AC idle up!

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slow94

Well-known member
Just wired in A/C idle up today on my truck and it definitely makes an appreciable difference in manners. In my opinion this is what should be recommended automatically for our trucks. I will give a brief description of how to do it as well. First thing to do is identify the power wire for your ac compressor as this is what will trigger the idle up. You can also use the blower fan motor wiring but it was easier for me to use the compressor 12v source as it already had it spliced for my cooling fans. You will then run that positive trigger wire to the 86 terminal on a relay. You will then tie the 85 and 30 terminal of the relay together and ground them. 87 terminal will now be your output wire and it will now be converted from a 12v positive signal to a ground signal which is what's needed for the ECU. Next step is to open your ECU case and install a jumper (supplied by stinger when you order) to position "j11" for table switching. The correlating pin for table switching on the ECU is 24... However there is no pin there from the factory 60 pin connector. You will have to drill out the back of the 60 pin connector on position 24 so you can insert a new pin into this position. Now you can either run a dedicated line from 87 terminal of relay, crimp a new pin on and insert into position 24 or you can simply use your unused map sensor output wire. From terminal 87 you can splice into the middle wire of the map sensor plug. This wire is green with a black stripe. However this wire ends up at pin 45 on stock 60 pin connector so you will need to de-pin it from 45 and move to the new 24 position. From here you can now go into the software under you idle settings, select AC idle up and turn it on via table switching. The rest of the settings are up to you but this will get you going! Big thanks to those who helped me get mine wired. Hopefully this can help someone in the future.

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Glad you got it working.

You can also have the ECU turn your electric fan on when you turn the AC on so the AC works properly if the engine temp isn’t calling for the fan to run.
 
Jamie V said:
Glad you got it working.

You can also have the ECU turn your electric fan on when you turn the AC on so the AC works properly if the engine temp isn’t calling for the fan to run.
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My fan controllers tie into AC power so they cut on automatically with AC thankfully. I just tied into that same wire for my trigger going to the relay for the idle up as well.

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I used it on the red truck, it's more a thing for the e-fans. I don't use it at all on the white truck and the only way you can tell the AC comes on is hearing the "click." However, no E-fans on the white truck.
 
I originally thought my fans were spiking and dragging it down but even with soft start controllers it still would do it.. not as bad but still there. I'm guessing the compressor engaging had more to do with it on my truck.

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slow94 said:
I originally thought my fans were spiking and dragging it down but even with soft start controllers it still would do it.. not as bad but still there. I'm guessing the compressor engaging had more to do with it on my truck.

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I've found some interesting things while looking over datalogs from the PDM. Soft start or not each one of my SPALs pulls 56 amps on start, I have not played around with different frequencies yet, but 100Hz seems to be what everyone does. Does your controller document what the soft start frequency is? Below the PDM shows 2 entries per fan because I had to use 2x 25A outputs per fan so you add them together.

As a tangent check out that Weldon FP start! I don't soft start it because Weldon says unless you can only pulse it at some super high frequency so don't do it. Plus I'd have to mess around with the priming pulse in the Megasquirt to give it time to build up pressure.


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I watched a video that mentions table switching via TPS for idle map.


Black FOX EFI guy does a remote tune. A/C idle up was one of the first things he mentions.
 
Raymond_B said:
I've found some interesting things while looking over datalogs from the PDM. Soft start or not each one of my SPALs pulls 56 amps on start, I have not played around with different frequencies yet, but 100Hz seems to be what everyone does. Does your controller document what the soft start frequency is? Below the PDM shows 2 entries per fan because I had to use 2x 25A outputs per fan so you add them together.

As a tangent check out that Weldon FP start! I don't soft start it because Weldon says unless you can only pulse it at some super high frequency so don't do it. Plus I'd have to mess around with the priming pulse in the Megasquirt to give it time to build up pressure.


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No unfortunately my controllers are just flex a lite soft start controllers. Now, they do a much better job than than just turning them on 100% but I still wanted my truck to act better. It wasn't bad before the idle up but it is a feature that is OEM on lots of ECU strategies so I believe it to be important.

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When your compressor clicks on there is load applied to the engine just like when the fan clicks on and the alternator’s voltage regulator calls for power.

The best thing you can do is add/remove timing in the idle section for load.

