Use a digital voltmeter and
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| Air/fuel gauge not reading accurately https://slantsix.org/forum/viewtopic.php?t=61048 |
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| Author: | armyofchuckness [ Thu Apr 20, 2017 9:35 am ] |
| Post subject: | Air/fuel gauge not reading accurately |
I have a feeling the answer to this is, "Because you bought a cheap gauge, dummy," but just in case it isn't, here's the situation: 1964 Valiant 225 with Edelbrock 500 4bbl Dual Dutra Duals with a Bosch one-wire o2 sensor in a Y collector feeding a 2.5" exhaust. SunPro Style Line Air/Fuel gauge Key on, we get the lowest red light on faintly and the highest green light on brightly. Start the car and it reads full rich as it warms up, which is normal. Then the rich reading starts to drop as it warms up until it's all the way down to the bottom of the lean side, then it leaps full rich as soon as any activity in the pedal happens. (See video at link below). https://www.instagram.com/p/BSUsqVtDoAS ... fchuckness I was told to try cleaning the o2 sensor off and let it sit for 10 minutes outside the tailpipe with the ignition on to "calibrate" it, but that doesn't seem to do anything. Has anyone else used this gauge on their Slant or experienced something like this? Thanks! |
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| Author: | Dart270 [ Thu Apr 20, 2017 9:55 am ] |
| Post subject: | |
Sounds like it is behaving as you might expect if the idle mix were lean and the accel pump shot is fat enough (or too fat). There is no calibration, only if it is totally carbon covered would it misread. Probably you just need to do some tuning, or just drive it and see how the gauge informs you of the different conditions of driving. At light throttle cruise with that kind of gauge, I would look for amber light or 1-2 lights into the red. On hard accel (WOT pull), look for 2nd or 3rd green light from the top. If you are seeing green on quick throttle blips, then your accel pump is working well, and you should fiddle with that LAST, after you tune idle mix and cruise mix and WOT mix. Things may change as the rings seat in, although not a lot. You might save fine tuning until after the motor is broken in (500+ mi). How does the car drive? Lou |
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| Author: | Charrlie_S [ Thu Apr 20, 2017 2:12 pm ] |
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I have the same gauge on my Diplomat, and it behaves very much the same, except at light throttle cruise on the interstate, it is off scale lean (no lights lit). |
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| Author: | emsvitil [ Thu Apr 20, 2017 4:19 pm ] |
| Post subject: | |
Use a digital voltmeter and
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| Author: | armyofchuckness [ Mon Apr 24, 2017 10:11 am ] |
| Post subject: | |
Thanks for the advice guys. Never used an o2 sensor so I wasn't sure what to expect. The car is running pretty well, but I definitely need to work with the timing, and carb mix some. I guess that will just improve with time. Took it for a drive last Thursday and there's a lot of potential there. Sorting bugs and taking another drive this week. Then it's off to be aligned and we can start putting some miles on it. Lou, what sensor do you use in your ride? Is the one wire ok or should I get a 3-4 wire? It's definitely getting hot enough. It's in the Y collector for the Duta Duals, so it gets up there in temp pretty quick. |
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| Author: | wjajr [ Wed Apr 26, 2017 7:38 am ] |
| Post subject: | |
Quote: Bosch one-wire o2 sensor in a Y collector feeding a 2.5" exhaust.
