I have a turbo LT1 with a FAST ECM. Its been running for almost a year now with barely 400 miles put on it because it keeps running into minor problems and i take my time in fixing them. I have tuned it myself to get it drivable but it still has a long way to go to make big power and run real smooth. One of the big questions I have is when to use closed loop vs. open. I have a surging/bucking problems at certain RPMs and I am trying to get rid of them. And I have noticed that the car idles better when in open loop and seems to hunt in closed loop. When does closed loope need to be used?

 

you honestly dont need to go into closed loop, you can tune it out. just set the closed loop enable temp to like 250 degrees.

closed loop is there to basically get you as lean as possible during light throttle cruise, but if youve got a big cam, the overlap messes with the readings

 

i have tuned a few fast ecus, none of them have idle'd worth a crap in closed loop. i go into closed loop over 1500 rpm and set the limits to not allow it to pull any fuel in boost areas of the ve table; only allow it to add fuel.

ymmv; but its worked for me.

 

Same here... Idle should definitely be in open loop.

If you have lean pop issues at tip-in, it's because of the bank-to-bank setup (fuel is already dumped in and there's more air than expected). I assuming that's what you meant by bucking... It's usually low rpm and big jumps in MAP.

The best solution for that is to use open loop and run it a bit fat to keep the lean spikes down. This won't happen at higher rpms because you go through a full bank cycle much faster.

 

cool, thanks for the suggestions I will give them a try.