Hey everyone,

Been reading this part of the forum for sometime now and still have some basic questions that I can't seem to find answers to. Hopefully someone can help out.

Closed loop, is anything below 100 load. Are only O2 sensor readings looked at and timing/fuel is calculated based on that only?

 

Close loop operation is conducted at loads exceeding 100 as well. Fuel trims will constantly be adjusted by the ECU when in closed loop operation. This is the reason many "tuners" simply disable it all together.

Some, myself included, have found it beneficial to leave it on but tune the car in a manner that there isn't any trim changes applied to WOT pulls. By doing this you benefit from better drivability (in my opinion) gain better fuel mileage and still have the ability to have wonderfully tuned WOT pulls.

As for only the o2 calculations being use....that would be no. Many engine parameters are affected by and use by closed loop operation.

 

So at close loop, the timing is still read from the ecu table under 100 load?

If I'm getting knock at vacuum (only about 1 or 2 counts nothing to worry about) but in theory I should be able to get rid of it by tuning cells under 100 load?

 

Yes, that's correct. Your timing tables your see in ECUFlash are for closed and open loop.

 

^ I see thanks. Since I'm getting some good responses I'm going to ask couple more

So when I knock, what timing does the ECU use? Is it always from the lower octane map or does it interpolate between high octane and low octane?

 

When you knock, two things happen:

1. The ECU will pull 90/255* of timing for each knock count. Or, you can think of it as 1* per 3 knock counts. You can think of this as an immediate or short term knock trim.

2. If you knock counts are sustained at 6 or above, the octane number (0-100)will begin to decrease and the ECU will begin interpolating between the low and high octane maps. At an octane number of 0, you are 100% on the low octane map, at 50 you are in the middle of the two, at 100, you are 100% on the high octane map. You can think of this as a long term knock trim.

 

in a nutshell:

closed loop is when the ECU reads from sensors and provides duel to suit. this happens most of the time beside WOT (unless u turned off via the periphery bit)

open loop: the ecu does what the maps (fuel) contain. this happens at WOT.

 

Thanks Rolly.

I still got your email. I will hit you up when winter is over and we can mess around with my tune.