I've been thinking of installing a Autometer Air/Fuel meter in my ZZ430 equipped 69 Camaro to help tune the carb. Are these things accurate and worth the money? I would like to tune the motor without having to pull the plugs all the time. Those headers are HOT! I would also like to know if It's a good idea to install a O2 sensor on both collectors to check each bank. Autometer suggests a toggle switch to get readings from each side if two O2 sensors are used. It seems like a lot of trouble to go through to set up a carb, but having the gauge to look at when engine problems arise might not be a bad idea. Your thoughts are appreciated.
Thanks
Jim

How about welding in 2 bungs and switching the sensor after you have it dialed the carb in on the one side. The other side should be the same readings as the first side but the extra bung would give you peace of mind. Just a thought.

They are pretty accurate. The laws of physics and chemestry dicate that the sensors respond to the concentration of oxygen or hydrocarbons. It's very repeatable.

As for sensors on the market, it depends on the sensor. Plain jane O2 based AF meters use narrow band sensors. They'll tell you when you're hovering around 14.7, but not much else. Wide-band based sensors on the other hand give a fairly linear response from at least 20:1 to 8:1. Excellent tool.

It's just too band the aftermarket is selling these things way over priced (like $400 bucks last I checked). Many folks are building there own AFM based on wide band sensors. Not as pretty as the aftermarket type with fancy displays, but does the job well.

-dnult

Thanks for the replies
Not sure about the Autometer sensor/s in the kit. I'll have to check to see what they are. I guess the narrow band would be all I need, but if I'm going to install one of these things, It may as well be a good one. If anyone out there has built their own, or has found a good wide band system, could you post the part numbers and names?
Thanks
Jim

Auto meter asks about $100 for just the O2 sensor kit, the gauge is another $75. You can get an ordinary 3 wire O2 sensor from about a 94 S10 truck with 6 cyl for a 1/4 of the cost and it works just as well. Just get the gauge and your own O2 sensor.

I have a narrow band sensor and it works much better than trying to read plugs. The narrow band sensors are most sensitive right at 14.7:1 A/F ratio. As a result the gauge tells you when you are at stoich but it doesn't tell you how rich or how lean very well. Still, I have found it usefull and worth the time.

ps. just put it in one collector and don't worry about the other side. You aren't likely to see much difference between the banks anyway.

Just my opinion.

Eric68

I have a new 3 wire O2 sensor for a 94 or 95 8 cylinder full size 350 cu. in. pickup truck. It has two brown wires and one purple. Don't remember why I got it. I think It was for a friends or a relatives truck and I never used it. I will do some part number research and see if It's the same as the one you mentioned. I know how O2 sensors work with a computer in a factory installed system, but I've never installed one with a gauge in an application like this before. Is it as simple as It appears?? I can make up a harness from the sensor to the gauge, but where do I buy the weld in bungs? I've never seen them for sale individually before. Just In kits like the one from Auto meter.
Thanks
Jim

Muffler shops will carry the bungs, or just go to the auto parts store and ask for sparkplug savers. Those are the things that screw into the sparkplug hole to protect the plug from oil and such on worn engines. The ID thread is the same as the gasketed type spark plugs, you will just have to cut off the OD thread with a hacksaw.

Though the band is very narrow using the gauge is helpful. I was able to take a lot of fuel out.

I ended up making a three wire pigtail harness that exits the console between the base and carpet next to the drivers seat. The matching pigtail connector attaches to the gauge and is about 3' in length. The power to the sensor and the gauge is tapped into the console + power. This way the gauge can be easily attached and when not in use the pigtail can be tucked away unnoticed. For the gauge I used an 1/8" thick piece of plastic formed by heat into a "J" shape. The gauge mounts into the long leg of the "J". The hook fits over the rear view mirror so that it is easy to see without having to take my eyes off the road. A few heavy rubber bands holds it to the mirror. The extra wire length is so that a passenger can hold and observe the gauge.

I bet you will be fine with the O2 sensor you already have. The two brown wires (I'm 95% sure) are the heater wires. The other wire is the signal wire. The signal wire goes to the meter, one of the two brown wires needs to go to +12V power and the other to ground (polarity is not important).

The bung can be bought at your local speed shop for about $8. Mine was in a Holley package, so I know Holley sells them. I bet if you called Summit or Jegs they could look up the part # and get you one pretty cheap.

The Autometer A/F gauge is really just a voltmeter. Each LED on the face of the gauge represents .05 volts DC (50 millivolts). The richer your mixture, the higher the output voltage from the O2 sensor is. The voltage range the gauge can read is between 0 and 1.000 VDC which is from roughly 10:1 to 19:1 A/F ratio.

