oscillating idle

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KAT PWR
Helpful MS/Extra'er
Posts: 42
Joined: Mon Jan 16, 2017 2:55 pm

oscillating idle

Post by KAT PWR »

I've got my idle stable at 13.5-13.8 and down to my target but anytime I add a load it starts surging 200-300 rpm. Today, I changed from adding ignition time at the leftmost column to stabilize idle, to using idle advance and idle correction curve. now the idle is always stable with no load and no longer will stall while surging. looking PWM Idle Duty its it'll swing up to 9% which is a lot of air with my BMW Bosch idle valve. I feel like the idle closed loop is overreacting with this large idle valve, wide open it can idle +4000rpm. So my question is, how do I go about taming the Closed-loop idle PID?

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Matt Cramer
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Re: oscillating idle

Post by Matt Cramer »

First, I'd get the spark and fuel tables dialed in so that it has a steady idle in open loop without idle advance correction. See if you can get good results with that, then switch closed loop back on.
Matt Cramer -1966 Dodge Dart slant six running on MS3X
whittlebeast
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Re: oscillating idle

Post by whittlebeast »

I have found that you have to get the timing and PW stable to get the idle to calm down. Once stable, you can start playing tricks.

Not exactly this topic but see https://www.youtube.com/watch?v=XSyeko0-etk

Andy
goodysgotacuda
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Joined: Sun Oct 05, 2014 5:07 pm

Re: oscillating idle

Post by goodysgotacuda »

Leave the IAC off for now and tune to a stable and slight high idle. Use timing to bring the idle sped down, slightly, and it will take load better.

Fwiw mine seems to idle best around 13.0AFR


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