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Stutter/misfire under boost

 
Old 07-18-2018, 03:12 PM
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Default Stutter/misfire under boost

Specs about the car:
1999 10ae
FM 3071r turbo kit
FM big flex fuel kit with 1000cc injectors
FM Big spark kit (ls3 coils)
Hydra nemesis 2.7 ecu

Two main problems:

1. Engine stutters hard under boost (15psi), but runs better when closer to redline. It runs fine when out of boost though. Bought someone's project, so unsure when it started occurring.

The stutter/misfire went away initially when I swapped in new NGK Zfr6f-11 spark plugs gapped to .0025", but returned after about a month. Swapping in new plugs didn't help.

2. Car also doesn't like starts, takes 7cranks and then reluctantly turns over. Won't even do hot starts.

Is it possible that the issue is spark blow out? Seems electrical as it's intermittent, and changing the spark plugs the first time fixed the issue for a month.
​​

Last edited by FoxingLikeAPro; 07-18-2018 at 03:31 PM.
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Old 07-18-2018, 03:29 PM
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Tune came with the car. I plan on getting it re-tuned, but want to fix the issue before i bring it to my tuner.

Link to the tune itself:
https://www.dropbox.com/s/gnal8jjy6i...0tune.hyd?dl=0

Link to datalog of stuttering:
https://www.dropbox.com/s/1a05kovkt7...ering.rdf?dl=0
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Old 07-18-2018, 03:59 PM
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I would offer to assist but I do not speak Hydra. Not many do.
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Old 07-18-2018, 07:21 PM
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Had the same issue , similar setup . New plug wires fixed it for me. The LS coils are like little arc welders , mine will push a spark across a 3/4 inch gap. Do a data log and check the knock values when it stutters, I've had issues where too much timing was causing the Hydra to go into knock avoidance mode with the same results . Fredb
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Old 07-19-2018, 01:50 PM
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Originally Posted by fredb View Post
Had the same issue , similar setup . New plug wires fixed it for me. The LS coils are like little arc welders , mine will push a spark across a 3/4 inch gap. Do a data log and check the knock values when it stutters, I've had issues where too much timing was causing the Hydra to go into knock avoidance mode with the same results . Fredb
Any recommendations for replacement plug wires that worked for you?

And good call; checking the datalog I do see some unusual knock activity under load. Though I'm really new to tuning and not 100% sure exactly what it means or the solution (pull timing?)....

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Old 07-19-2018, 01:54 PM
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Originally Posted by sixshooter View Post
I would offer to assist but I do not speak Hydra. Not many do.
I've considered replacing the hydra with a megasquirt because the community is so great and people actually know it.
I looked into getting a digital gauge cluster setup, which is super simple for megasquirt with a raspberry pi. But Hydra? Have fun playing around with CAN bus.
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Old 07-19-2018, 02:25 PM
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I had to go with FMs wire set , and then shorten them up a bunch because I’m running a custom bracket. Yah , I’d start by pulling some timing in those regions on the map . I’m not entirely convinced that it is actually knock in my cars case . If it’s the same issue I was having the miss / pop / hesitation a second or two after swatting the throttle , but doesn’t seem to happen if you roll smoothly into it. Fredb

Last edited by fredb; 07-19-2018 at 02:36 PM.
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Old 07-19-2018, 04:07 PM
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Sometimes launch control has that effect in MS. Not sure if it's the same for hydra, but you might turn it off and see if it goes away.

*edit* I should clarify: I had a similar symptom on my MS3, and turning off launch control got rid of it. I think for some reason LC was pulling timing straight to 0, so it acted like it was cutting out.
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Old 07-19-2018, 05:37 PM
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Worth a look , Iíve been meaning to take a closer look at my throttle pump setting as well. Fredb
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Old 07-20-2018, 02:30 PM
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I had the same issue and the only thing that fixed it was a tune by someone competent. Make sure your tuner has experience with Hydra. It is a weird beast.
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Old 07-20-2018, 03:56 PM
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Hit up 18psi (Vladi) he tuned my hydra 2.6 without issue. I've got the big spark kit too. One thing you might consider, is the LS3 coils are not OEM you could have some trouble there. I've gotten misfire before on mine, they are denso brand. Thats north of 24psi though. But I agree a retune from a good tuner would help.
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Old 07-21-2018, 01:41 PM
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Originally Posted by fredb View Post
Had the same issue , similar setup . New plug wires fixed it for me. The LS coils are like little arc welders , mine will push a spark across a 3/4 inch gap. Do a data log and check the knock values when it stutters, I've had issues where too much timing was causing the Hydra to go into knock avoidance mode with the same results . Fredb
Looking like this was the issue!

Checked resistance of the wires, cylinder 3 was 1.87 kilohms and cylinder 4 was a 1.44 kilohms. Per conversation with FM, the wires are rated between 2.2-8 kilohms. Jiggling the wires actually caused the car to run better. Just waiting on getting them warrantied now.
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Old 07-21-2018, 01:44 PM
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Originally Posted by miataman04 View Post
Hit up 18psi (Vladi) he tuned my hydra 2.6 without issue. I've got the big spark kit too. One thing you might consider, is the LS3 coils are not OEM you could have some trouble there. I've gotten misfire before on mine, they are denso brand. Thats north of 24psi though. But I agree a retune from a good tuner would help.
Getting a good tune is the next item on my list. I'm in NJ, so was looking at Jeff Evans Tuning as i've heard good things about him.

There aren't many hydra tuners, let alone miata tuners near me, so will see what I can find.
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Old 09-01-2018, 10:01 AM
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If you dump too much fuel in the engine you'll get a shudder. Find out what the source of the issue is. Buddy thought he had bad struts and warped rotors. Turned out he had a low fuel pressure problem.
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