SR20ve low timing at idle? [Archive] - SR20 Forum

: SR20ve low timing at idle?


mr.sentra_specv
05-28-2009, 05:10 PM
OK well i have a VE setup running off a calum basic board and i am in the initial stages of tunning it. at idle i have some slight issues. first off after a few seconds usually 5-10 the stock o2 sensor hits about .83-.85 and sits there the afr drops slightly from 14.7-.15.1 down to 13.9-14.1 at about the same time the ignition timing drops from 15 at the ecu side down to 7-11 deg. i have the actual base timing set to 15 deg confirmed by timing light. so i am not sure what i should do as timing and AFR maps show the correct values but it looks like the ecu pulls some other info after the car sits at idle in neutral for a few seconds.

billc
05-29-2009, 06:26 AM
OK well i have a VE setup running off a calum basic board and i am in the initial stages of tunning it. at idle i have some slight issues. first off after a few seconds usually 5-10 the stock o2 sensor hits about .83-.85 and sits there the afr drops slightly from 14.7-.15.1 down to 13.9-14.1 at about the same time the ignition timing drops from 15 at the ecu side down to 7-11 deg. i have the actual base timing set to 15 deg confirmed by timing light. so i am not sure what i should do as timing and AFR maps show the correct values but it looks like the ecu pulls some other info after the car sits at idle in neutral for a few seconds.

I don't see anything to be concerned about in your description of how your car is behaving.

Both my cars (B13 DE and VE) also demonstrate this change in idle AFR, but mine do it after 20 to 30 seconds. The AFR richens a point or two -- it's very predictable, and it happens with Calum, JWT, and B13 OEM ECUs. In the DE, it seems to be associated with activation of the AIV, so my hypothesis has been that there is some residual trigger that has been carried forward in the Calum and JWT ECUs like some bad DNA. Nothing to worry about, and I don't know how to fix it.

Many times at idle, the narrow band will read either rich or lean for extended periods of time. Hold the RPM at 2500 to 3000 and observe the behavior of the narrow band O2 sensor read out. It should flip back and forth, rich to lean, every couple seconds. If it does, you are good to go. If it does not, then your mixture is way off or your O2 sensor is not working properly. All of this assumes that your ECU is set up for closed loop operation.

Setting your timing to 15* -- both physically and in the ECU just means that this is where the ECU starts from when it comes to idle timing. Unless you are in Set Timing Mode, the ECU will constantly adjust timing and AAR settings to keep your idle speed close to spec. If you put the car in Set Timing Mode, your timing will read 15* on your computer regardless of the physical setting (which you have to set with a timing light) and it will be rock steady.

Here endeth another overly long post -- hope it's helpful. Please respond if I have missed something.

Billc

mr.sentra_specv
05-29-2009, 08:50 AM
yeah it basically does every thing else perfectly. the second i put my foot on the gas the o2 switches lean/rich and verified by the voltage. i was just hoping to be able to get the AFR a steady 14.7 at idle.

billc
05-29-2009, 12:10 PM
yeah it basically does every thing else perfectly. the second i put my foot on the gas the o2 switches lean/rich and verified by the voltage. i was just hoping to be able to get the AFR a steady 14.7 at idle.

I don't know what others have experienced, but your car is doing what mine do.

Calum
05-29-2009, 01:33 PM
Bill- does it do this even when you unselect the O2 feedback bit?

mr.sentra_specv
05-29-2009, 02:16 PM
i have a some what fix i tried this morning and it seems to work awesome. i was referencing some JDM stock bins and some sr20de stock bins and noticed that on the TPS closed timing table the ve bin i was using had 0 set from 60 degc-110c and the stock bins had 5 from 60c-110c so i changed this part of the bin. i also took 2 point off the top on the top 3 spots for the idle stabilization timing retard. the car now idles down to 15-18 deg timing and afr at idle stays around 14.4-14.7 on the wide band. those numbers are what my timing and afr maps are set to for the idle cell area.

billc
05-29-2009, 08:09 PM
Bill- does it do this even when you unselect the O2 feedback bit?

I'm not sure -- will have to try it when I get a chance.