pandin

Has anybody had experianced this:

Idle timing 20 degrees total, rpm 600-625 injector ms 2.4 O2 swings 600 mv.

This is a nice flat O2 swing starting at 450 mv and slowly rising to the 600 mv, takes 400 sec to get to 198 F.

Idle timing 30 degrees total, rpm 625-650 injector ms 1.8 O2 swings 0 mv.

O2 swings start at 450 mv climbs to 600 mv then drops to zero at 55 sec and stays at 0 mv from 75 sec on.

Steady idle, same tune, (arap modified) same coolant temp at 198 F "cold/overnite start". This is with the closed loop temp set at 304 F (open loop?).

The 10 deg spark change was made in the "Spark Correction Coolant Temp vs LV8" table location 010F .

Tried spark at 25 degrees and O2 were in the middle low with a lot at zero, average .3 mv

1tpi

I would like to know also

gta324

I guess you dont have a heated O2?

The raised timing will lower the EGT and cool down the O2 sensor.

On my car "open loop" idle
28deg timing 1000deg
32deg timing 850deg

/N.

pandin

Mine acts just the opposite at 40, 35, 30, the idle O2 sets at zero no swings. At 25 I get O2 swings, but they are low 300 mv and a large percentage are zero, and at 20 they are a perfect 600 mv average. This is in open loop.

I have tried three different heated O2 (4 wire) and 3 unheated all acted the same. Some new, some used. The biggest challenge was after adding the true dual exhaust. Found I had so much exhaust suction that the air pump check valves were being pulled open, they are capped now.

gta324

Do you have a WBO2?

Raised timing -> leaner AFR (mostly) and a NBO2 is only accurate at 14.7:1 (depending on temp/cam overlap...) and if you have true AFR of lets say 16 (with the timing raised) the narrowband can have 0 mV......

pandin

Yes I have a WB just not hooked up yet.

I had exhaust leaks that allowed air to enter pre O2 and also have a gnd issue when any bigger electrical load is added (AC, Fan, Lights) , the O2 drops by 100 mv.

Cam overlap 41 degrees.

Injector Pulse width also changes from 1.8 ms at 30 Degrees, to 2.0 ms at 25, to 2.2 ms at 20. 24# injector at 50# fuel pressure.

pandin

The odd part is that O2 swing points don't rise as the ECM adds more fuel, it just drowns out the motor.

pandin

Found the ground problem, the bolt above the oil filter was tight in the hole but the wire ends were loose. The bolt only turned a 1/8 of a turn and the wires moved. I installed this engine two years ago, just must have missed that.

Now the with the same Open loop tune spark at 25 degrees total the O2 swings at 836 mv avg, 839 mv median, max at 879 mv, min at 693 mv.

The same tune with Closed loop enable blm's at 128 and O2 swings at 447 mv Avg, median 453 mv, max at 892 mv, and min at 36 mv.

The injector pulse stayed at 2.1 ms during both tests, this is a little rich by the the past data logs on a more stock exhaust (1.8 ms)

The next step is to return to the higher spark advance and see what changes.

Thanks for the replies.