cruise control 2.5TD

[robertmnorton]

Hi Ken,great stuff,however,i am confused on how it operates in comparison to the vacuum control system.I understand it only needs speed information to control the pump but as Dman notes the EPIC still uses cable control to the pedal position sensor and a vacuum actuator to position the quadrant and therefore pedal.There is no output from the EPIC ecu that can reposition this quadrant.Is the pedal position sensor ignored once cruise is engaged and the pedal returns to idle when you take your foot off ? Can you accelerate above cruise set speed and does the car return to this speed and the pedal to idle when it's released ?
robertm

[Dieselman]

There is no output from the EPIC ecu that can reposition this quadrant.Is the pedal position sensor ignored once cruise is engaged and the pedal returns to idle when you take your foot off ?

Exactly. The accelerator pot is just a reference for the ECU, but it can generate it's own reference when the CC is selected and as the pump operation is drive by wire, the ECU just controls it as required.

[robertmnorton]

Hi all,thanks Dman,so why did Citroen go to the expense of all the additional hardware when a simple wiring mod would suffice ? Was the re-engineering itself too costly with the production run winding up ? The same applies to the Xantia. After all this EPIC cruise control was already fitted to the Synergie.There are variances in the ecu's fitted to all 3 vehicles.Does anyone know which system is fitted to the 406 ?
I had looked into the wiring and ecu configuration some years ago,but as it wasn't broke it didn't need fixing and i was unsure about the function of the pedal position sensor in conjunction with cruise.
robertm

[davoxx]

me too .. i soooo want to stick cruise control on an hdi xantia .. any help would be great!!

[kenhall]

Hi Ken,great stuff,however,i am confused on how it operates in comparison to the vacuum control system.I understand it only needs speed information to control the pump but as Dman notes the EPIC still uses cable control to the pedal position sensor and a vacuum actuator to position the quadrant and therefore pedal.There is no output from the EPIC ecu that can reposition this quadrant.Is the pedal position sensor ignored once cruise is engaged and the pedal returns to idle when you take your foot off ? Can you accelerate above cruise set speed and does the car return to this speed and the pedal to idle when it's released ?
robertm

Hi Robert,

As John has said both the 2.5 and 2.1TD's have cruise control already built in to their respective ECU's and the only hardware required to activate this feature is the panel switch plus the column stalk control (and possibly brake and clutch microswitches / relay if not already present). All the panel switch does is to supply an enabling 12v+ to the stalk control which in turn can apply this voltage to 3 pins of the ECU depending on which one of the three possible directions the stalk is operated in. The fourth ECU pin requires a constant 12v+ but can be interrupted by any one of two switches in series, one on the brake pedal and one on the clutch pedal.

The system operates exactly as described in the XM owner's manual. The throttle pedal and potentiometer play no part in maintaining the cruise set speed apart from when you wish to accelerate beyond the set speed, eg for an overtake, then when you take your foot off the accelerator the speed drops back to the previous set speed. IMHO any system using a vacuum actuator will either have a mechanical pump or maybe have an non Citroen aftermarket kit fitted.

I have attached a circuit diagram from the French article describing an installation for a Xantia 2.1TD ( with Epic ECU). The author did not bother to fit the brake and clutch switches which would normally go in the 12v+ wire to ECU terminal 1.

Cruise control circuit 2.1TD .jpg

Ken

PS Robert - my 2.1TD XM currently is operating on an ECU obtained from a scrapped 1996/7 406 with the 2.1TD Epic engine - don't ask why!!

[robertmnorton]

Hi Ken,many thanks,i had already prepared a set of schematics a couple of years back when the cruise gave trouble (it was the speed sensor) and will compare them.The cruise installation is a Citroen factory fit on my 2000 auto and the reason i was curious all that additional wiring and hardware was fitted.The fact that it is a 406 ecu you have fitted, i suspect this may be the explanation.As previously mentioned the Synergie had integrated EPIC cruise function and its' ecu p/n differs from that of the xm - it is no longer available as a replacement part - as it does the xantia.This may only be operating parameters,i really have no idea,but remain curious.
robertm