Table of Contents
Advertisement
Advertisement
Table of Contents
Related Manuals for CITROEN DS series
Summary of Contents for CITROEN DS series
- Page 1 The Citroën Technical Guide...
- Page 2 There are many car manufacturers, makes, models and versions on the road today but—as we all know—none of them compares to Citroën in its engineering excellence, especially regarding suspension comfort, roadholding, and stability. In this book we tried to describe how the various subsystems work.
-
Page 3: Table Of Contents
Table of Contents Fuel Injection Self-steering Rear ....42 Brakes Electronic Fuel Injection ....5 Diesel engines . -
Page 4: Fuel Injection
Fuel Injection... -
Page 5: Electronic Fuel Injection
The Citroën Guide Fuel Injection: Electronic Fuel Injection Electronic Fuel Injection The Otto engine needs a mixture of fuel and air up, the mixture can return to normal, but the temperature for its operation. It would be the task of the fuel of the incoming air still plays a significant role: the cooler supply—carburetor or injection—to provide the the air, the denser it becomes, and this influences the... - Page 6 The Citroën Guide Fuel Injection: Electronic Fuel Injection Idle speed is more compli- EFI MONOPOINT cated: the throttle is closed, fuel exhaust so there has to be a bypass to let the engine receive fuel to coolant run. In simpler systems this by- not present in all systems pass is constant (but manu-...
- Page 7 The Citroën Guide Fuel Injection: Electronic Fuel Injection lay depends heavily on the EMS MONOPOINT voltage the injectors are fed fuel exhaust with. The same pulse width would result in shorter open- coolant ing time, hence less fuel in- not present in all systems jected if the battery voltage drops below nominal (which...
- Page 8 The Citroën Guide Fuel Injection: Electronic Fuel Injection eration—, the momentum of the car is sufficient to rotate vacuum increases with the engine revolution, its sucking the engine through the wheels. To save fuel, the injection is force rotates the inner part of the distributor slightly away cut off.
- Page 9 The Citroën Guide Fuel Injection: Electronic Fuel Injection Both changes have to do with the fact that the enhanced By using platinum (Pt) or rhodium (Rh) as a catalyst—a system, whose new task is to generate the ignition signals catalyst is a substance whose presence is required to enable as well, cannot at the same time build on them as inputs.
-
Page 10: Diesel Engines
The Citroën Guide Fuel Injection: Diesel engines Diesel engines Diesel oil has been a contender to gasoline for diesel oil, indicated by the cetane number), the more fuel many decades. Earlier diesel engines were not re- will enter the cylinder, leading to harsher combustion, with fined enough to win the hearts of many drivers the characteristic knocking sound. - Page 11 The Citroën Guide Fuel Injection: Diesel engines ß accelelator fuel from/to tank full idle pedal low pressure regulator Ý Þ high pressure adjusting screws fuel å to tank Ü á fuel stop fuel valve æ ã fuel pump â ignition switch Û...
- Page 12 The Citroën Guide Fuel Injection: Diesel engines The excess fuel will finally leave the pump unit through STARTING IDLE SPEED an overflow valve ã, flowing back to the fuel tank. pedal pedal ß ß Something needs to be corrected… Ý Þ...
- Page 13 The Citroën Guide Fuel Injection: Diesel engines sure that the amount of fuel injected as well as the timing increase in engine speed, the rotational speed of the tur- provide better combustion and lower pollution when the bine (note the quadratic relationship) would become exces- engine is started and operated at low temperatures.
- Page 14 The Citroën Guide Fuel Injection: Diesel engines Towards a cleaner world Exhaust Gas Recycling (EGR) systems were used—depend- ing on the market—as add-on units. An electronic unit mea- suring the coolant temperature and the position of the gas pedal control on the pump (with a potentiometer fitted to the top of the control lever) controls a valve which lets part of the exhaust gas get back into the inlet.
