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Old 03-24-2016, 11:33 PM   #1
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Default slight misfire

ill keep this quick and short.

94 1.8
Hydra 2.7
36-2 crank wheel with CAS
flow force injectors
stock coils

I am getting a slight misfire under light load at 2k and 4k. the events are random. it also misses under load at about 5.5k and 7k

Iv adjusted dwell and tried to adjust dwell trims at the rpms where the issues are, but that hasnt fixed it.

I am thinking i am having issues with the trigger wheels but i cant do a trigger test when the event happens because i dont know when it will happen.

Has anyone else had this issue and resolved it?
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Old 03-24-2016, 11:50 PM   #2
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Had a similar issue , try running the manifold wetting coefficient up 10 points at a time and retesting. Data log your afrs and see what they are looking like when it's missing. May be running a bit lean.
Alternately give Jeremy at FM a call Monday morning a get some professional help , he'll be able to give some real advice . He'll want to see some data logs for sure . Welcome to the Hydra world , misery loves company. Seems like I'm always trying to fix some minor hydra issue with my car. Mostly it works well but it's never perfect. Fredb
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Old 03-24-2016, 11:57 PM   #3
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i called jeremy already about the dwell settings he sent me. they are stupid and i dont want to run my coils like that. he said he'd been doing this for 10 years and this worked for them.

The car has also already been tuned on a dyno and iv gone in and logged afr. they are all good. i also tried to see if turning off ltft and stft off and that didnt change it.

other than that iv been happy with the hydra much better than MS. if i cant sort this its off to adaptronic or aem infinity.
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Old 03-25-2016, 12:12 AM   #4
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Bear in mind Jeremy has been tuning Hydras in Miatas forever. If he says the dwell settings are good , odds are they are . The problem most likely lies else where . It's unlikely you know more about the dwell settings than him. Good luck , and learn to use the shift button will you .
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Old 03-25-2016, 12:21 AM   #5
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this isnt my first stand alone. iv had aem and MS. again iv played with dwell both ways less and more. dwell isnt the problem. i am thinking the issue is the CAS signal and some diode mod that this box may or may not have
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Old 04-04-2016, 08:31 PM   #6
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The random, low load, singular misfire in 2.7 is an issue I've been chasing for years. It's a bug, and as far as I can tell the last one I haven't found & fixed. In most cars it's rare or a bit of an annoyance, but not a problem. It will happen at a very specific RPM so the issue is if that RPM coincides with a spot you normally drive in. Huge update though, last week I finally found some evidence for Hydra's engineer that I think was a huge revelation. We're analyzing it now & when it's fixed I'll definitely email my owner's list about it.

On the top end under high load misfire, if you're feeling something & you're confident that it's not knock, it is probably that you don't have enough timing advance after torque peak. I see this a lot on turbo cars with our 3" exhaust system. As backpressure goes down with bigger pipes, the engine wants a more aggressive positive advance slope after torque peak or else it can misfire. Alternatively if you can't safely run more advance I've fixed it in the past with more dwell trim in those RPM ranges.

As the owner of the system if you're an experienced calibrator you're welcome to run whatever dwell makes you happy. In a perfect world you'd run the least amount of dwell you can without it causing misfire. That said, I'd move the whole curve around & leave the shape how it is.
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Old 04-05-2016, 12:24 AM   #7
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This purely a hydra internal issue and not the tune because it is almost identical to my MS and AEM tunes on the same exact motor with the same hardware. car is non turbo so its not a back pressure issue/knock.

Interested in this "update" also Jeremy, if you could check my box to see if its had the resistor update for the cam signal that would be great.

There are some inconsistencies with dwell settings iv noticed the "Base" maps are Running a full 1ms less than the tune you sent me to use. Something you probably overlooked but no big deal cause dwell is not the issue here.
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Old 04-05-2016, 11:11 AM   #8
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If you give me your box serial number I can check to verify if it has the 5v diode update from a few years back.

There are different dwell curves for 90-93, 94-00, and 01-05 coils. Also different for the LS3 coils. I've used the same numbers in 2.1, 2.5 & 2.7. In 2.6 for some reason I had to roll them back by 1ms, never knew why. If I'm having a dwell issue on a particular car I generally manipulate the dwell trim as opposed to the base dwell.
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