Hot Restart Idle Issues
#1
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Sorry for the novice question, but can someone check out my idle logs. The car idles pretty good when cold started and into hot, even after driving and everything, just as long as it started cold it will idle fine. When I turn it off and wait 10 mins or something it won't idle anymore. I don't really get whats going on. I'm new to ms3 and I'm not the best idle tuning. I just got the car started not long ago and haven't been driving it much because I can't figure out this idle issue. If anyone can maybe check the logs and tune file to see the issues, there probably are a lot. (cold Idle log is too big to upload since its from cold to hot)
#8
Retired Mech Design Engr
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It is not a Returnless problem. I have direct experience with converting from RL to Return style on my '99. Did not change this. Either way, one tunes idle VE and dead time. The injectors get hot from the sitting engine. This changes the resistance of their copper windings, and the dead time (the real dead time) increases (ohms law... V stays the same, R goes up, I goes down). It is I that drives the injector to open. Thus the fueling goes down. To compensate, you have to increase the PW. Same effect whether RL or R style. My guess is that if heat soak is worse in NB it would have more to do with the amount of engine heat that is trapped around the injectors between the various intake designs. Then, once the fuel and air flows for a bit, cooling the IM and the injectors down, the dead time shortens and more fuel is delivered, so the PW can be brought back to normal.
IAT heat soak is easy to deduce. Is the reported MAT higher than real or not? Log shows MAT = 53*F. Air Corr is 100.4. Those two things together do not indicate a heat soaked IAT. If it were heat soaked, it would show 100* or something, and then the correction would be around 98% per MAT correction curve. Still not drastic. I don't think it is the driver in this case.
Go to the linked thread above and see just how much ASE, Taper, and EGO are needed to make hot restart issues disappear.
EDIT: You may wish to change the EGO authority in idle area (or near idle) from 5 back to 15.
DNM
IAT heat soak is easy to deduce. Is the reported MAT higher than real or not? Log shows MAT = 53*F. Air Corr is 100.4. Those two things together do not indicate a heat soaked IAT. If it were heat soaked, it would show 100* or something, and then the correction would be around 98% per MAT correction curve. Still not drastic. I don't think it is the driver in this case.
Go to the linked thread above and see just how much ASE, Taper, and EGO are needed to make hot restart issues disappear.
EDIT: You may wish to change the EGO authority in idle area (or near idle) from 5 back to 15.
DNM
#9
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Thanks, yea I have an NA. I recently swapped my head for a vvt head, this only started after the swap. Gonna continue to work on the hot starts, today i got it so it doesn't die anymore on the restarts but its still lean, like 15.6 or so a little after the start. I still have to work on it but thanks for all the help.
#11
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What does your OEM system idle at normally?
When it's at the 15ish hot, does it idle smoothly still?
Even the OEM system will lean out on a hot start.
My NB with the OEM ECU + narrowband (plus a separate wideband not wired to the ECU) will generally idle around the 15ish AFR area for maybe 5mins after a hot start.
Even the OEM system will lean out on a hot start.
My NB with the OEM ECU + narrowband (plus a separate wideband not wired to the ECU) will generally idle around the 15ish AFR area for maybe 5mins after a hot start.
#12
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Normal idle, once warmed up etc fluctuates between about 14.5 and 15 (typical closed loop narrowband pulsing)
Ice cold start it will idle at around the 12s for maybe 1 min before tapering back up to the usual 14s
Hot start it will often idle around the low/mid 15s for 5mins or so (or until you start driving and come back to idle)
Setup is a stock 99 Aussie spec MX5
OEM ECU
EGR deleted, coldside short intake
Extractors with OEM narrowband in stock position on #3 runner.
Separate wideband installed just past bellhousing (MTXL) (not hooked up to ECU)
#13
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It is not a Returnless problem. I have direct experience with converting from RL to Return style on my '99. Did not change this. Either way, one tunes idle VE and dead time. The injectors get hot from the sitting engine. This changes the resistance of their copper windings, and the dead time (the real dead time) increases (ohms law... V stays the same, R goes up, I goes down). It is I that drives the injector to open. Thus the fueling goes down. To compensate, you have to increase the PW. Same effect whether RL or R style. My guess is that if heat soak is worse in NB it would have more to do with the amount of engine heat that is trapped around the injectors between the various intake designs. Then, once the fuel and air flows for a bit, cooling the IM and the injectors down, the dead time shortens and more fuel is delivered, so the PW can be brought back to normal.
IAT heat soak is easy to deduce. Is the reported MAT higher than real or not? Log shows MAT = 53*F. Air Corr is 100.4. Those two things together do not indicate a heat soaked IAT. If it were heat soaked, it would show 100* or something, and then the correction would be around 98% per MAT correction curve. Still not drastic. I don't think it is the driver in this case.
Go to the linked thread above and see just how much ASE, Taper, and EGO are needed to make hot restart issues disappear.
EDIT: You may wish to change the EGO authority in idle area (or near idle) from 5 back to 15.
DNM
IAT heat soak is easy to deduce. Is the reported MAT higher than real or not? Log shows MAT = 53*F. Air Corr is 100.4. Those two things together do not indicate a heat soaked IAT. If it were heat soaked, it would show 100* or something, and then the correction would be around 98% per MAT correction curve. Still not drastic. I don't think it is the driver in this case.
Go to the linked thread above and see just how much ASE, Taper, and EGO are needed to make hot restart issues disappear.
EDIT: You may wish to change the EGO authority in idle area (or near idle) from 5 back to 15.
DNM
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