Smog help: need to reduce HC

[Terry Burger]

Yet another question for the experts...

I almost passed the smog check, but failed the HC @ 25mph (I had 50ppm vs. 37 max allowed).

I did all the usual tricks (got it really hot, etc), and it came pretty close.

So my questions:

1) What impact does ignition timing have on HC? If I back out 6 degrees across the board, will that help or hurt?

2) Both the 15mph and 25mph test were done at 1700rpm (due to my torque converter). I could theoretially rig the shifting tables so that the the 25mph test was at 2500rpm. Since I have a cam, would that help? Would having the torque converter lock up during the test help?


Thanks,
Terry

[EC_Tune]

Timing affects HC big time. Try dropping your timing.

[Terry Burger]

Will do! Is 6 degrees reasonable? 8 degrees?

[EC_Tune]

How much are you running currently?
Factory is about 17 deg. With a 230 cam like you have I'm guessing that you need about 25-30 deg to make it idle "nice" but probably stock to 20 deg to make it pass.

EC

[DaddyCool]

Terry....

Just courious...What state do you live in? Also, is this an engine conversion? Most states do not "roll" OBD II cars and light duity trucks.

Dave

[Terry Burger]

CA rolls everything.

[S2H]

I've seen road side emmissions testing in CA...sucks..get pulled over for speeding..and they pull out a portable sniffer and check the pcm for codes...

[EC_Tune]

Terrry,

What's the latest? Did you get it through?

EC

[Terry Burger]

Terrry,

What's the latest? Did you get it through?

EC

Not yet, but I backed the timing down 4 degrees across the board, and I'm going to run a 90% gas 10% alky mix next week.

[EC_Tune]

Did they measure oxygen content in your last check? If so what was it?

EC

[Terry Burger]

It was .2% both tests, CO2 was 14.7% both tests. Although they measure these figures, there isn't a max for them, only HC PPM, CO%, and NO PPM.

I'm just thinking of other tricks, is there a way to rig the air pump in the PCM to stay on for the entire test?

[EC_Tune]

You may want to look at the o2 crossings vs airflow in the closed loop parameters. Reduce the Mode 0 & 4 values about 150 mv and the car will run a bit leaner at idle and increase the 02 content in the exhaust. Did they have the "average vehicle" results for O2 concentration?

EC

[Terry Burger]

I assume it would also run leaner at 15mph & 25mph? They don't do an idle test, just those roller tests.

[EC_Tune]

Yep, you're right.

Just need to see what the MAF is reading at the test params, then adjust the o2 crossings.

[Terry Burger]

Now I need to wait for the emmissions readiness tests to complete... I wish I could just force a test from HPTuners...

[Terry Burger]

Result: Passed! Thanks guys

[EC_Tune]

Congrats!