A/F Ratio
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,469
Likes: 6
From: Winchester Ontario
A/F Ratio
Other than a wideband sensor during a dyno run, can you find your A/F ratio from using a Snap On scan tool?
I think I remember people saying that they use DiaCom or whatever and have that plugged into their laptops for reading engine data.
I don't have a laptop, but I have a mechanic that has a SnapOn scanning tool. From this, I've seen him read quite a bit of engine data, but can A/F ratio be read using it?
I think I remember people saying that they use DiaCom or whatever and have that plugged into their laptops for reading engine data.
I don't have a laptop, but I have a mechanic that has a SnapOn scanning tool. From this, I've seen him read quite a bit of engine data, but can A/F ratio be read using it?
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: A/F Ratio (black_89_vette)
A good scan tool will show you O2 voltage readings from the O2 sensor. From this data you can:
1) at part throttle in closed loop see if the values are swinging between about .4-.9 Vdc which means the ECM is maintaining the stoch A/F ratio.
2) at WOT see if the value is around 900mV meaning about 12.8:1 ratio which is about right for best power.
While it's true that the stock O2 sensor isn't accurate at WOT, it will still give a good idea if the A/F ratio is about right for best power.
1) at part throttle in closed loop see if the values are swinging between about .4-.9 Vdc which means the ECM is maintaining the stoch A/F ratio.
2) at WOT see if the value is around 900mV meaning about 12.8:1 ratio which is about right for best power.
While it's true that the stock O2 sensor isn't accurate at WOT, it will still give a good idea if the A/F ratio is about right for best power.
Advanced
Joined: Sep 2000
Posts: 75
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Re: A/F Ratio (black_89_vette)
According to all I've read is oxygen sensors are only good at values of air/fuel of 14.7:1 and are very non linear.
I'm not sure you would know if you have 12.5 or 13.5 to 1 with 800mv at WOT. And that's a big difference in exhaust temp.
I think the best you could do is find a gross problem with it.
Just my 2 cents.
I'm not sure you would know if you have 12.5 or 13.5 to 1 with 800mv at WOT. And that's a big difference in exhaust temp.
I think the best you could do is find a gross problem with it.
Just my 2 cents.
