Hello,
Another issue i have is that when i turn my A/C on, my idle drops from 1050 to 900.
With 900 rpm idle, when i flip the throttle or release the paddle, rpm goes to 300-500 and sometimes the engine stalls.
No matter what i do, the A/C keeps bringing down the idle RPM.
Any idea how to over come this? Do you need any conf files to review, maybe?
Thanks,
I would like to know this solution as well. My 1.8t 20v swap does the same thing..
My only added info that helped me, was adding 2*-4* ignition timing over standard idle rpm in lower rpms 500,800. That helped the lower rpm idle recover quickly and nearly eliminated stalling with the a/c on. It still happens once in a while when really hot out side. 100*F
Good to know i am not the only one with this problem. I also use advance in the lowe RPM to avoid stalling. at 500 RPM i have 18 deg and on 1000 RPM i have 12.
The thing is that my OEM ECU actually brings up the idle once the AC is on, while the VEMS is bringing it down.
So there are 2 option:
1. I didnt tune IAC well enough. My idle RPM is set to 950, but its actually 1050, until i turn on the A/C and it drops to 900.
2. VEMS is not dealing with AC compensation , it was simply designed for cars without A/C (?)
It is easy to maintain idle when a/c engages with switchable config.
Or do you use it for other purpose??
How can i switch config when A/C engages?
This is not a big problem to me, at least not with a properly setup IAC valve and idle ignition advance control enabled.
The ignition takes care of quick changes, the valve catches up for the larger changes.
Many people use too much idle ignition advance to begin with, 5-10 degrees at most on modern DOHC engines. Then let idle ignition advance control raise that by 5-10 degrees further to avoid stall and quick recovery. The IAC valve reference curve should be significantly higher than the target rpm, the regulator takes care to close the valve only to bring rpm down. Set "IAC integral under lowmap" to 0 and you get better recovery from slight throttle movements, as the IAC valve will go to ref curve value and then gets regulated down.
This stuff works better with many trigger teeth (36-1, 60-2, etc..) as only one tooth per cylinder is not enough at idle to get good help from the idle ignition advance control, the speed of the engine changes too much between teeth.
Of course, this could be solved even better if "idle rpm target" was added to the anytrim functions, and let the "A/C on" switch activate a free analog input.
Quote from: fizban on May 04, 2012, 02:30:22 PM
How can i switch config when A/C engages?
You need to connect either 0V-5V or 0V-floating signal to one of analog inputs. (do not use 12V signal!!! - use relay then to invert it)
Config switch is easy - just configure input channel at Configswitch (you can review it under RAW ADC window [just hit Backspace]). Open your current config in offline mode, rise IAC reference curve by couple percent, save it; and then go to config upload advanced and upload new config to B only. That's it.
I think it should work faster than target rpm change from analogue input.
Gints
for weak engines i use config switch with more ref_DC for idle.
For strongest, ign advance control + big D(150-250) in PID control.
Thanks for the answer, guys, but the vems was PNP. You lost me in the 0-5v to analog input.
Which analog input? ???
Heave you some paper with it? You have some analog inputs in 6pin connector.
No papers, but i will consult DP engineering (they made the ECU)
Also - my PW in idle is 2.1ms. When i turn the A/C, it goes to 2.7ms even though the RPM drops to 900. VE table values are almost the same (if not lower) at this level.
Is this expectable (because of the extra load of the A/C)?
Expectable. At higher MAP reading but same VE value final PW will be higher.
Thanks. I will try to consult DP-Engineering about analog inputs. :)
im with Mattias on this one.
i have tested 2 audi RS2 with A/C and idle settings according to his guidance and the idle drop when A/C works is minimal and valve/timing is very quick to control it.
No need for configswitch for such an issue anymore.
I just wanted to post a +1 to MWFire, having a big D for the pid control helps immensely.
At least on a bosch 3-wire IAC...sans a/c I had a very low value that worked well but once the heat hit and the a/c was on I had a nice stumble....raising the D upwards of 200 worked wonders.
So thanks for sharing ;D
If you read what PID stands for through the interent, you may realise that having a high D may actually produce problems.
From my experience in having a high D in my car, never worked, because idle never came back to the defined level. It always stood higher than normal, as it went into a uncontrolled loop. It may be working if other settings are off from the idle specs.
Mattias has posted a procedure to get the idle to work properly on this forum. Search it. It seems to work!
Because of high D value idle do not stood or cycles somewhere. It becomes "noisy".
Cycling can be result from too high P or high I together with too wide I-limit. It also can be a result from bad fueling at idle region or too steep ignition map close to idle region.
