I've never failed emissions before (even with DP Tuner)... pretty frustrating to say the least. I did, however, found out that I have pretty good size hole in my exhaust right above the rear axle. I bet that is the culprit... Opacity was at 98.7, limit is 30

I would have thought a hole in the exhaust would have made opacity reading better than normal.

Can someone explain what Opacity is when referring to these emission tests?

 

Opacity is how thick the smoke is. They use it to determine the particulate your pumping into the air. Yours is real thick. If you can't find out why, then maybe Jody can make you a tune to clean it up, run alittle leaner. The hole means nothing, except where I am it is an auto fail.

 

was that in stock tune?

 

98.7 percent of the light was blocked by the exhaust gasses. That is virtually impossible. Their testing equipment had to be broken or calibrated incorrectly. Think of the diesel truck sled pulls.....the smoke coming out their stacks would measure in the 95-98% range. Was your truck pouring smoke like that?

 

There was no black smoke exiting the rear of the truck during the test. Besides, when have you ever seen black smoke come out of the exhaust pipe when in park. No load on the motor. I think the hole in the exhaust is why I failed... it has to be.

Yes, it was in stock tune.

That's exactly what I am thinking too... like I said above. The ONLY time I get black smoke is when I am under load. Not sitting in park and revving the motor. These emission tests are just an excuse for them to get more revenue! And the crappy part about it is the people running the tests have no clue as to what the results mean. A number that high should have raised some red flag... and maybe re-run? Or check the machine?? Not send me on my merry way and tell me that I need to have a certified technician diagnose the problem before re-testing.

 

id goto another station and if you pass with considerably less numbers then id get in contact with the agency overseeing smog stations....

 

I had the exact same thing happen last month in my Mercedes 300. I was the first diesel test of the day on a cold, damp morning. Luckily the testing agent knew what was going on. He said sometimes on the first test of the day on a cold morning the mirrors in the machine will fog over resulting in a high opacity reading. He ran the test a second time and the result was in line with previous years results and passed.


edit: I just remembered he also went into the office and got a Q tip to clean the mirror before re-testing.

 

Talk about "smoke and mirrors" in state controlled emissions testing... that was great contribution of experience to this thread that is sure to help future members! Reps sent.

 

I can't rep Bigb, as I have to spread it around some more before repping him again, but as Y2K stated, very good addition of experience in this situation.

 

I guess my explanation was bad. Opacity at 98% would be a slight blue wisp of smoke at idle . My failed with 100%, and you could barely see the smoke. Fixed it up and it passed no problem, but was clean as a whistle at idle. So Opacity is how thick the smoke is, but 100% doesn't mean you can't see threw it. Its actually quite clean at 100%. The factor is un burnt fuel. The race trucks smoke is a whole lot of un burnt fuel and is up in the 300 to 400% range on the opacity meter. Basically there saying if your truck meets the 30%, then it is running and burning the fuel well enough to pass the test. Your not burning enough of the fuel. That could be lots of things, sensors, boost, weak pump or injectors, low compression. Even crappy fuel. There is nothing wrong with there test, other than its too strict. lol

 

Thanks for this explanation! This makes a lot more sense. I plan on doing an oil change and getting the exhaust fixed as well as making sure the intake filter is clean. Then re-testing with the DP Tuner unplugged this time

 

I don't know what I was smoking that day... or maybe cuz I just got done working out. But I had my DP Tuner in 80hp tow mode when I had emissions tested!!

But before I have it re-tested I am going to fix the exhaust and do an oil change.

 

Hahaha, that explains everything. OOPs! Guy probably had fun testing it though. lol