At 06:20 PM 8/28/99 -0400, you wrote:
>
>I'm new to the Triumph world, but love the red TR6 I bought one month
>ago. There is a lot to learn, having been a Sprite Mark II driver. The
>big problem for me now is I failed the New Jersey exhaust emissions test
>twice. Though I passed the two main emissions test, they told me I'm
>reading 1200 Hydrocarbons, when it should be 500 to pass. This is Greek
>to me. On my old Sprite '62, there was just a hose hanging down for
>emissions. Can anyone give me some ideas on how to get my exhaust
>emissions to pass?????? Thanks from a TR novice, D Michael
>
Hydrocarbons (HC) are unburned fuel. The limit of 500 refers on a molecular
level to 500 PPM or Parts-Per-Million. Your test results of 1200 HC's could
come from either of two problems, or a combination of both.
Probem 1. Carbs too rich - if the stoichometric ratio of air to fuel is less
than 12 lbs. air to 1 lb. fuel (14.7:1 is ideal), the remaining fuel does
not burn as there is no more oxygen to combine with in the combustion
chamber. The remaining unburned fuel goes out the tailpipe in the form of HC.
Problem 2. Ignition Misfire. If there is no spark, all of the fuel in the
combustion chamber goes out the tailpipe as HC.
If the car seems to run well otherwise, I would look at the ignition first.
Especially check the plugs and wires - hook a timing light on each wire and
watch for any miss in the sequence/pattern on the light. Investigate
further any irregularities you find here. A condenser on the way out can
also cause a misfire at idle. Coil problems usually manifest themselves at
higher RPM first, so don't go out and buy a new one unless you have reason
to suspect otherwise.
If all checks out there, look at the mixture at the carbs. There are many
ways of checking the mixture from colortunes to oxygen sensors to simply
listening to the note of the exhaust - pick your method of choice and adjust
accordingly if too rich. Another carb problem that comes up is weak vacuum
on a tired engine. Worn valve guides and throttle shafts bleed off manifold
vacuum and can really upset the Stromberg carb so that the mixture is
constantly wavering from lean to rich, but never holds quite right. If this
were the case, you would probably also have a high CO reading (carbon
monoxide) which you implied was OK.
Chances are good you'll find a source of excess HC somewhere in all of that.
If after checking all of the above you realize the motor is in need of
significant surgery to make right, I would retune the engine to more
emissions friendly settings and try for a retest - retard the timing as far
as you can and still have the car run smoothly - probably have to turn the
idle up as well - and back-off the valve adjusters until you have about
.025" clearance cold. This will effectively raise the manifold vacuum and
lower the peak cylinder pressure which will help reduce emissions. Once
through the test, set everything back to where the car runs the best.
Good luck!
Brian Schlorff
Power British
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