VW Vortex - Volkswagen Forum banner
1 - 17 of 17 Posts

· Registered
Joined
·
3,271 Posts
Discussion Starter · #1 ·
Ive heard mixed feelings about this... i know its not the "most accurate" but dammit its a light show, thats why im getting it... to be "cool" seriously. My car is far from a racer so it doesnt need to be tuned perfectly at all times so i could care less. Now i hear u can just tap into the green wire from the o2 sensor. Or you could run a single wire o2 sensor (taping into the cat with another bunghole) which is recommended. But is tapping into the o2 sensor THAT BAD? does it kill ur o2 sensor? Let me know the good and bad of it.
Daren
 

· Registered
Joined
·
3,699 Posts
Re: Wiring Air/Fuel Ratio Gauges....Tapping into O2 sensor wire GOOD OR BAD? (MK2NRG)

If you tap in with a HIGH impedence load - its not bad at all.
An example of a high impedence load is a modern DVM or other solid state electronic device such as most A/F meters that I have seen that use a stnadard voltage sensing dot driver "chip" - i.e. LM3914N
The current draw that yout device will then pull is so LOW that the 02 sensor voltages are not affected much.
If you tap in with a low impedence load (such as a test light) - well thats different - you pull so much current that the voltage outputs of the o2 sensor are "off" and may impact running performance...
If yer that worried about blowing up the electronics... maybe you should get some assistance....
But if ya wanna roll yer own....
http://www.scirocco.org/tech/misc/afgauge/af.html
 

· Registered
Joined
·
2,011 Posts
Re: Wiring Air/Fuel Ratio Gauges....Tapping into O2 sensor wire GOOD OR BAD? (ewongkaizen)

I am running my autometer A/F tapped into the the O2 wire. no problems here. just be sure to tap it into the computer harness side of the connector, and not the O2 sensor side. http://****************.com/smile/emthup.gif
 

· Registered
Joined
·
14,951 Posts
Re: Wiring Air/Fuel Ratio Gauges....Tapping into O2 sensor wire GOOD OR BAD? (ewongkaizen)

Quote »
An example of a high impedence load is a modern DVM or other solid state electronic device such as most A/F meters that I have seen that use a stnadard voltage sensing dot driver "chip" - i.e. LM3914N
The current draw that yout device will then pull is so LOW that the 02 sensor voltages are not affected much.

That would be correct.
There no ill effects. Also, the sensor signal wire is black, green is the one on the gauge(well, as certain kind
)



Modified by Batan at 8:34 AM 1-7-2004
 

· Registered
Joined
·
4,801 Posts
Re: Wiring Air/Fuel Ratio Gauges....Tapping into O2 sensor wire GOOD OR BAD? (ewongkaizen)

Now you've got me thinking. If you were to tap into the O2 sensor with your DVM, what would you expect to see? I've considered a A/F meter to troubleshoot an ongoing problem, but I really don't want to have the thing there permenantly.
http://****************.com/smile/emthup.gif
 

· Registered
Joined
·
14,951 Posts
Re: Wiring Air/Fuel Ratio Gauges....Tapping into O2 sensor wire GOOD OR BAD? (vwgti1986)

One advantage of the gauge(LED bar or NEEDLE type) VS the digital VM or digital display gauge is that numbers jump around so much that it renders it usless. A lit up LED is a lot easier to see going up and down.
 

· Registered
Joined
·
4,801 Posts
Re: Wiring Air/Fuel Ratio Gauges....Tapping into O2 sensor wire GOOD OR BAD? (Batan)

I just don't want it in there permenantly. I also don't want to run the wires for something I am going to keep a short time.
Anyroad, I don't think a specific number would matter too much. Since I think it goes super lean under certain conditions, my thought is that if the numbers went in the appropriate direction I'd verify what my butt thinks.
http://****************.com/smile/emthup.gif
 

· Registered
Joined
·
3,699 Posts
Re: Wiring Air/Fuel Ratio Gauges....Tapping into O2 sensor wire GOOD OR BAD? (vwgti1986)

Read the Charles Probst book on Bosch Fuel Injection.
Voltage on an o2 should scroll back and forht between
zero volts and "x" volts where x is like 5v or maybe 1v (I dont recall).
Yer most woried about the number of cycles it makes in a minute - that tells you that the EFI is adjusting the fuel levels for an optimal "EPA" cycle between cat burn off and NoX and Co production....
 

· Registered
Joined
·
14,951 Posts
Re: Wiring Air/Fuel Ratio Gauges....Tapping into O2 sensor wire GOOD OR BAD? (ewongkaizen)

Quote, originally posted by ewongkaizen »
Read the Charles Probst book on Bosch Fuel Injection.
Voltage on an o2 should scroll back and forht between
zero volts and "x" volts where x is like 5v or maybe 1v (I dont recall).
Yer most woried about the number of cycles it makes in a minute - that tells you that the EFI is adjusting the fuel levels for an optimal "EPA" cycle between cat burn off and NoX and Co production....

