When you need repairing CO potentiometer

155 Q4 has a CO potentiometer for carbon adjust when idle
its adjust air-fuel mixture at idle

if its faulty or removed, ecu read zero value
range is -64 to +64

if your fuel pressure is 2.5 bar (std)
zero value is correct and not need adjust

but if you need it ?
when fuel pressure 3bar ?


generally need re-soldering for repair
CO trimmer has one 1k resistor and one 10k potentiometer

http://b1210.hizliresim.com/12/d/dvj6u.jpg

http://b1210.hizliresim.com/12/d/dvj6m.jpg

http://b1210.hizliresim.com/12/d/dvj6n.jpg

http://b1210.hizliresim.com/12/d/dvj6r.jpg

Quote:

---

Originally Posted by MaxiBoost

if your fuel pressure is 2.5 bar (std)
zero value is correct and not need adjust

but if you need it ?
when fuel pressure 3bar ?

---

That would depend on why you need to raise the fuel pressure in the first place. If it is raised then a new ECU written for the car I'd say no. But if you use an off the shelf chip and raise the fuel pressure I'd say it might need adjusting.

Not a very helpful answer was it?

I want to know exactly what it tells the ECU to do. Is it simply just inject less fuel at idle?

Quote:

---

Originally Posted by Steve Webb

That would depend on why you need to raise the fuel pressure in the first place. If it is raised then a new ECU written for the car I'd say no. But if you use an off the shelf chip and raise the fuel pressure I'd say it might need adjusting.

Not a very helpful answer was it?

---

and i've just get rid of this device, and connected wideband signal to corresponding pin in the ECU :thumbsup:

regards

ws

dear friends this answer very late Im sorry.

co adjust working only when car is idle
idle setting is different work on ecu

when car idle ecu not use injection and ignition tables.
its use co trimmer potentiometer for fuel mixture.
also ecu have some small map for idle ignition and some other map (idle valve).
there are run only when car is idle, otherways ecu use std fuel and ignition tables.


why we need rise fuel pressure on Q4 ?
our fuel pressure std 2.5bar.
our fuel injectors 384cc when fuel pressure 3bar.
our ecu is 8bit (range is 0 to 255 raw and 16x16 fuel table)

if we want more power need to rise up fuel pressure
because standard Q4 fuel table max value ~250 already use
(standard Q4 already use injectors %90-%95 duty, high boost and full trottle)
I can not write this ecu fuel table 270 or 310 when I want rise fuel !

I need change injectors OR rise up some fuel pressure and rearrange in ecu fuel map.
finally, if I rise up fuel pressure our idle co trimm setting goes to high, we need adjust it.