I posted in some detail about this a month or two ago, but if your base table is too high and idle goes over your max idle rpm window the ECU won't bother to bring idle speed down, if you're using closed loop control in the first place. I find it helpful to disable close loop idle speed control (make upper rpm something low, like 500 rpm) then setup the base table with no interference from the ECU.

 

Hmm.. Interesting point. So between shifts it won't try and bring idle speed down? it will just hold it (at say 7K rpm)?

I haven't driven on the car that fast so i'm not sure what it would try and do..

 

This was whil running MAP or MAF?

I'm currently running on the MAF and it's using the stock MDP, so there wasn't an additional setup...

 

It will if the base table is setup properly, since the ISC will close to the predetermined value in that table and idle speed will drop accordingly. That's different from the closed loop feedback working though and what I've noticed about it.

As an example, I've had times where the idle would be above the upper RPM slightly, and feedback won't bring it down. With the brake on, I'd use the clutch to drop the rpm slightly, and the closed loop feedback system would take over and adjust idle speed properly to my desired value. I would have expected the feedback to only not work when the desired RPM is over the upper limit, not the actual RPM. I've only seen this on my car and have not verified it on another, FWIW.

In the end, what it comes down to is that you want the base ISC% table ***** on, requiring the closed loop system to only have to make a 2-3% change in either direction to account for weather changes and the like. Just like O2 feedback, you want minimal corrections required. I could never get it to work as well as a stock ECU, so I run open loop idle speed control and the hell with the feedback. YMMV.

 

So i spent some "quality" time with the ems this weekend and the car now idles rock-solid..

Basically, Idle% vs Target table was completely off. By several % and causing to idle high. Also, the high-idle speed was pretty high (2700 rpm) and the Idlt tps was high. Once i brought these down into a reasonable range, it is solid on.

The thing is, i basically re-tuned the idle to make it work. I thought this would be done better in the base maps (which is why i didn't think i'd have to adjust all of it), but i guess not..

 

The base% table will be different on every car, and changes with things as simple as a BISS screw change. Even timing change will change base % requirements. The point is that the base map can't possibly have something as sensitive as idle control setup right on, it's up to the user to make it work for his or her car. Glad it's working now.

 

I don't know that i completely agree with this statement though. That's like saying every engine from the factory is hand-tuned. I don't see them tuning the stock ecu like that, it's just a plug and play sort of thing..

I'm not saying that it didn't need some massaging, but this was *way* off...

Anyway, yeah, it's working now and working well... Just need to do the real tuning and then the new turbo kit goes on

 

Stock ECU control is completely different, with short and long term trims. And yes, each car is "tuned" to set the ISC at the center of it's available travel via the BISS screw. Contrary to popular belief, the BISS is NOT to set idle speed, but to properly set up the ISC for each indidual car. Since every car will have the BISS in a different place, the base ISC % table requirements will vary accordingly.

 

But that's saying that the car is tuned to the ecu - which makes sense. So that would mean to me that it would be easier to set up a single base map and not have to do as many adjustments

If it was the ecu tuning to the car, that would seem to be my problem.

What i'm saying is if there's a standard ecu (stock for example) and you adjust the biss screw to center the idle control, shouldn't it be easier to make a standard base map given you use a "stock" car for the original tune? It's not like the factory is custom tuning stock ecus to account for car differences.

 

this is normal, as the engine runs and gets warmer, the idle will drop gradually to like 800-900 RPM's

There is a way that you can adjust idle with a graph on the EMS software

 

No, it would do it after it was warm, not while it was cold.

It ended up being a tps vs idle % problem. It was way to high.. Once i adjusted that, incremental adjustments to the idle seem perfect now.