Air / Fuel Mix Gauge

930LDR · 08-03-2005, 07:55 AM

I am looking to install an Air / Fuel Mixture Guage in my 930 in order to evaluate whether or not I am running rich or lean under boost.

Curious to see what anyone else may have gone with in terms of type of guage or placement.

Thanks!

MotoSook · 08-03-2005, 08:19 AM

Rob,

Your best bet is a wideband O2 sensor setup with a dash gauge.

Innovative makes an LM1 that you can buy here on Pelican. There are some other brands available. The nice thing about the LM1 is it's logging capable and not just a readout/gauge driver.

sammyg2 · 08-03-2005, 08:43 AM

I bought a basic A/F guage on E-bay and wired it to a heated O2 sensor. I took and old clock I had laying around and cut it apart and fabricated up the guage in the clock housing, then installed it where the clock goes in the dash.
I tried using the same O2 sensor that the lambda brain uses, it didn't work. It was supposed to but didn't. If I disconnected the lambda brain the guage worked, if I hooked it up it didn't, so you may have to install an additional O2 sensor.

hobieboy · 08-03-2005, 09:01 AM

I also use an LM-1 though I dont have a gauge. I peek over to read the LM-1 display but really uses the data logging capability to make sure I'm good.

sammyg2 · 08-03-2005, 09:10 AM

I dunno if I have the cojones to be looking over at a laptop when on full boost, stuff happens kinda fast

Early_S_Man · 08-03-2005, 09:29 AM

Here is a Pelican tech article you may be interested in:

http://www.pelicanparts.com/techarticles/mult_air_fuel_monitor/mult_air_fuel_monitor.htm

Here is the web page where a data sheet for the NS LM3915 chip can be downloaded:

http://www.national.com/pf/LM/LM3915.html

fireant911 · 08-03-2005, 09:30 AM

Rob,
If you wish to simply see the values I would recommend the Westach A/F gauge. I installed this a while back and I find it very informative.

My installation is shown below (CHT gauge with switch for Left and Right engine bank, A/F gauge, switch to deactivate the Lambda computer and go to open loop, and evaporative cooling switch):

hobieboy · 08-03-2005, 09:58 AM

Quote:

Originally posted by sammyg2
I dunno if I have the cojones to be looking over at a laptop when on full boost, stuff happens kinda fast

That is why you log it then look at it with a cold one in hand

In fact, I hooked up the analog out of the LM-1 to my digital display from the old narrow band meter in parallel so I can read the signal in real time too

klatinn · 08-03-2005, 01:55 PM

Well,

A gauge running of a narrowband O2 sensor is pretty useless when on boost. Any GAUGE connected to a NBO2 is overkill. It really needs only 3 LEDs, rich, lean, stoich. Because that's ALL a NBO2 sensor can indicate, sorry. Any number on such a gauge is just paint.
When on boost, a NBO2 sensor will indicate RICH, wether you are spitting fuel rich or just a few points below stoich and burning your engine up. It's output voltage below 14.7 AFR is pretty much solely dependent on EGT, not much else, because that's how it's chemistry works, no matter how much people wish it otherwise.

You are right that on boost you can't watch a laptop. Neither can you watch a gauge. The only function is to warn you if something's wrong.

(Product plug warning)

If you look here:
XD-1 Manual

You'll find a AFR gauge that connects to the LM-1/LMA-2/LMA-3 and is programmable for different kinds of warning conditions (and has a lot of other programmability too)

(End product plug warning)

Regards,
Klaus

sammyg2 · 08-03-2005, 02:49 PM

On mine it had different colors, red meaning very rich, yellow meaning stoich or close to it, and green meaning richer than stoichiometric.
All I had to do was to glance over and see green, I was happy. My engine is not tuned on the ragged edge so I'm not that worried about it.

WinRice · 08-03-2005, 06:56 PM

Take a look at a Zeitronix Zt-2 - www.zeitronix.com. EGT, Boost and Wide-band O2. Hook it to your tach wire and throttle position sensor and you have a pretty complete data logging setup.

I took a chance on the Zt-2 after reading a few reviews, and after using it to tune my '86 930, I'm pretty impressed!

I mounted in place of the ash tray, so I didn't have to modifiy the console, fits fairly well.

don911 · don911's Garage

I've been kicking around the idea of an A/F gauge too. I want an anolog and have only found this. It comes with a black bezel but don't know if it's norrow band O2.

http://www.nordskogperformance.net/products/auto/proanalog/detail/d7014.htm

930LDR · 08-04-2005, 06:27 AM

Don -

That was more along the lines of what I was looking for.

Could someone help me to understand the concepts / differences between narrow and wide band as well as which I would be taping into if I simply hooked up an analog gauge to my existing O2 sensor without any additional hardware?

Thanks guys, as always you are very helpful.

ValveFloat · ValveFloat's Garage

I have one of these:
http://www.widebandcommander.com/
I have a black faced gauge, but I need to paint the silver bezel so it matches my other gauges. It has logging ability with or without a laptop connected. It has a warning light in the gauge that can be set with the software. It does some other stuff too that I am not using, yet.

WinRice · 06:20 PM

Whichever gauge you choose, make sure it has data logging capabilities. You really need to be able to play it back and see what the AFR was at the redline. With CIS the curve changes too fast to watch the gauge, tach and try to shift and drive at the same time. I tryed that one.

A narrow band would be almost useless with a turbo car, make sure it's wide-band. The correct AFR under boost is beyond the range of narrow band gauges.