Stoichiometer (air/Fuel)

I am on the hunt for an Air/Fuel guage to mount on my XJ750 before taking it out this spring. Autometer has some nice kits that include a wideband sensor and the guage, but they are all at least 2 1/16" round. Many of them have a small rectangular digital display in the middle and I was hoping to find something like that by itself.
I figure that with the added security of a guage I would be able to truly see what was happening in the motor real time when changing altitudes and temperatures. I know that it would only give you a basic average across all four cylinders and tuning seperately is still necessity, but it would be a nice "gadget" and possibly a help in tuning.

Has anyone seen a nice guage they can recommend? Opinions?

 

It'd sure be nice to have one for tuning, but at $350-400 a crack, I think I'll pass.

 

Innovate motorsports has a very good A/F gauge. K&N has a rectangular gauge but it's a narrow band. Edelbrock also has a narrow band rectangle gauge that uses a 3 wire sensor. A 3 wire or wide band sensor can draw up to 10 amps heating up the sensor. You can get any of these @ Summit Racing ( summitracing.com). TECHLINETOM

 

Here's a link to one you can build yourself for cheap...if your innovative enough you could possibly incorporate it into your OEM instrument cluster.

DIY Stoichiometer

 

I have installed O2 sensors with Intellitronix bar graph readouts on both my XS1100 and 750 Seca. Since we have to get emissions tests every year it's easier to use that to adjust it than it is to strap on an exhaust gas analyzer every time. It's just a narrow band sensor but that is more than adequate to monitor the mixture to tell if it's too rich or too lean. One big problem with this is that you have to use a 3 or 4 wire sensor with a heating coil in order for it to get hot enough to work and most of them draw too much current to be used on a bike's electrical system. You want to always check the heating coil resistance when choosing O2 sensors for a bike or you might not have enough power to run it.
The O2 sensor I used was a Bosch #13154 with a 16 ohm heating coil for a
1999 3.4L Toyota 4 Runner that draws only about 1 amp. The drawback
to using this part is the list price of $142 so it's best to shop around or get
them on ebay. A commonly available model like the #13190 for a Chrysler Daytona for $32 will work but it only has a 3 ohm coil and would draw 5 amps or so and the battery wouldn't charge then. A Bosch #13249 for a 92-94 Honda Civic with a 9 ohm coil wouldn't be too bad at 1.5 amps but I wouldn't go any lower than 9 ohms or the battery will always be running down, headlight will be too dim, turn signals wouldn't work at idle, etc. These are all narrow band O2 sensors. I don't have any
wideband models and don't know their specs.

 

Where in the exhaust stream did you position your sensor(s)? I've never had any issue using one wire sensors from 1000cc Geo Metro engines on liquid and air cooled 40cc and 50cc 2 strokes. I position the sensor about 3-4" from the exhaust port to do my testing though so this is likely why I suppose.

 

Good question. There are header plugs just before the collector, but they're not big enough to stick an O2 sensor into, methinks.

As for the sensor itself, I know the ones for my 1996 Tercel cost quite a bit less than that last I checked, and the specs say the heater circuit ohms out at 11-16 ohms - simiar to the one for the 4Runner. A quick bit of calculating shows that a 16 ohm resistance on the heater coil, given a 12v supply, will yield a 750mA draw.

Steve: I've heard about the emissions testing out there on bikes. The funny thing is, out here in California -- where you'd expect them to do that sort of thing -- they don't. :?:

 

For anybody interested!

Edelbrock #6593

Approximately $130 for gauge and sensor plus all wiring

According to Edelbrock Tech Support it only draws 1.5 amps
maximum during Heating cycle

 

I have a 4-1 header and there aren't any ports on it or anything so I drilled a hole in the part where the 4 exhaust tubes go into one big tube under the engine and mounted the sensor beneath the transmission right above the
center stand. You could have a bung welded on to screw it into but I just stuck the sensor in the hole and put a nut on the inside to hold it. The sensor is the same size and shape as a spark plug with similar threads. It's not easy to find a nut that size but they are available. Putting the sensor down that far from the engine means a one wire model won't get hot enough to work so it has to be heated. You do have to be careful about how much current the heater uses though. There's a motorcycle and old car parts swap meet about 1/2 mile down the road and I bought a like-new LED air/fuel gauge there for $2.00 last month!