-
Page 15: Electronic Diesel Control
The Citroën Guide Fuel Injection: Diesel engines Electronic Diesel Control Just like it is the case with gasoline engines and carburetors, stances and conditions in and around the engine (air, en- a mechanical device—even one as complicated as a diesel gine and fuel temperatures), the injection system can injection pump—cannot match the versatility and sensibil- achieve better characteristics, lower fuel consumption and... - Page 16 The Citroën Guide Fuel Injection: Diesel engines tentions of the driver. The ECU uses this sensor to learn tem ease the compromise between the turbo pressure and about special conditions like idle speed or full load as well. turbine speed: the pressure is kept at the usual value for Air temperature is measured by a sensor in the inlet mani- higher engine speeds (limited by the maximum turbine fold (but if the air mass is measured by a heated platinum...
-
Page 17: Diesel Direct Injection
The Citroën Guide Fuel Injection: Diesel engines Diesel Direct Injection I think that at this point, soot burning filters will have to be cut out of the PDF and put in at a similar ecological section under DI/HDI—since that is the only system that actually makes soot burning practical, and the only system that im- plements it. -
Page 18: Suspension
Suspension... -
Page 19: A Suspension Primer
The Citroën Guide Suspension: A Suspension Primer A Suspension Primer From the early days of the automobile—and even When a deflected spring is released again, the energy before, in the time of horse-drawn carts—it was stored in it will be released but as there is no actual load for already well known that the body of the car, hous- this energy, the elastic element, the mass of the suspension ing both the passengers and the load, has to be... -
Page 20: Hydropneumatic Suspension
The Citroën Guide Suspension: Hydropneumatic Suspension Hydropneumatic Suspension As we saw, the ideal suspension would require The volume changes are controlled by hydraulics, a tech- elasticity decreasing with the load, constant nology in widespread use in every branch of the industry. As ground clearance, shock absorbers integrated liquids are non-compressible, any amount of liquid intro- into the suspension—all these beyond the obvi-... - Page 21 The Citroën Guide Suspension: Hydropneumatic Suspension The steady connection between the sides requires an ex- pension on Citroëns. In a spring system, there is a consider- ternal management of body roll. Ideally, for any vertical able amount of interaction, a significant flow of energy in movement of the car body, the two sides of the suspension both directions between the suspension and the bar.
- Page 22 The Citroën Guide Suspension: Hydropneumatic Suspension A typical example: the BX rear strut & sphere rear brake front brake front strut & sphere brake valve main accumulator & pressure regulator LHM feed security valve front suspension HP pump rear suspension height height front brakes...
- Page 23 The Citroën Guide Suspension: Hydropneumatic Suspension With the back pressure now vanished from behind the rod do not change the position of the height corrector, only piston 1, the pressing force of the accumulator fluid drives those are large enough to exceed this free play. In addition, it down at once: the regulator is switched off now.
-
Page 24: Hydractive I
The Citroën Guide Suspension: Hydractive I Hydractive I The Hydractive I suspension system appeared During normal driving, the computer keeps the suspen- with the XM. Unlike the simpler hydropneumatic sion in soft mode most of the time but—based on the input suspension used on the DS, GS/GSA, CX, BX and provided by many sensors (steering wheel, accelerator some XMs, this one has two modes of operation,... - Page 25 The Citroën Guide Suspension: Hydractive I ing, movement due to uneven surface—or the vehicle SOFT MODE height altered by the driver), the computer equalizes the pressure periodically by enabling the control block to as- suspension pressure sume the soft position for a short period of time. system feed pressure Hard mode serves three reasons.
- Page 26 The Citroën Guide Suspension: Hydractive I strument panel informs about the setting selected (it does The brake pressure sensor is a simple pressure acti- not indicate the mode the suspension is currently in). vated switch located on a hydraulic conduit connector The second input comes from a vehicle speed sensor.
