mike1986fyrbird

I am having some issues forcing open loop idle (idle in PE) with the '730 ecm. I have read other threads and came up with the following; Enrich Power Enable %TPS Set both the 1200rpm and 400rpm values to 0 to enable PE at idle. Enrich Power Change to AFR vs RPM Change the idle area of this table to offset the fuel added from the Enrich Power Change to AFR vs Temp table. Problem: I don't think it is going into PE(effectively open loop) at idle as the BLM/INT move around the the 02 volts bouce around from the loads of gas added from the idle BLM/INT. When I disable closed loop to tune with open loop all the time the car idles nice, doesn't stink as bad, and the 02 volts stay at .1mv Thanks.

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1987 Trans Am GTA, Turbocharged 357ci 470rwhp/565rwtq 11.12@124mph

JP86SS

You don't use "PE" Power Enrichment at idle.
Set the PE tables back to the old settings and shift your o2 constants at idle.

mike1986fyrbird

I tried moving the 02 constants without success. I tried different settings in .100mv decrements ranging from the .6~ factory swing points down to the .1mv where the car idles in open loop.

The car still stinks like fuel pretty bad at .3mv swing points but surges at .1mv swing points..

Thanks.

Blue1989RS

Is the cam your running in your sig? If so, you might have too much overlap at idle. Thats what I'm going through right now.

too much overlap means unspent fuel and air is being blown through the engine. the o2 sensor only thinks its running lean, which it isn't. So it richens it up, making the problem even worse.

Right now I'm going through the process of leaning it up with the VE tables. I've increased the "minimum temp for closed loop" to be 154*C so the code doesn't try to correct. Since the o2 sensor doesn't work at idle due to the cam, I'm going off of smell. Does this sound like what your going through? Mine was running so rich it would seriously gag you and burn your eyes. Its been much better since I lowered the VE in the "Idle volumetric effeciency table".

mike1986fyrbird

Thats exactly what i'm going through and why i'm trying to force open loop at idle only.
The car is my daily driver so i'd like to be able to run closed loop during cruise conditions so highway fuel mode works. May not be possible though.

As for the VE Table, i'm not sure how much lower I can go in the idle VE area. The cam idles around 60kpa at 900rpm. I've been trying to tune the idle VE area in open loop based on smell but i'm scared to go to lean. VE in the idle area is currently set at 35%. Idle spark advance is 28*.

Thanks.

Z69

The BLM & INT can only remove so much fuel.
Once you go to a bigger cam with a 110lsa and raise the idle.
You add a lot of fuel that the engine just can't use at idle due to the lowered vol. eff.. The lower efficiency more than offsets the excess o2 in the exhaust so you end up with excess fuel.

Check one of your logs and see if the blm/int are bottomed out.
You can also change your blm min to 96 which gm did in some bins.
And try 25% VE.
The actual number isn't really an issue unless it drives your PW less than 1.5ms at idle. In which case you will then have to tweak the low PW offset table too.
You could raise your idle another 50-100 rpm also. And you have plenty of timing, if not too much.

I can already see I'm going to have to add lots of notes to S_aujpv4 so that people don't go to open loop idle and stay there by mistake.

Gary Anderson

There is a constant at L8601 that must be set to 00 and a minimum MAP at L85FF must be set below your idle MAP.

If you use Tunercat and your ECM file is older than Bsomething the constant (L85FF) was backwards. Good luck.