Holley 950 User Manual download pdf (Page 15)

2.2 Alpha-N

An Alpha-N system is similar to a speed density EFI system, except that for step 1, the ECU will look at engine speed and the

position of the Throttle Position Sensor, instead of the MAP Sensor, to determine the value from the base fuel map. The

following flowchart (Figure 2) illustrates this example.

100.8%

1000 RPM

ENGINE

SPEED

THROTTLE

POSITION

(TPS)

MANIFOLD AIR

TEMPERATURE

MODIFIER

(Air Temp Sensor)

ACCELERATION

ENRICHMENT

(change in TPS and

MAP Sensor)

COOLANT

TEMPERATURE

MODIFIER

(Water Temp Sensor)

100.0%

180

BASE FUEL MAP

VALUE

AMOUNT OF FUEL

INJECTED

(Pulse Width)

3.1 ms

0.82v

CLOSED LOOP

FEEDBACK TO

MAINTAIN 14.7:1

AIR/FUEL RATIO

(Oxygen Sensor)

CLOSED LOOP

OPEN LOOP?

AMOUNT OF FUEL

INJECTED

(Pulse Width)

3.8 ms

Open Loop Closed Loop

100.0%

No Change

Sensor Data

Input

ECU Calculations

and Adjustments

Key:

Figure 2 Engine at Operating Temperature – Alpha-N ECU Strategy Flowchart

1 2 ... 10 11 12 13 14 15 16 17 18 19 20 ... 97 98

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Holley 950 User Manual Page 15

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