V-twin front cyl runs much hotter than rear--- Why?

[grippo]

Just the room heating up can cause a performance drop, although the ecu correction for air temp should keep the afr from drifting too far. I would put a big fan on the tank and open doors/ windows to maintain a stable air temp.

Here is the code with the mod to skip map sampling on every other tach cycle with odd-fire engines. Plus it will allow you to trim the spark adv and fuel pw for each cyl separately. In this version the dual table option works so that you can also specify to use ve table 1 for cyl 1 and ve table 2 for cyl 2. The fuel timing will now take into account the odd angle. I also included your msq converted for the new code and an ini file to be used with this code. In the msq I set the fuel timing as 120 deg, ~= 30% of the 360 deg tach cycle, but it is now to be specified in terms of degrees. Please check all the inputs are as you want them.

[Norzilla]

OK ... I have loaded up the new code, ini and msq and have the bike running. First impression is that the idle definitely smoother, as the MAP at idle is much more stable, with being able to set the map sampling timing.

I like the ability to have the second VE table linked via a % chg on the first VE MAP, this means that I can use my single WBo2 on the rear and use autotune to tune both front and rear. ( not perfect but better then no tuning effect )

I will be able to dedicate more time to the bike over the weekend to see explore the enhancements, MAP sample timing more and also the timing of the injectors.

Many thanks to Grippo!!

[Norzilla]

Just the room heating up can cause a performance drop, although the ecu correction for air temp should keep the afr from drifting too far. I would put a big fan on the tank and open doors/ windows to maintain a stable air temp.

Here is the code with the mod to skip map sampling on every other tach cycle with odd-fire engines. Plus it will allow you to trim the spark adv and fuel pw for each cyl separately. In this version the dual table option works so that you can also specify to use ve table 1 for cyl 1 and ve table 2 for cyl 2. The fuel timing will now take into account the odd angle. I also included your msq converted for the new code and an ini file to be used with this code. In the msq I set the fuel timing as 120 deg, ~= 30% of the 360 deg tach cycle, but it is now to be specified in terms of degrees. Please check all the inputs are as you want them.

[800vtwin]

What was the final outcome?

Just to add, 2 things come to mind.

All things being equal - normally the rear should be hotter going down the road. The front has more airflow. But, its more of a cylinder filling comparison. Vtwins can just have alot of weird pulsing going on.

1 - vtwins can require drastically different fuel. A dual table setup would be much better if you are trying to match cylinder outputs. But unless they have the same intake and exhaust tracks, they may never be real close. And it changes per rpm. Dual tb's and equal length headers are your best bet. You'll never achieve equal pulses if they dont get the same, equal fresh air charge.

2 - your cams have 40* overlap. You could have quite a bit of reversion going on. Expecially if its a common intake. If #2 is getting diluted with alot of exhaust gas, it wont have the pulse as the front. This is common. Check the underside of your throttle plate for carbon / soot and you will know if exhaust gas has been there. And you will need to run dual tables and pull alot of excess fuel from #2. And add some timing offset to help too. Besides taking up space in the chamber, hot exhaust gas also heats the air in the intake (= less dense), so this makes a cylinder charge even worse. Run it lean to keep some extra oxygen in the exhaust gas to help.

I have seen some vtwin engines wanting up to 6* more timing on the rear. And this would equal out the fuel the engine wants wot (dual tables are within 1-2 point wot) and even 2-3* more advance on the rear produces the best power output and gives up a couple more hp. Not that all vtwins are the same. But its something to test if you are really trying to dial it all in. I would first invest in a dual afr setup.

One of the best things I have learned - don't tune to what "you" think the engine wants. Or what you want. Tune it to what the engine itself wants. You have to learn to read the signs but it will tell you. And keep in mind, just because one cylinder wants something, doesnt mean the other one does. They are not equal. So, because you want 13.5 afr at idle, that doesnt mean that cylinder 1 doesnt want 12.5 and cylnder 2 doesnt want 17. You just need to find a happy medium that you are satisfied with. And try not to loose too much hair in the process.