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Sorry to go back to the CO2 settings which has been very well covered on the site, but I thought I would let you know that after purchasing a 900 in October 23 with 13500 miles and living with the rubbish snatchy throttle, I finally got round to checking the bikes CO2 settings. Ive done the airbox mod, ie disconnecting the wire from the ecu and thought it was about time that the settings were checked. To my surprise C1 was on 28 and C2 was on 10. Ive reset them to C1 15 and C2 on 20 as a start and will check to see if the bike feels any better, when the rain stops!Â
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Im sure there must be many TDM owners who live with this issue, but my 2003 appears to be well out of spec and I believe checking the CO2 readings should be something all owners should check, just for piece of mind
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As mentioned by Nog, the CO settings seem to only be idle jet equivalents, which are only relevant in low load and low speed situations.
There needs to be some correction allowance made for fuel injectors, because they all deliver slightly different volumes of fuel. This is a very common situation in cars, when you replace an injector they need to be 'programmed' with a number corresponding to a value written on the side of the new injector. This usually is a correction value corresponding to a flow rate for the injector, depending how far from the ideal flow rate it is, under test conditions
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The ECU uses this value to open and close the injector for longer or shorter, depending on it's flow rate
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In the airbox, underneath the air filter, there are two snorkels connecting from the airbox to the throttle bodies. These 2 snorkels have different lengths. In tuning, a longer snorkel gives more low torque, and a shorter snorkel gives less torque but more power. This might mean there is some tuning effect in play on the TDM too (although there is the possibility that the asymmetry of the design maybe helps with noise instead. Not sure)
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The different snorkels have different flow rates, and again, this affects how much fuel should be injected.
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Having played around with the CO on my bike quite a bit, I came to realise that, in a case like yours, where there was a difference value of 18 points, when you come to increase the value of one cylinder you should change the value of the other cylinder by the same amount, importantly retaining the difference between the two original CO values.
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In your case, C1 was 28, C2 was 10'. I believe it's safe to increase these values, but always keep a difference of 18, as that is what the factory chose, presumably while the engine was on a test rig, or because those were the batch correction values of those particular injectors.
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As you've reset them to 15 and 20, you've made the difference between them 5, in the opposite direction. As an experiment, using your C2 value of 20 as your desired C2 value, try setting C1 at 38, thereby restoring the difference of 18, and see if it makes much difference.
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Note that a lot of this is conjecture, as there is no information available from Yamaha about the real meaning of this setting.
Diesel fuel injector coding is almost required when replacing a diesel injector (they refer to the correction value sometimes as 'trim codes' , but if you don't do it the vehicle will still run, just not as sweetly.
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For petrol vehicle's, modern ECU's learn each injector's parameters by sampling the exhaust gas.
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I think new injectors are probably 99% close, and the trim/correction value gets the injector operation to be 100% accurate
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I don't think the ECU in the 900 is sophisticated enough to be self adjusting injectors.
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Another way the injector flow can be calculated (and then compensating for it) , is by monitoring the common rail fuel pressure during the firing of an injector. Perhaps this method works best for diesels, which run with enormous fuel pressure. But, the TDM900 doesn't have a fuel rail pressure sensor, it uses a more primitive pressure relief valve to control fuel pressure instead
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Interestingly, the Yamaha R6, a four cylinder bike, only has two CO settings too, C1 and C2, and not C1, C2,C3,C4 as you would expect.
It uses C1 to control the injection for outside cylinders, and C2 for the inside two cylinders. So that throws a spanner in everything !
(Inner cylinders run hotter)
They suggest only increasing values by a maximum of 7 for the R6, but that could just be hearsay/guesswork.
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So, there's nothing absolutely conclusive here, But I assume each injector has a slightly different flow rate, which is critically important to get right, at low load/low speed running, and we know there are two different throat lengths of snorkels, so it would be unusual for both settings to be identical, so to my mind, if the CO value is a correction parameter, the most important thing is to keep the initial difference between the two values the same, whichever way you tune them, higher or lower
Tuning the 900 using the dashboard buttons
), around 2016 Fixitsan mentions that the CO (not CO2) levels are really just like the idle jets on a carbed bike, nothing more, as above around 3k rpm the CO values are ignored as the O2 sensor is used and then simply the ECUs fuel maps.
orry:
 Sorted and on the Road Mick 
 
