Understanding WBo2 sensors and the figures generated by them

Streaky · Post by **Streaky** » Sun May 04, 2008 5:47 am

I'm not sure if this is the right area for this post but here goes.

Ever since I had a 4.6 Efi engine built locally here in dubai I've been having some problems with it. Massive over fuelling was my primary concern and lack of performance was close behind.

It's been a two year learning curve but eventually we think that we may have found a major flaw with the build. One of the heads was over- skimmed to a point where the compression was rediculas.

I purchased a Tech Edge WBo2 sensor and LX2 display from Australia and this week we completed the instalation along with the latest TEWBLOG software to log some of the perameters.

My unit will give me;
1) The Fuel / Air ratio at the Y peice and also on the two down pipes.
2) The RPM taken from the coil.
3) The TPS voltage taken from the TPS sensor.
4) The AFM voltage taken from the AFM wires.

Driving home last night was surprised or pleased to see that my Fual / air ration has gone from a 12/13. figure to a 15+ figure. 14.7 being the honest medium I'm told. So now I have gone from running super rich to running a little lean. Hopefully I can adjust this.

My main question is this. After logging a 50km drive I now have a set of numbers on my laptop in the way of a Windows Notepad file. It shows all of the values logged during my drive home.
How can I get to interprete these numbers and understand what they mean?
I know what the correct voltages should be at my TPS & AFM etc....these show up quite nicely along with the RPM AFR ratios.

Something else that surprised me was when I was running both the TEWBLOG software and the ROVACOM at the same time....the TPS & AFM figures shown on the display were different. ??!! How could that be?

Eliot · Post by **Eliot** » Sun May 04, 2008 8:10 am

Are the values you see seperated by commas? i.e value1,value2

if so, you can use excel or another spreadsheet to work on them. You need to apply a forumla to convert the voltage into an afr reading.

I'm trying to search the techedge site, but i have a screeming kid sat next to me.

Streaky · Post by **Streaky** » Tue May 06, 2008 3:49 pm

Thanks Eliot.

Graph is now sorted via Excel as you described.

Now to get find someone who understands all these numbers and translate them into my kind of language.

Regards.

S.

Eliot · Post by **Eliot** » Tue May 06, 2008 4:28 pm

Post the spreadsheet up.

sidecar · Post by **sidecar** » Tue May 06, 2008 4:38 pm

If you know that you were running 12:1 and 13:1 at some point then you must have been able to translate those lambda figures into ratios? Do you just need an indication of whether these A/F ratios are OK?

The Des Hammill book on Rover V8's has a chart at the back that gives lambda to air/fuel ratio.

The book also gives some A/F figures to aim for. I don't think that you were too far off.

It reckons 13.5:1 at tickover, 12.5:1 when eccelerating hard and at wide open throttle and hight revs (Basically WOT) and it reckons no leaner than 15:1 when cruising with a small throttle opening.

I have no reason to dis-believe the above figures and my tests so far using an LC1 innovate probe tend to agree with them.

The only figure that my engine would not be happy with is a cruise of 15:1, my motor does not like it any leaner than 14:1, infact I'm running 13.5:1 most of the time and I am finding it quite hard to richen up the settings whilst keeping the cruise at 13.5:1 (I run a fairly hot 4.6 carburetted lump, I will post some Edelbrock carb settings up when I've worked them all out and tested them).

The book states that these figures are pretty much universal for the Rover lump regardless of the state of tune.

By the way I would not trying going too lean with a 4.6 lump, Rover tried it and look at the mess that they got into!

Pete

EDIT...Just read your post again and I guess it was the "other" figures that you need help with rather and the A/F ratio! Oh well the above info might be of help to someone!

Streaky · Post by **Streaky** » Wed May 07, 2008 2:57 pm

Once I've completed some proper logging I will most certainly put the data on display here.
The first set of figures where taken when had the lamdar in one of the primary manifolds. I've now moved it to after the Y peice so the numbers of the AFR will be for both banks combined.

To be honest with Mr Side Car...my problem is not with the TPS or AFM readings. They are text book settings/voltages.
My problem is knowing how to interprete the AFR's.
Am I commiting a cardinal sin by aiming at 14.7 as a means average? Whilst dring the other day I couldn't help but notice that everything on the AFR side was pointing towards 'LEAN'....even the AFR's were beyond 15.3 and higher.

Yes...I must these figures posted here for some proper feedback.

Thanks for the feedback.

Regards.

S.

sidecar · Post by **sidecar** » Wed May 07, 2008 4:31 pm

Just what I've read about Rover V8's but I think that although 14.7 is not actually classed as chemically lean it is a little lean in the real world for a RV8. It would be ok on cruise but at full throttle, high load conditions I'd want to be running around 12.5:1.

Others may disagree!

Pete