Idle and AAC

[R33Tech]

RB25det with the R32 RB20det ECU.

It idles, when warm, at about 1,100RPM. The AAC screw is all the way in, the throttle is closed fully and the TPS reading .45v. AC is not on.

I tried playing with the Idle AAC Duty which I could bring the idle down to a nice 850 by adjusting the warm columns down to about 80, but it drops RPM very easily when taking off and sometimes when I clutch in. Sometimes dying completely.

Is there another setting to play with?
Is this the function of the AAC duty?
Why does only the Idle AAC duty 2 table seem to make a difference?
Is it normal for the AAC to activate when driving around? I have seen it at about 60.

cheers

[KidNeko]

Worth double checking hardware before trying to force a tune with huge offsets.

- Set (reset) AAC base idle and base timing as per Nissan's suggestion (ie. TPS unplugged and using active tests)
- Clean throttle body & AAC
- Possible boost / vacuum leak?
- MAF malfunction?
- Others... XD

If everything checks out, you might then want to take a few logs to see what's happening the moment the RPM drops

[R33Tech]

Thanks for the tip. I have discovered that if I pinch off the PCV hose (inlet cover to the intake manifold) the idle drops way off. Doesn't seem to make much difference on the other breathers. So I bought a new PCV and the grommet, but that did not help at all. Not sure what is going on.

[Matt]

Check the TPS idle indicator (post a log here if you need someone to look at it).

The TPS idle should be active when the TPS idle line is triggered. For RB25DET in R32 RB20DET the TPS idle indicator should be triggered using the FP1/FP1.1 firmware by setting the "TPS idle trigger" parameter and when TPS value is underneath this the 'TPS idle' indicator in the consult panel should illuminate. Try checking this first

[R33Tech]

Thanks Matt. I did not notice the idle indicator was not on. I have adjusted the parameter and now it idles nicely.

[R33Tech]

Since adjusting the TPS threshold, it seems to run more lean on decel, like off the scale. Is this healthy? Is there a way to give it fuel on decel, or should I? Is it normal to have the TPS Idle on when deceleration?

I have attached a log and my bin. The ramp starting at 8.600 is the point of interest.

I would like to know what is causing the timing spike at 14.515?

Also, am I too rich at 12.500 at 10.5 LAFR, considering it is a N/A engine with high compression?

[Matt]

When you decel, it will do two things

1. When TPS idle set, it will use idle timing. The spike you see is it going between idle/not idle
2. The 'MAX load (TP) Decel' table is used for antistall. If you find it is going lean too quick increase the load numbers

I've uploaded 1.4.6 today which fixes an issue with switches not showing on playback, so I can see your TPS idle indicator now

The spike @ 14 shows TPS idle (10deg), not idle normal timing (40 deg) and then TPS idle again (10 deg)

Thee max load table, try setting 2000- 6000 to TP value = 80 so it reads the map. This limits the TP to this value when TPS = idle

[R33Tech]

Thanks for working on the update to see the switches, that's awesome.

I made the changes to the 'MAX load (TP) Decel' table, but I don't think it made any difference to what I am looking at, which is the super high AFRs on decel. But from what I have since read, it is normal to be high. Does it look normal to you?

So much to learn, but it is fun. Glad I did not pay someone else to do it.

[Matt]

I've had a look through and nothing unusual from what I can tell. On decel where it goes lean, the load cuts (showing injection time as latency)

Normally this happens between TP cut and TP recover

Then it goes back to a non-cut situation and you see the AFRs return to normal afterwards

[R33Tech]

Thanks Matt. Good to know. I doubt I will stop fiddling with it.