Miatapower List Archive

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Mail From: "Kevin Sullivan" <(email redacted)>

For those that expressed an interest, my car ('91 Aerodyne, newly installed
FMII ECU) passed emission testing with no problems. The only tuning I did
before the test was to slightly lean out the idle zones (from 42 to 39) so
that the O2 sensor could straddle the 0.65 volt target.

In MA we just test CO and hydrocarbons at idle, I got values of 0.7% CO and
120ppm HC at 900rpm. These are about half the maximum for '91 cars so I
passed OK, but it's interesting that these numbers are higher than those I'd
seen over the years with the stock ECU, which were typically 0.1% CO and
0ppm HC.

I'm wondering if the O2 target might be a little low, resulting in a slight
miss when the ECU cycles to the low side of the target. Watching the sensor
output an the tach I notice that the RPM drops and the engine -almost-
stumbles when the O2 voltage drops. Maybe a couple of misfires under these
extreme lean conditions are producing this extra CO and HC? Maybe next year
I'll richen up the idle target a few millivolts and see if the numbers
improve. Meanwhile there are much more interesting zones to explore.

Kevin




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This read-only message was archived from a public mail list.
Mail From: "Malcolm Gray-Stephens" <(email redacted)>

Talking to Bill on this issue and you could be right about low targets but
the oxygen sensor is non linear and suddenly drops at 0.50 Volts to near
zero. Hence the ECU is slowly leaning out and watching the oxygen sensor
when the sensor drops like a stone at 0.50 to say 0.10, any figures
in-between are seen on the transition to 0.10. At this point it starts to
add fuel again; until it finally gets the oxygen sensor shooting back at
0.80 or so and in my case overshoots to 0.90.... and so the cycle
continues. This is my current status but I am going to explore my earth
having done a 50% earth mod which is appropriate for a 1.8 (cut out feed
from wiring loom and take supply from block for this) not the full 1.6 mod
of cutting both wires (Please note 1.8 ECUers.. long pain to learn this
one!).

Making ECU faster to alter might make it less audible but talking to Bill
on this he seems to have tried altering response rates.

Making ECU slower in altering ... might make it better but I guess Bill has
been there..

Switching off Lambda might work better ... but I think you would have to
set fraction fuel numbers or have your six 100/200 numbers with a
separation to imply those fraction fuel numbers.

Malcolm Gray-Stephens
'94 Eunos FM2 ... no emission until the Autumn.

----------
> From: Kevin Sullivan <(email redacted)>
> To: (email redacted)
> Subject: FMII Tuning for emissions: success
> Date: 17 May 1999 13:40
>
>
> For those that expressed an interest, my car ('91 Aerodyne, newly
installed
> FMII ECU) passed emission testing with no problems. The only tuning I
did
> before the test was to slightly lean out the idle zones (from 42 to 39)
so
> that the O2 sensor could straddle the 0.65 volt target.
>
> In MA we just test CO and hydrocarbons at idle, I got values of 0.7% CO
and
> 120ppm HC at 900rpm. These are about half the maximum for '91 cars so I
> passed OK, but it's interesting that these numbers are higher than those
I'd
> seen over the years with the stock ECU, which were typically 0.1% CO and
> 0ppm HC.
>
> I'm wondering if the O2 target might be a little low, resulting in a
slight
> miss when the ECU cycles to the low side of the target. Watching the
sensor
> output an the tach I notice that the RPM drops and the engine -almost-
> stumbles when the O2 voltage drops. Maybe a couple of misfires under
these
> extreme lean conditions are producing this extra CO and HC? Maybe next
year
> I'll richen up the idle target a few millivolts and see if the numbers
> improve. Meanwhile there are much more interesting zones to explore.
>
> Kevin
>
>
>
>
> _______________________________________________________________
> Get Free Email and Do More On The Web. Visit msn.com