Emissions failed & Octane question
 

OK: This is a two-parter, and maybe could have been done as two posts, but this all could relate.

1. My '87 Coupe failed emissions here in CT. Hydrocarbons passed with 96 ppm out of allowable 156, telling me the motor is not necessarily running rich... although it does have a bit of "that smell." (We all know that 911s can be pretty exhausty.) Nitrogen level was higher than I'd have prefered (846 out of allowable 1094.) What it failed on was the CO (carbon monoxide) level: .54% on an allowable .50% limit. A lousy .04%!!

I'd assume that a 911's emissions are going to be higher at idle, or the relatively low speeds they typically test at, since these motors are designed for high revs and hard driving. But perhaps this is a false notion; perhaps they are supposed to be "clean" at all RPMs and speeds, including idling, and apparently the CT emissions program would agree.

My local shop (who specializes in Porsches, among other German cars) has done a cat test and says the cat is working fine, that their results looked good. If timing and plugs and air filter and other obvious "tune up" stuff seems fine, I'm interested in hearing comments as to possible causes of the high numbers and -- specifically -- the subsequent CO failure.

2. Octane. I've seen a few comments and posts, but wanted to hear some more. Is it true that the computer will automatically make some air/fuel/timing adjustments based on the octane of the fuel it sees? And does the octane grade of gas affect the emissions output at the tailpipe?

On my '87, inside the gas door, there's a factory sticker that says, "Oktan Min (RON+MON)/2 = 91" Now, me being a redneck from Memphis, I surmised this means the car wants 91 octane gas MINIMUM. Unless, of course, there's such a thing as "European" octane rating versus "American" rating, like Fahrenheit versus Celsius? I recall reading in threads that the motors were designed to run at 87... So which is it really?

Sorry if these are rudimentary questions, but I have no doubt there are a bunch more folks out there who've been in my shoes... and I'm not too proud to wear a dummy hat!

Thanks in advance, guys; I'd appreciate your words of wisdom!

--Steve

By the way, FWIW, I've been using 93 octane for as long as I can remember.

--Steve

if i recall lower octane helps come smog test time.

When your shop did their tailpipe test, did it duplicate the CT smog guys results?

A search using the terms "air fuel mixture chart" finds many threads including this one: http://forums.pelicanparts.com/showthread.php?s=&threadid=131425&highlight=air+fu el+mixture+chart

If you like charts, this is how mixture affect CO, HC and NOx (thanks to Bosch Fuel Injection & Engine Management )

http://forums.pelicanparts.com/uploads/EMISSION.gif

or Maybe this will help (thanks to EMCON5):

Begin big-ass cut/paste:-----------------


The following guide is intended to help the owner of a car which has
failed an emissions test to understand what may be wrong with the car.
Since I am not a mechanic it may contain emissions :-) or errors. If so
I'd appreciate comments as it is intended for emailing to peope who post
emissions queries in the rec.autos. newsgroups.

thanks.

====================================





Emission (smog) test problems.
==============================

What to look for when any of CO, HC, NOx too high.

CO: rich fuel mixture
HC: incomplete combustion
NOx: hot combustion and rich fuel mixture
CO, HC, and NOx: incomplete exhaust conversion

80%-85% of vehicles pass emissions tests.
an in-tune well-maintained vehicle should pass.
allowances are made for the age of the vehicle.
for the rest some details are provded below.

note that both CO and HC rise in the absence of O2 (oxygen) in
combustion and in exhaust, and that NOx rises in the abscence of
O2 at high combustion temperature. HC also rises when there is
too much O2 in combustion.

