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Kev · # 10 26-11-08, 01:25

Hi Nick, welcome to the XT forum, I will try to answer your questions as you have many.

Hi Kev,
Your advice has been much appreciated since I bought an 05 xtx a few months back, I did the "Kev" mod & altered the CO value & tried changing the TPS value but my bike still banged & popped on a closed throttle ( You need to block off the AIS pipe to stop the popping, the popping is mostly caused by air injected into the exhaust port for emission control) from any rpm & the surging improved slightly but remained. What are the last 2 numbers on your engine ECU 00 or 01?
To learn more I installed a O2 sensor port in the header and fitted my A/F ratio meter and went for some rides. Not sure what type of A/F meter you are using is it a wideband sensor, what data logging rate does it use? Y ou need to block off the AIS pipe before you can get any accurate A/F reading. As the AIS valve can open at any time & throw out the readings.
I worked through each mod in sequence and monitored the result.
Each mod produced a slight change in exhaust O2 readings around idle and slightly above but none of the changes affected the indicated fuel mixture at cruise or full throttle ! I use Tunelink software on the dyno & now have a WB2 commander that data logs throttle position as well as A/F ratio from 10 to 18:1 using a wideband O2 sensor for quick on the road testing.
I tried going both ways on the CO value to the point of stalling on a low setting but still no change on rpm above fast idle. You are corr ect, once the TPS reads over 18 on the dash it will run on the fuel map. The fuel map can then only be adjusted by the sensor inputs, coolant, air, air pressure, throttle position & rpm signals within a small parameter.
This data corresponds to the "feel" of the bike as I could only detect changes around idle performance and no change in general engine behaviour.
My bike has hi flow air filter, Yamaha racing pipes I would recommend you to run a Power commander with those mods to gain full control over the fuelling, also add a stage 2 DNA filter for more gains. and I cut the "crimped" end off each header (4mm) as the flowbench showed significant restriction from that, Thanks for the info I do not know that it was also causing a lot of flow through the ballance pipe which as the headers are paired obviously could not go anywhere. The H section is there to improve bottom end torque.
As many other riders have found improvements from the mods across the entire rev range I am curious why my bike hasn't responded the same but the test rig I used has proven accurate on other bikes / cars. Try disconnecting the AIS by blocking the pipe off so you are get a true A/F reading all the time. If you unplug the AIS at the connector the valve will remain open showing a constant lean mixture on the CO tester.
I'll keep at it until I find some explanation. The best fuelling mod by far is a power commander which will allow you to adjust the fuelling through out the rpm range +-.
Nick, Auck, New Zealand