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AFR Ratios

Discussion in 'A4/S4 forum(B5 Chassis)' started by Broken Byzan, Nov 3, 2008.

  1. Broken Byzan

    Broken Byzan Photographic Moderator
    Staff Member Moderator VCDS Map User Audi A4 quattro

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    Ok i have a glow shift AFR guage fitted, it splices into the narrow band Lambda sensor. At WOT it drops below 10:1 and on coast in gear its 17:1.

    Under normal driving it flickes between 10 and approx 13.5, then as soon as i go WOT it drops to the floor. I know that the guage isnt calibrated but surely it cannot be that far out. I bought it as a way of keeping an eye on the AFR to keep the EGTs acceptable, i realise that the low AFR will the EGT down, but at the expense of fuel economy and performance.

    The only change since being mapped is the exhaust manifold and FMIC neither of which should have an impact i can think of. So anyone have any ideas?

    Is it down to tuning or do i have a faulty componant somewhere?
     
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  3. aragorn

    aragorn "Stick a V8 in it!"
    Staff Member Moderator VCDS Map User

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    a narrow band lambda really isnt very useful for getting output on a guage.

    It will for sure drop to the "full rich" end of the scale on full throttle, as lambda isnt used by the management for fuelling over ~70% throttle, especially as its turbocharged.

    A normal working lambda will cycle between two values either side of stoich, your guage seems to be interpreting these as 10 and 13.5:1 but i suspect its lying because the ECU would have flagged a fault if it was really cycling between those readings

    I think if you want sensible lambda readings then get yourself a wideband, as thats the only way your going to get data thats actaully usable.
    http://cgi.ebay.co.uk/Innovate-LC1-Wideband-controller-and-analog-G4-Gauge_W0QQitemZ330264159156QQcmdZViewItem?hash=item330264159156&_trksid=p3286.c0.m14&_trkparms=72%3A1301|66%3A2|65%3A12|39%3A1|240%3A1318

    Something like that is probably going to be what you need.
     
  4. Broken Byzan

    Broken Byzan Photographic Moderator
    Staff Member Moderator VCDS Map User Audi A4 quattro

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    I knew i should have researched this beforehand!

    Cheers I had a feeling it was something like that, I only went for the guage to save import duty by doing them all together
     

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