zackyg
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whats the difference between throttle body injection and electronic fuel injection
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TBI VS EFI
- Thread starter zackyg
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Fobroader
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Basically a TBI is a fancy computer controlled carburettor. It has an injector that is controlled by sensors on the engine which measure different parameters. EFI has one injector per cylinder and injects the fuel close to the intake valves, or in the case of this fancy new "direct injection" directly into the combustion chamber. EFI has much better control of fuel, can be much better tuned and upgradable injectors are readily available. This is a coles notes of how these systems work and Im sure some mechanics will jump in to fill in any gaps Ive left out.
just to clarify, TBI is EFI. efi stands for electronic fuel injection, which TBI most definantly is. most TBI trucks even had an EFI badge on the tailgate....
basically the difference between TBI and other injection methods comes down to placement and number/size of the injectors, as well as firing method/timing.
here's a quick rundown:
injector placement:
TBI - Throttle body injecton, uses 2 (sometimes more) injectors which inject the fuel at the throttle body. similar to a carb, only the fuel is supplied electronically and controlled through the computer.
MPFI - Multi-point fuel injection is a method of injecting fuel using multiple fuel injectors (typically 1 injector per cylinder), where fuel is injected into each of the intake runner of each cylinder slightly before the intake valve.
DI - Direct injection, where the injector and fuel are injected directly into the combustion chamber, typically using 1 injector per cylinder
Injector timing:
Batch injection - this is where all injectors are firing simulaneously, this is typically either all injectors firing together, or a bank of injectors firing together.
Sequential injection - this is where each injector fires individually, typically synchronized with their specific cylinder's timing events
Common types of GM fuel injection:
TBI - GMt400 trucks up through 1995, using 2 batch fired fuel injectors
CSFI - central sequential fuel injection - used on 1996+ GMT400 trucks. similar to MPFI except instead of using fuel injectors, the CSFI system uses poppet valves which are supplied by a centrally located fuel metering body. the poppets act as injectors and fire the fuel in the intake runner. as the name suggests, this system is sequential injection. this system has alot of inherent problems which I won't go into, there is an upgrade part that replaces the poppets with tiny actual fuel injectors, however even though the replacement setup does replace the poppets it still suffers many of the drawback of the poppet CSFI setup. personally I don't consider the upgrade a true MPFI system.
MPFI - as mentioned above, unlike the CSFI, true MPFI uses externally mounted injectors supplied by a fuel rail, which injects the fuel into the intake runner. most MPFI systems are sequential such as the GENIII LS based engines, as well as gen IV, etc. This is mostly what has been run in GM cars and trucks from ~2000 until today.
TPI - Tuned Port Injection, used in late 80's vettes, camaros, firebirds, etc. which is a port injection setup that is usually run as a batch fire system in stock form, but depending on the engine management setup, can be run sequentially as well.
DI - GM currently does have some direct injection vehicles, some of them are called EcoTec engines. this is a newer and currently less used technology compared to the other forms of fuel injection. as far as gasoline engines, this is where the near future is going. beyond that is anyone's guess, but expect to see many more direct injection vehicles coming out very soon. DI has alot of interesting benefits, as well as some drawbacks, but overall a very beneficial setup.
every one of these setups are "EFI", I could spend alot more time on injectors and electronic fuel delivery, but I hope that helps clear things up/
basically the difference between TBI and other injection methods comes down to placement and number/size of the injectors, as well as firing method/timing.
here's a quick rundown:
injector placement:
TBI - Throttle body injecton, uses 2 (sometimes more) injectors which inject the fuel at the throttle body. similar to a carb, only the fuel is supplied electronically and controlled through the computer.
MPFI - Multi-point fuel injection is a method of injecting fuel using multiple fuel injectors (typically 1 injector per cylinder), where fuel is injected into each of the intake runner of each cylinder slightly before the intake valve.
