A normal (narrowband) O2 sensor tells you basically one thing: Are you rich or lean of stoich (14.7:1)? It's linear for a VERY small range around there, but functionally it just tells you if you're rich or lean, and not by how much.

A wideband tells you your air/fuel ratio. It's also much more complex to control, and a controller for it plus the sensor will easily run $300, and a high end unit can go for much more.

You don't *need* a wideband O2 sensor to tune a SAFC-II, but it helps.

I wouldn't consider tuning a turbo '7 (especially into the boost zone) without a wideband - go lean on those, and they have a way of ejecting apex seals through the turbo (detonation is nasty).

However, it's difficult (not impossible, but damn difficult) to get a non-turbo '7 to detonate, and even if you do, it's not nearly as damaging as on a turbo. I'm not saying it's impossible to blow apex seals on a NA detonating, but you'd pretty much have to be trying.

With this considered, you can put a voltmeter on the stock (narrowband) O2 sensor output, and see when you cross 0.5v - this is the stoich point. Richen things up a bit from this, and you'll be about right. Do this at a few points for wide open throttle, and you'll be pretty close to a good tune. Generally you'll be pulling 20-30% out at wide open throttle in the higher RPM ranges.

-=Russ=-

 

Sorry, I was thinking about doing it because I have a couple 88 T2 injectors at work not being used. When I said, "I'm unsing....etc" I meant that I was going to be using...etc, etc, etc. I country so I sometimes slip up and show my red neck in text.

Syonyk id dead right about that detonating an n/a thing. I bought my GTU in October of last year (06) and it's my first one, so I'm learning as I go. As it turns out, the guy I bought the car from had advanced my timing as far as the CAS would go. I guess to raise the idle. I didn't know that much about them so I just figured the TPS or something was bad. (the guy put a brand new TPS on it and turns out it wasn't the TPS that was bad, it's the OMP) Well it was very picky about when it did it, but it would start this very loud tapping (detonation) when I had it floored so I just quit racing it too much. It got really bad recently so I had my boss give me some pointers and he advised I check the timing. As it turned out....well you know. So, short story way stretched out, I detonated the **** out of my 90 GTU and now that I fixed that, it runs like a gem. Well, all except for the fact that retardating the timing brought my idle down to about 300 rpm with my idler screw completely open. But other than that and my OMP, I'm set.

By the way, I got the idea to use bigger injectors because I couldn't smell it running as rich as it used to, so I replaced the fuel filter and ran a bottle of Lucas injector cleaner through it, and it's back to popping little blue flame ***** when i shift. I have to say that's one of my favorite features of an rx7.

 

Having an Oswald Bates moment? Hehehe.
http://www.youtube.com/watch?v=O7dPprbzNSc

Proof of why it is smarter to pay for professional tuning rather than buying an O2 meter and attempting it on your own. Hoperfully your indicated AFR is leaner than the true AFR. Fortunately, even wideband O2 meters can be off by as much as 2 AFR, so hopefully this is your case.

 

I had a case of the blue ***** the other day. The gal next door took care of it though.

http://health.discovery.com/centers/...blueballs.html