Is itpossible that S&S, thru luck or good engineering, hit on a combination that what fuel it learned in closed loop was alsoapplied close enough in open loop because of the long term trim function? This rarely happens with mods because there often is not a correlation for fuelchanges of what happens at part throttle low-mid RPMs closed loopandwide open throttle mid-high RPMs open loop. I'll give S&S the benefit of my doubt in that it was good engineering and that any deviation from this combination would require custom maps and/or tuning.

 

As I understand the HD EFI and narrow band O2 sensors do not have any aspect of engine performance for the consumer in mind. The HD system with the narrow band O2 sensors only work in a limited range. It just so happens that limited range is that in which the EPA tests for compliance. The HD O2 sensors do nothing to help your high performance enginethey are there so the engines are EPA compliant. That is why aftermarket EFI systems either eliminate the O2 sensorsor replacethem with widebandsensors.

If you change your aircleaner and pipes and just run the stock EFI and O2 sensors will it run. Sure but not to it potential. If the system is correcting itself at all it is just within the range of the O2 sensor.

Peace
Joe

 

Joe, you hit the nail on the head! From the info I've been able to glean from this forum and other sources, the narrow band O2 sensors will do nothing good for me and my bike but are only to keep the EPA happy. My new bike will arrive end of March so I've got a decision to make asap.

 

Narrow band O2s are of huge value. Thay have that ability to give the stock ECU real time data to let it home in on the perfect VE to obtain14.6 AFR (can be sort of adjusted down to 14.2) Ther is also the ability to find out where your VE table need tweeking. Changes in your fuel pressure or dirty AC is automaticly adjusted for. Do not throw away this ability. If you have to have a mixture fatter than 14.2 then get a pair of Innovate lc-1's and rock and roll. I have fuel injected everything from a real 69 Hemi Cuda to a 7500 RPM jetski to a 8000 RPM Honda street car to 9.0 sec -154 MPH turbo Mustang 4 cylinder street car. This EFI stuff is good.

AW

 

I don't disagree with you, they do what they are intended to. However when your talking about performance add ons and tuning the EFI across a broad range with Harley based v-twins----The stock O2 sensors only do their job in a limited capacity.

Peace
Joe

 

The bike that this datalog came off of is a totally stock 2007 Sportster with the exception of a Rinehart 2-1 exhaust. The EFI map is the factory map dataloged by a SERT. If you look at these two logs (same data, different things plotted) you can see what amasterfull job the stock ECU did at fixing the fuel maps. This can be seen in the lower graph and the way the 02s are bouncing .25 to .8 volts just as designed. Note that this is a no load data log but I will be test and loging out on the street as soon as the streets melt. I have written software that will develop the next SERT map to test based on the results of the existing maps. I grant you that I will need to use a wide band to tune the 80 KPA and above maps but the narrow bands are far from useless. once theUCU develpoes the entire center of the map I will then change the AFR to the the AFR that I really desire and not the 14.7 that theECU nowtargets and run open loop on more of the map.

Narrow band are greatly under utilized. What they can do with incredible effency is find 14.7 AFR Learn to use them for what they are designed to do and rock and roll. The trick is knowing when to turn them off. EFI is nothing more than playing tricks to utilize all the software to YOUR advantage. The stock ECU gives youthe correct answer for 90% +/- of the time you ride.

AW