Equipment:
  • ECU 7427 on $OD
  • Mostly stock SBC 350 in a Jeep
  • Small computer compatible camshaft
  • GM TBI BJLH based BIN
  • Have a wideband O2 sensor inputed in the Linear ERG input
  • Larger 46MM TBI and Intake


I'm in the process of tuning my VE tables. I removed PE from my bin and changed the Closed Loop enable temperature to 150C. This allowed my ECU to remain in open loop and locked at 128. I spent the last couple of days performing TunerPro data logs with the WB AFR captured in the data log. The data was then exported into Dave’s wideband spreadsheet and used to fine tune my VE tables. In order to get Daves’ spreadsheet to accept my data, I manually changed column AJ from open to closed

After 5 or 6 logs, Dave's spreadsheet now shows 14.xx WB AFR in 95% of the populated tables, including the 80- 90 and 100 Kpa columns. I was thinking all was well but then I realized tuning for 14.xx in all cells of Dave's spreadsheet in open loop may not have been the right method to tune me VE tables. I just realized there is an Open loop - AFR vs Vacuum vs Temp table that is most likely in play while in open loop. What I tuned my VE table for (all 14.xx AFR) doesn't match the open loop AFR vs Vacuum VS Temp table. In the end, I plan to run closed loop with my setup. I just needed to lock the ECU at 128 to get the VE tables tuned.

Would it be better to let the computer go into Closed Loop and lock the MIN and MAX BLM's and INT settings to 128 for Idle and Open Throttle? This would allow the computer to go into closed loop mode (targeting stoich) but would NOT allow the ECU to make any BLM/INT changes. Dave’s spreadsheet could then use the delta from 14.7 to the recorded WB AFR value to fine tune the VE tables.

I once read about tuning VE tables in open loop but I may have misinterpreted what I read. VE tuning in open loop may have been for people who plan to stay in open loop after tuning.

Tim