- Page 27 The Citroën Guide Suspension: Hydractive I call for hard mode, the suspension will revert within body movement amplitude remains under the modi- 50 ms and restart the one-minute timeout period; fied threshold until the correction timeout elapses; below 30 km/h opening the doors or tailgate overrides suspension selector is set to the Sport setting;...
- Page 28 The Citroën Guide Suspension: Hydractive I and tailgate open sensors) , leaving the electro-valve en- ergized for the duration of the timeout. It is important to note that the suspension will switch to soft mode even with the ignition switch turned off. Early cars did not have this feature built directly into the com- puter but used an additional relay and circuits.
-
Page 29: Hydractive Ii
The Citroën Guide Suspension: Hydractive II Hydractive II The second incarnation of the hydractive suspen- however, when set to Sport, the suspension becomes more sion appeared at February 1, 1993 (ORGA 5929). sensitive and will sooner and more often switch to the hard It was designed to overcome the biggest problem mode. - Page 30 The Citroën Guide Suspension: Hydractive II The internal algorithm of the computer became more so- SOFT MODE phisticated. While the Hydractive I had only one computer controlled mode (Sport switched the suspension to con- stant hard mode above 30 km/h of vehicle speed), the newer system has two such regimes of operation: in both Normal and Sport it dynamically activates the electro-valves of the suspension control blocks whenever it decides that...
- Page 31 The Citroën Guide Suspension: Hydractive II Pedal press rate Pedal release rate Vehicle Vehicle (steps/25 ms) (steps/25 ms) speed speed (km/h) Normal Sport (km/h) Normal Sport < 14 < 19 15–49 20–78 50–99 79–168 100–134 168 > 135–199 199 > With the improved resolution of the vehicle speed sensor, the rules formerly referencing to 30 km/h are changed to 24 km/h.
-
Page 32: Anti-Sink System
The Citroën Guide Suspension: Anti-sink system Anti-sink system Many contemporary Citroëns—including both reg- pension. But as soon as the leakage in the struts, height reg- ular hydropneumatic and Hydractive Xantiae and ulators and the brake valve reduces the pressure in the main XMs—have an anti-sink system (SC/MAC) fitted, accumulator below the suspension pressure, the closing with the sole apparent purpose of tranquilizing... -
Page 33: Activa Suspension
The Citroën Guide Suspension: Activa Suspension Activa Suspension The Activa suspension—used only on some Xantia An additional Activa sphere in the front acts as an extra models—creates mixed feelings. Drivers requiring accumulator but the rear sphere can be connected or de- sporty handling and roadholding praise it be- coupled electrically. - Page 34 The Citroën Guide Suspension: Activa Suspension spheres, and making the coercive force be applied through a spring element which becomes progressively stiffer the more correction is needed. Hydractive soft The ECU controling the electro-valve uses sensors identi- cal to the Hydractive system. The values of vehicle speed, Hydractive hard steering wheel rotation angle and speed determine when the second mode of anti-roll behavior has to be enforced.
-
Page 35: Hydractive 3
The Citroën Guide Suspension: Hydractive 3 Hydractive 3 The new C5 has a new suspension system, doing rpm) operating independently of the engine, running away with many solutions used on Citroëns for only when necessary; the hydraulic units, including an accumulator 2 to even several decades, yet offering the same or even better comfort than before. - Page 36 The Citroën Guide Suspension: Hydractive 3 As usual with Citroëns, the driver can select from four HARD MODE height settings (although the selector is no longer mechani- cally coupled with the hydraulics, it is a simple electronic switch sending signals to the computer): high, track (plus 40 mm), normal and low.
-
Page 37: Steering
Steering... -
Page 38: Power Assisted Steering
The Citroën Guide Steering: Power Assisted Steering Power Assisted Steering The PAS steering (DIRASS, Direction Assistée) On the main illustration, the power assisted steering system used on Citroëns is not radically different from is shown when it operates with the steering wheel in the similar systems on other cars. - Page 39 The Citroën Guide Steering: Power Assisted Steering into the reservoir via the rotor of the control TO LEFT TO RIGHT valve. This pressure difference moves the pis- reservoir flow distributor reservoir flow distributor ton 7 to the left inside the cylinder, helping control control the car to make a right turn.
