I've taken a break from third gens for about six months and would like to get back into this. I was just getting started with burning files when I started so I'm basically starting over. I have two (what I believe) basic questions.

I started up the car last weekend for the first time in months. It all came back. When I'm running the 165, closed loop is attained in about five minutes. With the 749, it takes about three times as long. What do I need to change to get closed loop operation sooner?

Secondly and more important is the fact that when in open loop, it runs 14.7 - 15.5 to 1 A/F ratio. Once in closed loop, it stabilizes to 14.7 with a BLM of 126 - 130. So what governs A/F ratio when in open loop and how can I richen the mixture?

(I'm ready to start learning again!)

Willie

 

there a table open loop a/f vs coolant temp. it handle the cold opne loop a/f ratios.


ahh as for closed loop. wouldnt worry about the time till it goes in a whole lot. but there is a temp enable and a timmer enable in the constants.

 

I've not much experience with the 7749 but you might be able to locate similar tables / values to adjust.

To get closed loop operation sooner look for a "Minimum Coolant temp. for closed loop threshold. Also there may be a Cold Closed Loop Timer.

As for the A/F ratio in open loop the two tables that you should have a look at are Open Loop AFR vs. Map, and Open Loop AFR vs. Coolant.

Again my knowledge is with the 8746 $61 -- I'm sure you'll get more thourough answers from others.

 

The 749 is the only ecm I have played with yet. Of course it is the stock ecm for my truck also, making the decision easier.

I like to do all my tuning fully open, watching o2 volts, and wideband (when installed). Get the fuel where you want it via the 2 main fueling tables. (1 closed throttle, 1 open throttle).

If you need to scale a bunch of stuff, there is a rpm multiplier for massive across the board @ 1 rpm changes.

Under boost is a multiplier table, but you really need the main fuel table correct before playing too much with the boost multiplier.

As far as the cl determination, chances are it is just the coolant temp enable setting.