John Speake

You can use the WBO2 with the Sharktuner but IIRC you can't have a simulated NBO2 from it as well as the NB.

John Speake

I would use a short ground to the nearest chassis point.

If the A/F is really that lean then it means the O2 loop isn't able to hold the A/F to 14.7:1

Have you been through the idle CO setup proceedure in the WSM ?

KenRudd

Looking at ^^^^^this^^^^^^ now. Starts at page 24-205, right?

Updates: took car for a test drive. Engine fully warm, at highway cruise speed, with cruise cotnrol on to mitigate any manula pedal changes:

Looks lean to me. It does get rich when I mash the gas (not shown).
Also, although I epxected the readout to be "dynamic" I did not expected it to vary that rapidly/erractically. Is this normal?

PHIL928

If I'm correct highway cruising AFR is usually slightly leaner to conserve fuel (AFAIK this is the case in most modern cars)

CardinalCar

Yes that's about right. You're hovering around 14.7:1, which is stoich for gasoline. The cyclical behavior is because the LH is only getting what amounts to a binary signal from the stock narrowband sensor -- it's either too rich or too lean -- and it therefore makes a relatively coarse fuel adjustment to compensate. This is also how OBD2 cars know if the O2 sensor has failed; they count how many times the signal traverses the voltage equivalent of 14.7:1.

Attached is a screenshot from a later OBD2 car (via a bluetooth data logger) which has four O2 sensors and two cats -- each cat has a sensor on either side -- so you can see both how well the sensors work (upstream cycles, downstream remains steady because of the cat) and, by extension, whether the cats themselves are working.

KenRudd

Very useful thread here, thanks Porken et al. Much more informative than WSM.

dprantl

Not on a 928, in closed-loop mode it is always hovering around 14.7:1 (unless something is wrong). LH 2.3 is too old to have that kind of feature.

Dan
'91 928GT S/C 475hp/460lb.ft

worf928

Modern catalytic converters are able to clean the elevated NOx levels that result from leaner-than-stoichiometric combustion. OE 928 cats are not that modern.

It's important to note the operating context when using terms like 'lean' or 'rich.' So, to be pedantic, at low-to-medium loads - i.e. 'cruise' and light acceleration - the target A/F ratio is the stoichiometric 14.7:1. This maximizes efficiency within the region of lowest overall HC and NOx.

At high-loads the target A/F ratio will be around 12.6:1. This maximize power, but results in high HC.

The WOT/idle switch is what tells the LH in which context to operate.

worf928

Thanks John.

I will be blowing the dust off my Shark Tuner in a few weeks and I'm looking to supplement or replace the Innovate WBO.

U-928

I'm curious as to if you have a specific reason for this statement or if it's just your opinion. Sure the free air calibration isn't fun, but in the years and years of operation of multiple Innovate WB's I've only ever done it once, and likely didn't need to. I was always under the impression that Innovate stuff was the benchmark?

Ducman82

Innovate products have never let me down, unlike my old AEM unit (not this car) and old auto meter units.

KenRudd

I'll post back regarding any issues, but so far, very pleased with the AEM unit. Fits into OE clock opening with minor work, and at this point I am comfortable that it is showing correct values.

My current plan of attack is to install the new injectors and new O2 unit and then tweak the mixture as needed based on the WSM and Porken's write up in the above link. I'll be buidling a "Blink'r" for the adjustment and will compare those readings with what the AEM gauge reports.

123quattro

The heater control on the Innovative is very course. That leads to inconsistent temperature in the measuring element. That in tern affects the measured A/F ratio.

Innovative is much much better than not having a wideband. It's just not as good as the other widebands that are for sale.

neilh

Ken, I've got an Innovate full kit and a 'blink'r' plus Porken's special tool over here in Cary ( Holly Springs at Ten-Ten) if you want to borrow them?
PM me if interested -

Neil

KenRudd

PM sent. Thanks!