Exactly. Maybe it's just me but it's very hard to keep track of that info using the MDV.
 

· Registered
Joined
·
4,801 Posts
Re: Wiring Air/Fuel Ratio Gauges....Tapping into O2 sensor wire GOOD OR BAD? (ewongkaizen)

Quote, originally posted by ewongkaizen »
Read the Charles Probst book on Bosch Fuel Injection.
Voltage on an o2 should scroll back and forht between
zero volts and "x" volts where x is like 5v or maybe 1v (I dont recall).
Yer most woried about the number of cycles it makes in a minute - that tells you that the EFI is adjusting the fuel levels for an optimal "EPA" cycle between cat burn off and NoX and Co production....

Got that book on my shelf... maybe I should read it?

http://****************.com/smile/emthup.gif
 

· Registered
Joined
·
3,699 Posts
Re: Wiring Air/Fuel Ratio Gauges....Tapping into O2 sensor wire GOOD OR BAD? (Batan)

Quote, originally posted by Batan »

Exactly. Maybe it's just me but it's very hard to keep track of that info using the MDV.

Nicer DMV's have a bar graph (aka Fluke)
But yeah - no back light etc...
OK for diagnostic - not so good to look at while driving.
The guage puts out anice light show

My 4Runner has a 22RE motor that has another output for "fuel trip" that shows the offset from the base map - so I gots LOTS of LEDs to look at
 

· Registered
Joined
·
4,801 Posts
Re: Wiring Air/Fuel Ratio Gauges....Tapping into O2 sensor wire GOOD OR BAD? (ewongkaizen)

Quote, originally posted by ewongkaizen »
Read the Charles Probst book on Bosch Fuel Injection.
Voltage on an o2 should scroll back and forht between
zero volts and "x" volts where x is like 5v or maybe 1v (I dont recall).
Yer most woried about the number of cycles it makes in a minute - that tells you that the EFI is adjusting the fuel levels for an optimal "EPA" cycle between cat burn off and NoX and Co production....

Where in Probst's book did you find this info? Obviously I haven't read it cover to cover, but in my skimming I haven't come across it.
http://****************.com/smile/emthup.gif
 

· Registered
Joined
·
3,699 Posts
Re: Wiring Air/Fuel Ratio Gauges....Tapping into O2 sensor wire GOOD OR BAD? (vwgti1986)

Dont have it in front of me so I cant quote pages etc..
Theres a VERY good section on oerpating theory. Its quite technical in nature.
Theres a brilliant graph - that basically explains that as cool as those AF guages are - they arent that useful from a tuning prespective... (thats my opinion, others disagree). Im not saying that an AF guage is useless, just that is doenst do what most people intuitivley think an 02 sensor actually does. (i.e. most people think that an 02 sensor works like an WBEGO sensor does - but a WBEGO costs too much $$$ esp in production cars - so they are not often used on a mass produced car)
 

· Registered
Joined
·
4,801 Posts
Re: Wiring Air/Fuel Ratio Gauges....Tapping into O2 sensor wire GOOD OR BAD? (ewongkaizen)

Couldn't find it.

Did discover somethign though. My car should run if the diff pressure reg is unplugged. It won't. It won't limp in the limp home mode. It keels over and dies.
Stupid car.
 

· Registered
Joined
·
3,699 Posts
Re: Wiring Air/Fuel Ratio Gauges....Tapping into O2 sensor wire GOOD OR BAD? (vwgti1986)

Charles Probst Book "Bosch Fuel Injection & Engine Management" on Bentley press...
section 3 page 22
Figure 2-47
From here one sees that the o2 sensor varies between 0 volts and 1 volt.
One also sees that the A/F variance of stoich to rich is between 8 and 9 volts
One also sees that the A/F variance of stoich to lean is between 0 and 1 volts
That means unless yer guage is STABLE reading voltages between 8 and 9 volts ( and as far as I know most arent) and the o2 sensor is actually calibrated to read A/F ratios related to voltages in the stoich to rich region (again - most are not as far as I know - Honda's WBEGO sensor aside) the LEDs are just that - pretty LEDs
That being said - I have one and it sure is pretty!
The only guage IMHO that really worked correctly was the Edelbrock (?) 3 LED guage - which as far as I know is no longer around)
oh yeah - why the voltage scrolls isn explained on section 3 page 22-23
 

· Registered
Joined
·
34 Posts
Re: Wiring Air/Fuel Ratio Gauges....Tapping into O2 sensor wire GOOD OR BAD? (mk2dubbin)

Quote, originally posted by mk2dubbin »
I am running my autometer A/F tapped into the the O2 wire. no problems here. just be sure to tap it into the computer harness side of the connector, and not the O2 sensor side. http://****************.com/smile/emthup.gif

I'm confused, WHERE at to run the wire? What color is it?
THANKS
 
1 - 17 of 17 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top