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 DIY digital a/f gauge 
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Joined: August 25 2004, 2:01 AM
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Location: Edmonton, Alberta, Canada
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Post DIY digital a/f gauge
I stumbled upon this the other day and I've been pondering and wrapping my head around it so I think I'm going to try it.

http://www.2gnt.com/index.php?d=DVM

It is the instructions to make a digital LCD AFR display that will work off your existing narrow band O2 sensor. Now I'm no electronics expert, but basically the O2 sensor sends a voltage back to the ECU to tell it if it needs to trim or add fuel. So all this does is calibrate the digital display to give a reading that corresponds to the AFR.

The way that this guy wired the display puts the decimal at the beginning so for an AFR of 14.7 the unit will display .147. I think if you moved the wire that goes to DP3 on the display to DP2 it would show 14.70.

I'm gonna play around with it. I'll let you know.

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June 08 2010, 9:56 AM
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Joined: March 17 2006, 3:59 PM
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Location: portland, OR
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Post Re: DIY digital a/f gauge
That is interesting. I wondered why it wasn't done before. From what I understand, it's called narrow band, because it doesn't read very much more, or less than stoichiometric, so you'll see a narrow range of afr, like 14-16. < I know that's not correct, but it doesn't seem like it'll help much. It's kind of like the idiot lights, that say, "Hey, idiot, you're low on oil!". It wouldn't help much if it told you how low, by the time it's too late. Maybe the same thing can be done with a wideband.

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June 09 2010, 2:14 AM
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Joined: August 25 2004, 2:01 AM
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Location: Edmonton, Alberta, Canada
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Post Re: DIY digital a/f gauge
This gauge will basically tell you when your ECU is in open loop vs closed loop. The majority of the time you should be at about 14.7:1. If you're not, the ECU is either trimming or adding fuel. This readout will tell you when that's happening.

You're right, definitely not as useful as a wideband...but it's cool and fun. IF you have a wideband you can also do this...or just buy a $60 gauge that is already set up for your wideband.

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94' RS/GS/MS/CF Monster Turbo...coming soon.
93' GS SE, the Black Beast, the former love of my life...soon to be gutted and crushed.
94' GS, black on black, now in several small pieces...and one large crushed piece.
2007 Mazda3 GT Sport --- super fun
2004 Honda RC51 --- Lost forever to some theavin' bastard
My Worklog
My feedback thread
Never attribute to malice that which can be adequately explained by stupidity.


June 09 2010, 9:03 AM
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Location: portland, OR
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Post Re: DIY digital a/f gauge
Cool. I do like knowing what my car is doing. If I didn't have MS, I would like to have all of my sensors' info available in real time.

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'93 GS - P&P DE w/ ZE exh. cams/ pistns, KLG4 IM, 65mm TB, MSnS, Phenos, K&N RAI, UDP, Grnd wires, rear batt, filld MM, torq strt, TWM short shftr, Exedy, Lng tube hdrs 2.5" Side exhaust, H&R sprngs, Poly bushngs, strutbars, Alum. crss mmber&tiebar, 22mm swybar, solid links, Direzzas, leather int, Alpine 9805 stereo & alrm, keyless entry, 10 Boston Accoustics spkrs, Prjectrs, Blaster2, CF hood, FG hatch, Lexan


June 09 2010, 6:34 PM
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