For power drivers, an exhaust gas analyzer is just as important as any other tool in your tool kit. Once you have a handle on the mix of gases emitted through your exhaust system, you better understand what must be tweaked in order to get the engine back into the best shape possible. For extra protection, a five-gas analyzer measures the same gases plus nitric oxide. A four-gas analyzer reads emissions for four separate gases: oxygen, carbon dioxide, carbon monoxide, and hydrocarbon. Whether the car is just hesitating when you hit the gas or actually stalling at inappropriate times, the source of the problem is easier to narrow down when you know what the output is. An exhaust gas analyzer can tell you exactly what is going on with tailpipe emissions, giving you a solid idea what is happening in the engine itself. Your car is choking, sputtering, and making other odd noises, but you cannot figure out what the problem is. The advertised spec is 0.5%, but I don't know exactly what they mean by that spec (it could be a percentage of the full scale reading, or an absolute %CO variance, or something else.Find great deals for GUNSONS Gastester Mk2 Complete With Instructions. Over the range of interest, the %CO does relate quite accurately to the A/F ratio, but I don't know how absolutely accurate the Gunson %CO reading really is. But slight changes would show on the Gunson. The difference between a smog test pass and fail on the '78 was not enough to notice via lifting the piston, listening, monitoring a tach, or driving. And the '67 doesn't need to be nearly as accurate as the '78 needed to be. The SU HS4 carbs drift with temperature way more than the ZS did, and this showed with changes on the Gunson as the under bonnet temperature changed while trying to set the mixture. Small changes to the ZS carb did show up as %CO changes, and once warm it was reasonably stable on that car.

It allowed me to set the %CO on the '78 as specified in the manual for a smog pass.

It does drift a *lot* as it warms up, and it drifts some after warmed up, but much more slowly. I would hook it up to a stand alone battery and let it warm up for a while before trying to use it. I have a Gunson Gastester that I used to use on my '78.

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