We will be using an A/F sensor for the first time on our gas powered BBF dragster. what readings do you consider a good range under power and do you bother with idle numbers ?

I run alcohol but I use the gas scale. I am going to say this it is like a tire gauge yours may be calibrated different than mine. On mine it runs best at 12.9 to 13.1.

I do not pay much attention to idle mixtures. My main concern is at the finish line after it has had a little time to stabilize. I run 8 O2 sensors and check after every pass to make sure they are in range and none are out of line with the others.

What I would do is run it and make changes. Record your O2 and your ET and then what ever is your best would be your baseline. The ET is really what you are going for and the O2 is just a tool to help you get there.

Some may say it has to be 13.0. On your car it may run a 4.60 with an A/F of 12.3 and run a 4.75 with A/F of 13.0. So what is more important? Getting the perfect 13.0 or the better ET? Different sensors, calibrations and fuels. The only perfect number to chase is ET and then you use the O2 to help you stay on it.

Interesting I was guessing it would a bit richer like 11.5 to 12.5 or so. thanks for the info. I'm looking forward to see what we can learn with the Racepak

quote:

Originally posted by bracketsonly:
We will be using an A/F sensor for the first time on our gas powered BBF dragster. what readings do you consider a good range under power and do you bother with idle numbers ?

Who's fuel? Where did you put the sensor (sensors)?

Using Sunoco supreme, I am not sure of sensor location we have new Fab Shops being built i think they will be in the primary tubes though.

Where is the correct location for a sensor? I'm replacing my headers and need to weld in some bungs. I had them in the collectors of the old headers.

Usually before the first bend at approx 4-8 inches. Tuning with 02 can be tough so screw in a plug or two every run... plugs don’t lie.. Read the strap and porcelain.

My sensors are approx halfway down the primary tubes so they do not get contaminated by outside air.

As I understand it the A/F ratio should be the same almost all of the way down the tube as it is measuring the Oxygen (or lack of) in the pipe. Unlike EGT which changes all way down the pipe.

If you put the sensor in the collector be careful you are not getting any fresh air sucked into collector to mess up your results. I would say welded collectors and not too close to outlet.

Forgive me! We have 02 and egt...02 are at least 12 inches down... egt are close to flanges.

I was thinking the same thing about the sensor being in the collector. I work on Toyota and Lexus, I have experienced an exhaust leak near a sensor and it will show lean.

When we started logging we put the o2 sensors in the collector, and it would not read anything when at idle or on the throttle stop.

We were informed by our engine builder to put it about 8 inches from the header flange and now it reads correctly in all driving conditions.

I have found that looking at the idle ratios help me tune as to being on the stop. I do not see as much of an issue when running all out.

quote:

Originally posted by bracketsonly:
Using Sunoco supreme, I am not sure of sensor location we have new Fab Shops being built i think they will be in the primary tubes though.

Start at 13.3 A/F and tune it from there. Mine runs best between 13.3 and 13.5 with that fuel.

Thanks for the info, We ran the car last season with this gas carb so we have a little bit of a baseline.The car seemed to pick up in the evening more than I expected at times but the converter was a little tight also. we will be trying a new converter when we get back out latter this season along with the data info available.