Wideband Verification methods

Evening All,

How do you all verify Wideband data?.

On my LT1 I've installed a dual Zeitronix WB gauge, so i can log & monitor both banks.

mild cam 383 LT1 in Speed Density, 16188051pcm $EE
I'd noticed upon reviewing the datalog the LH side was more unstable & contains a lot more lean spikes in Closed Loop.
I suspected a manifold leak (had the gaskets sucked in previously) rather than a miss as the car drives pretty well.

LHS is actually reading RICH
I was playing with the controls in Steveo's EEHack and switched it to run 14.7 AFR Open Loop.
Both sides smoothed out but were around 12.6 & 13.8 AFR (about 1 to 1.5 AFR apart). Idle BLM's had been running previously at 115 which might explain the extra richness.
I've also pulled 4% out the LHS idle fuel adders to balance the BLM's up.

My WOT data logs are also recording about the same 1 - 1.5 AFR Difference which rules out a vacuum leak.
Narrow band BLM trims show a variation of 1 or 2 points between rich and lean sides

Any thoughts or ideas?

TIA
Mitch

It will be hard to tell, but something you can try is to swap sensors, controllers.

I will trust blms more than the wideband. If they are close to 128 on both sides and one wideband reads much more than the other it is something wrong in the sensors.

At 128 blm with higher airflow, the wideband should oscillates between 14.7-15.1.

yeah, if it's a closed loop rig, i'd check about 20 seconds of cruising in closed loop and make sure that the wideband data averages to stoich during that period.

for dual sensor i usually found just (leftbank+rightbank)/2 gave me better accuracy but i agree the AFR should be really close. if you have a dead sensor just ignore that sensor, you should only really care about one bank if you know you don't have a problem that's causing uneven fueling.

here's another one if you suspect it's your engine rather than your instruments.. if you shut your engine off, a minute later when exhaust gasses have reached natural equilibrium between both banks, do the widebands read evenly then? they sure as hell should.

Attachment 16120

I think I attached the image of the log.

I think the narrow band O2's may also be showing the issue

This log shows Left and right Wideband and Narrow band Open & Closed Loop on an 85+C idle.
The BLM's tend to sit several points richer (lower) on the LHS .
Open loop seems to agree with this.
Closed Loop, the NB doesn't seem to oscillate as low, lean on the LHS but AFR appears much leaner on the Wideband.

Confused. :-)

I'll pull the injectors and swap banks.
I'll check the O2's tomorrow. They are all newish, less than 1k miles

Thanks all.

Swap the wideband sensors first.

I suspect that you have some cylinder running way richer on the ac wideband. The blms try to lean it out but the other cylinders on the side get too lean, and you have some spikes there. Open loop shows much fatter mix on the ac wideband, due to richer cylinder.

One possible reason could be an injector that flow much more than the others.

For dual widebands I will run pin27 and pin 31 since they have the same pullup resistors. AC pin have slightly different pullup value, that might screw the reading.

Quote:

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Originally Posted by kur4o

Swap the wideband sensors first.

I suspect that you have some cylinder running way richer on the ac wideband. The blms try to lean it out but the other cylinders on the side get too lean, and you have some spikes there. Open loop shows much fatter mix on the ac wideband, due to richer cylinder.

One possible reason could be an injector that flow much more than the others.

For dual widebands I will run pin27 and pin 31 since they have the same pullup resistors. AC pin have slightly different pullup value, that might screw the reading.

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Thanks, That makes some sense, although I'm on my third set of injectors. I'll have a maul tomorrow.
I did do a voltage sweep of the two imputs as Steveo had mentioned that previously and they are within 0.04v of each other.

PCM EEHack WB AFR WB AFR
Voltage AC Pressure ACPressure D27

1 0.98 11.56 11.52
1 0.98 11.56 11.56
1 0.98 11.56 11.6

2 1.98 13.56 13.52
2 1.98 13.56 13.56
2 1.98 13.56 13.6

2.5 2.47 14.54 14.5
2.5 2.47 14.54 14.54
2.5 2.47 14.54 14.58
2.5 2.47 14.54 14.62
|| AT THE PCM (EEHack see 0.02-0.03v lower )
2.55 2.53 14.70 14.66 || Stoich... 2.5-2.55V
2.55 2.53 14.70 14.70 || Stoich... 2.5-2.55V
2.55 2.53 14.70 14.74 || Stoich... 2.5-2.55V

3 2.98 15.56 15.48
3 2.98 15.56 15.52
3 2.98 15.56 15.56
3 2.98 15.56 15.6

4 3.98 17.56 17.52
4 3.98 17.56 17.56
4 3.98 17.56 17.6

5 4.98 19.56 19.48
5 4.98 19.56 19.52
5 4.98 19.56 19.56
5 4.98 19.56 19.6

5.x 5.00 19.60 19.56
5.x 5.00 19.60 19.60



Thanks for the feedbackj. Most useful.

Ta.
Mitch

I swapped all the injectors over bank to bank. NO CHANGE at all.

As I stop the engine the Left Wideband ramps slowly up to 21.0 AFR. The RHS is A LOT slower to change. so I'll change that when it's not raining.

I guess the LHS has a vac leak then causing the lhs to dump extra fuel in & the lean spikes.

Thanks guys
Mitch

Just reran with a very stock tune & let warm up.
BLM's at 127 128.

switched to openloop and LHS is reading rich on both narrow & widebands
BOTH Widebands are fairly stable around 13.5 14.5
The RHS narrow band is more erratic and leaner so I suspect the leak on the RHS
LHS is around 950 mV rhs is around 750 to 950mV

Mitch