A/c bogs down motor
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On The Tree
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A/c bogs down motor I have a 5.3/4l60e swap in a 74 c10. It's a non-air truck so I installed a nostalgic air unit. I charged it up and I wired it to where when I turn on the a/c both fans come on. At idle when I turn on the a/c the motor either bogs down or completely shuts off. When I drive I feel a load on the motor.. it has a sanden compressor Mind you I do have a pretty healthy cam with a 3200 converter. What do I need to do to give the ecm a signal that tells it the a/c is on and to make the engine idle higher?
Unless you rewire/redesign the system so that the PCM is the primary source of AC control rather than the nostalgia unit, you have few options. I'm sure its the same crap I have dealt with on vintage air setups...engages compressor and both fans all at once and without any compensation or ability to compensate for incoming load... Very sloppy. But it is what it is. As it sits, to mitigate it you'd need to increase idle airflow, potentially reduce idle spark and definitely increase high error idle underspeed spark correction. If you can't tell the PCM the AC load is coming, the best you can do is react to it well when it does.
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On The Tree
Joined: Feb 2013
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Unless you rewire/redesign the system so that the PCM is the primary source of AC control rather than the nostalgia unit, you have few options. I'm sure its the same crap I have dealt with on vintage air setups...engages compressor and both fans all at once and without any compensation or ability to compensate for incoming load... Very sloppy. But it is what it is. As it sits, to mitigate it you'd need to increase idle airflow, potentially reduce idle spark and definitely increase high error idle underspeed spark correction. If you can't tell the PCM the AC load is coming, the best you can do is react to it well when it does.
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I have a 5.3/4l60e swap in a 74 c10. It's a non-air truck so I installed a nostalgic air unit. I charged it up and I wired it to where when I turn on the a/c both fans come on. At idle when I turn on the a/c the motor either bogs down or completely shuts off. When I drive I feel a load on the motor.. it has a sanden compressor Mind you I do have a pretty healthy cam with a 3200 converter. What do I need to do to give the ecm a signal that tells it the a/c is on and to make the engine idle higher?
As far as the tune look under Engine, Torque Model, Loss, A/C Compressor vs IAT. Double the numbers (as a start).
Then Torque Management, Engine, A/C Torque On Hold Time, set the whole table to 4.0 seconds.
Ramp in Rate add 10
Inertia Torque add 8
Fine tune it from there. This is assuming the rest of the tune is right. Assuming the a/c request goes through the PCM.
If you try other things you have to be sure it's a/c specific or else it'll (usually) cause idle problems like a cruise control effect when the a/c is not on.
If you do get it right you may need to reduce the throttle cracker airflow so it doesn't have a cruise control effect.
I can say that anything specifically airflow will not fix this problem without side effects when running without the a/c on. (AGAIN, ASSUMING THE A/C REQUEST GOES THROUGH THE PCM) In fact if it doesn't, there no reason to not make it.
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Verdad Gallardo yes I recently called my tuner and my ecm turns out to be a f-body pcm 2000 camaro to be exact. I read that the camaro/firebird n vettes ecm requires the a/c to have a pressure sensor in the system. That's what I'm missing but I'm gonna go the cheap route which is to reflash it as a truck and use what I have and I should be good to go
Call Brian at BP Automotive. He can explain how the pressure switch works. I'm sure he can sell you the stuff and your car will run like a factory car with or without the AC on. It's worked for how many millions of GM vehicles why try and reinvent the wheel?
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You don't need to reinvent the wheel, problem is you can't throw semi tires on your 1/2 ton without modifications.
Same with the a/c and cam. You can't throw a huge cam in and a fixed displacement compressor with a txv and expect the tune to work the same as it did for a camaro variable displacement compressor and orifice tube system that draws less power than what you have now. A big cam that makes less power at idle and an a/c set up that draws more power.
A/C specific airflow and torque needs to be adjusted in the tune.
What I suggested ramps up the torque when the a/c clutch is called for. It also increases the time it stays up by a few seconds.
As for the a/c request going through the PCM, something has to signal a relay to turn on. Take that signal and send it to the PCM, then let the PCM send it to the relay. When it's done this way you can hear the engine change before the compressor engages. It'll also disengage to prevent stalling. Sure you can rig the **** to run without it, but it doesn't know when the a/c is on or off so it's going to run for extra load when there is none and that gets annoying as hell.
I did mine. I adjusted everything I suggested one at a time to see what does what. It's all a/c specific so it does nothing weird when the a/c is off.