Gunson Gastester questions

[SCWDP911]

I have my Gunson Gastester now and wanted to try it out today, but I am sad to say I am one confused puppy. Car is 1983 with stock 3.0 and CIS.

I have been searching the last hour or so, but still not clear and I am running out of daylight.

I understand how to hook up my gastester and the warmup times. My questions are these:

1. if my cat has hypothetically been gutted by someone at some point, can I simply stick the probe into the tailpipe for my reading?

2. It says in Bentley to measure the CO with O2 sensor unplugged - OK, (sheepishly I ask) where exactly do I unplug my O2 sensor from?

3. The Gunson is set to a background of 2.0%. Are the numbers in the Bentley for proper CO % based on the 2.0% background (meaning the number they quote includes the 2.0% background?)?

4. Are there any ambient temp limits on the using the Gunson? I know to keep it out of a draft, but it has been in the 20's and 30's here today. Will it be alright to use after a 30 minute warmup?

Thanks,
Shane

[Rick V]

You unplug the 02 sensor right below the fuel filter. Be careful, the connector breaks easily.
when you get the tester set up and running (normal opersting temp for the car) just set it to 3-3.5. 3 being rich, 3.5 being lean. I like to set mine around 3.2.
And yes just stick the probe up the ol tail pipe.

[911nut]

Originally Posted by v8_ranch

I have my Gunson Gastester now and wanted to try it out today, but I am sad to say I am one confused puppy. Car is 1983 with stock 3.0 and CIS.

I have been searching the last hour or so, but still not clear and I am running out of daylight.

I understand how to hook up my gastester and the warmup times. My questions are these:

1. if my cat has hypothetically been gutted by someone at some point, can I simply stick the probe into the tailpipe for my reading?

Yes.

2. It says in Bentley to measure the CO with O2 sensor unplugged - OK, (sheepishly I ask) where exactly do I unplug my O2 sensor from?

It's on the left side of the engine down on the exhaust pipe just ahead of the cat. Follow the lead from the sensor to where it plugs in and pull it out.

3. The Gunson is set to a background of 2.0%. Are the numbers in the Bentley for proper CO % based on the 2.0% background (meaning the number they quote includes the 2.0% background?)?

Yes.

4. Are there any ambient temp limits on the using the Gunson? I know to keep it out of a draft, but it has been in the 20's and 30's here today. Will it be alright to use after a 30 minute warmup?

Doesn't the unit require a 10 minute warn-up? Thirty minutes should be plenty.

[SCWDP911]

It says in manual that it mnay require 30 minutes for warmup.

I thought I knew to unplug the sensor under the fuel filter there, but just was not sure how bad that was going to be. I thought I remembered it being a connection prone to damage when removing.

Thanks guys

[David E. Clark]

A quick internet search uncovered this gastester manual from an analog model and this manual from a newer digital model. There is also a good Gastester thread in the archives that you may not have found yet. Finally, here is a good article on engine tuning with the Gastester. Hope this helps.

[Rick V]

oops I forgot to mention you start the "sniffer" at 2. do this in an area free from exhaust.

[911pcars]

".....3 being rich, 3.5 being lean..........."

I believe it's the other way around. Higher percentages = richer A/F mixture.

Sherwood

[SCWDP911]

Originally Posted by David E. Clark

A quick internet search uncovered this gastester manual from an analog model and this manual from a newer digital model. There is also a good Gastester thread in the archives that you may not have found yet. Finally, here is a good article on engine tuning with the Gastester. Hope this helps.

Thanks David