... unless it is ALSO adjusting the mix based on a manifold vs. an atmospheric pressure sensor.
More info needed.
From what I understand, the ECU is not feedback based, so it has a loaded map that assumes you have the secondary flies in. It will run too lean if all you do is remove the flies.
Just to clarify, the Concours-14 FI ECU uses two fuel maps. At idle, and up to approximately 10% throttle position, the FI ECU uses an IAP (Idle air pressure) map. From 10% throttle position and above, the FI ECU uses a TPS fuel map. There isn't a fixed cut off where the ECU switches from the IAP map to the TPS fuel map, but it is approximately 10% plus/minus.
The throttle body assembly has a MAP sensor that is supplying feedback to the ECU, which the ECU compares with the current atmospheric pressure. So, at low throttle openings, there is a differential pressure that is monitored. Once the throttle is opened past a certain point, and there is no longer a pressure differential, the FI ECU switches to the TPS fuel map.
I expect this is why the boys with the ZX14 throttle body conversions are having some low RPM abruptness or other off-idle issues. The engine is obviously flowing more air, and it is likely confusing the ECU because the IAP map was for 40mm ID TB's, and not 44mm. The PC5 works perfectly for fuel tuning between 10-100% throttle position, but tuning from 0-10% would be a little bit of a moving target for the PC5 to 'correct' as it were.
(PS: I will be installing ZX14 TB's myself before too long, and will be doing a lot of tuning, both with a PC5, and inside my own ECU, so I will post lots of updates as I have them.)
Regarding the secondary flies removal without fuel tuning: It *shouldn't* be a problem, and I thought there were lots of guys that have already done this no? It's not really much different than all of the people that have been installing TRE's on Kawasaki's for years....they open the secondary flies earlier, with no fuel changes. Fuel delivery is still based on TPS, not the secondary fly position. I would still personally prefer to see a PC5 or PCIII installed.
Cheers,
Rem