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Discussion Starter · #1 · (Edited)
I need to smog my street car (MkII GTI with a built 2.0L 16V) again sometime in the next week at a CA Test Only station. Last time my CO# was average, my HC# was significantly above average but still well within spec, but my NO# was very nearly a fail (1016 PPM meas vs 1021 PPM MAX).

Last time I smogged the car I changed the oil a day or two beforehand, and made sure to try and get the car and the cat nice and hot before the test (drove around for about half an hour beforehand), and the car still almost failed the NO# part of the test.

Since it was so close last time, despite the above, I am looking for additional tips or tricks that can be done to try and help pass the test. I have heard that running higher octane fuel (e.g. 100 vs normal 91), or adding methanol or E85 can help. Any truth to this? What other tricks and tips do you recommend that could help lower my car's emissions numbers?

P.S. I have dumped a bottle each of STL fuel system cleaner and injector cleaner into the tank to try and help clean out the fuel system. Is that likely to hurt the readings? Should I try and run the fuel tank almost empty before filling up to try and purge the fuel system of fuel system cleaner, or is it in such small concentration that it is unlikely to affect the readings?
 

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Trogdor
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915 Posts
Misfires and rich running make for high HC, high combustion temps make for high NOx. CO basically correlates to fuel mixture.

So if you have good CO but high HC, you're misfiring or at least suffering from incomplete combustion. One way to make the engine run smoother is to retard the ignition timing a bit.

Likewise, retarding the timing will help NOx in a big way.

If I can make a carbureted rotary pass smog with nothing but a $30 converter and a check valve, you can make a 16v VW pass. :)



Speaking of $30 converters. If you have a cheap converter (rhymes with Batco) they often will fail NOx right out of the box. Usually they are junk after two years. Put a new one on if it meets this description.
 

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Discussion Starter · #3 ·
Techtonics high-flow cat approx 4 years old, but w/ only 9,000 miles.

Here are the detailed emission results from 2 years ago:

15 mph (1979 RPM):
CO2(%): Meas 12.80
O2(%): Meas 2.86
HC PPM: Meas 85 (Ave=41, Max=148)
CO (%): Meas 0.14 (Ave=0.13, Max=0.89)
NO (PPM): Meas 17 (Ave=399, Max=1191)

25 mph (2325 RPM):
CO2(%): Meas 13.50
O2(%): Meas 1.89
HC PPM: Meas 76 (Ave=29, Max=123)
CO (%): Meas 0.11 (Ave=0.11, Max=0.69)
NO (PPM): Meas 1016 (Ave=332, Max=1021)

Interestingly, NO (PPM) was super low at 15 mph, and almost fail at 25 mph.
 

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Trogdor
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That's to be expected, since they're loading the engine more at "25mph" than at "15mph". NOx production is tied to engine load (combustion temps, remember?)

I'd ring up Techtonics and ask who supplies their converter cores. If it's Catco, get a new converter and take about 5 degrees of ignition timing out. If they won't say, take 5 degrees out anyway and cross fingers.

edit: Those numbers actually look identical to my late '89 Golf (8v) when I had it tested at 155k or thereabouts. We have the IM2525 here, 25 seconds at 25mph, so it's probably the same procedure or Close Enough. When I tried running it at 210k, two years later, it blew NOx like you wouldn't believe. So I put a $30 converter on it to replace the OEM one, and it practically baselined the test. It only had to pass once, since I knew I was getting rid of the car soon... and I doubt it would have been around in 2011 anyway.
 

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I found out that 2 bottles of rubbing alcohol per full tank will reduce NOx significantly. Retarding timing helps too, but if it is not within spec, I am not sure what they will say.

Piers, give me a call when you have time.

George
 

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Where is your cat? Cats work better being hot, if its on the tailpipe, it might not be getting hot enough.


I'm not sure that will reduce NOx though... I just know it helps.
 

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150 K Right 4 Into Truck Dust
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A good friend, some beer and a few$$$$

PASSED.

It still is that easy, just gotta be in the know;)

Bill H.
 
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