Sticking above target is result from too high ref position together with too low I and/or I-limit.
I followed mattias guide and it worked very well...pid values were very low if I recall correctly. There was no cycling and target was fine until it became rather warm here and I had extra load from A/C. Adding the big d stopped that and the car hits the target of 900 rpms every time. Regardless, I don't doubt that you guys are right in saying that there is a lackluster setting or two, but it works, so I'm not sure what the rationale for changing it would be? ???
Essentially whatever works for you. On my car high D and low p and i made it only good for certain situations and carp on others.
I incorporated several of Mattias suggestions.
1 - ignition is now 10 degrees at idle. (950rpm) the cells are configured to be 10 degrees on the 900rpm column
2 - I now have a 700rpm column which ignition is 17 degrees, to help the engine recover.
This helps when the car is with A/C off. It didn't stall even once without A/C. it still falls to 800rpm, but recovers.
I noticed that idle kpa ia 37-40 without A/C and with A/C its 47kpa. so i added fuel in the 700rpm, 50 kpa cell - thinking it might help the engine to recover after releasing the throttle.
Well, it works a little better, but still, rpm drops to less that 500rpm when releasing the throttle from 1500rpm onward. If released from 2500 rpm and above, it might stall (maybe it related to fuel cut settings? 2500 cut, 1900 resume)?
Also - when A/C is on - ignition is advanced to 18 degrees (i guess by the idle control - which is limited to 8 degrees advance). maybe i need more advance at the 50kpa, 900rpm cell?
dont let too much distance between fuel cut and resume. Just leave 100rpm. ie. 1900-2000 wherever it works better for you..
if you have configured everything well, then the main thing to do is to tune PID. As i said it will have different values for different engines, and the best you tune that, the less drops you will get.
having higher timing or fuel below the idle rpm, was never required for me.
Also make sure the ignition timing idle control is able to make it's changes fast.
Thanks, AVP
How do i know if it works well, 2000-1900 for instance? Should i see changes engine recover when settling down?
The advance rate of change is 15 deg/256rpm
and the threshold for IAC is 2 deg
my pid settings are rather awkward, but that how it came with the unit (pnp) - PID is 10/15/200
Integral decease is 3 and increase is 8 (i dont know what these do)
I've taken a log file in idle with and without AC and got some very interesting stuff
config:
https://docs.google.com/file/d/0B6l1SB-S-teyaW1XODdjRGFNVlk/edit (https://docs.google.com/file/d/0B6l1SB-S-teyaW1XODdjRGFNVlk/edit)
Log:
https://docs.google.com/file/d/0B6l1SB-S-teyTzYyZjMxLWRCT0U/edit (https://docs.google.com/file/d/0B6l1SB-S-teyTzYyZjMxLWRCT0U/edit)
Here is a pic with the summary of what i saw - i've plotted points on it to explain my understanding on them:
(http://img707.imageshack.us/img707/6241/idleac.png)
Point A: Start of the file (no A/C). You can see the idle is 941 rpm. You can see EGO correction is 93% and gamma enrichment is 87%.
The correction is so high because of the MAT/TPS (default to 94%) and MAT temp of 46 degrees. I can (and) will tune it to minimal correction - but as MAT temp changes, it will go off scale again.
Point B: Then i press the throttle a little bit and you can see the excessive AE kicking in. You can see that RPM a little below 900rpm. Then it settles down and lambda is getting back to 1.
Point C: I push harder on the throttle. This time mixture is getting lean before settling down (i dont have a clue why - probably related to AE tuning). RPM again got below 900.
Point D: I then turn on A/C. you can see that EGO is off since its tuned now to stop below 800 (RPM dropped to 790). You can see mixture is rich (no EGO to correct).
Point E: I then press a little on the paddle Get richer because of AE and rpm drops to 600 and recover.
Point F: Now i press a little harder, rpm drops to 500. almost stalls - and recovers.
Point G: Then - something interesting happens! lambda is almost ok now. around 0.98! The thing is that at that point, the fans kicked in on high speed - voltage dropped from 13.76 to 12.5! So this means that injector opening time got slower - leaning the mixture.
you dont see it in here, but i turned off the A/C and EGO went back at 100/101% correction - because of the lower voltage.
So besides the A/C problem. I have an issue with the fans kicking at high speed - voltage is dropping and if i was boosting - it could be very dangerous to the engine!
How can i compensate the lower voltage?
Just pm me your email and the configure and I will try to do some corrections for you.
I will send you mine with whatever I can explain.
Pm me some of the details of the engine and location of isv
PMed. Thanks!