What is the richest fuel air ratio a SERT can provide? Can it go below 14 to 1 or do the narrow band O2sensors muddle things up?Any & all answers would be appreciated.

 

You can have whatever you want but outside the 14.6 : 1 the O2 sensor feedback is not used.

If you have a near stock bike with just air filter and pipes you shouldnt need to get much richer than 14.1 : 1.
This can be achieved with the CLB tables and the VE tables and you can retain the O2 feedback which will adjust for minor atmospheric and altitude changes.

You could if you wish however run at 10 : 1 but you wont like it and it will wash your bores dry.

WB

 

I'll be running a 103 kit with some headwork in the future.

 

If you will be running the 103 kit you will need to have it dyno tuned. Do your homework and find a tuner that knows their way around a SERT. Not all of them do.

 

The first thing to do with this sort of set-up is make sure that the tuner sets the correct VE values first, as they are unique to your engine. Everything else will follow. If these arnt calibrated to your bike, everything that follows will be meaningless.

WB

 

DRCLB: If you have the SERT,take a look at the User's Manual; it has good info fora basic understanding ofa/f, VE, and ignition timing; and,the range of adjustability available and what should be avoided.

Our bikes don't operate at a single a/f: the engine may need 12.8:1 at WOT at early rpms and something leaner as revs increase; it may need 13.8 while accelerating at less than WOT; etc.

Also, the narrowband 02 sensors are not what limits the bike's ability to adjust a/f automatically; it's HD's ECM programming that simply takes thesensors off-line so to speak.

 

Thanks very much guys! I'll make sure I'll read everything thoroughly and ask the tuner lots of questions.

 

There's also another feature of the (at least) '07 and later ECUs which is not covered in the SERT documentation. There's a routine called "adaptive fueling" which has a range about five times as great as that of the O2 sensors. While in closed loop operation if for some reason the O2 sensors are off their desired mark, even well out of their operational range sometimes, the ECU will (within its limits) adjust a multiplier (one per cylinder) against the current VE value to get the desired reading from the O2 sensor if possible. This multiplier is constantly in use against whatever VE value is being contemplated for the fuel calculations, even in open loop, and is constantly being updated if need be while in closed loop.

The result of the multiplier is indicated in the SERT data-logging software by the "VE New" value.

It's the best way to "autotune" with narrowband O2 sensors. Word is that the function (at least for H-D) was first put into use in the Buell line, some time ago.

It does not negate the necessity of having the VE tables accurately populated. In fact, it relies on that.

The multiplier evidently can only be manually reset to 100% via the Digital Technician interface.