FMII Hydra Idle Issues / Surge
I have had weird idle surge issues with my 1999 1.8 FMII and Hydra from the first day I purchased the car. I stumbled across an old thread on M.net and found some idle settings that worked nearly perfectly for me. I still need to dial in the cranking fuel trim for the appropriate temps, but the car idles the best it ever has with these settings. The Hydra is notoriously tough to get the idle right with and I wanted to post this here as I searched for a long time before coming across this info. Hopefully some other people on here may benefit from this.
Source: https://forum.miata.net/vb/showpost.php?p=7534362&postcount=52 To quote that post... Joining the conversation a bit late. I've had my Hydra 2.7 installed since November and had issues with both idle surge and droop. Following are summary of changes I've made (or tried and backed out) to deal with both:
to: 37.65; 37.25; 36.86; 36.47; 36.08; 35.69; 35.29; 34.9; 34.51; 33.73; 32.94; 32.55; 32.16; 32.16; 32.16; 32.16
Unrelated to idle, I have also made the following changes:
to: 5 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20[/QUOTE]" |
Much appreciated ! I've been fighting various idle and return to idle issues . I'll try these mods tomorrow and see if they improve things. Fredb
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Originally Posted by fredb
(Post 1443760)
Much appreciated ! I've been fighting various idle and return to idle issues . I'll try these mods tomorrow and see if they improve things. Fredb
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Cats awarded , much improved over what I was running. I'd feel better if understood which changes did what and why , but definetly improved return to idle . Much thanks . Fredb
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Cheers and yeah, not totally sure what the hell all that did but it seems to work very well.
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Many thanks, Luke, for the find and posting here. Even on a 1.6, the ISCV has responded well to the new settings. Decel has improved as well.
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I tried applying these settings to an 1.8 FMII hydra 2.5 setup as far as the settings are the same, but this left me with an idle speed of 1500. After some tinkering I got it to a point where it is sort of acceptable, I only get some idle dipping on startup and when idle control takes over from under ~1500 rpm. My settings: P=240, I=120, D=100, MIN PWM=16, MAX PWM=90, Valve steps=25.
What are your PID settings, or do these settings not exist in 2.7? |
Before first , make sure your TPS is calibrated and staying calibrated. All the high idle problems I've had have been related to either a bad TPS or the 27 year old wiring in my car. The 2.7 has P and I term but no D and no I don't know where or why it went. My P term is 100 and I is 68. Fredb |
I'm at P=100, I = 20, on 2.7.
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I purchased my hydra in 2017 and the idle has surged in my supercharged Miata the entire time. No issues, just embarrassing at stop lights for the most part. I could not get anyone to help.
I put in everything except the A/C stuff since no A/C, and it now idles awesome! It idles over 1050, but it idles. Now I have to get the idle down, but I’m so happy to find this. |
Good stuff!
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Did you get your idle lower? Like I said mine is high and I would like to get it down to more normal. If you got it better, what did you do.
Originally Posted by LukeG
(Post 1532743)
Good stuff!
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There is a setting for the idle rpm somewhere in the hydra software. It's been a while. I could only get down to 950-975 rpm at idle before having issues, so you aren't that far off.
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I need to give this a try... my idles issues have been mostly sorted compared to what I used to have to deal with, but I think it's time to boot up the old laptop with the serial port connection and check my settings against this post's suggestions. Thanks!
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