By Barry Gersten. We see it happen all the time. A driver complains about poor gas mileage. No codes are set. Is there a problem that can be fixed? Or, is the driver just hoping for a solution we can’t provide? Extensive testing of the engine, fuel system and ignition system may reveal that fuel injector service, a tune-up, or some engine repair is needed. However, it is much faster and easier and more professional to simply probe the tailpipe exhaust gas and know how to proceed without even raising the hood.
Test Exhaust Gases for
- Driveability Diagnosis
- Repair Verification
- Confirm Manufacturer’s Specifications
Which gasses should be measured and what would it reveal
HC – Raw, unburned fuel. Under 100 ppm is good.
O2 – Oxygen. Less is better, more indicates problems with A/F Ratio, intake leaks, misfires. Look for 1% or less.
CO – Fuel that has not been completely burned. Indicates fuel mixture, rich/lean. Usually, under 0.5% is good.
CO2 – Audit gas, how complete is combustion. More is better. Look for about 15% in a good running engine.
NOx – Oxides of nitrogen. Too much implies faulty egr, high engine temp, serious carbon build-up, over-advanced ignition timing or a failing catalytic converter. Expect zero NOx at idle, and less than 500 ppm under load.
Measurement of exhaust gasses will improve customer relations
- Customers appreciate the higher level of technology offered at a shop using Exhaust Gas Analysis.
- The nature of the driveability repair market makes the use of a 5 gas analyzer a very good idea.
- Very often diagnosis is made without raising the hood… very impressive.
The engineers in Emission Attainment areas know what they are doing.
For Driveability Testing Commit to Measuring all 5 Gasses. They ALL matter.
Quick Solutions to Driveability Concerns
We see it happen all the time. A driver complains about poor gas mileage. No codes are set. Is there a problem that can be fixed? Or, is the driver just hoping for a solution we can’t provide? Extensive testing of the engine, fuel system and ignition system may reveal that fuel injector service, a tune-up, or some engine repair is needed. However, it is much faster and easier and more professional to simply probe the tailpipe exhaust gas and know how to proceed without even raising the hood.
Ignition system problems resulting in a misfire always mean that a charge of air and fuel leave the cylinder unchanged. The Gas Analyzer will show high HC (unburned fuel) along with high O2 (air). When the other gasses are normal just find the cause of the ignition failure and don’t waste time looking for fuel problems.
Another example of “driver complains about poor gas mileage”. No codes are set. Same questions for us – Is there a problem we can fix? How do we start to figure out how to help? Extensive testing of the engine, fuel system and ignition system are not necessary. Simply probe the tailpipe exhaust gas and know for sure how to proceed without even raising the hood. In this case all the gasses are normal except CO, which is high at 3.5%. Normal CO is usually less than 0.5%. We can now proceed to solve a “Too much fuel” problem.
Other examples are very similar. Reading the exhaust gasses makes you the smartest technician in the neighborhood. The Best Driveability Pros make regular use of an exhaust gas analyzer.
For health reasons large cities with the potential for high levels of smog usually require automotive exhaust gas testing to minimize pollutants which contribute to ground level ozone. NOx is formed when engine combustion temperature gets excessively hot. In the presence of sunlight NOx will change to ground level ozone. Ozone is very reactive and even in very small amounts can cause eye and lung irritation
Ask the Right Questions – What concerns are important enough to influence my decision?
- Is the instrument really portable, will it fit comfortably in one hand
- Is it necessary to connect the instrument to the vehicle battery or is it self-powered
- How will exhaust gasses be removed from the vehicle interior
- Will it be necessary to use Calibration Gas to calibrate the analyzer
- Can the instrument show air/fuel ratio and Lambda
- Does the instrument have “Memory” to save test data for comparison and analysis
- Is the instrument able to read Propane and CNG for my fleet accounts using alternative fuels
- Can the pump be turned off while the bench stays on so the analyzer won’t need a warm-up period each time it is used
- Who makes the BENCH? The bench is the central measuring part of any automotive gas analyzer. It is best when one company is responsible for manufacture of the entire instrument
- What about cost of ownership as well as initial cost. With fragile instruments expect a recommended “Maintenance Agreement”
- Can the instrument be used for Diesel Exhaust Testing – New rules involving Diesel Exhaust are almost here
- Are all 5 gasses really measured or is it really a 4 gas Calculating a fifth gas
- Is the instrument Computer Compatible to Graph Gasses
- What about Training and Reference Materials
- Is Helpline Support included or charged for, or not even available
- When the O2 Sensor wears out (normal maintenance) will the instrument still function showing the other gasses or will it shut down pending Sensor replacement
Automotive Scope Applications. Call them at 888/717-1333 or check out their website at www.labscopes.com.