7427 ECU $OD Lock INT/BLM to 128 vs open loop for VE tuning

**tplasek** · 08-12-2022

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

**tplasek** · 08-13-2022

I decided to enable Closed Loop with locked BLM's and INT's at 128. Sure enough, after enabling Closed Loop but with locked values, the Wideband AFR values changed in Dave's spreadsheet. After a couple of data logs, I was able to shift the entire VE table to get it pretty close in the low to mid RPM’s and Maps. The areas requiring the most adjustment were the 80 -90 - 100 map areas. These needed around 8% more fuel to get the AFR’s in the 14.xx range with no PE. It only took a couple of logs to get the VE tables tuned in per the chart below and this is with the BLM and INT locked at 128. Now I am attempting to add the PE, but I can only get it to enable when the throttle is >98%. When it does engage at WOT, the wideband values match my target PE AFR table, so my VE table’s must be pretty close to correct.

With 40in tires on a 4,400 lb. jeep, I need the PE to come in long before 98% TPS. Maybe around 70% < 3000 rpms and 50% after that. I’ve changed the Fast PE delay time to 0 sec. I also changed the following PE vs TPS settings. For some reason I still cannot get the PE to engage unless am over 98% TPS.

Maybe it is possible the delay time cannot be set to 0. I’ll try 1 tomorrow to see if it makes a difference,

ve table.jpg PE vs TPS.jpg

**tayto** · 08-13-2022

have you tried Trimalyzer? https://ecmhack.com/trimalyzer/

seems like you are on the right track, not sure why your PE isn't working have you searched to see if there are more parameters?

**stew86MCSS396** · 08-14-2022

http://www.gearhead-efi.com/Fuel-Inj...PE-not-working

**tplasek** · 08-14-2022

Tayto, Thank you for the link. I went to the website and tried to download the file, but for some reason I couldn't get it to download. The description of the software makes it sound very much like Dave's automated wideband spreadsheet

Stew, thank you for the link. That was the exact information I needed. I previously read to set the PE delay to 0 but for some reason that alone did not work for me. After reading the thread from the link you posted, I discovered I also needed to set the Minimum TPS for Fast PE from 98% to 10%. Once I did this my PE would engage at the designated TPS %’s as set in the "PE vs TPS" and "Fast PE vs TPS" tables. Now I get instant, and I mean INSTANT PE as soon as I cross my set TPS thresholds. I decided to have my final PE settings engage at 50% TPS across the board and set both the "Fast PE vs "TPS" and the "PE vs TPS" tables to all 50%. When PE engages, it is like opening the secondaries on a 4 barrel carb. It takes off like NEVER before. It instantly richens up the mixture very close to my target AFR of 12.5 all while seamlessly engaging at 50% throttle. It also eliminated the last few knock counts I had that were occurring around the 2000 rpm/upper MAP areas. I’m good to go. No more knocks or sluggish performance and the Jeep runs great!
PE AFF results.jpg tables.jpg