help passing emissions - idle

[500orbust]

I was wondering if anyone can help me with my idle readings. My HC reading is about 1200 at idle and passing is about 220. I have passed all other drivability tests.
I have HKS 272 Intake and Exhaust cams, haltech e6x, 2.3 stroker. Im running 6 degrees at idle and 16:1 afr.

thanks.....any suggestions would be appreciated

 

[akdsmer]

I was wondering if anyone can help me with my idle readings. My HC reading is about 1200 at idle and passing is about 220. I have passed all other drivability tests.
I have HKS 272 Intake and Exhaust cams, haltech e6x, 2.3 stroker. Im running 6 degrees at idle and 16:1 afr.

thanks.....any suggestions would be appreciated

HC's are pure hydrocarbons that didn't get ignited. These come from very high fuel mixtures (but would have high CO as well), lean mixtures (what you have now), compression or ignition problems. They are also high when you run big camshafts, as the overlap allows raw fuel to escape into the exhaust due to the overlap. Vacuum leaks at individual cylinders (I had an intake leak on #1 cylinder that was a pain to find) can be identified by running brake clean or propane around the base to see if rpm picks up. Use alot of propane, a blowtorch unit doesn't work very well.

I would be concerned with the overlap with the cams (but don't have them myself to vouch for how bad they are).

Your A/F ratio needs to be close to 14.5-15.0 to keep the HC down. You can run it right into a lean misfire (read: HC) at 16:1.

Do a cylinder balance test (after a compression test) and see if you have any weak cylinders. You could have an injector or ignition problem also.

The rest of the emission test results would help us determine what the problem might be, if you could post them.

 

[500orbust]

HC in ppm
The idle reading is 1205 and passing is 220
loaded reading is 217 passing is 220
CO in %
idle reading is .18 and passing is 1.2
loaded reading is .12 and passing is 1.2

I advanced the exhaust cam 2 degrees and retarted the intake 2 degrees to take out some of the overlap. Im also advancing the timing from 6 to 12 at idle and unplugging an injector. I hope this works.

thanks for the reply akdsmer!

 

[akdsmer]

HC in ppm
The idle reading is 1205 and passing is 220
loaded reading is 217 passing is 220
CO in %
idle reading is .18 and passing is 1.2
loaded reading is .12 and passing is 1.2

I advanced the exhaust cam 2 degrees and retarted the intake 2 degrees to take out some of the overlap. Im also advancing the timing from 6 to 12 at idle and unplugging an injector. I hope this works.

thanks for the reply akdsmer!

DO NOT unplug an injector....You will then have lots of unburned O2 dumped into the exhaust where the O2 sensor will think it's lean. It will then richen up the other cylinders.

Do you have a functioning CAT? If you do not, then your vehicle is too lean. Richen it up a bit.

RETARDING the timing will increase cylinder temperature and thus help ensure more complete burning of the fuel.

 

[500orbust]

Im running a haltec e6x not a stock ecm....well i just returned from the emissions station and i cut the HC idle reading by almost half to 771. I Passed everything else with flying colors.
Are the HC's affected by a bad catalytic converter, or just the CO readings?
I think i cant pass with these 272's in here and Ill have to put some stock ones back on.

 

[akdsmer]

A properly functioning Catalytic converter will reduce both HC and CO by a pretty good amount. I can tell you that it didn't cut my 1000 ppm HC numbers but by 350-400 ppm, leaving quite a bit to fail by. They reduce CO very well and can drop a couple of percent +/- if it's good and hot.

I noticed the non-stock ecm which made me think you could alter your fuel trims and richen them up a bit......That would help drop your HC's, especially if you are really in the 16:1 range.

If you just change the cams and pass, please repost as I am interested in the effects of the larger cams.

If you have 4 or 5 gasses listed on your emissions report, such as O2, HC, CO, CO2 and NOX then I can compute and see what your a/f is and if your catalyst is good,marginal or bad.....

 

[500orbust]

I also richened the afr to roughly 14.5 at idle. I will post my relults after the swap to stock cams. This will probably be in about a weeks time.

thanks for all the help,

archie