Homemade O2 Sensors

[amalventano at sc.rr.com (Allyn)]

> (this opens the solder vs. crimp debate).

here, i'll attempt a quick end to the crimp vs. solder debate.

crimping or soldering work ALMOST equally well. to understand why you must
see how the o2 sensor interface works. the o2 sensor outputs a small voltage
(~0.5v), and due to the method by which that voltage is made, it is very
sensitive to loading. the slightest load will cause the voltage to drop
below what it is supposed to be. for this reason, the thing that reads this
sensor (ecu) uses a circuit with a very high impedance input (similar to a
digital voltmeter - which is also the reason that analog meters don't work
well reading o2 sensors - as they load the output down too much).

ok, so we basically have something making voltage that is very sensitive to
loading, and its measured with a circuit designed to put near-0 load on the
device being read.

ok, now what all of this tech stuff does for us is show that electrically,
it just doesnt matter if you solder or crimp this connection. reason being
that since the sensor is read using very high impedance, small differences
in resistance of the wiring will have no impact on the voltage reaching the
ecu. this is because there is ~0 current running through the o2 sensor
wires, so changes in resistance of those wires have no impact on the voltage
reaching the other end (cant have voltage drop across the line when there is
no current running through it).

ok, so we (thoroughly) covered the electrical. what remains is the
mechanical. the reason some prefer crimping over solder is because solder
joints usually fail. now dont get me wrong, solder IS the superior
connection method, but not when it is done improperly. lets face it, your
average joe cant pull off nuclear grade solder joints. if you dont properly
solder this connection, the solder wicks up the wire as its being soldered,
causing it to be rigid up to the point where the wicking ended. not knowing
this, the wire is not properly reinforced at the end of the wick, and this
junction is allowed to take the bending force of the wire. keep this up a
few times and the wire breaks at that junction.

...so its not that solder is bad, its that people shouldnt do it unless they
are competent enough to do it correctly.

Al

Allyn Malventano, ETC(SS), USN
87 Rieger Scirocco GTO 2.0 16v (daily driver, 190k, rocco #6)
86 Kamei Twin 16V Turbo Scirocco GTX (30% complete, rocco #7)
86.5 Occo 16v Trailer (rocco #8)
90 Passat GL 16V (the wifes new daily, 200k)

----- Original Message ----- 
From: "Ron Pieper" <rapieper@yahoo.com>
To: "James S. Danda" <jdanda@sunflower.com>; <scirocco-l@scirocco.org>
Sent: Tuesday, February 10, 2004 10:37 AM
Subject: Re: Homemade O2 Sensors


> Yes, I installed the same Bosch sender in a Cabby some time ago...worked
wonderfully.  Did you
>
> Should be OK...
>
> Ron
>
> --- "James S. Danda" <jdanda@sunflower.com> wrote:
> > Has anyone had luck wiring up a Universal O2 sensor (ie Bosch 13913) to
a 16v CIS-E car?
> >
> > I have one wired and installed, but I'm having problems getting my car
to run right. It misses
> > under load. In other words when accelerating it accelerates erratically.
Eventually I reach
> > steady speed and it runs great, but while accelerating it has power in
bursts. Its like a switch
> > is randomly thrown which gives small burst of full power. Otherwise
power is at 75%(guess). Oh,
> > and it only acts like this AFTER the engine has completely warmed up.
> >
> > I've done the following in trouble shooting: new filters(air, fuel), new
injector seals, new
> > plugs and wires, checked for vacuum leaks, and built a new o2 sensor.
> >
> > I'm beginning to think its the o2 sensor, but like an idiot I threw the
old one away so I can't
> > test it. It ran ok before changing my downpipe. While installing the
downpipe I figured I'd
> > replace the o2 sensor. I really don't want to spend $125 on an OEM
sensor, but if that gets the
> > car running right I'll start saving.
> >
> > Thanks,
> > jim
> > _______________________________________________
> > Scirocco-l mailing list
> > Scirocco-l@scirocco.org
> > http://neubayern.net/mailman/listinfo/scirocco-l
>
>
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