robertbartsch

...looking through my wallet recently I found an emissions test from 2000 when my car was 100% stock; the hydrocarbon output was very low at .15 PPM.

After some performance modifications the hydrocarbons emissions increased significantly:

Mods:

Ported ls6 heads, milled .055 (CR 11.2 to 1)
LT headers (FLP) with cats
220/220, 564/564, 112 cam
85MM MAF (SLP w/ electronic module)
Cold air - SLP
LS6 manifold w/air pump fitting
ported TB
Cat back
*********************
Initial test for 2003 - hydrocarbons = 70 PPM
Test after LS1Edit tune - hydrocarbons = 55 PPM

Any thoughts on why these hydrocarbons are so high; the high output is cramping my desire to do additional mods for fear of a non legal car.


The emisions output in New York was recently reduced retroactively to 60 hydrocarbons PPM ...so I'm now currently very close to the failure rate...

bomax

iTrader: (3)

Hydrocarbon emissions result from fuel that doesn't burn completely in the engine, perhaps you are running especially rich. I notice you had tuning done, so you probably (or your tuner did) intentionally set it rich.

Not only that but during the first one or two minutes of engine operation, engine components are cool and the conditions for vaporizing fuel within the intake manifold are poor. This failure to properly blend the fuel with the air results in large amounts of unburned and partially burned hydrocarbon emissions. Was the car completely warmed up when you performed the test?

You can increase timing when the car is idling in Open Loop to reduce the amount of hydrocarbons produced.

RPM WS6

iTrader: (3)

I don't think that NY will be doing tailpipe sniffers much longer anyway. Maybe someone can confirm that?

Most states have gone to OBD scan only for '96 and up cars now. It's faaaaaar easier to pass. You'll have no issues with it so long as you have no stored DTCs or an SES light.

emarkay

Or if the Inspector is EPA trained, or if there is any obvious "changes' to the car, or, or, or.... it's just a matter of time - there is an interesting thead 'round here somewhere about PA emissions recently...

HC is unburnt fuel, or oil entering the combustion chamber...

jimmyblue

iTrader: (11)

The big cam has to let a lot of overlap blow-through
happen at low RPM. Fuel/air straight to exhaust =
high hydrocarbons.

I would think your friend Ben Franklin could help you
find a suitably qualified emissions testing expert who
can get the car to pass.

wrencher

iTrader: (2)

Is NY still doing PPM testing or have they yet gone dyno /IM240?
I thought they where also going for OBD testing?
Well for those mods the #'s are good.
If the motor is tuned & running perfect, the cats are the key, the newer/fresher they are the better.
Hydro carbons is unburnt fuel, also the hardest to keep at a mininumn.
Oil burning can also have a influence on this #
Oil & gasoline are raw hydrocarbons.

RPM WS6

iTrader: (3)

Huh?

robertbartsch

NY is still a sniffer trest....the car was fully warmed up when tested...I also ran 10 small bottles of dry gas (methonal) in a 1/4 tank of high test 94 octane gas....to reduce hydrocarbons as much as possible...

The LS1Edit tune was done by me and a friend....we started with LTrims of +15 and reduced them to slightly negative....I'm assuming this means the car is no longer running rich ...at least I no longer smell raw fuel...

I remember the first mod I did in 2000; it was an 85 MAF from SLP....they asked me if I had any mods; I said no ...so they gave me a resister module to plug into the MAF sensor cable....

Question: Should I remove the MAF resister module or has the LS1EDIT tune (done in late 2003) already compensated for this?

Any other ideas would be helpful...

Thanks...

robertbartsch

..so INCREASING the timing at idle will decrease hydrocarbon emissions?

Can you quantify the amont of timing increase I should try in LS1edit?

Thanks...

jimmyblue

iTrader: (11)

Idle advance will give it more time to burn, but if
the problem doesn't relate to that, it won't do
much.

Incomplete combustion from too much or too little
air is why you get elevated HC at both ends of the
mixture range and minimum in the middle.

If you have not removed the AIR stuff, you might try
forcing it to run full time (on emissions day) and see
if the cats (which I presume are still there) can
burn the HC down when supplied air to do it with.

robertbartsch

They seem to test when the engine is running higher than idle; what if I slightly increased the timing across the board?