| You tune the engine by measuring the
engine’s temperature, and making the required adjustments
to make the temperature correct. There are two ways
to measure the engine’s temperature:
a) Temperature gauge method: Get the
engine up to running temperature, bring the car into
the pits and immediately take a temperature reading.
Place the temperature gauge directly over the engine,
pointed at the glow plug, and take a reading. It’s
easier to do if you have a second person to take the
readings for you. or you can have the on chassis units
that are connected to the head of the car via a lead.
b) Spit method: Get the engine up
to running temperature, then pull in as quickly as
possible and put some spit on the engine’s cylinder
head (quickly, so as to not burn your finger). The
saliva should just slowly boil off (2 to 3 seconds).
It should NOT dance around as if it were on a hot
griddle, nor should it lay there and steam. In short,
if your spittle will sizzle, it's too hot.
The best method is to get a temperature
probe, there are several different types on the market,
the kind that mount on the chassis of the car with a
lead that connects to the head of the engine to monitor
the temperature. Or there are the infra red hand held
units that are more precise but far more costly.
If the engine is too rich, the engine
temperature will be colder than desired (and vice
versa). If the engine is too lean, the engine temperature
will be hotter than desired. Go out on the track with
the top end rich. If you’ve got the mixture set right,
there will be heavy smoke from the engine on the straightaway.
Run four or five full laps to get the engine up to
running temperature before touching the carb. Bring
the car in, and take a temperature reading. Start
leaning out the top end by turning the adjusting screw
only 1/12 turn at a time (picture a clock’s 12 even
spaces). Take your time doing the adjusting - don’t
be in a hurry. It may take a while. Your goal will
be to get the car to just "punch clean"
when you come onto the straightaway, which is what
it will do when the mixture is set properly. For 1/8
scale cars, you’ll have the correct mixture when the
temperature is about 200 degrees. The 1/10 scale cars
run a little hotter, maybe around 250 degrees.
|
