Car idles fine when checking timing but other than that it has a sputter (misfire?)
07-27-2022, 07:01 PM
#1
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Car idles fine when checking timing but other than that it has a sputter (misfire?)
I have a 2000 miata with 1000cc fic injectors, mp62 charger, new denso stock fuel pump, newish plugs, flowforce ls coils. If you need more info please lmk.
im having an issue starting off tuning. The car has intermittent sputters from the exhaust. I finally got idle rpm and afr somewhat stable to where it doesn't hunt but I noticed that every in few seconds or so the exhaust sputters like it's misfiring. I don't feel it but I hear it. It's not rhythmic either.
Thing is when I go to verify timing with a timing light and setting it to constant I am at 10° and while I have it in this mode the sputter goes away completely and idles very well, perfect I'd say.
Is this a tuning issue? I am sorry if this is obvious and if my thread is dumb but im just trying to figure this out.
im having an issue starting off tuning. The car has intermittent sputters from the exhaust. I finally got idle rpm and afr somewhat stable to where it doesn't hunt but I noticed that every in few seconds or so the exhaust sputters like it's misfiring. I don't feel it but I hear it. It's not rhythmic either.
Thing is when I go to verify timing with a timing light and setting it to constant I am at 10° and while I have it in this mode the sputter goes away completely and idles very well, perfect I'd say.
Is this a tuning issue? I am sorry if this is obvious and if my thread is dumb but im just trying to figure this out.
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07-29-2022, 05:20 PM
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It might be just a side effect of having big injectors:
Just a hypothesis, but there's a certain range of pulse width as the injector comes close to its dead time where the spray pattern becomes unstable. That could affect air/fuel mixing and cause a misfire every once in a while. A 1000cc injector may be be within that range during idle on our little motors, especially if you consider variation between the four. This could explain why your problem goes away when you set timing to 10. You're taking away some efficiency (assuming you normally have it set higher), meaning more air has to come in to hold the same idle speed, meaning more fuel is required to hold the same mix ratio, which is just enough to push the injector out of that little sketchy zone down low.
But again, just a hypothesis. Unless you have a flow vs. pw chart for each of your injectors to give us, we can't know if this is true.
Anyway, lets see what the log and tune says.
Just a hypothesis, but there's a certain range of pulse width as the injector comes close to its dead time where the spray pattern becomes unstable. That could affect air/fuel mixing and cause a misfire every once in a while. A 1000cc injector may be be within that range during idle on our little motors, especially if you consider variation between the four. This could explain why your problem goes away when you set timing to 10. You're taking away some efficiency (assuming you normally have it set higher), meaning more air has to come in to hold the same idle speed, meaning more fuel is required to hold the same mix ratio, which is just enough to push the injector out of that little sketchy zone down low.
But again, just a hypothesis. Unless you have a flow vs. pw chart for each of your injectors to give us, we can't know if this is true.
Anyway, lets see what the log and tune says.
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07-29-2022, 05:55 PM
#5
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here is my current tune and a log of a drive, it happens at idle. also can someone check if i have fuel cut on because im pretty sure its on as the car cuts out at around 150kpa
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07-29-2022, 09:12 PM
#6
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Nope I was wrong, it should be far enough away. HOWEVER, 19 degrees at 800 rpm is pretty far up there, and it wouldn't hurt to see if your idle improves if you set it lower. And double check those injector dead times, I'm not sure if idle VE in the 90s is typical.
I suggest this because my idle quality has always fallen if I had ever started going higher than 15.
And yes, your boost cut is set to 150kpa.
I suggest this because my idle quality has always fallen if I had ever started going higher than 15.
And yes, your boost cut is set to 150kpa.
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08-01-2022, 10:16 PM
#7
I’d bump all your AFR figures to 14.7 in your idle cells at least <=1000rpm at the idle Kpas.
Consider the AFR table as your golden wish list. You definitely want your car idling at 14.7 at hopefully 850-900rpm like stock. If you are trying to compensate for some other problem, figure that out, or use another setting. That is what Ve and spark timing are for, Don’t use AFR to workaround some other problem.
Consider the AFR table as your golden wish list. You definitely want your car idling at 14.7 at hopefully 850-900rpm like stock. If you are trying to compensate for some other problem, figure that out, or use another setting. That is what Ve and spark timing are for, Don’t use AFR to workaround some other problem.
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08-24-2022, 06:37 AM
#8
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It might be just a side effect of having big injectors:
Just a hypothesis, but there's a certain range of pulse width as the injector comes close to its dead time where the spray pattern becomes unstable. That could affect air/fuel mixing and cause a misfire every once in a while. A 1000cc injector may be be within that range during idle on our little motors, especially if you consider variation between the four. This could explain why your problem goes away when you set timing to 10. You're taking away some efficiency (assuming you normally have it set higher), meaning more air has to come in to hold the same idle speed, meaning more fuel is required to hold the same mix ratio, which is just enough to push the injector out of that little sketchy zone down low.
But again, just a hypothesis. Unless you have a flow vs. pw chart for each of your injectors to give us, we can't know if this is true.
Anyway, lets see what the log and tune says.
Just a hypothesis, but there's a certain range of pulse width as the injector comes close to its dead time where the spray pattern becomes unstable. That could affect air/fuel mixing and cause a misfire every once in a while. A 1000cc injector may be be within that range during idle on our little motors, especially if you consider variation between the four. This could explain why your problem goes away when you set timing to 10. You're taking away some efficiency (assuming you normally have it set higher), meaning more air has to come in to hold the same idle speed, meaning more fuel is required to hold the same mix ratio, which is just enough to push the injector out of that little sketchy zone down low.
But again, just a hypothesis. Unless you have a flow vs. pw chart for each of your injectors to give us, we can't know if this is true.
Anyway, lets see what the log and tune says.
here is my injector data and this is what I have for deadtime settings with mspnp2
Flow rate 1190cc
deadtime: 1.178
Voltage offset: .180
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