C1 C2 couldn't be cylinder count
 

It Doesn't make any sense to have different mixture settings for different cylinders on the same engine.

What's the point of having a cylinder with richer/poorer mixture than the other ?

I've played around with C1 and C2 settings and found out that there is more to the C1/C2 than this cylinder assingment thing.

The settings may be different for lower rev or higher rev.

I might be wrong but in a bike with several cylinders it can happen that not all of them work at the same temperature due to the fact they get not the same cooling (specially when one cylinder is in front of another one). Maybe this could be something that justified different CO value settings. The headers might also be different which might let one cylinder get rid of the exhaust gases more easily then the other one.

As I am no expert what I have written might just be nonsense. Maybe Kev or Freeze could explain why different CO settings would make sense in a twin cylinder bike.

Spot on Miguel, not only can the CO's be different but also the fuel map for each cylinder across the whole rev range. We are are only talking about a very small percentage difference in A/F ratio.

We have a Aprilia Pegaso with the same engine and inherent problem with surging etc. There is an oxygen/lambda sensor on the exhaust which obviously reads the air/fuel ratio and sends this to the ecu which I would assume then corrects it to meet the emissions needed to pass the required law. Now if that is the case how does altering the CO achieve anything? I am new to bikes but have nearly 30 years on performance cars and I can relate to remapping etc but does the system work differenty on a bike as modern cars have little or no CO adjustment. Does the CO adjustment only affect idle? Last question, how much improvement does a power commander make?

Firstly welcome mate all bikers are welcome on the XT660 forum.

The CO2 sensor on the XT is used for emission control & is not a tunning device, the closed loop circuit works mainly on the cruise.

The O2 sensor reads all the time, the ECU decides when it will take readings from the O2 sensor depending on coolant temp & TPS angle & RPM. In the open loop circuit the ECU runs off the fuel map, in the closed loop circuit the ECU reads the O2 sensor & will correct the fuel map for emission control, this is where we get our surge from on the 07 08 models. On the 04 to 06 models they are just very lean for emission control

The Yamaha fuel map is way off for performance & fuel economy. A PCII will correct the fuel map & give you max performance for your mods or standard bike. If you have a 09 XTX/R go for the PCV.

Thanks for your explanation. I might have to look into a PCV in the future or maybe look into remapping, something I havent done for a while but I like a challenge lol

I am very keen to try a PCV with Auto Tune on my 07 XTX.

co mod on 2008 xtx
 

hi guys & gals
would this co mod work on my 2008 xtx as i have noticed this disconcerting surge when manoeuvring at slow speed or cornering out of junctions. plus it does keep cutting the engine out on dropping down the box. any ideas please??

:spam4:

before you try the CO2 fix, try to up your idle speed by turning the idle screw on the throttle body to increase your tickover to at least 1450rpm, that alone should stop your bike cutting out.

Then if that doesn't help you can try both adjusting the CO2 and the TPS lean angle.

All these are documented in the mods list.

CO2 will not adjust anything on the XT. CO1 will.