Traxxas TRX 2.5R, Руководство пользователя

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TRX 2.5R • 15
THE CARBURETOR
The Fuel Mixture Needles
The amount of fuel metered and atomized by
the carburetor is controlled by the two mixture
needles; the high-speed needle and the low-
speed needle. The low-speed needle is used to
meter the fuel used by the engine at idle and
low RPM (part-throttle) engine speed. The high-
speed needle is used to meter the fuel when the
throttle is open from part throttle to wide-open
throttle (WOT). Two needles on the TRX 2.5R
provide precise control of the air/fuel ratio across the engine’s entire RPM range.
The maximum possible fuel flow is always controlled by the high-speed needle. It works like the
main water valve on a garden hose. Turn it clockwise to close the valve, counter-clockwise to
open it. When the throttle is at idle or partially open, the low-speed needle again meters the
fuel flow at the outlet (needle seat) where the fuel enters the carburetor venturi. This second
valve acts like the spray nozzle at the end of the garden hose in our example. When you
accelerate from idle, the throttle opens and the low-speed needle is pulled away from the
needle seat. This allows more fuel to flow with the increased air flow. As the throttle is
increased, the low-speed needle is pulled completely away from the needle seat leaving it fully
open. At that point, fuel metering is entirely controlled by the high-speed needle. Again, using
our water hose example, when the spray nozzle at the end of our garden hose is fully open,
then the main water valve can be used to adjust how fast the water flows.
The engine’s performance is directly linked to the fuel mixture. Richening the fuel mixture
increases the amount of fuel in the air/fuel mixture ratio and leaning the fuel mixture
decreases the amount of fuel in the air/fuel mixture ratio.
• Slightly rich fuel mixtures deliver cooler
running and more lubrication but with
slightly less power.
Water Valve
(Controls Overall Flow)
High Speed Needle
Water Nozzle
(Controls Fine Flow)
Low Speed Needle
• Slightly lean fuel mixtures deliver stronger,
more efficient combustion and more power,
but with less lubrication.
See Tuning the TRX 2.5R for
Best Performance on page
22 for complete information
on adjusting the air/fuel
mixture and idle speed.