O2 Sensor Tweaking...and MAF Enlarging...

[Matt Boland]

Kurek, Larry wrote:

> Guys:
>
> There is a major debate going on the F-body lists concerning HP gains from
> "porting" the stock MAF. I am arguing that the HP gains being shown on the
> dyno (7-10hp), are the result of lean out since the MAF is now out of
> calibration and NOT due to the increased airflow. I think the stock MAF
> flows around 650-700CFM, which on a NA 350 is MORE than adequate. Also, what
> I am arguing, and has been proven by a few list members, is that this gain
> is short term, since the PCM will 'relearn" the correct fuel trim values
> from the O2 feedback, and adjust the mixture accordingly. So, any leanout
> effect will be compensated for by additional fuel and you will be back to
> zero gain. One list member has argued that any effect of this learning will
> not be applied at WOT since the computer is not in learn mode. Doesn't the
> PCM just use the last value in the BLM to adjust WOT fuel? Don't you need to
> force this BLM cell to 128 (with custom programming) when going WOT to
> negate any learning effect?
>
> Finally, and this is my major question to this list. Has anyone ever
> considered, or actually built, a voltage adder/subtracter for "massaging" of
> the O2 signal? From what I can tell, this is the ONLY way to seriously
> impact fuel curves (short of reprogramming) over the long term AND at WOT.
> I'm sure you could build something that takes an input voltage and adds or
> subtracts, say 0-100mv, and send this signal to the PCM. A nice dial setup
> (adjustable pot) could vary the range (I would assume a +/- 100mv range
> would work), and have the ability to synchronize two inputs (for a
> left/right O2 setup) with the one dial. Doable? If so, how? comments?
>
> TTYL!
>
> Larry



 You could use an opamp configured as a voltage adder for each side. You could
use a pot to derive your +/- 100mv and simply feed it to the adder along with
the O2 sensors signal.

--

Matt Boland                                     m.boland at cat.csiro.au
CSIRO Division of Exploration and Mining        Phone: +61 7 3212-4482
PO Box 883  Kenmore                             Fax:   +61 7 3212-4455
QLD 4069 Australia