Is there a DIY open-loop indicator?

[Focus-Ak]

I have an UltraGauge, and use it in 8 instrument mode. Unfortunately there is no way to show the the open/closed loop indicator when using that mode. That is available in the 4 and 6 instrument modes only.

Does anyone know of a way to make an open-loop indicator light, or of a commercial one?

(BTW, I have suggested to UltraGauge that a way to accommodate this in 8-instrument mode would be make the vertical line between the two columns of readings a dashed line for open-loop and a solid line for closed-loop. Hope to see that someday, and I hope there is a way to update the firmware.)

[Occasionally6]

If you have a narrow band O2 sensor the LED light air:fuel ratio gauges will tell you when you are in closed loop or not. If the car is in closed loop, the LEDs will oscillate about the central light. If not, they will be steady either rich or lean.

There's no real functional difference between a gauge bought assembled, one assembled from a kit of parts or one bespoke built from one of the better designs found on the interwebs.


If you have a wide band sensor a volt meter should do it. AFAIK they put out a 5V signal varying with the air:fuel rati, ~2.5V being stoichiometric ("closed" loop).

[Focus-Ak]

Thanks for your reply.

What I am looking for is a single LED light that comes on for open loop, rather than air/fuel ratio gauge that has a busier display. I haven't seen what I am looking for anywhere on-line.

My car has two narrow-band O2 sensors (up- and downstream of the catalytic converter), stock.

Apparently the UltraGauge detects a zero value for STFT (short-term fuel trim), so this is one way to access the necessary data. However, what I am looking for is simple, clear indication of the open-loop state, without a number that changes on a display, and without using one of the limited number of instrument readouts that the UltraGauge can display (4, 6 or 8 depending on the option used).

[Daox]

Autospeed had an article on a DIY circuit that would do this... lemme see if I can dig it up. Ah yes, here we go:

AutoSpeed - The Closed Loop Monitor

[darcane]

Buy an OBD2 splitter and run two Ultra-Gauges!
OBD2 OBD-II 16 Pin Splitter Extension Cable Male to Dual Female Y Cable Adapter Ship By EUB - Newegg.com

[Focus-Ak]

Originally Posted by Daox

Autospeed had an article on a DIY circuit that would do this... lemme see if I can dig it up. Ah yes, here we go:

AutoSpeed - The Closed Loop Monitor

Wow, you made my day. Thanks!

[Focus-Ak]

This thread:

Any one seen these DIY gauges?
The Closed Loop Monitor
http://ecomodder.com/forum/showthrea...uges-1286.html

... evaluates the AutoSpeed closed-loop monitor discussed above, but shows that its accuracy is questionable. And perhaps more so on some cars than others, depending on differences in O2 sensors and how particular ECUs operate. Just FYI, for anyone following this thread.

Does anyone know how the ScanGauge and UltraGauge determine when open-loop is occurring?

[firehawk618]

Originally Posted by darcane

Buy an OBD2 splitter and run two Ultra-Gauges!
OBD2 OBD-II 16 Pin Splitter Extension Cable Male to Dual Female Y Cable Adapter Ship By EUB - Newegg.com

Yeah, unfortunately most devices will NOT work with this simultaneously.

[Occasionally6]

Originally Posted by Focus-Ak

This thread:

Any one seen these DIY gauges?
The Closed Loop Monitor
http://ecomodder.com/forum/showthrea...uges-1286.html

... evaluates the AutoSpeed closed-loop monitor discussed above, but shows that its accuracy is questionable. And perhaps more so on some cars than others, depending on differences in O2 sensors and how particular ECUs operate. Just FYI, for anyone following this thread.

Once set up I can't see how it can be inaccurate. It might be worth using a regulated voltage for the reference - as per the breakout box at the end of the article.

[Focus-Ak]

Originally Posted by Occasionally6

Once set up I can't see how it can be inaccurate. It might be worth using a regulated voltage for the reference - as per the breakout box at the end of the article.

Apparently the reason it can be inaccurate (and probably is on at least some [most?] cars) is that it assumes a certain O2 sensor reading necessarily means the ECU is putting the engine into open-loop operation. As the article explains, however, the ECU is most likely considering other factors besides the O2 sensor output before it decides whether to enter (or leave) open-loop. That seems to me to make sense. Does anyone know differently?

It seems that the most accurate indication would be one (if there is one) given by the ECU itself. Otherwise, the open/closed loop state must be inferred somehow. Going to open-loop simply means that the ECU is relying on its own internal table of values instead of data from sensors -- does it tell us somehow that it is doing so, or does it just proceed to do so in secret, leaving us to infer the state of operations?

Today I inquired of the folks at UltraGauge how that instrument detects the open/closed loop state. The reply was: "There is a parameter defined in the OBDII specification which conveys various bits of information, including loop status." This seems to verify that at least for the Mk-1 Ford Focus (which I inquired about) that the ECU does give a definite indication of the open/closed state. However, the answer seems to indicate that this information must parsed out from a particular "parameter" stream that includes some other data.

I think therein lies the clue for how to determine the open/closed state by some independent means.

That said, for me the best solution would be if UltraGauge would devise an update that would make the 8-instruments page configuration modify the vertical column separator line to indicate the state (dashed line or solid). Even on the 4- and 6-instrument page configurations, though, the indicator is small and hard to decipher when on the road.

I think an accurate indicator of this is vital to hypermiling. I will continue to investigate how to make an accurate, independent indicator when time allows, if an update to the UltraGauge isn't forthcoming.

I think an accurate indicator of this is vital to hypermiling.