Automotive elitists really like to ridicule carburetors. "A barely controlled fuel leak," some of them like to say. Maybe so, but when fuel injection debuted on European cars back in the 1970s, carburetors seemed warm and familiar like Mom's apple pie in the face of three horrifying letters: CIS.
CIS means Bosch Continuous Injection System, a fully mechanical system that operates with high fuel pressure and which requires expensive special tools to set up. As the name implies, the fuel injectors spray continuously. Fuel pressure is regulated mechanically according to air flow into the intake manifold, which is also metered mechanically. Screw up the system and CIS will dump enough fuel into the engine to wash out the bearings in a matter of minutes.
There were varying CIS permutations in European cars throughout the '70s and early '80s, and as emissions regulations persisted CIS evolved in ways that spoke mainly to emissions and not performance. Still, CIS is very reliable once it's dialed in. Many of these systems were replaced with carburetors only to be switched back later with the advent of emissions testing in parts of the United States. German, Italian, British, and French cars all used CIS at one point or another, and all of them required one basic part to make the system run correctly: An exhaust CO analyzer to measure the amount of carbon monoxide in the exhaust gas for the purpose of dialing in the mixture.
We're not trying to "retro-out" on you. Lots of these cars are still on the road, they still need to be set up periodically, and exhaust gas analyzers have evolved from one-gas to five-gas, with the expected price increases. My 1977 BMW 320i is finally running, and my friend Vince Lispi's Snap-on two-gas performance analyzer, part number MT497A-the only gas analyzer to which I have access-was made obsolete by the manufacturer. We can't get the necessary filters for it anymore. Thanks Snap-on. There's a reason we pay you the big bucks. I'll let you know when I figure it out.
So, this was the perfect opportunity to review the Eastwood Company's Digital Exhaust CO Analyzer. It only reads one gas: carbon monoxide. One gas is all I needed, and all anyone needs to set up a CIS-equipped car to run correctly. Passing emissions, of course, may be a different story.
Made by our allies in England, the Eastwood Company Digital Exhaust CO Analyzer requires no filters and is user-calibrated. It measures CO level within a 0.5% margin of accuracy, which may seem like a big margin but it's really not-many machines that cost a lot more have similar margins, and you don't have to work with CIS for very long before you realize that it's not the exact science Bosch would have us believe. Lots of things affect CO level but you do want to get the car as close to specification as possible. Calibration is simple. Power up the unit with 12 volts, and allow the exhaust sniffer probe to sample ambient air. The calibration reading should be adjusted to 2.0%, because as the Brits wrote in the instruction booklet, "It is purely coincidental that air should measure the same as exhaust gas with 2.0% CO." I love reading British technical writing.
Once the sniffer is inserted into the tailpipe of a well-tuned car with the engine at full operating temperature, the CO reading can be adjusted at the engine mixture control. The Eastwood Company Digital Exhaust CO Analyzer can also be used to set mixture on any adjustable fuel injection system or carbureted intake systems. The unit costs $219 plus shipping, and I have to say that is a hefty sum. The device is so light I was tempted to disassemble it to see what's inside, but I didn't. Bottom line: It works, and it's a lot cheaper than any other new gas analyzer I could find. Most read four or five gases, but CO is all you need to set up CIS or carburetors.