Revs drop too quickly and nearly stall with AC on
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Joined: May 2011
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From: Miami
Revs drop too quickly and nearly stall with AC on
Hi guys, I have my tune and I am pretty happy with where I have it so far. Car idles great and drives great without ac. I know that the more knowledgeable people on this forum say to treat ac use as an adder and not to tune for it until other variables as satisfied such as stable idle and overall drivability. I think I have gotten to that point. Anyway, my car is a 92 with a MS3pnppro and I am running the stock 1.6 engine and IACV for now. The issue that I am experiencing is when I am driving in say second gear and shift to third gear with the ac on. With the ac on the revs while shifting if I am shifting rather slowly want to drop and stall out the car. It doesn't usually stall out the car, it hits my lower rpm threshold for engaging the ac, the ac disengages and the revs shoot up because the car doesn't know what to do for a few seconds and then it settles back down.
Attached is a datalog that I was able to get rather quickly. It looks like as my revs drop my iacv shoots up to 54% to ramp my revs back up and then the car plays reactive to everything related to ac. I have tried messing with the pid and dashpot in thinking that if the revs drops slower this issue wouldn't be present.
If I am at 1400 rpm and pop the car in neutral, the revs settle nicely where they should. Even at 2000 rpm they do that.
What do I need to do to get my revs to settle a bit slower and not disengage my ac and go through a separate ac loop. Attached is the datalog I gathered and also my tune.
Attached is a datalog that I was able to get rather quickly. It looks like as my revs drop my iacv shoots up to 54% to ramp my revs back up and then the car plays reactive to everything related to ac. I have tried messing with the pid and dashpot in thinking that if the revs drops slower this issue wouldn't be present.
If I am at 1400 rpm and pop the car in neutral, the revs settle nicely where they should. Even at 2000 rpm they do that.
What do I need to do to get my revs to settle a bit slower and not disengage my ac and go through a separate ac loop. Attached is the datalog I gathered and also my tune.
Last edited by andym; Nov 20, 2018 at 10:52 AM.
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Joined: Apr 2017
Posts: 1,232
Total Cats: 169
From: Greeley, CO
I couldn't really get closed loop idle to my liking in basic mode. Read up on tuning advanced mode.
Fix your idle VE first though or you'll be chasing your tail.
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Thread Starter
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Joined: May 2011
Posts: 560
Total Cats: 78
From: Miami
thank you for the input. When I get home I’ll try swapping out basic pid. I was reading through megamiatas website and I see that he used values of 30,20,10 for his pid but he has a lot of pid gain.
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