Can't get closed loop

[SloGN]

hey guys i can't seem to get my ecm to go into closed loop. what else could there be i'm gonna attach my GCT.file where i setup the closed loop parameters.


TIA for the help.


pat broughton



EDIT it will not let me attch a gct file

 

[Craig Smith]

Read the FAQ on this topic in the help section of C-Com. It covers all the needs of closed loop operation and what to look for if it isn't working.

 

[norbs]

Use winzip and convert it to a zip file, then it will be able to be attached.:smile:

 

[HighPSI]

Afterstart enrichment?

 

[SloGN]

what should the high and low rpms be set @ i have mine set as the high for 5500 and the low @ 600.

does it do closed loop for a set amount of rpm bandwidth?

 

[HighPSI]

i have mine set as the high for 5500

There's your problem. It won't go into close loop until it gets to 5500

 

[bobc455]

Good catch.

To give a bit further of an explanation, "high" and "low" are kinda backwards from what you would usually think. Intuitively, you would probably think that the closed-loop would work between high and low. Nope!

Instead, think of them like "on" and "off" switches. When the RPMs exceed the "high", it will switch on. When it goes below "low", it will switch off.

If you idle at 600 but don't want to idle in closed loop (it can sometimes cause the engine RPM to oscillate), you might have your "high" set at 900 RPM (i.e. it will go into closed-loop after you exceed 900 RPM), and your low at 750 RPM (i.e. it will go into open-loop when you drop below 750 RPM).

Make sense?

-Bob Cunningham

 

[Craig Smith]

What Bob said is right on the money. It's called a hysteresis band, and the purpose of doing things this way is to prevent the possibility of closed loop operation from oscillating when the engine is operating at or near one of the thresholds. The high and low settings are frequently thought of as defining a window of operation for closed loop. This is a nice and intuitive way of accomplishing this, but it's not without a host of ultra-yucky possibilities. Imagine in this scenario your high setting was 5500 RPM. Let's say you just hit 5600 RPM, and closed loop was adding 20% fuel when it suddenly shut off after crossing the 5500 RPM high threshold. Correction instantly goes to 0%, meaning that fuel flow just decreased instantly by 20%. That would suck big time under full boost! The hysteresis band is a tool to prevent this from happening. There are other benefits to this method, but this one is certainly most pertinent to the question at hand.

While I agree that the way this is implemented is not the most intuitive way of doing it, closed loop questions are thoroughly documented in the help section and this very problem is identified in bold lettering as the most common cause of closed loop not working. Press F1 from anywhere in C-Com WP and the full help menu will be at your disposal.

 

[SloGN]

i read the help section and it didn't give me any relative info on the high and low rpm settings.

Since cal told me that was the problem i went and set the too with a 100 rpm's in diffrence it worked. thanks guys


i have had the fast on the car for over a yr now and just now decided to put it in closed loop. i wanted to learn each step to make it a tad simpler to do.

tune one table at a time. so far i have a great tune from highway lean cruise to wot @ 20 psi. just taking my time and tring not to hurt anything in the process.

 

[bobc455]

i have mine set as the high for 5500 and the low @ 600.

Actuallly that is an interesting way to stay in open loop through first gear, then go to closed-loop in 2nd gear. Don't know why you would want to do that, but who knows...

It's called a hysteresis band

I had an uncle in a hysteresis band. He played the ukelele.

 

[Fuelie Nova]

i read the help section and it didn't give me any relative info on the high and low rpm settings.

Just out of curosity I looked at the help section 10.2.1 and 10.2.2. To me it is a pretty clear description of what the high and low functions are.

Tg

 

[HighPSI]

Actuallly that is an interesting way to stay in open loop through first gear, then go to closed-loop in 2nd gear.

Good idea Bob! If you have the correct firmware in the Classic box you can have it turn the O2 off when you ground a wire (ESC, I think). I used to use this to shut my O2 off when I was on the 2-step but still be able to have complete closed loop operation when not on the 2-step.