MegalogViewer & tuning fuel maps with a single wideband sensor

I've been tuning my '08 XB12 with BUE2D firmware and a single wideband sensor in the front hole. I've encountered an issue with MLV when I look at the rear hole and its NB derived EGO corrections. AFVs locked at 100%, closed loop enabled via the rear cylinder. I end up with a front EGO correction of 100% due to the WBO2 being present, the rear EGO correction is normal with the NB sensor. When I use VE Analyze, I have to select the AFR Field and the EGO Correction Field, which is straightforward for the front cylinder with the WBO2 since the AFR field is just the transfer function computed for the sensor and the EGO correction is 100% since there is no NB in that hole. However, when I look at adjusting the rear cylinder with the OEM NB sensor, I'm not sure what to select for the AFR Field. As a test, I set the EGO Correction Field for the rear cylinder to the front EGO correction field (which is all 100%), selected the Narrowband O2 for the analysis, and still ended up with adjustments made to the map. I was expecting no adjustments to be made due to the EGO Correction Field being set to 100% everywhere and the NB selected for analysis.

To avoid this problem with the cylinder that has no wideband installed, I just multiply the wideband-less cylinder's fuel map with its closed loop EGO corrections in Excel and use that instead of the output from MLV. Has anyone else encountered this?

So I've achieved a state of tune now, after about 10-12 iterations of tuning each cylinder independently, where the resulting fuel map adjustments are within 1-2 VE units. The process would be greatly accelerated by having done this on a dyno, but what's the fun in that? The process when using MLV HD requires that you use VE Analyze to remap only the cylinder that has a wideband sensor on it. No use of the EGO Correction field (set to None) and the EGO Sensor field set to the wideband AFR data. The narrowband cylinder is tuned the old school way, with only the closed loop region adjusted by manually multiplying the existing fuel map by the EGO correction map from MLV HD.

Prior to tuning, the bike pulled very hard everywhere, but now it pulls so hard that even at 120 mph in 6th gear I have to tuck in, lay my chest on the airbox, and get as forward as I can to help keep the front wheel on the ground. It's still skiddish because of the light frontend, especially if making power above 7000 RPM. The AFR readings are right on target with 13.4 at WOT. Comparing the stock map and the tuned map, there's quite a bit of major adjustments made to both front and rear cylinder.

Thats great news, sounds like a job well done:cool: And very satisfying, yes?

I forget, what pipe are you running?

Geezus!!! Sounds like you created a monster!!!! Nicely done!!!

Thanks, I must admit it did take some time to acquire all the data. Each cylinder took about 10-12 datalogs which I lumped into my morning and evening rides into work. The end result is definitely pretty satisfying. The only modifications I have to the engine are the K&N air filter and APH Engineering slip-on exhaust.

So this is really sad, but it's taken me until now (late 2021) to tune the rear cylinder on my '08 XB12Ss. It's a fairly simple procedure of locking out the AFVs and EGO correction, but installation of the rear wideband sensor definitely takes a little effort due to the removal of the rear cooling fan. Either way, after one pass of adjustments, I cannot believe how much more power the engine makes. I must've been riding it in a relatively handicapped state for over 3 years. I noticed that the rear spark plug was showing slightly leaner than the front after an oil change and inspection several months ago - that's what finally motivated me to tune the rear cylinder, but I had no idea how bad the rear cylinder was. Full throttle all the way to redline pulls super hard like it's not done before and actually makes it a bit hard to hang onto!

My first pass resulted in enrichment in many parts of the map, but my 2nd pass is now leaning it out again. I'll see how that works out.

Be sure to post up your dyno chart you get when you're finished! It's obviously a much more accurate way to quantify your gains. We can compare it to stock, or any of the ones in the muffler test too :eagerness: