Force Open Loop to tune

[eutu1960]

Can you tune in open loop without a wide band O2 and if so how can you force open loop. I have a 7727 ecm being used with a 383 sbc TPI.

[84Elky]

Can you tune in open loop without a wide band O2 and if so how can you force open loop. I have a 7727 ecm being used with a 383 sbc TPI.OL by definition means INT and BLM =128, so no way without WB. However, can set BLM min and max calibration values at 0x51D and 0x51E =128 and tune with the INT in CL and you'll get close to OL. This will eliminate the BLM-based BPW correction but will not eliminate the other 2 CL BPW adjustments:
--L00E8=Rough BPW Correction =INT +/- Prop Gain Counts (an adjustment based on the magnitude of the % Adjusted SLOW o2 Voltage Error) and
--the "Fine" BPW correction which =1/2 of the Prop Gain Counts in L00EC made in the opposite direction of the INT-based Prop Gain Counts correction

You can force OL by using S_AUJP v5 (Post #1 here): http://www.thirdgen.org/forums/diy-prom/713188-s_aujp-v5-now-available.html
and set the Scalar at 0x992 =xxxx RPM and OL will be maintained as long as RPM is < xxxx. But this will not allow OL tuning OL without a WB.
HTH

[eutu1960]

thanks for the input, I am not sure if I want to invest in a WB at this time for the amount of tuning I will be doing I may do so over the winter if I can swing it. I am not using AUJP,
I am using bin ANHU for my my 90 corvette with XDF $8D-1227730-Vi, I am pretty satisfied with my VE's but am looking to get starting when warm easier. the way it is now it takes quit a few turns before it starts when warm.

[Six_Shooter]

The easy way to with any GM (OBD1) code to force open loop is to set the coolant enable scaler to maximum (255 degrees). This way the input from the O2 sensor will not be used by the ECM to trim fueling.

A WBO2 is a great tool to have, even after you get the tune where you want it, to keep an eye on the AFRs to see if something else is happening.

[eutu1960]

The easy way to with any GM (OBD1) code to force open loop is to set the coolant enable scaler to maximum (255 degrees). This way the input from the O2 sensor will not be used by the ECM to trim fueling.

A WBO2 is a great tool to have, even after you get the tune where you want it, to keep an eye on the AFRs to see if something else is happening.

Thanks for the reply, if things go well this winter I will try and get a WB and give it a try.