Subject says it all - today I passed the Mass IM240 emission after failing
badly 2 months ago. I owe many thanks to LJ in particular and the Internet
in general as they both said reducing timing reduces HC emissions, which is
what I failed on. Here are my old numbers:

HC 2.11 limit 0.80
CO 0.66 limit 15.00
NOX 0.71 limit 2.00

Today's numbers:
HC 0.72 (-66%)
CO 0.08 (-88%)
NOX 0.37 (-48%)

All units are GPM (grams per mile?)

What I did was halve the main spark table, 400 - 2400 rpm, 25-75 map. I
also halved the closed tps advance table up to 2400 rpm. Finally I raised
the fan turn on to 105 deg C (not quite as high as stock). I also drove the
car a bit before it went up on the rollers - and let it idle over 3 minutes
before the beginning of the test to make sure it was in closed loop. I
really can't remember from the initial test how long after they started the
car before the test started.

To be fair since the last test I replaced the stock TB with a BBK 52
modified for proper IAC operation (drilling the bypass hole in this case).
I also put in the ram-air maf tables after inadvertently running "regular"
f-body tables since my obd-1 conversion. However, while the maf would lean
the car out at wot, the computer should have learned around it by now, so I
don't think it would have affected the test.

I drove to work today on my regular tune - long commute - and I flashed the
emissions program in the parking lot. After the test I flashed it back.

So, as long as I leave the plates on the car, I won't have to take emissions
again til Aug 04. Hopefully by then the obd-2 **** will be figured out.

So, I'm pretty happy with the car. Now I gotta do something about that
damned coolant leak/smell.

 

Wow, that's awesome, Joe. I'm going to have to save a copy of this thread for when I need an emissions tune.

 

Joe glad to hear you got your ride to pass the test. How did your friend do?

 

Mike,

He's up Monday but I'm pretty sure he'll pass now that he's got his fuel pressure accounted for. He only needs to take a 2 speed idle test since his car has traction control. I'm sure he'll put a similar emissions tune in his car when he goes. He also runs open loop so running 16:1 may help. That was going to be my next step if I failed today.

Joe

 

Joe what cam is he running? Let me know how he does.

 

Jim is running the XE 224/236-114 cam with 1.6I/1.5E rockers. He passed the 2 speed idle test today! He followed my lead - halved the timing, ran open loop with the afr set to 15.0:1, and kept the car good and hot. Last night we tried out his emissions tune, and one trip around the block had the headers glowing dull red in the dark (like mine did). I don't know his numbers since he didn't get his printout yet, but will post them. Now I think he may want to make an appt with Dean to see what he can do. He made 370 running pretty rich, so I think he could top 380 with some tuning.

Joe

 

Joe thats a wicked nice cam. I am still trying to decide which cam i want to go with. I thinking going with either the cam you have or the one that your friend has. Maybe you guys can help me pass. I don't have to worry about it till 2004 though.