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Frequently Asked Dyno Questions
What is it?
Electronic fuel injection systems work by delivering high pressure fuel to an electrically operated valve called an injector. The electronic wizardry comes in delivering the right amount of fuel, at precisely the right time for every engine operating condition, across the rev range..
Are your Sensors up for it?
With added power from a freshly bored out engine, cams or turbo installation comes the need for more air to be introduced into an engine. Your standard ecu may be able to handle the increased load, but without correctly checking, you may be running lean. Your timing may and fuel pressure regulator may need to be adjusted to compensate to delver more fuel at certain engine loads, or your ECU may need to be altered to allow for the injectors pulse duration to be lengthened to let in more fuel.
From the Tank to the Piston
Maintaining a good strong flow of fuel at all
times is vital for the correct fueling delivery
into your engine. Too much and you'll foul things
up, and too little and you burn things out. An
engine cannot work on fuel OR air alon e, it requires
a correct mixture, known as an Air/Fuel Ratio.
Too much fuel, and you will loose power, too little
fuel, and you'll cause things to overheat. Ensuring
your ECU is giving the right signals to the fuel
injectors so they place exactly the right amount
of fuel each time and every time is needed to ensure
the best possible performance as well as the best
possible economy.
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Understanding EFI Fuel Management
EFI computers have several modes of operation. These modes are determined by the output power needed from the engine's operating conditions:
Closed Loop Mode
The ECU measures teh air/fuel ratio (A/F) from the O2 (or lambda) sensor. THe ECU works to maintain a constance A/F ratio (14.7:1). This ratio is optimal for the catalytic converter to reduce exhaust emisions correctioly. Also, an 14.7 A/F ratio is the ideal sweet spot for the lambda sensor to work accurately, and this gives a good feedback signal.
Open Loop Mode
This differs from closed loop mode as the lambda sensor signal is ignored. The ECU controls the fuel injectors wihtout feedback that the calculated fuel delivery rate matches what the engine receives. Without feedback, the loop is open, there by giving the term "open loop."
Power Enrichment Mode
This only occurs at Widoe Open Throttle (WOT) and is only determined by the Throttle Position Sensor (TPS) from about 60% wot onwards. The ECU in this mode, ignores the lambda sensor and forces a richer A/F ratio than 14.7:1. This is becuase engines develop more power with a slightly richer mix. This is the area that modifiers are most concerned with.
Lean Cruise Mode
This mode can only used be used at light loads when the vehicle speed is above a certain value, for example 100kph cruising. The ECU instructs a leaner A/F ratio, increases spark advance, and occasionally returns to closed loop mode to assess itself.
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