Fake emissions test
 

How do I fake an emissions test ? Can it be done ? I hear all the time of how that hot rodders will have a buddy rig the numbers - so apparently it is easy to cheat.

Now, the reason that I am asking, is that my car failed inspection for an exhaust leak. I was handed the inspection form with all the test numbers.
I fixed the leak and went back a few days later. They drove the car in and ran the test over again.
I passed.
However, when I checked the numbers, they were absolutely identical. Everything was absolutely identical - even the RPM speeds ( 2,591 high speed and 690 for the low speed test.)

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.

How can car shops get away with this sort of thing ? Is it really so easy to just punch in any old numbers in an emissions test ?

Emissions is one part of Texas' Annual Vehicle Inspection, safety is another. Your car failed for safety reasons, not emissions. Your vehicle passed the emissions portion of the test the first time. It's not at all surprising it passed with the same numbers the second time around. (They redo the whole test the second time around because they're required to by law. 'Cause you might have done something stupid at the same time you repaired exhaust leak- like remove the guts of the catalytic converter.)

You can go to independant shops and have a 5 gas analysis done. I was looking into this when I was going to do some engine work. They said they'd charge me like $25. Thats the best I could find. I couldn't get the state to just do them for me for free haha. The emissions place should have a list of local shops that they can give you. They give this to people who fail and need to bring their cars in.

They have an additive at the autoparts store that can lower emissions for emission testing.

Test drive is right. Here's the page for exhaust from the link he provided for TX.

I guess I'm not understanding how this all works. A sniffer gets placed at the end of the tailpipe and measures the amount of pollution right ?
If there is a pretty good size hole somewhere in the exhaust system, the reading will be off because a lot of the pollution is spewed out the hole - is that right ? :)

Since the test is supposed to be done over*, why are the results absolutely identical ? I wanted to stress that even the RPM was identical in the second test - is this just a generic number or were they really testing both times at exactly 2,591 RPM ?

*[/QUOTE=(They redo the whole test the second time around because they're required to by law. 'Cause you might have done something stupid at the same time you repaired exhaust leak- like remove the guts of the catalytic converter.)[/QUOTE]

Cd -

I'll take a guess on the assumption that the exhaust leak was after the catalytic converter. The "proportions" of pollutants were the same at the exhaust leak and the muffler tip, therefore the readings were the same for both tests.

If the test measured the "pressure of the exhaust", I think that specific number would be different.

Does that make sense?

CarloSW2

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 :p

There's no reason to assume there was a "pretty good size hole". A pin-hole leak would be a failure. (The pin-hole leak would become a serious leak long before the next annual inspection.)

The lower rpm - 690 rpm - is just measured warm idle. The manufacturer's specification is no doubt something like 700 rmps +- 20 rpm. Baring gigantic holes in the exhaust or a plugged exhaust, no change is almost to be expected.

The upper rpm no doubt meets another specification. Maybe 2600 rpm +-50 rpm. The shop would use a tool to set the engine to temporarily idle within the specified range. It's a little surprising that it would come out to be the exact same number, but if you had the shop do multiple tests one right after the other the margin of error probably wouldn't be all that large. eg. Do a hundred test and the upper rpm might be 2,587 +-17 rpm or it might be 2,603 +- 19 rpm.

The car failed the inspection for safety reasons. The safety problem was fix and the car passed. With out more info, I'd give the shop the benefit of the doubt.

You did not fail for a safety reason

An exhaust leak by itself is not a safety issue unless it leaks or is directed into the passenger compartment.

You failed because it was not possible to give an accurate emissions test. In the US emissions are measured on a grams per horsepower ratio. If you have an exhaust leak it allows some emissions to escape their collection and detection instruments. This will reduce the grams per HP measured and if a big enough leak occurred it would allow a car that would fail to pass.

Moral of the story: if you can make a big enough leak that they can't detect or fits in a loop hole you will always pass.