NefMoto > Technical > Tuning > Idle misfire when cold
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Author Topic: Idle misfire when cold  (Read 3432 times)
cessnas
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« on: March 17, 2019, 12:05:16 PM »
Hey
Got some 875cc deka (i know the spray pattern sucks) injectors installed along with a 4bar FPR. So now they're tuned to 960cc.
Tuned KRKTE and TVUB with the dynamic KRKTE and TVUB calc and the car now drives fine.
The problem is that when i go to start the car in the morning it dies instantly, like it's over fueling. If i start the car again it runs after a tiny bit long cranking.
Also it misfires on idle but only when its cold? So i thought the warm-up enrichment was screwing with me but the AFR is almost perfect.
Any ideas would be greatly appreciated
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gman86
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« Reply #1 on: March 17, 2019, 07:46:51 PM »
Quote from: cessnas on March 17, 2019, 12:05:16 PM
Hey
Got some 875cc deka (i know the spray pattern sucks) injectors installed along with a 4bar FPR. So now they're tuned to 960cc.
Tuned KRKTE and TVUB with the dynamic KRKTE and TVUB calc and the car now drives fine.
The problem is that when i go to start the car in the morning it dies instantly, like it's over fueling. If i start the car again it runs after a tiny bit long cranking.
Also it misfires on idle but only when its cold? So i thought the warm-up enrichment was screwing with me but the AFR is almost perfect.
Any ideas would be greatly appreciated

Populate TVUB based on injector datasheet.
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cessnas
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« Reply #2 on: March 18, 2019, 01:02:24 AM »
Isnt TVUB Fuel pressure dependent? Can only find the datasheet with the injectors running at 3 BAR
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prj
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« Reply #3 on: March 18, 2019, 01:16:31 AM »
If you know the spraypattern sucks, then why are you wondering that you have misfire?
It's normal for these to misfire, and the more miles you put on them the more they're going to misfire.

These injectors are not meant to be used on a small engine, they don't work properly below anything under 1.5ms.
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cessnas
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« Reply #4 on: March 18, 2019, 02:47:53 AM »
Quote from: prj on March 18, 2019, 01:16:31 AM
If you know the spraypattern sucks, then why are you wondering that you have misfire?
It's normal for these to misfire, and the more miles you put on them the more they're going to misfire.

These injectors are not meant to be used on a small engine, they don't work properly below anything under 1.5ms.

Yeah, and it started misfiring even when the engine is hot too now. So looks like i'll just have to live with it.

Dont know why it dies when i start it up in the morning though, not a big issue either
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dal
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« Reply #5 on: March 18, 2019, 04:30:03 AM »
Why you are running 4bar FPR? With 3bar, you benefit from TVUB data already exists based on 3bar, and you will have slightly bigger injection time, with a more stable injected mass from the injectors.
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cessnas
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« Reply #6 on: March 18, 2019, 04:44:55 AM »
Quote from: dal on March 18, 2019, 04:30:03 AM
Why you are running 4bar FPR? With 3bar, you benefit from TVUB data already exists based on 3bar, and you will have slightly bigger injection time, with a more stable injected mass from the injectors.

I want to run an 3 BAR FPR but i dont have one. The A4 B5 comes stock with 4 bar. Yes i know i can order one but in 2 weeks i'll be gone for a year and i want the car to run ish properly before then
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