Jegs offers the weld in bungs here :

http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=86589&prmenbr=361

Summit probably has them too.

GMJim:

I have two Autometer o2 A/F gauges installed (only 1 hooked up though..am getting the one installed/hooked up next week or so). My o2 sensors were off of a Ford Thunderbird I believe, high 80's year model, its a 3 wire sensor, paid $30 a piece..I have one in each collector. I dont use it necessarily for tuning, just for it to tell me if I'm running lean or not. Send me a email if you need part #'s as this thing doesnt have a email notification if someone replies to this thread.

Don't see where you need 2 gauges, just a toggle switch to flip between the 2 sensors.

Here's an excellent write up on how to do just that. I've had this link bookmarked for quite some time, and I've always meant to try it out, but I've never taken the time. About halfway down, he gets into using an O2 sensor and a voltmeter.

Carburetor Tuning the Scientific Way (http://www.bob2000.com/carb.htm)

I use to have one of these on a Turbo car, it has 30 LEDs for more definition and gave me peace of mind when tuning the air/fuel mixture at high boost & high RPMs. Another helping tool is the EGT meter.
Air Fuel meter link (http://www.racetep.com/halmeter.html)
http://www.racetep.com/HalmeterAF30.jpg

Thanks everyone for your input.
I've been doing a lot of looking and reading about A/F meters. I realize the lower cost A/F gauge is just a volt meter with fancy LED lights, but how easy is it to use as a tuning tool for a carbureted car? The wide band devices out there are about 3 to 4 times the cost, but they give you an actual air fuel ratio reading. ORENCH the Halmeter you used. It appears to be the same as the Autometer gauge but laid out a little differently. How did you find it as a tuning tool? I guess what I'm asking is, how coarse or fine can the meter read? If all I need is the inexpensive or should I say less expensive set up, that's what I'll do. I don't really have to have an actual ratio reading (although it would be nice).
Thanks
Jim

yea, looks the same like my Autometer. What I would do is find out which BOSCH sensor they are selling and then buy a Autometer gauge.. LOL

I still would not tune a car based on a sensor like this. A two, three, four wire o2 sensor measures from 13.8 to 15.0 air/fuel ratio..the best sensors are 5 wire sensors used by WB sensors.

EDIT:
Ok, I talked to the guys that make HALMETER and they use a regular bosch 3 wire o2 sensor, but that this gauge is MORE accurate then the autometer.

EDIT #2:
Hmm..this doesnt make sense though. If they're using the SAME o2 sensor (regular 3 wire), how can the gauge be more accurate then a Autometer? You're depending on the o2 sensor for accuracy. M

Over on Chevytalk a while back, this was brought up. There wasn't really much said about it, though.

Innovative Motorsports Digital Air/Fuel Ratio Meter (http://www.innovatemotorsports.com/)

[ 08-04-2003, 04:31 PM: Message edited by: 69ProTouring ]

Jim, in my case it was simpler, I just were looking/worried to maintain the reading in the first LEDs of "rich/green" area of the meter while the car was at full boost. This by adjusting fuel pressure in proportion to boost. The meter was highly usefull to avoid detonation to the extreme that I used this car for 4 years with stock internals @ 10psi of boost and the spark plugs were a good shade of tan color. For cruising I maintained the reading in the "stoichiometric/yellow" area of the meter for better fuel economy. Oh BTW, this car was FI.

ORENCH, I think you have it figured out --- I also keep mine tuned to the green (closer to the yellow) at WOT for max power. Drag strip MPH confirms this is the sweet spot. Cruise is near stoich for mileage, and idle is red indicating lean. The idle in the red is where it sits after using a vac gauge to get the best idle quality.

I would not recommend just plugging in an AF gauge and start swapping jets. But after you have had one in for a while you get a feel for when the engine goes rich or lean. Much easier than reading plugs. Like tonight at the track when it started to cool off I noticed my AF gauge went into the yellow through the traps, so I went a size richer on the primary jets and bingo, back into the green and it picked up 1/2 mph on the next pass.

Thanks again for the feedback.
The site that Scott posted looks promising. A digital 5 wire for $350.00 is good! It's a hand held unit but at least it's afordable!
Jim

Jim, I'm considering it, too. For $350, it seems like a hell of a tool.

Oh yeah, and your Z/RS is one sweet ride!

Thanks Scott.
I'm tired of burning my fingers on headers and hot plugs. This meter looks like a real deal. I've been loking at some others and they are more expensive and not digital. I have some friends that want to chip in some cash as furure payment for setting up their cars. It just got a little cheaper! I think I will order mine tomorrow!
Jim

Wonder if they, Innovative Motorsports, would do a group buy?

Good idea. I'd be interested.