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Misfire at Certain Boost, but Not Higher Boost

Practical Reflash Tuning

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Discussion and questions related to the course Practical Reflash Tuning

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To preface; I know this is not a hardware related issue. New crank sensor, new coil packs, new spark plugs, Battery voltage does not drop. The issue did not appear until new software was used.

Does not have the issue in free-rev which is how I know it is load/boost related. It is not a boost cut as you will see.

As the car builds boost it is perfectly smooth. Once the boost hits ~16-17 psi it acts like ignition is breaking up. As a test, I turned the boost control up and did a pull. It hit the 16-17, broke up a little, then smoothed out all the way up to 44psi without issue.

Put it back to spring pressure, it won't accelerate once 16-17 psi is hit. It sounds like it is on a two step. Fuel pressure tests fine, there's no dip.

I did a second test, by adding just a small amount of boost and reducing the ramp rate, it would hang on the 16-17psi for a few moments, then it would break free and rev up to 28-29 psi perfectly smooth.

I have played with the torque tables some more (had an issue with the throttle opening all the way), and have not made it better. BUT. Moving the torque demand UP made the car cut out completely, it was like a very slow rev limiter (ignition cut), but moving them down did nothing.

All tables have been checked for rough spots or transient spots that could cause this. If anyone has run into this or has any ideas, I am willing to try almost anything. I tune a lot of these cars and this new software is just kicking my butt.

Log attached.

You can see at the low end of this graph how the power drops then picks back up, that is it breaking up before snapping free.""

You can hear the break up in this clip:

Video Of Break Up

Attached Files
  • torque_test_4FT1B_-_28-11-2022_16-06-53.csv
  • Attachments may only be downloaded by paid Gold members. Read more about becoming a Gold member here.

What's the car, engine, ECU (I'm guessing it's a reflash, which software)?

Nissan Juke, MR16DDT, ECUtek reflash. There's no one in the world doing what I am doing, so I have no one to really reach out to. I am figuring this out for everyone.

When you say that's a new software, you mean an update? As you said you tuned a lot of these before without issues. Did you reach out to ECUTEK, maybe they changed something in the definition that isn't right.

This issue remind me the good old CAS problem on the old RB engine where the crank signal is jittery and timing is acting crazy.

Is there any reason your throttle is moving 5-10% throughout the pull?

I switched from Uprev to ECUtek, uprev is having major software problems. So. I know its a software issue. There's a bunch of definitions not right, and ecutek has told me they "will look into it". They wont. The software and tune files have been out for years. I digress.

The throttle up and down is the ETC system nissan has. Ecutek has no way to control it. I have to find tune it via the torque demand maps. But no sense in spending time on fine tuning that if the car wont make a full pull.

I am quite frustrated. Theres two ways to tune these. One has software issues that is blowing up cars all across the country, the other has incomplete definitions on everything. Idle control doesnt even work. On top of that, half the ROMS dont even have fuel enrichment.

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