I have been unable to get Lean Cruise to work for me, so I have a theory about an alternative to lean cruise that needs test subjects to see wether it will work or not. Those of you who have a good grasp of tuning might even be able to help me come up with the appropriate settings.

I've read and re-read Rbobs paper on proportional durations and think there is a way to let the o2 duration spend more time below the switchpoint(lean) before it starts to correct, and less time above(rich),thereby increasing the average time towards lean, resulting in more MPG's over the whole driving range, not just when cruising. I use the 16197427 PCM with the OD mask.

Any takers???

 

Best lean cruise or overall MPG and power is to read in a WBO2 and use it as the closed loop sensor. Use the closed loop O2 tables to tune.

You can use the closed loop tables with a NBO2. You just won't get the repeatability that a WBO2 gives. Set the low MAP table values leaner.

I disable the lean cruise mode and just use the closed loop tables and adjust then so that light MAP values run in the 16.x:1 AFR range and high MAP values run in the 13.x:1 range.

 

Not an option, right now it's my truck with all the WB stuff hooked up, but I'm setting it up for my nephew who will be purchasing the truck from me next month. The goal is to have him getting MPG's around 20+ hwy, 15-16 in town using the stock o2. I'll be keeping all my tuning and wideband stuff for the next build.
Right now it Idles great and has great part throttle and cruise power while getting around 14 in town(350 W/204-214 cam w/vortech heads & exhaust, BB TBI) and WB stays on average between 14.5-15.2. WOT is good though staying right where I tell it. However,I know my VE is off everywhere else because I've never gotten around to load adjusting it(maybe thats why Lean Cruise has yet to work!) but I figured I'd get all my ducks in a row before I get down to the nitty gritty. Have all my options on the table so to speak.

 

Your theory on using the NBO2 is correct and you are looking for real world MPG with a truck. A simple tweak of the O2 threshold tables should get you there. You are using a heated NBO2 right?

BTW, I didn't know the 427 ECM code had lean cruise. What BCC did you disassemble to find the lean cruise code?

Is that 14.5 - 15.2 using 10% ethonal or straight gas. If that is E10 then you are already lean burning according to your WBO2 AFR.

 

I think it's either Dimented's or Haulin's interpretation of the OD hack using portions of the EGR strategy and open loop tables when in closed loop. My perticular code is BJLH, and from the way I understand it to work, the VE would have to be dead on for the WB to actually read commanded fuel as per the table. And since I haven't had the time to do that painstaking job, I figured I would let the computer run it lean for me using the o2 windows.

As for the 10% ethanol, here in Florida, or probably anywhere else for that matter, can you really trust what the label on the pump says?

 

Post for enabling lean cruise.
https://www.thirdgen.org/forums/post...8-post258.html

 

One thing I'm not sure about is the definition of the o2 error. Is it the timeframe from when the switchpoint gets crossed, and is moving away, until INT is able to add/subtract and bring it back across???

Also, is the slow o2 time constant @ 4CFB what actually defines wether the o2 is slow or not??? And how does it's "slowness" tie into everything???

 

If I've understand correctly you can enable open loop AFR at L400D b0 in the $0D mask to simulate highway mode like the $42 used. My question is this. I just pinned from a 747 to a 427 ecm and am using a manual trans so I have no VSSB. Is there a way to enter this pseudo hiway mode without the VSS signal. I am using the optical from the 747's pin A10 to pin F13 on the 427 and have set the VSS ratio to 2. Any way to make it enter highway mode without the TOS on pin F12?