Tuning with DataMaster / Heated O2 Sensor

[dave w]

I've been tuning on the '427 PCM upgrade http://coloradok5.com/forums/showthread.php?t=270253 using DataMaster. The single wire O2 sensor was not working, because I noticed several seconds of almost 0 volts from the O2 sensor on my first data logs. So as an experiment, I upgraded to a Heated O2 sensor down stream from the exhaust manifold. I've not seen any of the almost 0 volts readings from the Heated O2 sensor. So far I've only made adjustments to the injector flow rate. It seems the PROM programming (injector flow rates) for a 1995 454/7.4 liter are in the "Ball Park" for the 1987 GMC I upgraded to the '427 PCM. Using the injector flow rates for a 1987 7.4 liter engine showed a lean Histogram. Using the injector flow rates for a 1995 7.4 liter engine showed a rich Histogram.


dave w

 

[eagle mark]

Can't be much help but there is a big differance in big block injectors from the early years compared to later years including fuel pressure!!! This may be why your seeing changes...

 

[dave w]

There is a big differance in big block injectors from the early years compared to later years including fuel pressure!!! This may be why your seeing changes...

I agree, about the differences between early 454 TBI and later 454 TBI injectors. I thought posting back what I learned about programming the injector flow for the '427 PCM 87 GMC BBC would be interesting to some members.

I also learned that using a heated O2 sensor really helps stabilize the tuning I am doing with the ‘427 PCM upgrade. I would strongly recommend using a heated O2 sensor when converting to the ‘427 PCM.

The ‘427 PCM upgrade was dirt cheap, but I guess that depends where you are buying dirt? The ‘427 PCM is an AWESOME upgrade!!

dave w