CO Meter Recommendations

[porschedude996]

Hi all, anyone have a experience with a CO meter to test CO?

[spuggy]

I used to own a Gunson 4125 Gastester, which I bought to check/set CO on the 930 when it still ran CIS (it would idle identically for a wide range of settings, but anything less than 3.25% would result in lean surging climbing inclines on small/fixed throttle openings).

When calibrated and used per instructions, it took a long time, 15 minutes IIRC, idling to get a reading. Which ended up giving results very close to my wrench's 5 gas analyzer.

They're cheap units, so a bit touchy, not to mention slow. And a one-trick pony that's unnecessary with a wide-band lambda.

Unless you need it for emissions and don't have a wrench with a real gas analyzer, take a look at Souk's threads:

https://forums.pelicanparts.com/porsche-911-technical-forum/232089-cis-idle-speed-mixture-setting-without-analyzer.html
https://forums.pelicanparts.com/porsche-911-technical-forum/185926-its-time-year-again-cis.html

[Jeff Alton]

In our shop we use a Snap On 5 gas unit. Refresh in less than 90 secs, which is important in a shop environment... For personal DIY use, the Gunson has a pretty solid following of very satisfied people.

[RDM]

I've used the Gunson on several old vehicles, and it's given me what I needed.

[fanaudical]

I've got CIS on my 911 still and was having some trouble getting the idle set. I borrowed a friend's Gunson Gastester and got it set at the correct CO level but still had a few drivability issues. I eventually installed a wideband AFR gauge which proved very helpful in diagnosing problems as I drove the car around. It's also useful for setting idle CO level if you have access to this chart:

https://www.mgexp.com/article/co-to-air-fuel-ratio-afr-table.149

[AndrewCologne]

This table is no reference at all.
At combustion with an AFR of 14.72:1 there will defenitely result Carbonmonoxydes above 0.1%
A CO out of a CIS based 911 with Lambda 1/ AFR 14.7:1 (or 14.4:1 with 5% Ethanol-Fuel) will normaly result in a CO of 1.2 - 1.5 %. Proofen by myself with an emissions report out of an official 4-gas testing unit at a german TάV-Station.

https://nineelevenheaven-wordpress-com.translate.goog/abgasregelung-beim-sc/?_x_tr_sl=de&_x_tr_tl=en&_x_tr_hl=de&_x_tr_pto=wapp
(google translated)