1. CO (carbon monoxide) too high.
---------------------------------

causes:

a) not enough air (oxygen) in air/fuel mixture to make carbon
dioxide (CO2) so get carbon monoxide (CO) instead (mixture too
rich). can be too little air or too much fuel in mixture.

b) not enough air (oxygen) in exhaust system to convert CO to CO2

c) faulty catalytic converter.

look for:

a) too little air - dirty air filter, stuck choke, plugged or
sticking PCV or EGR system, plugged carbuettor or injector air
passage

b) too much fuel - carburettor or fuel injection system supplying
too much fuel

c) too little air or too much fuel - engine control system -
vacuum hoses, sensors (eg exhaust oxygen, temperature, air flow),
computer, actuators (eg fuel metering solenoid, air metering
solenoids), wires and connections (control system voltages are so
low that small resistances from dirty or loose connections make a
big difference), the computer uses the input from the sensors to
send signals to the actuators to keep the air/fuel mixture at the
optimum for power, fuel efficiency, and low emissions.

d) too little air in exhaust system - restricted outside air feed
to converter (eg air pump or pulse air system - hoses, electrical
connections, valve, pump, drive belt, sensors)


2. HC (hydrocarbons, ie unburned fuel) too high.
------------------------------------------------

causes:

a) not enough oxygen in combustion to burn all the fuel, or too
much fuel (mixture too rich), so excess fuel blows out exhaust.

b) too much oxygen in combustion or too little fuel (mixture too
lean) for uninterrupted combustion (engine misses), so unburned
fuel blows out exhaust.

c) sparkplugs not firing properly to ignite air/fuel mixture
(ignition system), so unburned fuel blows out exhaust.

d) combustion chamber too cold for complete combustion, so
unburned fuel blows out exhaust.

e) combustion chamber hot spots preventing complete combustion,
so unburned fuel blows out exhaust.

f) not enough air (oxygen) in exhaust system to convert HC to H2O
and CO2.

g) faulty catalytic converter.

note that HC in exhaust can combine with S (sulphur) from fuel to
produce rotten egg smell.

look for:
---------

a) mixture too rich - see a,b,c in CO section above. note that if
HC is too high but CO is okay then the problem is not a rich
mixture.

b) too much oxygen in combustion - leaks of air (hoses, gaskets)
and routing of hoses into intake manifold, leaks in EGR and PCV
valves

c) too little fuel - dirt in fuel/filtre/tank/lines, leaks in
fuel lines or connections, weak fuel pump, - mechnical problems
in carburettor (dirty valves or passages or linkages, worn parts
or gaskets) or fuel injection system

d) too much air or too little fuel - computer not mixing air and
fuel properly (see c in CO section above)

d) ignition system - sparkplugs fouled (type of fouling may
indicate problem), poor contact or insulation in high voltage
ignition wires or in distributor (cap, rotor), poor contact in
coil wires, low voltage in charging system (alternator,
regulator), faulty transistorized ignition control module

e) combustion chamber too cold - sticking EGR valve or sitcking
cylinder exhaust valve or bad cylinder valve timming letting
"cooler" exhaust gas into the combustion chamber.

f) combustion chamber hot spots - bits of junk (dirt, carbon) or
nicked or burned metal parts glowing red hot in combustion
chamber and igniting air/fuel mixture (engine misses) - can use
chemical cleaner in combustion chamber or take engine out on the
highway or both to burn off junk - overhaul engine to remove
nicked or burned metal parts or hardened junk

g) too little air in exhaust system - see d in CO section above.


3. NOx (oxides of nitrogen) too high:
-------------------------------------

causes:

a) too much heat in combustion chamber - air contains about 78%
N2 (nitrogen gas) which becomes chemically unstable above 2500
def F and combines with O2 (oxygen, making up about 21% of air)
to form NO which, released into the atmosphere, forms NO2 which
in the presence of sunlight combines with HC (hydrocarbons) to
form smog. note that NOx only happens when engine is under load
(car at crusing speed on road or rollers).

b) too much CO in exhaust (CO enhances the conversion of NO to
NO2).


look for:

a) too much heat in combustion chamber - the EGR system or the
valve timing is used to bring exhaust gas back into the
combustion chamber to cool it off when the engine is hot under
load at cruising speed - check the EGR system valves, solenoids,
wiring, hoses - if the car does not have an EGR system check
valve timing - (engine cooling (water) and lubricating (oil)
systems may have some effect on combustion chamber temperature?)

b) computerized engine control system - adjusts engine operation
to minimize emissions (see c in CO section above).

