2001 F-body Emissions Test

[joecar]

I went today for my 1st CA smog test on this car...

Results:

HC @ 15 MPH (1271 RPM): 2 ppm (allowed 50 ppm) -> pass
HC @ 25 MPH (1178 RPM): 1 ppm (allowed 34 ppm) -> pass

CO @ 15 MPH (1271 RPM): 0.03 % (allowed 0.48 %) -> pass
CO @ 25 MPH (1178 RPM): 0.02 % (allowed 0.45 %) -> pass

NO @ 15 MPH (1271 RPM): 679 ppm (allowed 414 ppm) -> fail
NO @ 25 MPH (1178 RPM): 464 ppm (allowed 701 ppm) -> pass

Please, any ideas...?

[cme265]

no(x)..... high combustion chamber temps....timing? lack of EGR.....high octane fuel?....the failure of high NOX on an e-test is the result of high combustion chamber temps.....i assume CA does the same IM240 test that colorado does?

[joecar]

G'day cme265,

2001 F-body came without EGR.

Using stock timing, minus a little at peak torque.
Using 91 octane fuel.

Using 180*F thermostat;
Fan Low On = 208*F
Fan Low Off = 200*F
Fan High On = 218*F
Fan High Off = 208*f
Should I set the turn on temps lower...?

Should I run a little richer (looks like I have room for this since HC/CO are very low), as this would lower combustion chamber temps...?

Yes, I do believe it is the same IM240 test.

Thanks,
Joe
:cheers:

[cme265]

well, i'm just thinking out loud, if you're running open loop, i would think if you richen up the mixture at that point it should help on the nox, just don't go to far as co will go up, give it a try, what's the worst that can happen, fail again?

[joecar]

I'm running closed loop, my car is all back to stock.

The test seemed to me to be light/medium load at 15 MPH (car seemed to be holding 2nd gear), so the PCM would have been in closed loop, I imagine.

If it's in closed loop, then I would have thought the AFR was in the right range for the cat efficiency for NO and HC/CO.

When I log on the street, I see around 0-2% LTFT, and HO2Sx1 voltages appear to be switching (altho not quite as high/low as I would like).

I'll change my front O2 sensors and try again (what's the worst that can happen...?)... :D

Thanks,
Joe
:cheers:

[cme265]

here in colorado we don't get the detailed report, just overall pass/fail so this is new territory for me, i'll see if i can bounce this off of some friends at work and get a collection of ideas, but either way post it up when it passes, curious to see what you had to do without an egr valve.....

[cme265]

don't know if this applies to 01 f bodies, but about 9 months ago i got a letter from gm stating the converters on my 02 f body were going to be covered for 10 years/100k miles, might be worth checking out?

[v8vegaman]

:notacrook: Could it be as simple as a thermostat change? Are you running a lower temp? It's probably a dumb answer but old school is still in effect regardless of year, engines are engines.

[joecar]

don't know if this applies to 01 f bodies, but about 9 months ago i got a letter from gm stating the converters on my 02 f body were going to be covered for 10 years/100k miles, might be worth checking out?OK, I'll check this out. :cheers:

[joecar]

:notacrook: Could it be as simple as a thermostat change? Are you running a lower temp? It's probably a dumb answer but old school is still in effect regardless of year, engines are engines.I have a 180*F TS, but good thought. :cheers:

[joecar]

I got a temporary tag from DMV so I have until Oct 31st. :cheers:

[cme265]

carbon build up? if fuel in CA is anything like it is here, it sucks

[v8vegaman]

:notacrook: What did you end up finding out on this?

[joecar]

I'm still playing with this, I will know this weekend.

[v8vegaman]

well I could be wrong but high NOX is usually caused by LOW temps in the combustion chamber not high, the manufacturers run these engines stock at about 210 to 220 F* to improve the NOX and as performance people we like to see it lower like 190ish but the NOX will go up, you mentioned the 180 thermostat, I'm not trying to beat a dead horse here but a 180 thermostat WILL cool the combustion chamber down, that is the intent of the lower thermostat. Lower combustion temp=higher NOX, I am curious though to see if the NOX can be tuned out or if it just a funtion of heat so I'll keep watching.:cheers:

[joecar]

When I smogged a few weeks back, I was running on the original NBO2 sensors (84K miles on them), and the engine was fairly hot.

But I am considering what you're saying, I am bumping the fan temps to 210*F.

I want to run in CL, so I replaced the front NBO2 sensors.

[joecar]

Finally passed (moderate HC/CO/NO):

HC @ 15 MPH (1285 RPM): 25 ppm (allowed 50 ppm) -> pass
HC @ 25 MPH (1278 RPM): 5 ppm (allowed 34 ppm) -> pass

CO @ 15 MPH (1285 RPM): 0.23 % (allowed 0.48 %) -> pass
CO @ 25 MPH (1278 RPM): 0.07 % (allowed 0.45 %) -> pass

NO @ 15 MPH (1285 RPM): 165 ppm (allowed 414 ppm) -> pass
NO @ 25 MPH (1278 RPM): 67 ppm (allowed 701 ppm) -> pass


Compare with previous results (very low HC/CO, excess NO):

HC @ 15 MPH (1271 RPM): 2 ppm (allowed 50 ppm) -> pass
HC @ 25 MPH (1178 RPM): 1 ppm (allowed 34 ppm) -> pass

CO @ 15 MPH (1271 RPM): 0.03 % (allowed 0.48 %) -> pass
CO @ 25 MPH (1178 RPM): 0.02 % (allowed 0.45 %) -> pass

NO @ 15 MPH (1271 RPM): 679 ppm (allowed 414 ppm) -> fail
NO @ 25 MPH (1178 RPM): 464 ppm (allowed 701 ppm) -> pass


Conclusion:
It seems that it's now running slightly richer than stoich,
the HC and CO are increased and the NO is decreased...
the balance between HC/CO and NO seems very fine.

Was previously getting 21 MPG, now getting 17 MPG... :bash:

[2002_z28_six_speed]

Thats a huge difference in MPG!!

NOx def from the AFR.