isamu

I know the cheap a/f gauges can be pretty stanking inaccurate but I have a question about the reading. I originally bought one for the TII but hooked it up in my n/a out of curiosity. At wot the gauge will go to the lowest lean setting and stay there. I did a search and found that it should read a bit richer, as a matter of a fact some said full rich. At around 3/4 throttle the gauge is at the leanest bar until around 3800 rpms and then it jumps right up to the last rich setting, I figured do to the secondaries coming online. I don't have the gauge hooked up any more, I just had it in for a couple of months to see what it said.

Also having my o2 sensor hooked up dramatically effected how the engine ran. When its hooked up the car will surge under acceleration and there is no difference at 3800 rpms. When its disconnected the car will accelerate without any surging and at 3800 rpms its like getting an extra push from behind. I'm thinking my 02 sensor might be bad or I should play with the timing a bit. I've had the timing slightly advanced for some time now, I figured it wouldn't hurt the engine since the n/a's run so rich. Maybe I fuggered it, but its been this way for most of the 10,000 miles that I've put on it since the rebuild.

Anyways sorry about the long post. I've just been thinking about this a bit.

roadkill669

Well first thing, a gauge is only as accurate as the sensor. A single wire O2 sensor isn't that accurate. Its good enough to tune it to some extent. For a better reading, people usually buy a wide band system. I personally think its a waste of money. Basically, you need between $400-$1000 for one.



I didn't think our cars really used the O2 sensors (coming from a TII POV). I've run my car without it and it seems to be okay. I have no idea about NA's.

j9fd3s

they do go full rich when the secondaries come on at 3800. below 3800 it should be switching closed loop @14.7:1.



mike

1987rx7guy

First of all I woule NEVER tune to any extent with a stock or any narrow band O2 sensor and an A/f gauge even if it is gold plated and has a spiner lol



Anyhow Get a new O2 sensor if your MPG is down. YES all FC's USE the o2 sensor. If I unplug mine I will loose around 40 miles per tank say around 260 miles to a tank from 300+ to a tank with it plugged in. So you have some other problem if you can't get your car to work ok with it on.



There are many DIY wideband kits around that you can make for under 400 dollars. Its not easy though.

isamu

Ok, thanks.