DI - Direct injection, where the injector and fuel are injected directly into the combustion chamber, typically using 1 injector per cylinder
Injector timing:
Batch injection - this is where all injectors are firing simulaneously, this is typically either all injectors firing together, or a bank of injectors firing together.
Sequential injection - this is where each injector fires individually, typically synchronized with their specific cylinder's timing events
Common types of GM fuel injection:
TBI - GMt400 trucks up through 1995, using 2 batch fired fuel injectors
CSFI - central sequential fuel injection - used on 1996+ GMT400 trucks. similar to MPFI except instead of using fuel injectors, the CSFI system uses poppet valves which are supplied by a centrally located fuel metering body. the poppets act as injectors and fire the fuel in the intake runner. as the name suggests, this system is sequential injection. this system has alot of inherent problems which I won't go into, there is an upgrade part that replaces the poppets with tiny actual fuel injectors, however even though the replacement setup does replace the poppets it still suffers many of the drawback of the poppet CSFI setup. personally I don't consider the upgrade a true MPFI system.
MPFI - as mentioned above, unlike the CSFI, true MPFI uses externally mounted injectors supplied by a fuel rail, which injects the fuel into the intake runner. most MPFI systems are sequential such as the GENIII LS based engines, as well as gen IV, etc. This is mostly what has been run in GM cars and trucks from ~2000 until today.
TPI - Tuned Port Injection, used in late 80's vettes, camaros, firebirds, etc. which is a port injection setup that is usually run as a batch fire system in stock form, but depending on the engine management setup, can be run sequentially as well.
DI - GM currently does have some direct injection vehicles, some of them are called EcoTec engines. this is a newer and currently less used technology compared to the other forms of fuel injection. as far as gasoline engines, this is where the near future is going. beyond that is anyone's guess, but expect to see many more direct injection vehicles coming out very soon. DI has alot of interesting benefits, as well as some drawbacks, but overall a very beneficial setup.
every one of these setups are "EFI", I could spend alot more time on injectors and electronic fuel delivery, but I hope that helps clear things up/
Super Silvi 1990
I'm Awesome
Adding thoughts
^^^^Couldnt agreed with you more except for multi point injection. You got it slightly wrong i think your wording makes it kind of hard to understand so dont cuss me out. Multi point injection is the use of two or more injection points for instance A regular TBI setup can be changed into a MPFI system simlpy by adding fuel rails and stand alone injectors to a specialized intake while still having a working Throttle body that is injecting fuel into the intake as well. Its usually used in High performance Drag racing setups because you can forget Gas milage. Some pics to help the education out. IM a visual learner
Direct injection
Fuel rail for efi
EFI/TBI or throttle body injection
And multi point fuel injection
^^^^Couldnt agreed with you more except for multi point injection. You got it slightly wrong i think your wording makes it kind of hard to understand so dont cuss me out. Multi point injection is the use of two or more injection points for instance A regular TBI setup can be changed into a MPFI system simlpy by adding fuel rails and stand alone injectors to a specialized intake while still having a working Throttle body that is injecting fuel into the intake as well. Its usually used in High performance Drag racing setups because you can forget Gas milage. Some pics to help the education out. IM a visual learner
Direct injection
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Fuel rail for efi
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EFI/TBI or throttle body injection
You must be registered for see images attach
And multi point fuel injection
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yeah, my wording may have been odd, I was trying to say the same thing you are. its just all about the injector placement....and its possible to convert inbetween different injection styles like you mentioned, it just takes time and money.
also something worth noting that can help people out, carb and TBI intake manifolds are typically referred to as 'wet' manifolds, because the fuel is introduced as the air enters the intake manifold, whereas MPFI, CSFI, other port injection, and DI, are 'dry' manifolds because the fuel isn't introduced until the air is exiting the intake manifold.
also something worth noting that can help people out, carb and TBI intake manifolds are typically referred to as 'wet' manifolds, because the fuel is introduced as the air enters the intake manifold, whereas MPFI, CSFI, other port injection, and DI, are 'dry' manifolds because the fuel isn't introduced until the air is exiting the intake manifold.
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