It's that time again to get the car smogged. Last time around with the exact same
setup (see mods list) the results were:

15 MPH
1952(RPM) 14.6(%CO2) 0.0(%O2) 50,9,49(HC PPM MAX,AVE,MEAS)
0.48,0.02,0.16(CO% MAX,AVE,MEAS) 414,57,32(NO PPM MAX,AVE,MEAS)

25 MPH
2162(RPM) 14.7(%CO2) 0.0(%O2) 34,7,25(HC PPM MAX,AVE,MEAS)
0.45,0.03,0.01(CO% MAX,AVE,MEAS) 701,50,6(NO PPM MAX,AVE,MEAS)

All I did for the above test was swap the OBDII PCM for the OBDI. Both PMCs are
programmed the same, except the OBDII is ignoring the KS since I don't switch it
out for the smog test. I have a 160 themostat, TB bypass, and dyno tune program.

It's the HC where I'm too high and would like to know things I can do to lower
the HC. I would imagine a stock thermostat would do it but I would like to know
if there are tuning and/or other non-wrenching ways to get the HC down.

Here is the old post when I passed smog back in 2005:
https://www.camaroz28.com/forums/sho...d.php?t=416331

 

Sorry I don't have any suggestions, your numbers are really good already. You'd easily pass here in Houston. What are the limits for HC and NOx where you are?

 

Unplug one injector. They don't care if it's missing.
Lived in LA for 9 years but it has probably all change since '96.

 

The HC limit is 50 ppm for the 15 mph test and I was 49 ppm measured. NOX is
414 ppm max and I was 32 ppm measured. It's only the HC that I need help with.
My numbers except for HC are very low.

I'm sure a stock thermostat would help, but I would like to know if there are
other options to tearing things apart.

Any one else have an idea on what to do??

 

new o2's, lower injector pulses, decrease fuel pressure.
at least thats what the smog guy told me today.

 

I wish people would state their results on here. Did these these adjustments work. My HCs and CO2s are high as hell 191/158 1.1/1.5% with new cat and O2s and anything would help. How much does oil/coolant temperature matter?

94 Z28 5.7 no engine mods.... yet.

 

"sykodave" has not been back to this site in almost 2 years.

You mention your "CO2" is high. That's not a pollutant. They just measure it to make sure you aren't injecting some other materials into your exhaust. The pollutant is "CO".

What is the basis for you numbers - e.g. 191/158 = measured/max allowable?

High HC and CO (if that's what you mean) generally result from running rich.

 

Yah I knew that about the co2 my little finger brains just do their own thing sometimes. Thats the result. 15mph/25mph hc 191/158 co 1.10/1.58

I got into tunercat and checked out a few things. Knocks were up in the 6-7Ks. One thing the guy at smog said is he was having trouble getting it to warm up. I told him that sounded like a weird complaint and he told me that if it can't get up to a strong running temperature then it will run rich trying to warm up. So I brought the fans on oil temp contstant up to 210F overwriting my summer 190F and my coolant temp tables up a bit too. Guage actually runs up to about 200F now after beating on it good 180F normally. So thats out of the way.

Now about those knocks. It seems they started in the spring when I put a stock program (based on vin) in it and I only adjusted the temps and skip shift since then. I noticed a bit of a loss in power and freescan showed me those higher knock counts. So I advanced the closed tps spark advance up from the stock 20-25 at lower RPMS up to 30-36 with the uppers tapering off to 45.

Power is back and the knocks are down to about 1K during a 5 minute idle and they don't go up until romp on it a bit running around the block a couple times. Even then at best I was able to get it up to 2200. Are those good knocks readings? Who knows but a hell of a good improvement all around.

So does it sound like the timing advance and higher running temperatures will get those high numbers down or will I just waste $30 going for a retest?

Thanks

 

Yes, running cold causes incomplete combustion, increasing CO and HC. NOx will drop. It would have to be running very cold to produce numbers as high as you indicate.

You appear to be referring to the "knock count" numbers as "knocks". That number is not important. What is important is the knock retard. If you don't have knock retard, you don't have a problem with knock. The knock count is a number that constantly increments, based on the PCM seeing engine operating conditions that MIGHT cause knock. But it does not trigger knock retard unless the knock sensor has actually picked up knock at some point recently.

The knock count will contine to increment upwards until it reaches maybe 60,000 then reset to zero and start increasing all over again. It isn't the number in the field that is important - it is how fast it is changing, and whether there is any actual knock. It isn't unusual to see the knock count increment by 3,000 counts on startup for example.

You are concerned about a problem that does not exist.

 

Yah it was running pretty darn cool. At Modesto temperatures of 115f in the summer I have to make some compromises. Those compromises bit me in the butt since it is January. Smog was due in July so that tune worked fine last time. :-) I should have just tuned for that before I went but I've learned more this way I guess.

Rains it pours. EGR just died. Cheep BWDs are a no-no I hear. After replacing it I shall find out if I got those HCs and COs down with the warmer operating temperatures.