[Diy_efi] Re: Diy_efi Digest, Vol 3, Issue 24

[Nikola Radenkovic]

Gianmarco,

I completely agree with your post. The only thing that you
underestimated is the percentage of fueling alteration that
an O2 sensor signal can introduce. You said that you have a
fine italian turbocharged car: well if it uses Weber
Marelli IAW management the limit for fueling alterations by
O2 sensor is +/- 20%!

But the strategy to detect faulty sensor is usually good,
so ECU will "know" the things went wrong with the O2 sensor
and ignore it.

And yes, there is a way to damage the engine by
manipulating the O2 signal. First you have to make strategy
intelligent enough to avoid ECU to detect a faulty sensor.
Then you should signal the lean condition to the ECU (you
should turn it rich when the ECU is approaching 20% fueling
decrease limit, otherwise it will recognize the O2 signal
is bad). So ECU will enrich to compensate by max 20%. On
long term this would cause more engine wear due to the bore
washing extensively by excessive fuel. However, this will
take thousands of miles to be noticed.

With regards,
Nick

> 
> Message: 4
> Date: Tue, 31 May 2005 12:35:13 +0200
> From: "Gianmarco Rizzo (BE/EAS)"
> <gianmarco.rizzo at ericsson.com>
> 
> David, i am no engineer, but in my limited experience
> with EFI's, damaging an engine just by use or misuse of a
> O2 sensor can be achieved only by dropping the sensor in
> the inlet manifold while the engine is running.
> 
> those who design EFI's and those who integrate them on
> engines know their business. O2 sensors can only correct
> fueling by a few % and maps are usually conservatively
> designed, so that any sensor failure won't damage the
> engine. i have a high performance turbocharged italian
> sportcar, which would be the perfect candidate for your
> theory. and i can assure you, there is NO way of damaging
> the engine by manipulating the O2 signal.