Fake emissions test

[Cd]

Originally Posted by trebuchet03

Sounds like the first numbers were in spec, but it failed for the reasons above....

The operator getting paid $6.55/hr knew this - and knew that completing the entire test would take away from his time drinking mad dog 20 20 in the parking lot....

Just sayin

I needed that laugh ! Thanks.*


OK everyone :

My little pea brain thinks that if you have a hole in your exaust ( for example - just a hypothetical example let's say " half the size" of your exhaust pipe, that would mean that your readings would be 50% cleaner than if you plugged the hole because half of your emissions are spewing out the hole.

Right ?

Concerning the hole in my exhaust, it was just in front of the muffler, and around 1/8 " X 1.5" .

*By the way, the fellow that tested my car was named Bubba.
( I think it must have been Bubba's break time .)

[Cd]

[QUOTE=Cd;69463]
Now most of you are thinking " Why gripe - you passed the test ! "
But you see I actually care about how much pollution my car is pumping out.QUOTE]

I hope none of you here think that I am implying that you do not care about your cars pollution.
I just re-read that, and I think it could be taken wrong.

[TestDrive]

Originally Posted by Cd

My little pea brain thinks that if you have a hole in your exaust ( for example - just a hypothetical example let's say " half the size" of your exhaust pipe, that would mean that your readings would be 50% cleaner than if you plugged the hole because half of your emissions are spewing out the hole.

Right ?

Concerning the hole in my exhaust, it was just in front of the muffler, and around 1/8 " X 1.5" .

The test equipment takes a small sample of the exhaust gasses and calculates (an) emission ratio(s). eg Hydrocarbons in part per million.

If half of emissions are lost out a hole, but absolutely no ambient air is introduced (exhaust pressure > ambient air pressure) by the hole - up stream of the sample taken by the machine, the emission ratios will not changed. Of course exhaust pressure isn't all that high and with a hole half the size of the exhaust pipe some ambient air would surely be introduced - causing emissions ratio readings below what the car is actually producing.

A 1/8" x 1.5" hole in front of the muffler might have some small quantifiable effect on emission readings, but my best guess would be none. If your emissions readings were anywhere but the high end of the acceptable range, Bubba may well have simply decided that his time was better spent else where. (That presumes that the equipment allowed him to retrieve your previously stored readings? If so, I'd guess that it would only allow him to do that provided the VIN and/or registration number of the tickets matched.) Back in the late '80 early '90 in California, doing something like that would have put Bubba's inspector's certificate in jeopardy. Maybe Texas is more lenient? My earlier statement that they were required to redo the test was a surmise.

Your car failed because there was a hole in the exhaust.

Was it an emission issue? With a 1/8" x 1/5" hole, possibly.

Was it a safety issue? Maybe not at that instant. If your car doesn't have holes in the floor boards, you're pretty safe from carbon monoxide poisoning. On the other hand the hole will only get larger. Eventually (easily less than a year with short trips in a humid climate - parts of Texas) you have a loud, very leaky exhaust system that's prone to depositing large, nasty chunks of debris on the freeway. "Very leaky" and "debris" are both safety issues.

[ConnClark]

Okay,

I was wrong on one part. Its not grams per HP its grams per mile. http://www.epa.gov/otaq/cert/veh-cert/b00001a.pdf

It sure as hell isn't parts per million.

As I stated before any leak in your exhaust skews the results in your favor.

[Metrosexual]

I'm in washington state -so it may be different in your state, but the emissions test here will fail you if the CO+CO2 readings are below a certain percent -indicating a diluted exhaust stream. These specs may not be printed on your test form. if your engine is running well, the other gases that are tested may not change much, as there isn't that much to begin with.
What were the readings before and after?

[TestDrive]

Originally Posted by ConnClark

Okay,

I was wrong on one part. Its not grams per HP its grams per mile. http://www.epa.gov/otaq/cert/veh-cert/b00001a.pdf

It sure as hell isn't parts per million.

The pdf chart you're citing can be found at Federal and California Exhaust and Evaporative Emission Standards for Light-Duty Vehicles and Light-Duty Trucks | Cars and Light Trucks | US EPA where it clearly states -

The following tables of exhaust emission standards attempt to consolidate federal and California standards and implementation rates to facilitate comparison and to provide a one-stop resource for these emission standards. However, these tables are not a substitute for the official federal or California regulatory text. In addition, these tables do not reflect some emission standards, such as the federal cold temperature carbon monoxide standards and test procedures, or some optional standards that might apply to some manufacturers (e.g., small volume manufacturers). Each of the tables is potentially confusing without the accompanying Footnotes, Abbreviations and Definitions (PDF) document to help you sort things out (e.g., California calls cars "passenger cars" while EPA calls cars "light-duty vehicles").

The vehicle in question (a '93 Civic DX) is Tier 0 LDV (meaning a passenger car manufactured 1981 - 1993) and the very first line of data in the table applies. Since the car is over 10 years old, by federal standards it's exempt. But I assume Texas is expecting it to pass the 5 years / 50,000 miles standard.

