What is exhaust emission and why we need to perform diagnostics on it? What is a gas analyser and why we need to use one? Those are questions often asked and even more often left unanswered. Simply put, the exhaust emissions are the gases that are produced during internal combustion in the engines and exhausted through the tale pipe. Some of those are harmless, others really vicious gases that we don't want to breath. Besides the need of running "clean" cars, the emissions can tell a diagnostic technician a lot about what is happening in the combustion chamber and what actions to take to make the engine run as it was designed to do.

     The gas analyser is your best friend in diagnosing exhaust emissions and the more you understand it the better chance you stand to fix those problems faster. There was a wide spread joke in SA that "one doesn't need a 4 gas analyser to see that there is a hole in the exhaust" but thankfully more and more technicians now see the true benefits of well equipped workshop. Using gas analyser is a fast and reliable way of checking the overall condition of engine, ignition and injection systems. It takes 5 min. to take a gas sample and find out is this engine burning the right amount of air/fuel mixture at the right time. Talking about fast service. Otherwise, how exactly, one will know why is the customer complaining from high fuel consumption or lack of engine power. Don't just "Look at this smoke..."

Use the links below to read more about exhaust emissions:

Exhaust Emissions Theory Using Lambda Lean Mixture CO HC
Diesel Smoke Emissions AFR / Lambda Rich Mixture O2 NOx

Take a Gas Quiz 

Catalytic Converters

Engine Faults


SOx & PM


Petrol Exhaust Gas Analysers Q & A

Why do I need a Gas Analyser?

If you think about the Engine as a Power Plant the only way to see if it is burning its fuel fully, is to monitor the smoke coming out of the chimney. This relates straight to its fuel consumption and performance. Automotive engines make no difference. The only way to see if the engine is economical and performs to its best is to check is it burning the fuel completely. In times when petrol price tends to go only high, economy is one of the best things you can give to your customers. Besides, a Gas Analyser is the only tool that can prove you have done a proper Tune-Up! The proof of the pudding is in eating it!

How many Gas Channels?

Simply put, the more the merrier. 4 Gas (CO, HC, CO2 and O2) is probably the best for most workshops. If you are in to “hot engines” or “performance tune-up” using Dino equipment, only then the 5’th gas ( NOx ) is a must.

Do not be tempted to get less than a 4 Gas Analyser. With any missing gas channel, you will be missing part of the diagnostic capabilities a 4 gas analyser provides.

4 Gas Analyser VS (any) Lambda Sensor:

Don’t be fooled by the advertisements! You can use Lambda Sensor/s to MONITOR a well tuned engine. In the end of the day, this is what the engine manufacturer’s use. But there is no way you can rely on a Lambda Sensor ALONE to “hot-tune” an engine or repair any emissions problem. Remember you can get Lambda=1 under different circumstances and with different gas values. (Clearly Rich mixture of HC = 1547, CO = 3.5, etc. etc. can still give you Lambda=1).

What to look for when choosing a Petrol Exhaust Gas Analyser?

  • First and foremost is back up service and maintenance. Most Gas Analysers have to be calibrated (or at least checked) to maintain optimum accuracy at least once a year.
    You don’t want to get something that no one can service or repair if needed. User maintenance (on modern units) is usually down to changing the filter/s when necessary.
  • Is it DOT/MOT tests capable?
  • Does it have Automatic vapour/water extraction?
  • Are the digits clearly visible when away from the machine (at least 2 metres)?
  • Can it Record the gas values for later evaluation?
  • Does it have Diagnostic capabilities?
  • Does it provide any Help when you get stuck for any reason?
  • Does it have a Customer Database to save their results for later printing or evaluation?
  • Does it have acceptable printing capabilities? Some print on small sized paper.
  • Can it include your Customer names in the Print outs?
  • Can it be Upgraded later to 5 Gas if necessary, and what is involved?
  • Can it measure also CNG, LPG (i.e. natural gas fuels)
  • What More does it have to offer, compare to other makes and models?
  • Is it reasonable priced for what it has to offer?

Diesel Emissions Testing - read here


Automotive Equipment - in tune with the Future

Crypton Diagnostic Equipment - Automotive Diagnostic Workshop Equipment as used by Dealers and Garages

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