reduced timing belt noise.
There are four engine mounts -- two stationary mounts and two liquid-filled mounts -- which help diffuse engine vibrations for a smoother, quieter and more comfortable ride.
- One liquid-filled mount is connected to the engine, the other mounts to the transmission.
- In addition, the two stationary engine mounts are larger and more rigid than their predecessors.
One way the engineers hoped to accomplish their quest for larger interior with the same exterior dimensions, was to make the engine compartment smaller. They felt this could be accomplished by moving the steering gearbox to a new, centralized, high-mount position. But first, the physical size of the engine itself had to be reduced to make room for the gearbox. This was accomplished in part by creating a new plastic intake manifold.
- Engineers changed the manifold design -- mounting it higher on the engine -- and made it of plastic. This shortened the space occupied by the engine and manifold from 617 mm to 574.5 mm.
A number of changes were made to the engine to reduce weight by 8 percent without impacting performance or affecting emissions. These changes include:
- To reduce weight, the sub fan shroud has been changed from steel to plastic.
- The cast-iron manifold has been replaced by one made of stainless steel.
- The engine valve cover was changed to magnesium from aluminum.
- The side mount engine brackets and the air conditioner bracket are now made of aluminum.
There are three different transmissions available on the 2001 Civic, and each one is a new design. Drivers can choose from a 5-speed manual transmission featuring shorter shift throws and a sportier feel. Or there is the electronically controlled 4-speed automatic transmission. Finally, the natural gas powered Civic GX Sedan and HX Coupe are available with a revised CVT -- Continuously Variable Transmission.
*5-Speed Manual Transmission
For drivers who prefer doing their own shifting, the all-new 5-speed manual transmission brings a new level of "feel" to the experience. Providing this sporty responsiveness is a new "click stop" feel when shifting from gear to gear.
In addition, these changes further enhance the shift feel of this new transmission:
- Increased synchro capacity -- first gear now has a carbon-faced synchro to allow for easier downshifting.
In addition, thin double-cone synchronizers are used for second gear for ease of shifting.
- Flexible flywheel -- with this design, the flywheel and the crankshaft are joined together using a flexible plate, which allows for the absorption of the engine vibration that naturally occurs when coupled with a manual transmission.
- The location of the shift lever itself has been moved closer to the driver's shoulder point so it is easier to shift.
- The actual amount of transmission oil has been reduced slightly -- this helps reduce friction, which in turn helps increase fuel economy.
- Fuel economy for vehicles equipped with the 5-speed manual transmission increases up to 4 miles per gallon, the biggest gain being shown by the EX model which goes from 29 mpg city to 32 mpg and from 35 mpg highway to 37 mpg. 2001 fuel economy numbers are estimates pending EPA certification.
4-Speed Automatic Transmission
The automatic transmission in the 2001 Civic is a new design. It is again electronically controlled so there is less "shift shock." And the lock-up clutch has a linear solenoid "active lock-up" system -- improving the efficiency of the transmission and as a result, fuel economy.
- Typically, a feature like the "active lock-up" system is only found in luxury cars that have 5-speed automatic transmissions.
- With the "active lock-up" system, this transmission has a broader lock-up range, depending on the driving conditions.
- This new automatic transmission is a compact design, which helped the engineers when shortening the overall length of the 2001 Civic.
- Fuel economy for Civics equipped with the automatic transmission are expected to jump 2 and 4 miles per gallon, from 28 to 30 (DX, LX) or 31 (EX) mpg in the city and from 35 to 38 mpg on the highway. 2001 fuel economy numbers are estimates pending EPA certification*
Continuously Variable Transmission (CVT)
The CVT is standard on the Civic GX Sedan and is available on the HX Coupe. Introduced in 1996, the CVT has undergone significant changes for the 2001 model year including:
- a new linear solenoid which improves the transfer of belt torque.
- a new pulley clamp improves pressure accuracy.
- adopting a new shift control valve for smoother operation.
- utilizing a new metal belt for improved transfer of power.
- using a single planetary reverse mechanism to reduce noise in reverse.
On the Civic HX Coupe equipped with the CVT, fuel economy is expected to improve from to 36 mpg in the city (from 34 mpg) and 41mpg on the highway (from 38 mpg). 2001 fuel economy numbers are estimates pending EPA certification.