1998 vs 2000 VFR Fueling

Hi All,

I need some help from some of you that are more familiar with our ECU than I am. I have a 2000 VFR (with cat) that Ive ordered a 98 header for in order to get rid of the cat. With my O2 sensor eliminators which negates closed loop will the fueling per the ECU be exactly the same on the 2000 as it is on the 98? In other words in 2000 did Honda just add a cat and O2 sensors or did they also modify the open loop fueling?

 

That's incorrect. The 2000 and newer VFR's are closed AND open loop. The bike will go from closed to open loop depending on conditions unless the O2 sensors are disabled in which case it will stay in open loop.

 

This is above my paygrade.

 

Its unlikely for the bike to go directly to the same settings as 98 one. There is no engieering logic. If you have problems with O2 it can be a problem that corrects the fueling totally opposite on the setting. This means its possible, when it should give +0.8v for it to give -0.8....... its a possibility. This means that the base map will be a lot more richer than a map without O2 sensor,because it has to compensate for the fuel trim which is around 20% sometimes even 25%, so most likely your idea will not work. Because 20% of 14.7:1 which is the ideal situation is basically ~18:1 all the time and that is too lean. And usually the starting setting is ~ 10:1. limp mode is a serious problem in cold conditions. When you start the bike due to the trim it can get up to 7:1 , which is very annoying to ride, it stalls easily in low rpm. Honda engineers are good, so this will most likely not happen, but still i am positive , what you try to achieve is not possible, simply because the Closed Loop logic makes adjustments to the Open Loop one, because of the failed sensor.

 

I'm in line with Gips.
I don't know motorcycle ecu programming but know cars. I would assume bikes are similar to cars.

On a car the ecu runs closed loop from 0 to about 60% throttle openning (varies by manufacturer) using the O2 sensors to trim the fueling map. The ecu does this by cycling fuel up and down slightly at the 14.7:1. You can watch it on an air/fuel meter cycling. The computer is doing this constant adjustment to make sure it is running at the ideal point (usually very slightly lean on production cars for fuel mileage and emmissions)

Above 60% throttle the ecu goes into open loop mode and only relies on the fueling maps.

If the ecu does not see O2 sensor signals below 60% throttle setting it jacks up the fuel trim so it is definitely running very rich as the safe option compared to lean. But this causes part throttle driveability issues as mentioned before.

If you are removing the cat it is probably more important to have the O2 sensors to trim the fuel map. I am pretty sure that I read the FI programming was changed for the 2000-2001 which makes sense when the exhaust flow is changed.

The big question is does the ecu fuel trim from a 00-01 have enough range to compensate for the loss of the Cat. The closed loop at large throttle opennings will not change of course. If the exhaust flows better with the loss of the cat you might find it running lean. Not a good thing at high engine loads.