Whoa. I hit the fucking jackpot with the following link. Sure wish I'd thought of this myself because I'd be a genius and chicks would dig me. Here's the deal: EFI engines use sensors in the exhaust to tell the injectors to adjust the amount of fuel so that the mixture is correct, right? (the answer is yes). Why can't one of those same sensors just tell ME if there needs to be more or less fuel at specific throttle settings/revs so I can adjust my carbs accordingly? Like most other auto electronic sensors they just relay a variance in voltage depending on the info they're sensing. So read the fucking thing with a volt meter, all we need to know is what voltage corresponds to a good mixture (.70V-.90V apparently) & that lower voltage= a lean mixture; higher voltage=a rich mixture.
From my perspective this info should solve most all of the world's problems. Indeed we have stepped forth out of darkness and entered a new age in the advancement of civilization. So children... go forth and be free. Tune, race, dance, and procreate in the streets.
Here's the couple paragraphs from this guy's Kehin FCR tuning guide(minus the couple graphs that wouldn't copy):
Reality check. Nobody likely to be reading this page can afford a four gas EGA. So you can't use CO as an indicator. You need something to go on, because reading plugs will drive you craaaaazy. Do not do not do not do not buy an EGT setup. Using exhaust gas temps to determine air fuel mixture is so much more trouble than you can possible imagine. It's worse than reading plugs, because you think you've got good info, but it's all wrong, except for when it's right, only you won't know when that is. So. Hook up a Bosch four wire lambda sensor, generic one size fits all style, that you can get for like $40 at any auto parts store. Do what you have to, to mount it in the exhaust collector. Yamaha had this really neat setup on Scott Russell's YZF750 at Daytona a billion years ago with a wide range lambda sensor (that'd be the $600 version) mounted in the mid pipe, between the header and muffler, so they could gather data during practice, then take it out and mount a regular, unmodified mid pipe for the race. That might be a nice place to mount yours. So... you want the four wire sensor because it has heaters in it, which bring the sensor up to temp a lot faster, and they have to be hot to work. And it's nice to have the sensor wire plus a real ground wire back to the sensor instead of how a three wire sensor makes you ground back through the exhaust, engine, frame, all that nonsense. You can read the voltage with a high impedence digital volt meter, or you can buy a really spiffy gauge from Nordskog Performance that shows you the true voltage signal coming from the gauge. They and K&N also sell gauges that supposedly tell you the air fuel ratio. They don't work, exactly. That's just not how the sensors work, so the gauges can't possibly give you a true value for air fuel ratio. I think you're better off just getting the pure voltage signal, and interpreting it yourself, than relying on a gauge that's telling you a fib. If you buy a gauge from Nordskog, you might as well buy a sensor from them too. They get $60 for a four wire NGK/NTK lamda sensor, but if you're busy it's probably worth it not to have to make a trip to the auto parts store and sort through all the $150 gauges to find the $40 one. I'm not going to go too deep into how lambda sensors work, but they're super sensitive around stoiciometric, and less so once you get away from there. Google on do it yourself lambda sensor stuff and I'm sure you'll find the relevant info. There's probably reams of info on the DIY EFI site. Here's a rough graph of voltage versus lambda that I stole from someone so long ago I can't remember who it was to give them credit: (missing charts)
The long and the short of it is you'll be aiming for a voltage reading somewhere between about 0.90 and 0.70 volt for best performance. Higher voltage is richer, lower voltage is leaner. Stoiciometric is right around 0.50 volt. But it's not linear. 0.60 volt is richer than 0.40 volt. But 0.80 volt is a lot richer (but probably still a tiny bit lean of best full throttle mixture). And 0.95 volt is total misfiring black smoke out the exhaust and all that. Anyway, enough of that. Lambda sensors are useful. They are not as good as a CO reading, but they're a whole bunch cheaper than an EGA, and they react FAST, like fractions of a second. So it's good for seeing transient stuff.
From my perspective this info should solve most all of the world's problems. Indeed we have stepped forth out of darkness and entered a new age in the advancement of civilization. So children... go forth and be free. Tune, race, dance, and procreate in the streets.
Here's the couple paragraphs from this guy's Kehin FCR tuning guide(minus the couple graphs that wouldn't copy):
Reality check. Nobody likely to be reading this page can afford a four gas EGA. So you can't use CO as an indicator. You need something to go on, because reading plugs will drive you craaaaazy. Do not do not do not do not buy an EGT setup. Using exhaust gas temps to determine air fuel mixture is so much more trouble than you can possible imagine. It's worse than reading plugs, because you think you've got good info, but it's all wrong, except for when it's right, only you won't know when that is. So. Hook up a Bosch four wire lambda sensor, generic one size fits all style, that you can get for like $40 at any auto parts store. Do what you have to, to mount it in the exhaust collector. Yamaha had this really neat setup on Scott Russell's YZF750 at Daytona a billion years ago with a wide range lambda sensor (that'd be the $600 version) mounted in the mid pipe, between the header and muffler, so they could gather data during practice, then take it out and mount a regular, unmodified mid pipe for the race. That might be a nice place to mount yours. So... you want the four wire sensor because it has heaters in it, which bring the sensor up to temp a lot faster, and they have to be hot to work. And it's nice to have the sensor wire plus a real ground wire back to the sensor instead of how a three wire sensor makes you ground back through the exhaust, engine, frame, all that nonsense. You can read the voltage with a high impedence digital volt meter, or you can buy a really spiffy gauge from Nordskog Performance that shows you the true voltage signal coming from the gauge. They and K&N also sell gauges that supposedly tell you the air fuel ratio. They don't work, exactly. That's just not how the sensors work, so the gauges can't possibly give you a true value for air fuel ratio. I think you're better off just getting the pure voltage signal, and interpreting it yourself, than relying on a gauge that's telling you a fib. If you buy a gauge from Nordskog, you might as well buy a sensor from them too. They get $60 for a four wire NGK/NTK lamda sensor, but if you're busy it's probably worth it not to have to make a trip to the auto parts store and sort through all the $150 gauges to find the $40 one. I'm not going to go too deep into how lambda sensors work, but they're super sensitive around stoiciometric, and less so once you get away from there. Google on do it yourself lambda sensor stuff and I'm sure you'll find the relevant info. There's probably reams of info on the DIY EFI site. Here's a rough graph of voltage versus lambda that I stole from someone so long ago I can't remember who it was to give them credit: (missing charts)
The long and the short of it is you'll be aiming for a voltage reading somewhere between about 0.90 and 0.70 volt for best performance. Higher voltage is richer, lower voltage is leaner. Stoiciometric is right around 0.50 volt. But it's not linear. 0.60 volt is richer than 0.40 volt. But 0.80 volt is a lot richer (but probably still a tiny bit lean of best full throttle mixture). And 0.95 volt is total misfiring black smoke out the exhaust and all that. Anyway, enough of that. Lambda sensors are useful. They are not as good as a CO reading, but they're a whole bunch cheaper than an EGA, and they react FAST, like fractions of a second. So it's good for seeing transient stuff.
I have to say though that I'm glad my days of carb tinkering are over - fuel injection's the devil's work but i'm a convert.