808 ECM with 12p on a sc v6 with cam idle issue

[dmac_25]

Ok so playing around with the car this morning what I have changed.

I have managed to get it to idle at around 900rpm but not sure if it's the ideal way of getting it to do it.

I set the IAC desired to 900
IAC threshold to 40kpa any higher and it won't bring the idle down

Then I changed the EST idle spark advance from 25 deg down to 10deg and then would hold idle but was only running around 5 deg idle spark on the gauge so I slowly bumped it up to 15deg.

I then got a hunt when the fans turned on so I changed IAC adjustments high speed fan IAC step increase up to 20 steps so it ads 20 steps straight away and I left the decay at 2 seconds which that works great stopped the hunt when the fan comes on and then drops back nice.

The only issue now is I can not seem to find a table I can change so when the fan turns off and load is taken off the alternator that I can bump up IAC steps to stop the hunt on fan switch off.

I also changed the base IAC steps down from 32 to 25 which seems to help but not sure if it is required.

I could not find a table listed as IPS spark but I did max out the blm Params low temp.

Just to double check people process of saving the bin ready to burn to a memcal. Once all setting are final and happy with the tune I turn BLM low back to 80deg save the complete bin file ready to burn.

Unplug existing Ecu/battery to reset it plug in memcal with new tune start it all up and let it learn the settings??

[antus]

IPS is a scalar "IAC - Idle spark Adjustment params - Idle spark correction limit". It defaults to about 5.27 degrees, set it to 0 degrees to turn it off.

It sounds like your taking the right approach, but im not sure the best approach to help with a fan off stumble.

[dmac_25]

Thanks Antus I did see that table and I turned it down to 2 deg but I will turn it off.

Do you know of any tables that control voltage load vs iac or timing so I could adjust that so when the load comes off the system it can bump up the idle steps

[Holden202T]

there are settings for fan on and a/c etc for iac step increase, but you shouldn't need any for when they come off, the IAC should decrease accordingly.

[dmac_25]

I did change the on steps up from around 2 I think to 20 and that helps but it was with the fan turn off it would hunt until it settled.

I just changed IPS from 0 to 50 and not sure what that does but smoothed it out a hell of a lot more

[VL400]

Another cause of idle instability and hunting, particularly if it happens with fans turning on/off, is not having the injector voltage table setup correctly. Check that the table "Injector - Injector Bias vs Battery Voltage" is setup for your injectors. If they are large injectors then it might need "Run A/F Param - Minimum BPW for sync double fire fuel delivery (Upper Value)" and "Run A/F Param - Minimum BPW for sync double fire fuel delivery (Min Value)" setup to use single fire at idle.

With the change from the tuning to customer ECU all the learnt IAC steps will be lost. Same goes if you reset your tuning ECU (unplugging it or disconnecting the battery), may also idle high if the base steps are too high. The ECU uses a base number of steps initially after a RAM or power reset. During normal driving it resets the IAC by commanding 180 steps when RPMs goes above 2k RPM. It then goes back to the base or learnt steps. The base steps are continually learnt, stored in RAM and used as its start point when dropping back to idle.

I just changed IPS from 0 to 50 and not sure what that does but smoothed it out a hell of a lot more

If you can copy/paste the name of the table/scalar can help further on what it does.

[dmac_25]

The car is running stock sc injectors which should be around 36lb with the base fuel pressure turned up 10psi over stock but I do say that those tables will be slightly wrong with these injectors from what stock v6 settings are.

I was thinking of not bothering on swapo g the PCM's over but rather just pulling the nvram board and fitting the correct memcal with the tune setting finalized. Then on the next job just fit up the write wire and coms plug to the next Ecu's

I was referring to the table IAC-idle spark adjustment Params- idle spark correction limit. If I have that at stock or 0 it wants to hunt bump it right up and the hunt goes away.

[antus]

Thats how many degrees the computer will swing either side of the programmed spark advance. So 50 is probably too high. If you stall for some reason the computer might try and add up to 50 degrees which you probably dont want. There is a maximum advance scalar and that would limit it short of 50 degrees (i think its about 45), but in practice take a look at your expected idle spark, decide how many degrees you think is safe above this and set the IPS value to that. In the factory calibrations they program the spark a fair way lower than the engine can take, so that there is some torque available just by adding spark when you take off. This is why in a manual if you take your foot off the clutch in first with no accelerator it'll generally take off and start moving. The car will pull the revs down and the ecu will put more spark in providing more torque which will prevent stall if your not too rough with the shift.

[dmac_25]

I did think 50 was a tad to high I just threw it in to see what it will do. I'll play with it and bring it down to where it's happy and doesn't hunt and idles happy.

Do you think it's better to leave the PCM I'm using to tune on in the car and just re burn the memcal and put it in the PCM all ready plugged in so the iac steps are still learnt in the PCM??

[Holden202T]

it doesn't matter, removing the battery will clear learnt stuff like that, but it will only take it a few times to re-learn it, generally you want to get it up to temp and put it through the gears and it will then re-learn all the steps needed.