Hi,
need tips to lower HC emissions of my engine.Engine set up is:
355sbc
-hotcam
-EQ vortec heads
-stealthram
-SLP tri-y headers(no air injection)+3" exhaustpipe without cat
-30lbs fms injectors(43psi)
-870 ecm+Lsracingchips tune

HC emissions are now 2000ppm at idle(sniffer test).Max allowable is 1000ppm at idle.Idle speed is 750 rpm(max allowable idle speed 1000rpm)Ignition advance at idle is ~25 degrees(base advance+computer advance)If I remove est wire and measure HC when engine is idling(engine has then 6 degree ign. advance),HC measurement is~400ppm.Seems that engine runs lean at idle when it is closed loop(lambda is 1.2)Emission measurements are done without cat.So what to do to lower those emissions?

-Jari-

 

Are the smog-techs able to tell if you have the EST wire unhooked? If you can sneak that past them, just disconnect it and run the test that way. My 89 L03 car had the same problem at idle. I disconnected the EST, removed the SES bulb from the dash, timed it a 8 degrees intial advance, and made sure the idle speed was correct. It passed easily with the EST disconnected at both the idle test and the 2000 rpm test. Just make sure to set everything back once you get home from the test. Mine pinged some on the way home with the EST unhooked, so you don't want to leave it that way for long. Btw, I was running a gutted cat, and had the AIR system diabled, and it still passed by disconnecting the EST. It may be a low-tech way to fix the problem, but it worked long enough to pass the test.

 

Propably not,if I remove SES lamp.I think this high HC is tuning problem.Does EST unplugging force ECM to open loop?Also how much does usually hotcam/vortec combos need ignition advance when they passed emission test?

 

So,I was today at inspection.Sniffer test HC emissions were ~700 to 1100ppm at idle(750rpm)Passed inspection(but it was very close that I did't..)This was with removed ses lamp and unplugged est.Any good quess how much I can reduce HC emissions by tune????

-Jari-

 

Who cares? You passed now, can't you leave it be for another few years before pulling the EST to pass again?
1000ppm HC's aren't going to hurt the environment too badly, at least if I were you i'd still sleep well at night.

The hotcam has gobs of exhaust duration, there's not much you can do to avoid that.
Your injectors might be a tad too big for your application, maybe backing off fuel pressure could help, rather than going down a size on injectors?

 

The Vortec heads dont have EGR, and you're not running a cat. No wonder it wont pass. I'm shaking my head here.

Instead of these ethnically engineered cheats to pass, why not put a cat on it??? Its too late to do anything with the heads, but a cat or two will help a ton.

 

Well it depends how you think it.Camaro is my "hobby" car.It is enough old that it is not required to use cat.Ofcourse using cat is easiest way to reduce emissions,but in my case I think it's more tune problem.Because I'm not burning my prom's I'm limited to these "cheap tricks".
A while ago I talked with person who has afr ,hotcam,haltec combo ,and he told me he has HC ~300ppm at idle without cat.How about idle rpm,does it help if it idles ~900rpm instead 750?

-Jari-