TBITrucker

I am considering buying an air fuel ratio guage to help with tuning.
I have looked a a lot and I am confused on what model would be accurate enough and if I have to get a new O2 sensor or a heated or a wide band for it to even be worth it.

I don't have a lot of cash and I am not tuning to race or anything like that so having said that what guage should I get?

Any recomendations on guage choice and tips on tuning with the guage would be appreciated.

BMmonteSS

By tuning I hope you mean chip burning. There is very little you can do by just cranking on the fuel pressure.

A narrow band O2 guage is about useless in my opinion, the stock NB sensor's sole purpose in life is to signal when the AFR is at 14.7 to 1. It's more of a switch that either reads higher than .450 volts when rich and lower than .450 volts when lean. Putting a guage on this type of sensor will only give you a crazy dancing light as the ECM try's to get the NB to switch back and forth several times a second. At WOT it will indicate rich but is completely useless as to exactly what AFR you are at.

Enter the wide band O2, this type of guage will tell you exactly what your AFR is and one of the most usefull tools a gearhead can have. The only catch is that it's about useless unless you put the AFR information with all the other sensor information from the ECM. I use a zietronix WB that allows you to log several other sensors at the same time. This lets you correlate an AFR with a rpm, map reading and a TPS reading. Like I mentioned earlier without chip tuning you really can't do anything about it if it's wrong.

88L035speed

i put an auto meter a/f gauge it its not working right, i spliced into the o2 sensor wire and ran it from tehre and its like giving me weird readings im about to just take it out.

Ronny

iTrader: (1)

I have a Autometer that I installed about 3 years ago. It will tell you in general terms if the fueling is lean stoich or rich. I am removing it and in its place in pod is going a digital to receive output from my WB controller. will sell cheap. It does look very cool(chick magnet) but i doubt car is any faster.

88L035speed

i got the same one sucks lol either that its broke when i bought it.

BMmonteSS

It's not broke, that's just what your O2 sensor is really doing. You stock O2 will just flip back and forth across .45 volts several times a second, which is causing the flickering you're seeing on your guage. You should see the guage sweep rich at WOT and sweep lean when you lift off the throttle. It really doesn't tell you much. Even with a WB it's hard to read the guage while your screaming through the gears. That's why they make datalogers.

88L035speed

yea definatly i agree im just going to take it out, tho it does look neat im takin it out and i got a question, me running my fan off of my blaster coil make my car slower (drain power).

BMmonteSS

I'm not quite sure what you're asking, are you running the power wire for your fan off of the ignition hot for your coil???? If so then yeah that's a bad idea unless you are using a selenoid.

88L035speed

i have an msd blaster 2 coil hooked up insted of the stock coil which lays next to the disturber, it has a positive and negitive side to the coil which goes into the harness, and it has the main wire running out of it to the top of the disturber so heres my question is running my fan off of the blaster coil draining the power form it or is it ok? becuase it turns on with the ignition. seems to be ok but idk.

BMmonteSS

It's never a good idea to piggy back any other electrical wires onto the coil wiring as any drain is not good. If you are not using a selenoid to activate the fan then I'll garantee that it is messing with your ignition.

88L035speed

roger that lol ill hook it back up to the stock wires locations.

The_Punisher454

I see alot of people bad mouthing Nb O2 sensors. They do suck compared to a WB setup, but its not a total waste of time using them to tune with. I have in the past made AVR microcontroller based AFR meters using both GM and ford 3 wire sensors. On a carb engine I was almost always able to get fairly stable voltage readings both above and below 450mV. They ARE NOT linear, and have a horrible AFR/Voltage curve and I needed to use lookup tables with a lot of interpolation between points.
The problem people have with NB sensors voltage switching from low to high has quite a bit to do with the fuel injection system. On a carb I was almost always able to hold steady voltages around 100-200mV on one end and up into the 800-950mv range without a lot of "switching" going on.
The NB sensors of course will do a lot of "switching" on an EFI engine and they are also very sensitive to temperature. On my old instruments I corrected for the temp problems with more lookup tables and used the heater as a temp sensor. WB sensors are much better in that area.

BMmonteSS

The reason why you see so much switching going on with FI is because the ECM tries to maintain 14.7 to 1, how fast the O2 switches and how long it dwells on each side of .450 volts lets it know which way the AFR is trying to go so it can correct for it before it gets too far out of wack. If you ran the carb at exactly 14.7 to one you would get a lot of switching back and forth, but it's just not possible without some kind of feedback system. If you disabled the fuel correction routine in your ECM then you would see the NB calm down quite a bit.


If you ever compared a NB to a WB side by side you'll quickly see that .200 volts will almost never line up with the AFR of the WB no matter what lookup table you use with or without corrections. Most people don't realize that WB's aren't just a heated sensor like the 3-wire setups that GM and ford uses. A WB has provisions so that the WB controller can regulate the temperature of the sensor which greatly improves accuracy. This is also why placing the WB too close to the engine can cause accuracy problems as it will be heated so much the temperature controller can't do it's job. I personally have tried tuning with a NB several times and have never had the AFR be anywhere within a full point of what the WB read.

You sound like you know what you are doing, but the average DIY tuner isn't going to take the time to correct the reading from their NB. They just want to aim for 4 or 5 lights past the middle of the guage....which can spell disaster.

Street Lethal

iTrader: (16)

If you already settled for a narrowband AFR gauge like I have, there are various aftermarket companies out there that offer M-series wideband controller's, along with converter's, that allows for your narrowband AFR gauge to read ratio's between 10:1-20:1. In conjunction with a wideband 02 sensor, of course....

The_Punisher454

Oh , I wasnt trying to imply that NB sensors were accurate, just that they get unfairly labeled as a switch. The switching back and forth from lean to rich is caused by the ECM, its not a natural characteristic of the sensor itself.
That being said, they are not very precise. Accuracy at 14.7 is okay but it gets bad quickly as you move away from 14.7. My old technique of using lookup tables to get some usable numbers was never intended to be accurate, or super repeatable, but it was plenty good enough for carb tuning back in the day. The numbers I was getting werent ever treated as accurate.
What was important at the time was that more was more and less was less. If you were to look at the display and then stab the throttle, It was easy to see if you had enough accelerator pump to get a good increase, if it dipped you needed more pump. That sort of thing.

as far as shooting for certain numbers with a WB goes, there are a few pitfalls there too. Some people seem obsessed with 14.7:1 at part throttle as being "perfect". But alot of engines are happier slightly leaner or richer.

as far as heat goes, the LSU4.2's we used to use on the Dynojet's WB were in a external block with a vaccum pump on one side and a sniffer line on the other sucking exhaust from the tail pipe. The sensors internal heater worked awesome with the near absence of exhaust heat.