Air Fuel Ratio Question
Thread Starter
Teching In
Joined: Feb 2005
Posts: 41
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Air Fuel Ratio Question Just had my car dynotuned. THey did a before and after pull and told me that the car was too rich initially.
On the dynojet sheet, the before average A/F looks like about 11.5:1. When they were finished, the chart reads about 12.8:1.
I checked it with a Scanmaster before I took it in and it showed me .878 volts on the O2 sensor at the top of 2nd(5900). WHen I got it back it was showing .875 at the top of 2nd.
According to the chart I have, .875 O2 volts converts to about 13.7:1 A/F ratio.
My question is am I converting this accurately? Does anyone have a good conversion chart for O2 volts to A/F ratio??
Also, how can the Scanmaster show me the same O2 volts before and after when these guys told me they leaned the car out substantially??
ANy thoughts?
On the dynojet sheet, the before average A/F looks like about 11.5:1. When they were finished, the chart reads about 12.8:1.
I checked it with a Scanmaster before I took it in and it showed me .878 volts on the O2 sensor at the top of 2nd(5900). WHen I got it back it was showing .875 at the top of 2nd.
According to the chart I have, .875 O2 volts converts to about 13.7:1 A/F ratio.
My question is am I converting this accurately? Does anyone have a good conversion chart for O2 volts to A/F ratio??
Also, how can the Scanmaster show me the same O2 volts before and after when these guys told me they leaned the car out substantially??
ANy thoughts?
first off, do you have dyno charts. It would be alot easier to guide you if you had some charts for us to look at.
forget about the 02mv. You cannnot go by those to accurately determine your a/f ratio thus there aren't any reliableconversion charts.
Based on the information you've provided it sounds like you are on the right track as far as them leaning the car out with the before and after a/f ratios.
forget about the 02mv. You cannnot go by those to accurately determine your a/f ratio thus there aren't any reliableconversion charts.
Based on the information you've provided it sounds like you are on the right track as far as them leaning the car out with the before and after a/f ratios.
Thread Starter
Teching In
Joined: Feb 2005
Posts: 41
Likes: 0
Hi Doug,
Thanks for the input.
Here's the dyno sheet. It's basically a before & after on a head/cam install. THe car was bone stock for the first pull. I had to chop up the scan a little to get under the 100K limit and still be readable. They could not get the torque reading to work for some reason, so there is only HP.
I guess my real question is whether the Scanmaster is of any value in tuning the car, and I take it from your last response that you don't think so, at least as far as A/F goes. I used one quite a bit for tuning my Buick GN and it worked well. The A/F reading had some quirks, but once I figured out how to use it, it was very useful for dialing in fuel pressure among other things. Of course we don't do that kind of thing on the LS1 and that Buick ECM is very primitive compared to the LS1.
Thanks for the input.
Here's the dyno sheet. It's basically a before & after on a head/cam install. THe car was bone stock for the first pull. I had to chop up the scan a little to get under the 100K limit and still be readable. They could not get the torque reading to work for some reason, so there is only HP.
I guess my real question is whether the Scanmaster is of any value in tuning the car, and I take it from your last response that you don't think so, at least as far as A/F goes. I used one quite a bit for tuning my Buick GN and it worked well. The A/F reading had some quirks, but once I figured out how to use it, it was very useful for dialing in fuel pressure among other things. Of course we don't do that kind of thing on the LS1 and that Buick ECM is very primitive compared to the LS1.
Judging by the chart the A/F seems to look pretty good. I'm not real familiar with the scan master. If it's got some other parameters you can monitor it could prove useful but most will not use it to tune a/f anway.
