So yesterday I was chatting with an old timer that has been working on carbs all his life professionally. He owns a well respected shop locally and is known for his tuning abilities. Here in AZ we have to run vehicles through emissions and many fail the test. This guy tunes the vehicles to pass the test.
He mentioned that he tunes carbs with a 5 gas analyzer where the probe inserts into the tail pipe. He runs the vehicle at different rpm's and checks CO readings. He jets accordingly. I've done this in the past but now it has me wondering.
Why do the emission stations load vehicles on rollers like a dyno while reading emissions with a 5 gas analyzer? This old gent says it's not needed. To his credit; he does get cars through emissions without the use of a dyno.
He stated that revving the car to 2500rpm in park will give accurate CO readings and that they don't change when loaded on the highway. The same with WOT runs in park.
Any former techs here that would like to throw in their two cents? I have the use of a five gas for free versus buying an Innovate wide band tool.
but the dyno was a Dynojet inertia dyno. It doesn't load the vehicle from what I understood. The operator told me he could only give me WOT readings. What's weird is that my dyno sheet showed an A/F graph from 2500rpm on up. Why even use a gas analyzer on that type of dyno when it can only give you WOT readings? Maybe to save the engine if you go lean at high rpm's?