----------------------------------------------------------------

sources:

"Automechanics" (Prentice-Hall, 1988)
"Import Car Manual 1983-1990" (Chilton, 1989)

Excellent info, Harry... Keep the thoughts coming...

Interested in hearing more about octane rating, too, paricularly the 87 vs. 91/93 topic, i.e., is anyone familiar with the Carreras spec'ing out 91 min. octane, contrary to discussions in this forum about the acceptable use of 87?

Also, would anyone else concur with k911sc's suggestion that lower octane fuel can help lower emissions output? I'm not looking for a particular octane fuel to solve my smog problems, I'm just curious to know if there's any effect. (Of course, the recent 20-25 cent increase in fuel costs doesn't help things... and it's only gonna go through the roof...)

Thanks, everyone --

--Steve

I was told that the 911 was a tuff car to pass in Ct because the system is so screwed up with the testing. I believe that you can buy an additive to help you pass. I also read a thread were pelicanites dissconect one of the injectors making your car a 5 cyl with a air pump on the 6th therfore cleaning up your hc & co.

CT has a tough test, indeed. I failed the first test, then failed the retest. The test itself takes a half hour -- based on age of car. The retest took nearly an hour and a half (!) due to the machine not getting good readings, and them having to reboot it at least once. They have a closed-circuit TV to watch the whole thing from the waiting room. More than once, I saw them trying to get the probe itself from falling out of the exhaust tip (FYI: they need to get the probe at least ten inches into the tailpipe to get a good reading. On 911s, this requires a bit of finagling and bending to get it to stay far enough in there, made difficult by the short 90-degree bend the muffler tip makes.)

My Porsche shop was surprised the car failed the first time, based on their evaluation of things, and after running the cat through their calibrated tester. The universal consensus was that the emissions testing facility was getting bad readings from a questionable test -- improper readings at the pipe, etc. Plus, these cars were meant to be driven a certain way, and the usual low-speed idle tests aren't a fair representation of how these engines perform in a real-world scenario.

CT does, indeed, have a spotty history and reputation with their new emissions program. Cars that fail might fail because of poor testing, and many cars that actually pass perhaps shouldn't have. The whole thing leaves a pretty bad taste in ones mouth.

Nonetheless, after a few calls with The Man (CT Emissions overseers AGBAR / A+ Technologies), they are sticking to their guns with their findings and testing practices. They have politiely told me to go pound sand, but to please keep them updated with what I find. My point to them was NOT that I'm denying I may have a problem with the car, but rather to rule out the possibility of a faulty testing procudure.

--Steve

I will be testing mine soon did they still have the form saying if you spend so much they will pass the car ? What part of Ct are you from and who is your garage .

Hey there--

I'm from the central/shoreline area, but usually use Glastonbury Foreign Auto right on Main Street in Glastonbury, when I'm not doing my own work. They specialize in German cars and have Porsches in there all the time. Busy shop. 860-633-3116.

As for the waiver, yeah, they say you might qualify for one if you fail the retest, but -- get this: You have to have shown that you spent at least $660 trying to get things fixed. PLUS, you have to have the work done at an emissions program-authorized shop. From what I recall, the list was not too comprehensive; a lot of car dealers and Midas-type places. Like the local Toyota shop is gonna know what to do on a Carrera! Ha! Oh, and if you do your own repairs, or use a non-authorized shop, your expenses do NOT count toward the $660 waiver expense. Basically, the whole thing smells like extortion and kickbacks. (Can you tell I'm a cynic?)

They will probably threaten you with everything from burning you at the stake to stealing your first born child if you fail to get the car passed, or else pay the $660 blackmail (did I say that out loud?) Of course, you can always try a different testing facility; there are perhaps so many wild inconsistencies between systems and shops -- despite the assertion that they are all calibrated and working fine -- you might get lucky where you previously failed. That may be MY "plan B." The emissions program's worst enemy right now is their horrible image, bad PR, and negative press. And much of it is their own (un)doing. What CT is essentially saying is that ANY car can drive legally on the road, as long as you made an attempt to get things fixed and have paid the $660 "fee." Basically, it would seem you can spew pure gasoline out the tailpipe, as long as you can post bail.

--Steve