Fc Question Re Idle Control And Idle Ignition Values

[GTRNUR]

Hi all,

As I understand it an FC will set the idle igniton advance at 20 degrees for an RB26, and I think SR20's are 15 degrees at idle. No amount of stuffing around with the low load points on the ignition map will have any effect on the idle ignition values, as in it is locked at a pre-set ignition advanve setting right?

It would also appear that when the ignition falls back to the 20 degrees idle lock, the IAC valve will operate. But the moment the throttle is cracked open just a little the ignition map values come into play and idle control is no longer performed right...?

The reason I am asking this is that I am tuning an R33 gtr that the ignition map values are actually having an effect on the delivered ignition values when the car is idling. Add to this, the idle speed controls arent working. So I figure its got to be something to do with the throttle position sensor right?

Im going to plug the FC datalogit back into my R34 tomorrow and look at the absolute TPS values if I can, and then compare them to the values the R33 is reading.

Am I on track with working this problem out? Any other suggestions?

Cheers,

Ian

[paulr33]

you are correct in that the ignition timing is locked at idle

what would affect the timing however would be any correction such as water, air, battery, boost etc

these all play a part and could drive the timing up or down, but this again, shouldn't be applied at idle

check out SETTING, ING/INJ which is the temp adjust, it shows you the realtime IGN value the FC is reading from the with correction applied

compare that to what you see at the CAS for any clues

[GTRNUR]

Idle ignition lock definantly isnt working, as altering the igintion values at N02/P02 (active load point at idle) definatly change the delivered ignitoin value

Ive also reviewed a datalogit file from the R33 and the lowest recorded value for Advanced TPS V is 0.54. This compared to a log of my R34, the idle value is 0.43. 0.11 volts diference isnt a lot. But the threshold to switch to idle lock could be that small.

Ive tried a standard ECU in the car and the idle speed circuits are working, so the FC and a standard ECU might have diferent thresholds where idle control takes effect.

I'll be seeing the car again soon, so im going to try adjusting the sensor at idle to get a lower closed throttle voltage and see what happens from there. Ive seen the desired voltage mentioned somehere in the service manual before but cant find it again... just reading through the manual again now.

Any other suggestions?

[JonnoHR31]

from memory my 25 tps read .43v when closed. try adjusting it

[GTRNUR]

So update... just got to have another quick look at the car. I have adjusted the TPS sensor so the voltage is now 0.42 at closed. I also found the page in the service manual that says between 0.4 and 0.5v is where it should be set for idle... so all good right?

Wrong... Idle lock still doesnt appear to be working. With the car idling at 850 RPM, map changes in the idle cells are still having an effect on the delivered ignition values, and I suspect as a result for the same reason as the ignition issue, the idle control valve isnt working to regulate engine speed when the aircon is turned on and off.

Idle speed is set to 900 rpm in the map, so it should be regulating to that speed with the throttle closed.

I tried a factory re-set and was going to go through the idle setup procedure but that made no diference so ive re-loaded the tuned map.

I have attached a copy of an data log and ecu map for the car idling for a few minutes. Im pretty much out of idea's now. Is there anything else to check as to why the ECU wouldnt be going into idle lock mode?

Daryl_idle.dat.txt

Daryl_idle.txt

[GTRNUR]

check out SETTING, ING/INJ which is the temp adjust, it shows you the realtime IGN value the FC is reading from the with correction applied

compare that to what you see at the CAS for any clues

I noticed you mention that setting in you manual regarding "Can I have a lumpy 'cammed' idle?"...

I cant do this as I dont have a hand controller. I am using the latest datalogit software though. Do I need to source a hand controller to change some specific setting here, or can I change the settings I need with the datalogit?

I thought this is just a temporary "override all" thing that you were suggesting be done to determine how much ignition needed to be retarded to get the engine to idle rough, and then once done you suggested offsetting the whole ignition map a certain value. I dont see how this relates to idle lock.

Edited June 28, 2009 by GTRNUR

[GTRNUR]

Another observation.... Fuel cut on de-cel doesnt appear to be working either. It does mean back-fires instead, and the wideband is showing lean but it should be going to 20:1+ AFR on a de-cel when rolling down hill. At least it does for the R34 GTR's PFC...

[STATUS]

is it d-jet or afm pfc? as djet models have the option of IG idle control in the options menu. Failing that i have had a few pfc's come in with blown idle control circuits from panel shops jump starting cars incorreclty.

[GTRNUR]

Its a AFM PFC. I found out last night that the data I had on setting the TPS voltage too was incorrect too, so im going to have another shot at that.

Failing that, and assuming it is a blown idle control circuit, have you successfulyl repaired them? Im an electronics engineer so provided compatible parts can be sourced I can repair it.

Cheers,

Ian