Using Gunson CO Tester
 

I recently purchased a Gunson CO tester and want to make sure I'm using it properly for testing my 83 911SC. The Cat has been replaced with a by-pass pipe.

JW says the optimum CO should be 3.5. Is this at idle or at a certain RPM. Should the test be done at idle? How about the O2 sensor? Should it be disconnected?

Thanks in advance ............................... Randy

I set mine at 3.5% at idle. I do not run an O2 sensor.

You will also need a 1/4" outer diameter tube to get into the cat bung. I went to Home Depot and found some copper ice maker tubing that worked great.

No need for the extra tube as I replaced the Cat with a by-pass. Readings can be taken directly within the tail pipe.

Randy

Set the CO at about 1.5 to 2.0% before the CAT without the O2 sensor connected
with the RPM at 2000 to 2500. The 3.5% is a little too rich for the SC with CIS
injection.