A/C tuning? Surge when at idle

[exploder]

I have all kinds of problems with this car, but I have got everything sorted except for this. When I originally tuned the car I did Auto VE with the A/c off and had everything as far as driveability tuned where it was +-2 %. I then tried turning the A/C on and it was running super rich at idle and driving about 12.8-13.4 everywhere. I then went in and did an autoVE run with a/c on and got it back to where it needs be. Now when I turn the A/c off I'm idling in the 15-16 range AFR. Is there no other way to compensate for this? Or did I do something wrong with AutoVE?

Second problem is it idles great when A/C is OFF but when I turn it on at an idle it has a serious surge up and down and the A/c light starts to flash and will eventually settle itself out. Is this a timing problem or an airflow problem or both? What PIDS should I log?

[5.7ute]

This is a good question that has been asked many times on here but not really given a definitive answer.
I have a car coming in tomorrow with similar issues & this is what I am going to try.
First I would log the idle trim pids with aircon off. Then again with aircon on pids. This will give you the difference in the airflow values.
If the difference is positive (adding air) you then increase B4356. Negative decrease this value.
You may also have to tweak B4328/B4329 minimum & maximum correction values but this shouldnt be necessary if you can get the values slightly positive.
There is a default aircon added airflow table in the pcm that I have not yet defined or been able to test in your OS. I will have a look later today & if I can find it & I will post up a .cax file. (I havent tested it in my OS yet either & it may not be active)

[Frost]

I have personally had good success with the following for cammed cars... I don't know all of the EFI Live lingo yet, so bear with me.

I don't usually have a problem with A/C if the car is not at idle, and since cam-surge is very prominently linked to excessive airflow, I try to avoid adding airflow except where the car seems to need it to stabilize (at idle). When doing running airflow tuning, I disable LTITs (0 them) and I typically leave these disabled as well on a dialed in car. I do this as well for the A/C (or only allow a tiny bit of offset) so that a positive learned offset is not applied at cruise (back to the cam surge thing).

B4356 is A/C Tq loss at idle. For weak idle with A/C on I bump this table. If you are in the dark on where to start, use 8-15% I'd say.

If you get it stable with the A/C on but but the RPM's take a hit when the comp clutch engages, B4354 controls the ramp-in of the airflow offset. You can bring in airflow faster to eliminate the initial dip by adding to this table.

[exploder]

My problem isn't that the rpms want to dip or go too low per se but they actually increase and flare back up and down. Ok I went out a logged several idle pids...now what do I do with this info. You can see in the log the first time I turn the ac on it starts to surge and timing goes up and down up and down. The second time I do it I give it a little gas and then slowly let the revs come down and it catches and just holds a decent idle. Where do I go from these numbers? Log attached.

On a side note I raised the ac torque enable 15% like frost said and it seems to have cleared the problem up. go figure...heres a log anyways

[exploder]

ok I guess I shouldn't have said anything because as soon as I pulled out of the driveway and hit the first stop sign it came back. what else do I need to go in and change based on the log I posted. I hate idle surging.

[5.7ute]

IMO (and I am no expert here)
Rafig is showing negative trims so you have too much air here. Reduce desired airflow where necessary. (Paste & add the values from the map)
Once the aircon is active you already have too much air from the desired airflow table, add to this the torque loss airflow & possibly default airflow(I am working on the .cax now) & you have a surge from the excessive airflow. Since B4328 is set to zero you can not learn below 0.00 g/sec so the excess air can not be trimmed out.
Get rafig nailed & then relog.

[Frost]

RPM does not seem to have been logged. Destabilizing swing can come from several things. If you get a large dip that pushes into over correction, you can get some 'ringing'. It's a shade unusual to have too much airflow, but you can always go back to the tables that I listed and the appropriate reduction as well.

Generally speaking, I'm a by the numbers guy, but A/C changes by the seat of the pants have yielded excellent results for me from tweaking setups over time.


--edit just looked back at what Mick mentioned. I didn't see them overly negative, but I only looked through a few samples. If it's a couple tenths of a gram or less you should be good. I generally try to get it to about a -0.1.

[5.7ute]

A/C tuning has always been one of the black arts. That is one of the reasons I am trying a by the numbers method.
The most important thing though IMO is to get the base idle nailed. A weak idle with added corrections can easily end up in a wild swing once extra loads are added.

[exploder]

I did RAFIG a few times and it kept coming up with negative numbers everytime and eventually as I started applying them after the 3rd or 4rth time it would hardly idle anymore. What causes that? It seems that I am about -.50 for the most part. I guess I should change b4328 some to see if it will help as well.

[mr.prick]

B4356 is A/C Tq loss at idle. For weak idle with A/C on I bump this table. If you are in the dark on where to start, use 8-15% I'd say.



+1
:good:

I bumped {B4356} up 70%-80% after {B4307} was good.
At idle I would turn the A/C on/off and if idle dipped I would bump it 10%.
I kept doing this until idle was stead while turning on/off the A/C.

If you don't have the luxury of RTACS then try bumping it a good bit first, 50% or so.

My RAFIG is usually -.02 to .02
It is more stable with MAF on. :nixweiss:

[5.7ute]

I did RAFIG a few times and it kept coming up with negative numbers everytime and eventually as I started applying them after the 3rd or 4rth time it would hardly idle anymore. What causes that? It seems that I am about -.50 for the most part. I guess I should change b4328 some to see if it will help as well.

With mine, after doing RAFIG I had to readress the fuelling at idle as well. It took a few goes but eventually idle became solid. FWIW I end up with a lean wideband reading at idle to get stability. (around 15.4:1) This is with a 23x 24x cam though.