Gunson Gas Tester- Where should I stick it?
 

Well,

I finally got my Gunson Gastester so I can tune the CIS and get my car to pass smog. I searched the archives and consulted both the Bentley and the sticker on my decklid. All suggest measuring the CO pre Cat. When I removed the cat test port plug, the gunson's probe tube would not fit in the hole. Anyone else have this problem? I ended up just putting the tube up the exhaust but shouldn't the numbers I am tuning to (2.5% +/- .5%) be lower?

What is the right way to do this. On a side note, the Gunson seems to be well worth the price.

GB

Can't help since you have the O2 sensor. But for emissions testing purposes, stick it in the exhaust outlet and turn to CA smog specs. Tjis is where they measure the CO2 and all the other stuff.

You can stick your Gunson Gas Tester right up your....exhaust pipe. Yes, pre-CAT. Post CAT numbers should be very different. It'll run and sound better if you use a gutted CAT and set the mixture richer than stock. Rich mixtures can hurt CATs.

Oh now I see you want to pass smog. Smog testing will be done at the tailpipe. So you should be able to see what they will see.

Hey Super...Jim, I've had a Gunson for a few years..don't use it much/don't have to...if I sample a few times I get a clearer bell curve idea on an acurate gauge reading.and it is within a 5%-10% of a good shop expensive tester.I wrote down if my readings are higher or lower than shop tester/don't matter.I have a base line for a clearer true reading..might be cool to be able to gas test each tube on a SSI with PMOs.............RonSmileWavy

Thanks for the replies everyone.

Paul, my set up is the same as yours: No O2 sensor.

I was able to tune mixture to between 2 and 2.5 % (with the smog pump disabled) but that was with the probe in the exhaust. I do have a test port pre cat but the Gunson's probe tube diameter is larger than the port. The sticker on my lid says set to 2.5% PRE CAT. If I tune to 2.5% POST CAT am I still too rich? I do not think that this has been addressed yet on the board.

Maybe John Walker can chime in here?

GB

Woo hoo!

I took my newly tuned car into the shop yesterday and passed smog with flying colors. Free and clear for the next 2 years. The Gunson and advice from this board made all the difference. My CO% output dropped by an order of magnitude compared to the test I failed.

Now. Where should I set the CO to get best performance? 3-3.5%? Just a side note. (The engine temp is now significantly higher with the CO set to ~2%CO.)

GB

what's a gunnson?
 

I've never heard of a presumeably affordable CO meter? Anybody got a weblink to this thing?

Here is the link, It is a nice machine, but I am still not convinced of its accuracy.

SSoar

Here is a link to a discussion thread on the Gunson.

http://forums.pelicanparts.com/porsche-911-technical-forum/73819-gunson-co-meter.html?highlight=Gunson

GB

Is there anyone in the CHicago/Naperville Area that might allow me to borrow one of these for a few hours?