Closed loop?

[Jeff Niceswanger]

Originally Posted by KRatcliff

There are multiple reasons why I wouldn't run closed loop. The ECU can calculate very quickly, but the information coming into the ECU isn't reliable nor can the ECU read the information and make the necessary change to improve the performance within the short time of the pass in my opinion.

Our passes are only a few seconds and they are even shorter when you consider the gear changes. The ECU would have to make these adjustments reading off a single O2 sensor that isn't exactly in a sealed environment and it is only reading on bank of cylinders for an average. Plus the O2 sensors don't exactly like the fuel that we run.

When you consider these factors the ECU would be behind the curve in reading the data, calculating the change, and then effecting said change. I tune our cars in Alpha N/Open Loop in 10 different sections (for a 3 speed). The 2 Step (this would be chaos for closed loop) and 3 sections for each gear for a total of 10.

My fuel map leads in at each section similar to how we all use timing advance. There is also a cumulative affect that needs to be considered. None of this is possible with closed loop in our applications in my opinion. If closed loop was an advantage down track the Pro Stockers would run it. Closed loop is best suited for street cars.

Hi Kyle !


Kyle and I disagree on this one. It's like Chevy and Fords. There are two distinct different theories. I do not tune in Alfa, as its old school. Very similar to a Carburetor. It repeats and does the same exact thing every run. And many people prefer that approach. When your running a carb, you have the availability of rods and jets to stay on target. Air goes from 1000 feet on Thursday to 3000 feet on Sunday, you can change rods. The Alfa on open loop is locked into what ever tune is in it.. It just repeats.
I use VE, usually with a Alfa idle circuit. All the low RPM #'s are in Alfa with a separate Alfa Map,. But as soon as you start getting into the higher RPM's it switches into VE. VE is just a glorified Speed Density Program. On some tunes I stay with Speed Density, as I already have pre made tunes that are really close to the customers combos (in SD). Its just easier and quicker to use one of them. I've seen no advantage ET wise in either of the two.
The trick is to get the tunes to where you can feel confident you need no Closed Loop Compensation. That includes burnout, and slightly after (milliseconds) you go full throttle after launch.
That way, you can set your Closed Loop Compensations very low, like 3 or 4 percent, and know that the tunes will stay dead nuts during the entire run. Even IF, the air changes. If you look at your Data after the run and your car was using more than that 3 or 4 percent of adjustments, then your tune is not correct. You will know that as your Learned Compensation is 4 percent in places and your Target will be slightly off. Reason being that 4 % was not enough and the CL "Could not get there" . There are dis advantages to having CL active. IF the 02 fails, and they do occasionally, the 02 always fails lean. Meaning the Holley will think it's in a lean condition and puts all what's available in the tune. In this case all 4 %. But if your up high, like 50%, the car will instantly go full rich, die or be impossible to keep running. If it does run, it will be horrible. Its not a bad idea to change 02's occasionally if your depending on your 02 ....
Hope this helps...