like subject....how is it possible the CO gets higher with the time.....more then once in a year i have to turn my CO down.....

how is this possible it gets higher.....

i have a L8 comp....

 

have the same problem with my L6, was told they need calibrating but not convinced

 

Easy this one !!!

Dont forget, the cosworth ECU is a "speed density" air flow type.
I.E. it does NOT directly measure the airflow of the engine.
It relies TOTALLY on the mapping.

So over time as your air filter blocks up and the pistons reduce there seal as the
rings wear, less air will be drawn in and the ecu CANNOT measure these
very small changes that occur over time.
(There are other factors but you get the picture)
These are only small enough to affect light loads. (idle/low to mid range)


As a result, less air upsets the AFR at low loads and causes higher CO
I.E. excess fuel compared to air.


This is why cars have a lambda sensor now as these auto compensate the fuel
ratio over time for all variables that change with age and use.

 

Cheers for that simon been wondering for ages what it was that caused this to happen

 

maybe true simon.......but my air filter doesnt get that dirty in a short time.......maybe over the years ok...i can follow that...but not in that short time..

i have to turn my CO down more then once a year.....if it is true what you say then i will have no bhp left soon...?

 

wimwerf,

The air filter was probally a bad example but an engine will wear with use and
my explanation is still valid.

You cannot expect an engine to be EXACTLY the same after use.
It does not take much to upset the AFR at IDLE because of the relatively small
volumes of air and fuel required.

Andother example is the fuel injectors do clog up with use which is why you must
clean them regularly aswell.

Ther are MANY factors !!