Think about WOT tuning, when you add timing you make more power (to a point) when you take timing away you loose power. Same thing at idle, when a load is applied you need the engine to make more power at idle not to have the rpm drop. It’s the same when load is removed, you need to pull timing at idle when that happens to keep the idle from going up.

Everyone tries to get the iac to compensate for that but they are not fast enough.

I unplugged the iac and messed with that timing vs load until I could turn stuff on/off and put the truck in/out of gear and the rpm barely moved up/down then I hooked the iac back up.

It took a ton of time to get it right but it was worth it.
 
That's exactly what I've done with the white truck, Jamie. I use a more aggressive spark-based idle RPM adjustment.
 
FMOS Racing said:
That's exactly what I've done with the white truck, Jamie. I use a more aggressive spark-based idle RPM adjustment.
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Yeppers, and if you listen to that Youtube Required posted the remote tuner does the same thing albeit on a MUCH larger and more complicated scale with table switching.

When I 1st got my truck going I spoke with both Jamie and Jerry and they gave me great advice for idle setup and I did the same process as Jamie outlined which resulted in tuning closed loop idle control (uses a small VE table of its own) along with a plethora(yeah I used that word) of settings in addition to idle advance and idle RPM timing correction. Mine behaves wonderfully now.
 
My spark based idle adjustment is very aggressive. I also built in a timing "cradle" in the ignition table. The AC idle up just makes it all a bit more seamless. Also I find it better to add a bit of rpm for idle charging and air conditioner performance.

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Jamie V said:
Everyone tries to get the iac to compensate for that but they are not fast enough.
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Is that just with the Ford PWM IAC? Has anyone tried the GM pintle IAC? I got the GM for my truck because I've never liked Ford's way of doing it. Someday I'll actually get it all put on and hopefully running.
 
oilwell1415 said:
Is that just with the Ford PWM IAC? Has anyone tried the GM pintle IAC? I got the GM for my truck because I've never liked Ford's way of doing it. Someday I'll actually get it all put on and hopefully running.
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I do not know anyone who has tested the PWM Ford vs the GM stepper, although the guys that do use them have no problems with Megasquirts or other EFI and getting them dialed in. If I swap over to the Motion Raceworks TB I'd have to use a GM stepper. Anyway I think the moral of this story is exactly how Jamie phrased it, you're simply managing engine TQ at various loads (AC, fans, or in/out of gear, etc, etc are a sudden load) no different than any other area of tuning and the best tool at your disposal is timing. I will say this, you've 100% have to get your idle AF right before diving in to idle timing and control, all too often people want to do idle 1st, but for me that's later on as you get other things sorted.
 
Well you have all sent my head spinning reading this! :ROFLMAO: I contacted Black Fox this morning for some tuning work. Hopefully he can get me sorted better. I just don't have enough knowledge or confidence yet to get really involved, but maybe I can pickup somethings while he does his magic plus I'll have a well sorted tune I can be confident in down the road.
 
No one is going to tune your stuff better then you are at cold start/idle/part throttle.

Your not really going to hurt anything at those engine rpms. You have to experiment like we do, just make sure you have all your files saved in a way you know what they are so you can go back if you mess done thing up.

Learn the software.
 
I’m learning… just slower than I’d like too. I tend to do better when I have someone telling me what they’re doing and why. I’m more apprehensive than I need to be… just need to man up and do it.


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Jamie V said:
You guys think we’re all professionals, we’re just regular guys like you who just fumble through learning it ourself because we are too cheap to pay someone and more importantly don’t trust anyone to do it right.
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Truth
 
core-rider said:
I’m learning… just slower than I’d like too. I tend to do better when I have someone telling me what they’re doing and why. I’m more apprehensive than I need to be… just need to man up and do it.


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I think it’s a great way to get into it quickly. Steven is very good at what he does and acts as he does in the video. We went through a lot with my truck with the 1st MS 2 system I had and then the Pimpxshift that I now have. He knows about MS and he will talk through it with you and is very patient and easy to deal with. He saved me hours and hours of trying to figure things out and tuning. I’d pay the money again in a heartbeat! I tune VE and timing tables, cold start, etc.. now with the information he showed and told me but the truck is just about tuned perfectly. Drivability is great, feels strong although I still work on the cold start here and there.


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