-
Page 40: Diravi Steering
The Citroën Guide Steering: DIRAVI Steering DIRAVI Steering Another gem of engineering, the DIRAVI steering, an opposing force, increasing with the vehicle speed. With made its debut on the SM, excelled in many CXs this setup, in spite of the very high gearing, it is very easy to and the flagship, V6 XMs (left hand only, the use it during parking, yet it offers exceptional stability at small amount sold in the UK never justified the ex-... - Page 41 The Citroën Guide Steering: DIRAVI Steering Thus, the lower mechanical link, the feedback from the sponding to the position of the steering wheel; due to the closed valve 3, the steering gear and the roadwheels are hy- roadwheels does not extend beyond the hydraulic unit. Ev- erything the driver feels is generated artificially.
-
Page 42: Self-Steering Rear
The Citroën Guide Steering: Self-steering Rear Self-steering Rear sasasa... -
Page 43: Brakes
Brakes... -
Page 44: Standard Braking System
The Citroën Guide Brakes: Standard braking system Standard braking system dasdsadsa a damping ??? is used to smoothen the changes. Bypass 3) Back to the suspension and brakes for a second. The rear sinks imperceptibly or not at all when braking—the amount of LHM that goes into the rear brakes is infinitesimal—prob- ably on the order of 1–2 ccm. -
Page 45: Anti-Lock Braking System
The Citroën Guide Brakes: Anti-lock Braking System Anti-lock Braking System Models with higher performance level came fitted To actually control the pressure, the system uses a three- with ABS. unit hydraulic block (one block each for the front brakes, one for both rear brakes). All three units comprise two elec- tro-valves, an inlet 1 and a return 2 valve. -
Page 46: Electrical Systems
Electrical Systems... -
Page 47: Multiplex Network
The Citroën Guide Electrical Systems: Multiplex network Multiplex network Circuit layouts already universally adopted in com- The multiplex wiring first seen on late XMs and later puters finally made their way into contemporary used on newer models like the Xsara Picasso or the C5 intro- cars. - Page 48 The Citroën Guide Electrical Systems: Multiplex network Each message or command is a sequence of a few num- messages generated in one network has to be relayed to bers, specifying: another, just one example is the suspension computer— the sender and the intended recipient of the message connected to CAN—being interested in messages about (every device connecting to the multiplex bus has its the open or closed position of the doors—communicated...
-
Page 49: Air Conditioning
Air Conditioning... -
Page 50: Air Conditioning
The Citroën Guide Air Conditioning: Air conditioning Air conditioning Once considered pure luxury, air conditioning and other forms of climate control have became stan- ambient air dard items on today’s car. After all, creating an condenser cooled air acceptable environment for the driver is more than a mere question of comfort, it contributes to refrig. - Page 51 The Citroën Guide Air Conditioning: Air conditioning The sensor before and in the heat exchanger as well as the teperature selection, influence the AC part, i.e. the oper- ation of the compressor. For instance, the compressor will not operate below a certain external temperature. Also, it will not operate if the temperature is set to maximum.
-
Page 52: Appendix
Appendix... -
Page 53: Orga Number
The Citroën Guide Appendix: ORGA number This number shows the day when your car was actually as- Calculating the production date is very easy using the fol- sembled on the production line. The dealers and parts lowing table. Locate the largest number in the table still less stores use this number (often called ORGA or RP number, than or equal to your organization number. -
Page 54: Index
Index... - Page 55 The Citroën Guide Index: Index AAV ......7 DIRASS ..... . 22, 38 ABS.
- Page 56 The Citroën Guide Index: Idle speed ..... . . 6 stiffness regulator ....36 idle speed control valve .