Different readings between AEM UEGO display and e-Manage Ultimate A/F samples? - Miata Turbo Forum - Boost cars, acquire cats.

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Old 09-11-2007, 05:20 PM   #1
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Default Different readings between AEM UEGO display and e-Manage Ultimate A/F samples?

Why does the gauge of the AEM UEGO read leaner A/F measures than the e-Manage Ultimate samples?

Any ideas anyone?

Timo
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Old 09-11-2007, 06:11 PM   #2
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ground offset
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Old 09-12-2007, 12:28 PM   #3
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I have the same problem on mine. The gauge and EMU disagree by about 0.5 at midrange. Gauge and EMU are sharing the same sensor ground lead and the same supply wire.

I've just learned to live with it, and adjusted the calibration of my A/F Target table accordingly.
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Old 09-12-2007, 05:54 PM   #4
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Cheers guys, I'll check both ground wiring and supply wiring.

Did any of you read Flyin' Miata's manual on installing the AEM UEGO unit?

http://www.flyinmiata.com/support/in...gauge_type.pdf

I do not recall myself cutting printed circuit board copper lines, do you? Why do they do this?

Timo
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Old 09-12-2007, 06:02 PM   #5
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Quote:
Originally Posted by tkouwenhoven View Post
Cheers guys, I'll check both ground wiring and supply wiring.

Did any of you read Flyin' Miata's manual on installing the AEM UEGO unit?

http://www.flyinmiata.com/support/in...gauge_type.pdf

I do not recall myself cutting printed circuit board copper lines, do you? Why do they do this?

Timo
This only applies to the Link ECU.
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Old 09-12-2007, 06:49 PM   #6
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are the calibration calculations off in the Emanage?
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Old 09-12-2007, 10:35 PM   #7
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Quote:
Originally Posted by paul View Post
are the calibration calculations off in the Emanage?
Hard to say.

The AEM manual gives a very detailed table showing a linear output of 0V (10:1) to 5V (20:1) for gasoline operation. That table can be viewed here: http://img520.imageshack.us/img520/9931/tablebs6.gif

The EMU software has two fields where you specify the range of the sensor, as shown here:


What it does not specify however are the voltages corresponding to these ratios. It's not in the software, nor is it in the section of the manual dealing with the Parameters screen. I assumed that it is 0 to 5V, however now that I think about it, I suppose it's possible that it could be 0.5 to 4.5V as is the case with the MAP sensor input. I'd never really bothered to track down the error, I just always remembered to offset the values by a known amount. However this should be relatively easy to track down. For starters, I can yank the cable from the gauge, feed in a known reference voltage, and see what the EMU displays.

Weekend project identified.
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Old 09-13-2007, 12:09 AM   #8
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using that same chart for my AEMWB linear yielded the same kind of results with my MSPNP. the megatune display showed much different numbers than the gauge did. I just adjusted the input value till they matched.
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Old 09-15-2007, 08:00 PM   #9
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Well, no luck.

This morning I removed my AEM gauge from the dash and connected the output of a lab power supply to the white and black wires in the AEM harness. As I ramped the power supply from 0 to 5V while watching the EMU logger, the AFR value displayed on the EMU tracked perfectly with the chart in the AEM manual. So I conclude that the EMU's WBO2 input is in fact 0 to 5V, and that the calibration on the Parameters window is accurate. The fact that the (-) terminal of the lab supply was connected to the exact same ground that the AEM connects to also rules out any ground offset.

Nevertheless, when the engine is running and I watch both the AEM display and the EMU logger, the EMU seems to indicate about 0.5 points leaner on average than the gauge is showing. For now I have mashed the two into calibration by changing the "upper" window on the EMU software from 20 to 19.5, and this seems to have rippled down to an approximately correct reading around stoich.

What really concerns me however is not knowing which part of the AEM system is wrong. Is the analog output improperly scaled, or is the display itself in error? As much as I'm not a huge fan of the design of the Innovate system, it's starting to tempt me.
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Old 09-16-2007, 12:00 PM   #10
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Thanks for your 'laboratory' test. We may indeed rule out ground offset. I think that 20:1 as a value cannot be used as an appropriate max for the lambda sensor, having read the AEM manual I've changed the max in e-manage to 19.98 instead of 20 leading to a slight improvement, after that I changed it to 19.5, like you did also, to get correct measures in critical areas. The Bosch UEGO sensor LSU4.2 is probably giving correct values, it's trusted as a proper instrument by people with 20K$ engines like Skyline Nurspecs or Nismo's, hence I trust it on my rebuilt miata engine:-)
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Old 09-16-2007, 12:06 PM   #11
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Quote:
Originally Posted by tkouwenhoven View Post
The Bosch UEGO sensor LSU4.2 is probably giving correct values, it's trusted as a proper instrument...
It's not the Bosch sensor that I question, it's the AEM controller that its hooked up to.
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