tuning with an o2 gauge

[gmonde]

looking for some feedback on carb tuning with a stand alone o2 gauge/sensor system, what kind of accuracy will it have with open headers,any info would help thanks gmonde

[Ed Wright]

Originally Posted by gmonde

looking for some feedback on carb tuning with a stand alone o2 gauge/sensor system, what kind of accuracy will it have with open headers,any info would help thanks gmonde

At idle with open headers it will normally look very lean. Overlap cycle pulls fresh air back in the collector, so you will normally be seeing bogus numbers. If you want to check very low RPM, not WOT, you need to get an extention made, preferably with a bend in it. At WOT the air/fuel ratio your car likes can often vary. Different fuels often run quickest with the same engine at different indicated air/fuel ratios. You just have to find what your engine and your fuel likes. Most will fall between 12.5-1 & 13.5-1. Seldom outside that range. I had some fuel that liked between 13.3-1 and 13.6-1 in my old bracket engine. What I have now does not like to run that lean. Usually between 12.7-1 and 13.0-1 will be real close for most engines. Many carbureted engines need more fuel to keep the manifold walls wet. Port injection tends to want to run a little leaner with the same fuel than TBI or carb would. What makes the most power on a chassis dyno is seldom what runs the quickest. Very lean usually looks better on the dyno than the race track.

Good luck, Ed