CO analyzer

[Nick Triesch]

I want to do the proper CO measure on my 3.2. Could someone recommend an inexpensive analyzer I could buy ? Thank you , Nick.

[fanaudical]

The Gunson Gastester has been the amateur mechanic's go-to for a while. I don't own one (have borrowed a friend's unit) and found it OK but not exactly "confidence-inspiring". I went the route of permanently installing a wide-band O2 gauge in the car.

I see other companies (like Nova Gas and Bridge Analyzers) are offering portable gas analyzers that look more sophisticated than the Gunson; they also look like $$$.

[Nick Triesch]

Many people here talk about an analyzer but it seems few have them. I would like to know if anyone has used one of the small portable ones I see online ? Need to set mixture.

[Schulisco]

I have one. They're too inaccurate for injection cars, especially when they're equipped with a catalyst. It's got a accuracy more than +-0,5% which is quite good for a DIY CO gauge for a reasonable price, but in fact not precise enough because the CO level for e.g. a 911 SC with 930/16 engine with catalyst has to be adjusted between 0,4-0,8% CO...so the Gunson is ok for a quantative measurement at home (too see if the car doesn't run way too rich e.g.), but I won't rely on it for those cars...After adjusting the mixture with the Gunson you always have to verify the result with a certified gas tester.
When you look in the Porsche service manual /workshop manual Porsche recommends always to adjust the CO screw for lambda controlled cars like mine from lean to richer mixture to minimize CO and so to surely pass the emissions check. The CIS lambda systems were not that precise as the later Carreras were.

https://www.gunson.co.uk/product/G4125/Gastester-Digital

Thomas

[Damon88]

subscribed..

[Nick Triesch]

Holy smokes! So it’s best to test CO at home and then double check at a shop?? I still would like to know if one of the smaller hand held units could do a good job. I would like to just get the reading ballpark because just doing it by feel seems way to off. Is there a Gunson model number I should look for ? Thank you.

[Schulisco]

Originally Posted by Nick Triesch

Holy smokes! So it’s best to test CO at home and then double check at a shop?? I still would like to know if one of the smaller hand held units could do a good job. I would like to just get the reading ballpark because just doing it by feel seems way to off. Is there a Gunson model number I should look for ? Thank you.

Yes. Laboriuos, but this is the way for all injection (and streetlegal) cars I would say..

Gunson G4125 as denoted in the link...

Thomas

[Nick Triesch]

Just no Gunson’s available at this time. Hard to find

[walt]

Years back when my Gunson gave out, I found a really nice KAL unit on E-Bay. They are out there but buying used electronics is always a risk. Plus, I don't know if the sensors in these have a limited lifespan, that's why my Gunson bit the dust.

[911obgyn]

I built a wide band O2 gas analyser from an innovate guage and o2 sensor with clips for power. Remove O2 sensor install, hook it up. Works on my 80s cars with cats. Have to check before the cat anyway.

[Ian Comerford]

When I realised my CO reading was probably not where it should be I took my car to my local garage and paid them for 30mins on their CO meter. They set the meter up and left me to adjust the setting. I quickly learned that after each small adjustment you need to allow a minute or two for it to settle into the new setting. Given how easy this was it doesn’t seem worth buying a meter for home use when I have a fairly amenable garage about five miles away, with a tested CO meter

[dw1]

I had a Gunson and found it to be largely worthless, both for my 3.2 and other newer cars. It was helpful to get my old carburated Brit sports car "in the neighborhood", but beyond that - n.g.

I strongly agree with Ian's approach of finding a friendly garage and paying them to use their meter unless you want to spend big $$$ on a good one.

[Funracer]

Originally Posted by dw1

I had a Gunson and found it to be largely worthless, both for my 3.2 and other newer cars. It was helpful to get my old carburated Brit sports car "in the neighborhood", but beyond that - n.g.

I strongly agree with Ian's approach of finding a friendly garage and paying them to use their meter unless you want to spend big $$$ on a good one.

Agree. The issue around here is garages don’t have them anymore. Florida does not do emissions testing and hasn’t for a long time so shops don’t keep them around. I had a Gunson it was tricky to use and very fragile. It fell off a chair and never worked after that. Threw it away. Ended up with AFM gauge which works much better.

[john walker's workshop]

[Nick Triesch]

I could also go to a smog shop and pay to use their machine to adjust CO. But it would be after the cat. I wonder how different the results would really be ?

[porschedude996]

I have a Gunson and an old late 70’s or 80’s Penske CO meter that is battery powered. One could even set up the three major components on the car and drive it. The three components are the meter dial, the sensor/battery pack, and the exhaust probe. I bought it on ebay in the original box and it works, but I don’t think it’s very accurate. The Gunson is good for setting, with a few ounces of luck, and pass a California Semiannual Emissions Test. That is what I had to do to get my 911SC titled.

[proporsche]

Originally Posted by Nick Triesch

I could also go to a smog shop and pay to use their machine to adjust CO. But it would be after the cat. I wonder how different the results would really be ?

Or,you could just remove the bolt in front of the cat to measure the c/o ....
Ivan

[PeteKz]

Originally Posted by Funracer

Agree. The issue around here is garages don’t have them anymore. Florida does not do emissions testing and hasn’t for a long time so shops don’t keep them around. I had a Gunson it was tricky to use and very fragile. It fell off a chair and never worked after that. Threw it away. Ended up with AFM gauge which works much better.

Same here. I installed an AFR gauge and don't understand why you would continue to use CO an analyzer.

[NY65912]

Just came across this thread after I listed my NIB Gunson G4125 on ebay. PM if anyone is interested.

Cheers

[TimT]

AFR and CO have a linear relationship.. Get a AFR gauge and extrapolate.

The almost perfectly linear relationship between CO and A/F ratio yields a very simple way to setup a carburetor or fuel injection

https://www.bridgeanalyzers.com/wp-content/uploads/2016/07/17-CO-HC-Graph-vs-Lambda-CE-Perf.-Tuning.pdf