WS7 Exhaust Gas Analysis(Petrol)

In this test, we use an Exhaust Analyzer, stick it in the tail pipe and run the engine. 

Exhaust Analyzer should be warmed up and recently calibrated. That also means we have to expose the tip with fresh air as possible for it to calibrate correctly.

This analyser is integrated with a display computer, which essentially shows all the main gases created after combustion: HC, CO, CO2, O2 and NOx

(picture)

Combustion chemical react equation(normal, "perfect" condition) 02 + N2 + HC => H20 + CO2 + N2

"Real pollution with sunlight radiation and with real air(partly polluted) 

Polluted air + HC + sunlight => CO + NOx + HC.

Combine the two possibilities we have such gases as exhaust gas: 

HC(<100ppm): unburnt fuel(vapor) after combustion

CO(<0.5%) : Toxic gas created by combustion, the leaner and more efficient combustion the less CO created.

CO2(>14%): combustion's compression efficiency rating gas, not really toxic but not a life-supported gas.

O2(>1% is considered lean)

NOx(very toxic): Caused by lean mixture, makes longer burn time, heat is maintained longer so N2 and O2 have higher chance to become NO or NO2, which are commonly called NOx.

With the analyser recalibrating, clean air is to be sensing:

Gas	Amount	Verdict
HC	7ppmvol	Just some still caught on the tip of the EA, there is none of this thing on air.
CO	0.00%	No combustion on air
CO2	0.00%	No combustion on air
O2	20.98%	O2 takes up about 21% of air, N2 takes the rest 79%, there is still 1% of smth else.

Start cold engine idling:

Gas	Amount	Verdict
HC	1839ppmvol	Rich mixture is drawn for cold starting, can't burn them all but will make the car heat up faster.
CO	4.465%	Very high resultant from very rich mixture
CO2	9.88%	Low compression, too much fuel, lack of air, low efficient combustion.
O2	9.26%	Still a lot of normal air in the tail pipe

Warm idle:

Gas	Amount	Verdict
HC	30ppmvol	Leaner mixture control for warm idle by ECU
CO	0.02%	Leaner mixture produce a lot less CO.
CO2	14.33%	Leaner mixture, higher compression, more efficient combustion.
O2	0.78%	Good reading, not so lean or rich.

Warm 2500RPM

Gas	Amount	Verdict
HC	8ppmvol	Only get a little bit richer when accelerating, the rest is quite lean when 2500rpm stays
CO	0.052%	Engine runs a little bit richer, producing a little bit more CO
CO2	14.65%	Lean mixture at cruising speed, high compression, high CO2 produced.
O2	0.34%	A little bit richer mixture for keeping it at 2500rpm

Rich mixture extra Propane, LPG or carburetor cleaner

Gas	Amount	Verdict
HC	197ppmvol	Rich mixture, but not quite high because it is flushed out by the extra gas
CO	1.859%	Pretty high CO by trying to burn richer mixture
CO2	14.07%	Extra gas are easy to burn, maintaining the level of efficiency
O2	0.79%	Extra gas are easily burned so they burnt off with the air, leaving a little bit air left.

Running air leak

Gas	Amount	Verdict
HC	959ppmvol	MAP says high while TPS says Idle, ECU struggles to give the right amount of fuel
CO	0.175%	It's extra lean mixture running. Fuel are too atomized so vapors quickly instead of burning with air
CO2	7.75%	Low efficient combustion, not enough fuel, too much uncompressed air.
O2	9.65%	Too much air because there is a leak.

High snap acceleration:

Gas	Amount	Verdict
HC	2313ppmvol	ECU puts a lot of fuel into acceleration
CO	3.947%	Rich mixture produce a lot of CO
CO2	12.59%	More CO, less CO2
O2	0.58%	Rich mixture, less O2 left.

One spark plug disconnected

Gas	Amount	Verdict
HC	1291ppmvol	Fuel in 1 cylinder is not being burnt
CO	0.5%	Low CO because this condition does not enrich overall mixture rating
CO2	12.4%	Less combustion, less CO2
O2	7.61%	Less combustion, more unburnt O2

One injector disconnected

Gas	Amount	Verdict
HC	217ppmvol	ECU detects a lost injector, try to increase fuel for the rest to compensate for power loss.
CO	0.2%	This condition temporarily doesn't enrich the overall mixture
CO2	11.68%	No more fuel to burnt, less CO2 produced.
O2	7.61%	Very lean combustion @ one cylinder repels a lot of O2

Electrical load(power steering, air conditioning)

Gas	Amount	Verdict
HC	56ppmvol	A little bit richer as ECU raises the idle to compensate for power loss due to power steering or air conditioning.
CO	0.6%	A little more fuel, a little more CO
CO2	14.7%	Still efficient
O2	0.55%	Normal combustion, not too lean or rich.

After testing, we round up some assumptions:
1. What differences would we get with or without CAT converter:
Most of CO and NOx are turned into CO2 and H2O by the CAT converter, without it, we will get more CO and NOx instead.

2.Light off point means the temperature at which the CAT converter will get melt down. When HC or Diesel Vapor gets down to the CAT, it operates at a very high temperature already to eliminate NOx and CO. This could ignite the fuel and raise the temperature up to which will actually damage the CAT converter.

3.Instead of a huge gas analyzer, we only need a small lambda sensor on our car, for narrow band it goes 1-4 wires. 2 for heatings, 2 for signal. More than 5 wires O2 sensor is a wide band.