In any case, footnote 39 of Footnotes, Abbreviations and Definitions (PDF) applies to both THC (Total HydroCarbons) and CO (Carbon Monoxide)

39. CERTIFICATION SHORT TEST (CST)

EMISSIONS FROM GASOLINE VEHICLES SHALL NOT EXCEED 100 PPM HC OR 0.50 PERCENT EXHAUST GAS CO AT IDLE AND 2500 RPM AT 4K MILES; COMPLIANCE STATEMENT ALLOWED (IN LIEU OF DATA)

Certification Short Test (CST) is also known as the Two Speed Idle (TSI) test. Which ever name you want to call it by, it measures HydroCarbons (HC) in parts per million (PPM). Read this Texas Department of Public Safety page Texas Emissions Testing Procedures and near the bottom you'll find.

What type of emissions test will my vehicle need?

El Paso, Travis & Williamson County Motorists
In conjunction with the annual safety inspection all gasoline powered vehicles from 2 through 24 years old which are registered or primarily operated in these emissions counties will be subject to one of the following emissions test.
1995 and older vehicles will receive the Two Speed Idle (TSI) test while 1996 and newer vehicles receive the On-Board Diagnostic(OBDII) test.

DFW and Houston/Galveston Area Motorists
In conjunction with the annual safety inspection all gasoline powered vehicles from 2 through 24 years old which are registered or primarily operated in these emissions counties will be subject to one of the following emissions test. 1995 and older vehicles will receive the Acceleration Simulation Mode (ASM) test while 1996 and newer vehicles receive the On-Board Diagnostic (OBDII) test.

If the car lives in El Paso, Travis or Williamson county, it was subjected to a TSI test. If it lives in the Dallas, Fort Worth or Galveston area, it was subjected to the more stringent ASM test.

If the TSI test was used, Hydrocarbons were measured in PPM. And if it was the ASM test?

Read this MOTOR MAGAZINE article -
http://www.motor.com/magazine/pdfs/051999_01.pdf
titled ASM testing getting a passing grade. If you're in a hurry, look at the table on page 3 of the pdf.

Originally Posted by ConnClark

As I stated before any leak in your exhaust skews the results in your favor.

Any leak? By a measurable amount? Do you have test data or can you cite a source to backup this supposition?

As I stated before: The exhaust system operates under positive pressure - above ambient atmosphere. If there is a hole, exhaust spews out the hole. Unless air enters the hole at the same time exhaust is spewing out (unlikely if the hole is tiny - quite possible if the hole is 1/8" x 1.5"), the emission ratios will not be affected. So far as I know, no testing equipment measures grams per mile directly. Grams per mile is always a calculated result based on a number of parameters. And some sort of emissions ratio always one of the required parameters in the calculation. An emissions ratio is the second to last step in each of the methodologies illustrated in this diagram - http://www.epa.gov/nvfel/methods/chemstry.jpg

[ConnClark]

Originally Posted by TestDrive

So far as I know, no testing equipment measures grams per mile directly. Grams per mile is always a calculated result based on a number of parameters. And some sort of emissions ratio always one of the required parameters in the calculation.

They also measure volume of gasses emitted from the tail pipe and from that plus the ratio of emissions gasses they can calculate grams per mile or grams per HP.

If it were solely based on the ratio of gasses detroit would just pump fresh air into the exhaust instead of spending a grand on a catalytic converter.

And with this info as I have stated before, any leak in your exhaust system will benefit you on your emissions test.

[cfg83]

ConnClark -

Originally Posted by ConnClark

They also measure volume of gasses emitted from the tail pipe and from that plus the ratio of emissions gasses they can calculate grams per mile or grams per HP.

If it were solely based on the ratio of gasses detroit would just pump fresh air into the exhaust instead of spending a grand on a catalytic converter.

And with this info as I have stated before, any leak in your exhaust system will benefit you on your emissions test.

But that seems to go back to the original question. The observed readings were identical for both tests.

Do you think that, based on the size of the leak + the accuracy of the readings yielded an accidental co-inky-dink of identical readings?

CarloSW2

[TestDrive]

Originally Posted by ConnClark

They also measure volume of gasses emitted from the tail pipe and from that plus the ratio of emissions gasses they can calculate grams per mile or grams per HP.

If it were solely based on the ratio of gasses detroit would just pump fresh air into the exhaust instead of spending a grand on a catalytic converter.

And with this info as I have stated before, any leak in your exhaust system will benefit you on your emissions test.

If ASM and/or TSI tests (The tests Texas uses on '95 and cars like the one in question.) measured the total volume of gases emitted from the tail pipe, your point would be made, but they don't.

From the previously cited Motor Magazine article on ASM Testing (pdf).

During an ASM test, only a portion of the exhaust gas is measured. To make the test fair for different-size vehicles, the limits are adjusted. During the test, the GVWR from the vehicle sticker is entered. Once this information is known, the limits automatically adjust for the test.

And before the test is run the year, model, engine size ... are entered. Please look at the actual test results cited in the above article. The readouts are all in either PPM or %.

If you still believe I'm mistaken, feel free to cite a reference or give a link to any reputable source supporting the contention that either ASM or TSI measures total volume of gases emitted.

[ConnClark]

Please look at the sentence just before your quote.

"Instead of being measured in concentrations, the gases are measured in grams per mile."