Distinguish between JBI and PFI system
Sr. No.
|
TBI system
|
PFI System
|
1 |
Fuel is injected into the center of the throttle body
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Fuel is injected into the port.
|
2 |
TBI uses bottom feed injector
|
PFI uses top feed injector
|
3 |
Fuel injector needs to be flushed continuously- to prevent formation of air bubble
|
Fuel injector need not be flushed
|
4 |
1 or 2 Fuel injectors are used.
|
Fuel injectors are equal to the number of cylinders
|
5 |
TBI is comparatively low pressure injection (differential pressure = 0.7 to 1bar).
|
PFI is comparatively high pressure injection (differential pressure = 2 to 3.5 bar)
|
6 |
Cheaper fuel pump is sufficient to generate the required low pressure.
|
Costly fuel pump is required to generate the required pressure.
|
7 |
Mixture mal-distribution may occur.
|
All cylinders receive equal quantity and quality of air: fuel mixture.
|
8 |
Less accurate fuel injection control gives moderate fuel economy.
|
More accurate fuel injection control is obtained. Therefore increased fuel economy is obtained.
|
9 |
This is a cheap system
|
This is costly system.
|
10 |
Exhaust emission is above the permissible emission norms.
|
Very low exhaust emission is achieved to meet the strict emission norms.
|
11 |
Moderate throttle response as the fuel is injected at the throttle body and longer length of travel for fuel to enter the engine cylinder.
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Better throttle response as fuel is injected on hot back side of intake valve and shorter length of travel for fuel – to enter the engine cylinder
|
12 |
Lower power output due to lower volumetric efficiency caused by bulky injector body at the throttle body
|
Hither power output due to low resistance at intake manifold and higher volumetric efficiency.
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