Idle Air Control
The idle stepped does something, but I'm not confinced it's right. I connected the 4 wires from the stepper to the A,B,C & D channels (on the EC18 connector) going clockwise round the motor looking at it from the connector end. My stepper is an "anti-stepper" like Marcell's... It was operating the wrong way round at first.
Idle controls
Idle afterstart RPM (added value?) - Value to add to base idle speed when the car is first started.
Idle afterstart duration (s) - the duration to do the above for.
IAC afterstart (steps per 160 rpm) 0 is OK (this was a hint to the ECM, dropped from firmware recently)
Max steps to extend - total number of steps the motor can do. I managed to shoot the pin out of the end of mine. Don't do this as they get stuck in awkward places...
IAC step sequence - Lots of things, depending on how you wire up your motor. Mine was 201. ie drive C, then B, then D, then A.
stepper speed (ms) - Speed motor moves at. ie time between steps. 0 ms is fast and can shoot the pin a long way (see earlier). 3..7 msec is common. Surprising that your stepper works so fast.
iac_conf RAW - bitflags, see global.h . The values you copied from Marcell should be fine (precise idle=on; stepper=on; asymetric PID=whatever you like)
See the IAC section of: MembersPage/MarcellGal/EngineSwap/AirFeed for more info. on config
I thought I'd cracked this. but I havent: I still can't get a stable idle without the engine racing. Hmmm.
Config
| Idle cold | 900 |
| Max cold idle temp | 66 |
| Idle warm | 800 |
| Min warm idle temp | 75 |
| Idle afterstart RPM (added value?) | 100 |
| Idle afterstart duration (s) | 4.0 |
| IAC afterstart (steps per 160 rpm) | 25 |
| Max steps to extend | 250 |
| IAC step sequence | 201 |
| stepper speed (ms) | 2 |
| Idle control P | 80 |
| Idle control I | 10 |
| Idle control D | 5 |
| Integral time speed | 60 |
| Integral decrease limit | 6 |
| Integral increase limit | 25 |
| Integral deadband | 10 |
| IAC deadband | 10 |
| Seconds between overclosing | 5 |
Idle step bins:
220 (why so high??) when at 71.1 degrees (no point in including the rest of the table as it's a warm idle problem)
The idle valve says it is at 80% on Megatune's display page, yet the idle still races at 1300 to 1400 RPM. I don't think there's a leak in the plenum, as that's all I can think of that would cause the problem.
- Play with mdi.. where .. is the 2 hex digits from 00 to FF.
- set back to mdi00 at the end for automatic control
- set Integral decrease limit according to I value (though 06 sounds right)
- Decrease the reference positions, a bit (like 5..10) higher above than the best mdi.. values (temp dependent). As high that still allows reaching target RPM, but does not allow much lower). Decreasing from a high value until RPM target reached is probably the easiest way. Do it for every temp as it warms up.
Update
A couple of problems were found.
- The plenum did have a slight leak from an unused fitting.
- I had a partially blocked pre-cat on one side of the engine (Main cat was OK) causing the revs to drop half the time!!
- With the leak fixed and pre-cats removed, it idles smoothly but a little low.
- don't forget that the temperature dependent reference positions are just hint to the PID. The RPM target ("final word") depends on the (2 point, cold and warm) idle RPM points.
- With the mapping tweaked a little bit usign the help above, it seems to work happily for warm idle.
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