F-You Colorado! more emission headaches, I may loose my registration Options

[newto914s]

With the help of some of the great Colorado 914 guys(notably Mike and Chris W) i got my car to pass the e-check. Read about it here.
I thought everything was fine and dandy. With my 5 year collector plates on it I never have to worry about emissions again(bring on the SBC).
But in Colorado they have these white child molester looking vans that sit on the highway entrance ramps. They use a laser to measure the emission of all the car entering. I drove by one and got a letter in the mail. Now I have to bring my car to a state inspector for another evaluation or my registration will be revoked and a $100 fine imposed. Their's no way I'm going to pass now, with no Cat an no smog pump.
The irony is my car runs better than it ever has. F-U CO

[orthobiz]

Please explain: how does some roadside sniffer detect your emissions with a ?laser? And doesn't have to pull you over to go right to the tailpipe? How far away can they accurately do this?

Just seems beyond high tech.

Too bad that govt guy Scott met wasn't at the BBQ. We coulda swayed him over to the collector's side of things!

Paul

[Gint]

Please explain: how does some roadside sniffer detect your emissions with a ?laser? And doesn't have to pull you over to go right to the tailpipe? How far away can they accurately do this?

Something I dug up. I haven't even read it myself yet.
http://www.motorists.org/emissions/home/ho...-sensing-works/

[ArtechnikA]

Something I dug up. I haven't even read it myself yet.
http://www.motorists.org/emissions/home/ho...-sensing-works/

I read most of it.
Salient points are - they claim they can test a car a second.

With "better than 10% accuracy." (The way I read that, it means it's right 10% of the time. maybe they mean each reading is within 10% of its actual value - but that's not what they say.) Any way you look at it, 10% accuracy is pretty sucky - but they also claim "Inspect & Measure" programs have the same "10% accuracy" rating, so something is wrong with the reported data...

Something I have an issue with is tailpipe height - I get the IR absorption spectrosopy. I don't see how they can sense a raised 4x4 with a tailpipe 3' off the ground one second and a lowered 914 the next.

[jhadler]

With "better than 10% accuracy." (The way I read that, it means it's right 10% of the time. maybe they mean each reading is within 10% of its actual value - but that's not what they say.)

No, that's exactly what they say. 10% accuracy means that an indicated reading of 3500 ppm could be anything between 3150 ppm and 3850 ppm.

Any way you look at it, 10% accuracy is pretty sucky - but they also claim "Inspect & Measure" programs have the same "10% accuracy" rating, so something is wrong with the reported data...

10% is really not that bad. If you look at what they are measuring, and how they are doing it, 10% is really quite an impressive accuracy. As for the mobile system having the same claimed accuracy as the permanent testing stations? I don't know, it's possible that the they both have the same accuracy, but are based on different principles. I would hazard a guess and say that the mobile system is more maintenance intensive, and that there is more work required to keep it operating at that 10% level. The

Something I have an issue with is tailpipe height - I get the IR absorption spectrosopy. I don't see how they can sense a raised 4x4 with a tailpipe 3' off the ground one second and a lowered 914 the next.

They're not looking at the pipe itself, but the cloud behind the vehicle. Granted, a lifted 4x4 is likely to measure less than the 914 as the system no doubt is designed to look at passenger cars, and not big rigs.

Note: While I'm impressed with the design of the system, I'm not necessarily supporting the way it seems to be used.

-Josh2

[ArtechnikA]

No, that's exactly what they say. 10% accuracy means that an indicated reading of 3500 ppm could be anything between 3150 ppm and 3850 ppm.

What you have described is not 10% accuracy - it is 10% error. But it's semantics, mostly...

They're not looking at the pipe itself, but the cloud behind the vehicle.

But that's quite an issue. THE cloud behind THE vehicle - at 1 vehicle a second. How much of the leading vehicle's cloud is still in the air when I pass through right behind him?

[jhadler]

No, that's exactly what they say. 10% accuracy means that an indicated reading of 3500 ppm could be anything between 3150 ppm and 3850 ppm.

What you have described is not 10% accuracy - it is 10% error. But it's semantics, mostly...

In metrology, "accuracy" a crude term used in the statement of the uncertainty of the measurement. "error" is not a generally used term, although that is what it is widely interpreted as. What I would really like to know is what is the basis of their 10% number? 1-sigma? 2? 3? Makes a BIG difference on what the REAL uncertainty of the measurement is. And I wonder if they would even release that information. My guess? It's a 1-sigma statement, and at that point, 10% is not so great.

But that's quite an issue. THE cloud behind THE vehicle - at 1 vehicle a second. How much of the leading vehicle's cloud is still in the air when I pass through right behind him?

Agreed. And if a car is right in front of you belching a cloud of mosquito killing smoke, how well does the system compensate for the leading cars' contamination of your measurement? I would hope the sampling rate is high enough that it can average multiple measurements per vehicle pass, and be able to set a background level prior to the next vehicle passing by.

Getting back to the original topic, the numbers the system displayed on the vehicle in question showed a really high HC value. It didn't say if there was a background correction, but it did seem to have a radar gun measurement coupled with it, and it indicated that the car was -slowing- not accelerating. Okay, looking at the data, it did say that there were 8 samples for the given measurement, but how fast was the sampling rate? And it does not indicate if there's a background correction.

I dunno, I just plan to avoid the stations for time being... Right now they're not like photo radar (which can be placed anywhere), they are placed at specific locations, at specific times (check the website). Just don't go there...

A good idea, but may not be well executed...

-Josh2

[ArtechnikA]

...Just don't go there...

If by 'there' you mean 'Colorado' I agree.
I wonder if the Colorado Tourism Commission realizes how many people are starting to think the whole state is A Place To Avoid...

I was last in California 6 years ago and aside from the carne asada burritos I'm not sure why I'd go back. Colorado was longer ago than that - drove through part of the state on the way to PA when we moved here - just over 6 years ago.

So I gotta ask - if "10% Accuracy" means ±5% - what does "90% accuracy" mean ?

edit - left off the smiley... :-)

[jhadler]

...Just don't go there...

If by 'there' you mean 'Colorado' I agree.
I wonder if the Colorado Tourism Commission realizes how many people are starting to think the whole state is A Place To Avoid...

I'm torn on this one. On the one hand we need the revenue, on the other hand, there are a lot of tourists that I can personally do without...

Just spent last week in a very high tourist concentration, had a great time, but could definitely tell the locals from the yokels with little difficulty...

So I gotta ask - if "10% Accuracy" means ±5% - what does "90% accuracy" mean ?

Well, I would interpret their statement to mean ±10%. As for something that says "90% accuracy"? I would rack that up to something brewed up by a marketing goon that doesn't know anything about statistics or experimental measurements... Make it sound good to joe six-pack and they'll buy it.

-Josh2