so I fixed my smog issues with high nox..

[sil80phobia]

Just figured someone might find this useful.

So my 95 S14 failed smog last week, just BARELY. Bone stock except for Injen CAI. My car is EXTREMELY clean and well maintained, so it pissed me off.

Max allowable NOX was around ~700/736 ppm for idle/25mph tests. I was testing 710/745 .. just a hairs breadth from passing. Based on my calculations, I only needed a ~2% improvement to pass.

1. first thing I did was inspect the EGR setup. Not surprised to find the lower EGR vacuum line rotting. (pretty common as I've searched). So that and the FPR line was replaced with silicon tubing in short order

2. I had timing at 20.3 degrees when it failed. They allow +/- 2 degrees so I backed timing down to 18 degrees.

3. I unplugged a vacuum line and ran an entire can of intake/throttle body cleaner through the engine at 3000 rpm.

4. Drove around a week with a bottle of guaranteed to pass in the gastank (with 91 octane as I've read it helps lower NOX) for a week.

5. overinflated the rear tires to minimize load on the dyno. also had less than an 1/8 of a tank of gas and I emptied my trunk and took out my spare - not sure any of this did anything, but someone had suggested it - anything to get me that 2% margin I needed to pass!

6. changed my oil.. was due anyway.. all in the name of minimizing load on the engine..

7. drove the piss out of the car for about 20 min (nice sustained 5k RPM canyon run) prior to testing

The results blew me away. I was hoping for a 2% improvement on my previous 710/745 result. What I pulled off today was 77/92 !!! thats right.. 77/92, not a typo. Essentially 30 min of my time and $10 in stuff. Didn't touch my 02 sensor, left my original 165k mile cat on.

[unwed_transient]

very nice.

we californians have to sweat the crap out of smog unless we want to spend 200 bucks on a special.

my 89 ka-e passed with flying colors with only a 1/4 tank of 91 octane, altgough i didn't come close to those nox numbers though.

[drift freaq]

Originally Posted by sil80phobia

Just figured someone might find this useful.

So my 95 S14 failed smog last week, just BARELY. Bone stock except for Injen CAI. My car is EXTREMELY clean and well maintained, so it pissed me off.

Max allowable NOX was around ~700/736 ppm for idle/25mph tests. I was testing 710/745 .. just a hairs breadth from passing. Based on my calculations, I only needed a ~2% improvement to pass.

1. first thing I did was inspect the EGR setup. Not surprised to find the lower EGR vacuum line rotting. (pretty common as I've searched). So that and the FPR line was replaced with silicon tubing in short order

2. I had timing at 20.3 degrees when it failed. They allow +/- 2 degrees so I backed timing down to 18 degrees.

3. I unplugged a vacuum line and ran an entire can of intake/throttle body cleaner through the engine at 3000 rpm.

4. Drove around a week with a bottle of guaranteed to pass in the gastank (with 91 octane as I've read it helps lower NOX) for a week.

5. overinflated the rear tires to minimize load on the dyno. also had less than an 1/8 of a tank of gas and I emptied my trunk and took out my spare - not sure any of this did anything, but someone had suggested it - anything to get me that 2% margin I needed to pass!

6. changed my oil.. was due anyway.. all in the name of minimizing load on the engine..

7. drove the piss out of the car for about 20 min (nice sustained 5k RPM canyon run) prior to testing

The results blew me away. I was hoping for a 2% improvement on my previous 710/745 result. What I pulled off today was 77/92 !!! thats right.. 77/92, not a typo. Essentially 30 min of my time and $10 in stuff. Didn't touch my 02 sensor, left my original 165k mile cat on.

hehehe, you figured out my little secret for making what would be a gross polluter pass. In fact I had a test only car that came up gross polluter. I took it home and basically did a variation on what you did above, without putting any fuel additive in the tank. I took it back the next day and it passed so clean, the smog tech asked me what I do for a living, hahahhahaha, he was convinced I was a pro mechanic.

[IngS14]

can i do the same liek you guys to pass the smog on my s13 rb25det motor?

[crioten]

i didnt know s13's had rb's in them

i dont know if it will work, but you can try

[DP_Michelle G]

your rb powered s13 will never pass smog. without paying around 150 to 200 bucks for the smog

[-usmd-180sx]

really? i wonder why his rb powered s13 would never... ever pass smog.. hmm

[drift freaq]

Originally Posted by IngS14

can i do the same liek you guys to pass the smog on my s13 rb25det motor?

can we say TROLL!!! hahahhahhaha,

[balmo]

i just have a question with running a throttle body cleaner w/ a running engine. are there any adverse effects with doing this? how will the motor behave while doing so?

[BigVinnie]

Originally Posted by sil80phobia

2. I had timing at 20.3 degrees when it failed. They allow +/- 2 degrees so I backed timing down to 18 degrees.

Actually you are allowed -/+ 3degress from stock BTDC. I passed at 23BTDC. Although my hydro carbons were too high, I know the smog tech and we slammed the car into 3rd gear.... Technically I didn't legally pass, but only if I had an adjustable timing gear to adjust my cam timing. Would of had lower HC.

[drewford]

damn i need to try all this. i got a 1700/1483 on my NOX test. lol if only my SATs were that high. fuggit!! thanks for the tips.

[Lurkable]

If I try this on my KA (basically stock), does anyone think I'll pass CA smog test even though I have NO CAT and a blocked off EGR? Or am I just wasting my time...

[BOROSUN]

are you serious?

[MtxWrl]

well i failed horribly so imma go ahead and try ur lil trick and also replace my cat... i scored a 2670/1913 on nox..... everything else was just BARELY over.... so ya think that should do the fix?