I also have same Sunpro gauge and lights run lean to rich as engine lopes while idling. To reasons for slow reaction of gauge during warm-up come to mind: o2 sensor may be too distant from head so temperature of hot gasses not hot enough; second a heated o2 sensor reacts much quicker during warm up. O2 sensor needs to be 600 degrees or higher to produce correct voltage signal to gauge or VOM. I have found setting idle mixture much easier by voltage output than by gauge on dash following graph provided by emsvitil.SunPro Style Line Air/Fuel gauge I have an o2 sensor located aft of Clifford header collector gasket in exhaust pipe the services front three cylinders. Its a three wire sensor one wire for voltage signal the other two conductors power a heating element embedded in tip of sensor. It works well as soon as engine fires off. During WOT (Holley 390 carb) the gauge lights all its colored lights in a high speed flicker, and small throtle tip-in gauge will dip to lean until enrichment circuit (controlled by low vacuum) kicks in. Sensor I used was cheapest three wire one I could find on Rockauto, and may have been one listed for 90''s Chevy Astro van cost around 19 bucks six years ago. |
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| Author: | Dart270 [ Wed Apr 26, 2017 9:02 am ] |
| Post subject: | |
I have used 1-wire and 3 or 4-wire and never really noticed a diff (sensor mounted just after the header collector on Cliff shorties on front bank). You should be fine with 1-wire. Happy tuning, Lou |
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| Author: | armyofchuckness [ Wed Apr 26, 2017 9:21 am ] |
| Post subject: | |
Great advice. Thanks, guys! Hopefully we'll be on the road soon. |
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| Author: | DusterIdiot [ Wed Apr 26, 2017 4:14 pm ] |
| Post subject: | Fyi... |
I have used the standard Bosch 1 wire narrow band for rough tuning over the years (tell the parts counter guy you have a 1991 S-10 Blazer with a 4.3L)... I can tell that the readings aren't right until the sensor is warmed up (a minute or two depending on the warm up and your idle mix settings). Location does matter, since we can't tap and thread the old manifolds, so putting it about an inch or two away from the manifold outlet is pretty close, or as most sources state putting it in the header collector is preferred. Make sure never to use leaded gas... I think my last old pair stopped giving useful readings a few minutes after the 110 race gas was being digested by the hi-po build.... Also make sure to read your plugs on a regular basis, to get perspective on the readings, I know that the 1 wire sensor will stop giving good readings if the mix is rich and the sensor gets sooted up real good... and they don't like to get cleaned by certain solvents....  Once you get the hang of it, it really does make carb tuning easier.... |
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| Author: | Reed [ Wed Apr 26, 2017 4:17 pm ] |
| Post subject: | Re: Fyi... |
Quote: we can't tap and thread the old manifolds
But we CAN use the 80s era lean-burn exhaust manifolds that have a bung for the O2 sensor in them or run one of the reproduction manifolds that all come with the O2 sensor bung. 
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| Author: | DusterIdiot [ Wed Apr 26, 2017 9:43 pm ] |
| Post subject: | But... |
Quote: But we CAN use the 80s era lean-burn exhaust manifolds that have a bung for the O2 sensor in them or run one of the reproduction manifolds that all come with the O2 sensor bung
If you had one handy from the very late run of trucks, but one couldn't really justify cutting a new one up for making a Dutra Rear just to put an o2 sensor in it.... breaking out the wirefeed MIG, buying the bung for a couple bux, and using a unibit to bore the hole in the downpipe is much easier and cheaper...
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| Author: | Pierre [ Wed Apr 26, 2017 9:50 pm ] |
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Narrow band sensors don't lend themselves to those types of gauges very well. They are good at telling you you're very lean, very rich, or near stoich (14.7 afr). Don't expect to see "a little lean" or "a little rich". If you want more resolution you need a wideband. |
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| Author: | armyofchuckness [ Thu Apr 27, 2017 6:42 am ] |
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Yeah, the 80s manifold is cool, but I like my dual Dutra Duals too much.  I think since it's a street car, I'll be ok with the narrow band tuning, at least for now to get the car roughed in for drivability, and upgrade later to the wideband. Thanks again for all the advice, guys! |
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| Author: | Reed [ Thu Apr 27, 2017 7:16 am ] |
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DI makes good points. But if I saw a late 80s manifold in the boneyard I would grab it. |
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| Author: | Dart270 [ Thu Apr 27, 2017 7:39 am ] |
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I used NBs for a long time and they were very helpful. You can get by fine with that. That said, if you can afford it the WB is more accurate for tuning. I have used exclusively the AEM WBO2 gauge kits in 4+ vehicles and they are golden. I have never even burned out a sensor (7+ yrs and 30k miles for oldest one, with plenty of drag racing and even occasionally leaded race gas). Here is I think the equivalent of what I have bought in the past. AEM 30-4110. Price keeps coming down... https://www.summitracing.com/parts/avm-30-4110 Lou |
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