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Old 12-05-2010, 02:36 PM  
Poolside OP
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Fuel Injection - Operational Chart

Here is a table summarizing the operation of Electronic Fuel Injection. After the chart is a Glossary of Terms.

I'm hoping to make the subject of fuel injection a little more understandable, or at least approachable. You may not believe it, but the fundamental operation of EFI, if not the electronics and software themselves, is fairly easy to grasp.

A lot of people who ride are interested in knowing what the ECU is doing, good and bad, to affect the pleasure of riding. If you're one of those people, I hope you find this useful.

How to read the chart:

Begin at the top left, and work your way down the blue column. The blue column lists a common sequence of rider inputs. For example, traveling at a constant speed, rolling on the gas, speed increase, rolling off the gas, speed decrease, etc.

The green boxes along the top are the ECU subroutines, or algorithms if you like. The subroutines are triggered to 'execute' based on what the rider is doing with the throttle. The subroutines are a set of instructions and procedures designed to carry out a particular task.


The IICE Air operates in the Blue range - Really ramps up open loop acceleration.
The IICE Cool operates in the Violet ranges - Puts the punch back into the throttle response.
The IICE Smooth operates in the Pink range - This one is the fix for Surging! But it also goes a long way to improving throttle response.

Following the chart is a definition of terms.



Steady State
Just like it sounds. Throttle is steady and the motor is turning at a constant RPM. Steady State includes a constant throttle and speed on uphill or downhill grade.

Tip-in
Refers to an opening throttle movement. An increase in throttle angle. Tip-in isn't the amount of throttle movement, it's the movement itself. Specifically refers to the duration of time when the throttle angle is actually increasing.

Tip-out
Refers to a closing throttle movement. A reduction in throttle angle. Tip-out isn't the amount of throttle movement, it's the movement itself. Specifically refers to the duration of time when the throttle angle is actually decreasing.

Overrun Fuel Cutoff (or OFC)
Starting from any steady state throttle position, if the throttle is tipped out 15% or more the ECU cuts off all the fuel flow. If the rider closes the throttle completely and allows the bike to slow, fuel cutoff continues. Fuel delivery resumes below 1700 RPM, and is felt as a distinct lurch.

Leading Throttle
Say you're traveling at 35 mph and you tip-in the throttle to 75% and hold it there. The bike is increasing speed but hasn't yet reached its final velocity for the new throttle setting. You can think about that condition in terms of the motor trying to 'catch up' to the throttle. The throttle is ahead of the motor, and is 'leading' it to a new RPM.

Trailing Throttle
Opposite polarity to Leading Throttle. You've backed out of the throttle some and bike is slowing but hasn't yet reached its final velocity for the new reduced throttle setting. The throttle is trailing the motor.

Closed Loop
Closed control loop operation is probably the most complex routine in EFI systems. But to explain it simply, Closed Loop is when the ECU is using O2 Sensor feedback to adjust its fuel calculations. When the ECU is running in Closed Loop, some sensors are ignored and are left out of the fuel delivery calculation.

Open Loop
During Open Loop operation the ECU does not use O2 Sensor feedback to adjust its fuel calculations. And similar to Closed Loop, when the ECU is running in Open Loop, some sensors are ignored and are left out of the fuel delivery calculation.

Transient Enrichment (aka: Accelerator Pump)
Whenever the throttle is opened, while you're twisting the grip I mean, additional fuel is momentarily required. Throttle movement is a transient event, and the additional fuel is called Transient Enrichment. Without Transient Enrichment, the motor would stall when the throttle is opened. With the right amount of transient enrichment, throttle response is crisp. It puts a smile on your face. With an insufficient amount, as typical for an emissions-based motor, the throttle feels soft.

Transient Enleanment
The opposite of Transient Enrichment. How's that for sidestepping the answer? Seriously though, the two terms are actually the same term, but different signs. You know, one is positive and the other is negative. One momentarily adds fuel and the other momentarily removes fuel. Generally the two terms, Transient Enrichment and Transient Enleanment, are collectively referred to as Transient Fuel.


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Poolside screwed with this post 12-13-2013 at 04:20 PM
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