Could someon please explain ITB's?

[procan]

I have read a few good threads on here about ITB builds, but I don't really understand what ITB's are, except that it stands for "Individual Throttle Body", and from what I can tell it looks kinda like a carb with EFI?

Could someone please enlighten me?

[HawgRyder]

ITB's are for injection systems.
All they regulate is the air flow.
Bob

[AlfonsoR]

From Wikipedia: Throttle - link: Throttle - Wikipedia, the free encyclopedia

Internal combustion engines
A cross-section view of a throttle valve

In a gasoline internal combustion engine, the throttle is a valve that directly regulates the amount of air entering the engine, indirectly controlling the charge (fuel + air) burned on each cycle due to the fuel-injector or carburetor maintaining a relatively constant fuel/air ratio. In a motor vehicle the control used by the driver to regulate power is sometimes called the throttle pedal or accelerator.

The throttle is typically a butterfly valve. In a fuel-injected engine, the throttle valve is placed on the entrance of the intake manifold, or housed in the throttle body. In a carbureted engine, it is found in the carburetor.

When a throttle is wide open, the intake manifold is usually at ambient atmospheric pressure. When the throttle is partially closed, a manifold vacuum develops as the intake drops below ambient pressure.

Usually the throttle valve is controlled with a throttle pedal or lever via a direct mechanical linkage. In vehicles with electronic throttle control, the manual throttle control sends a signal to the Engine Control Unit (ECU), which then directly controls the position of the throttle valve. This means that the operator does not have direct control over the throttle valve; the ECU can finely control the valve in order to reduce emissions or maximize performance.

In a reciprocating-engine aircraft, the throttle control is usually a hand-operated lever or knob. It controls the engine power, which may or may not reflect in a change of RPM, depending on the propeller installation (fixed-pitch or constant speed).[1]

The power output of a diesel engine is controlled by regulating the quantity of fuel that is injected into the cylinder. Because the engines do not need to control air volumes, they lack a butterfly valve in the intake tract. An exception to this generalization is newer diesel engines meeting stricter emissions standards, where a throttle is used to generate intake manifold vacuum, thereby allowing the introduction of exhaust gas (see EGR) to lower combustion temperatures and thereby minimize NOx production.

Throttle body
The components of a typical throttle body

In fuel injected engines, the throttle body is the part of the air intake system that controls the amount of air flowing into the engine, in response to driver accelerator pedal input in the main. The throttle body is usually located between the air filter box and the intake manifold, and it is usually attached to, or near, the mass airflow sensor.

The largest piece inside the throttle body is the throttle plate, which is a butterfly valve that regulates the airflow.

On many cars, the accelerator pedal motion is communicated via the throttle cable, to activate the throttle linkages, which move the throttle plate. In cars with electronic throttle control (also known as "drive-by-wire"), an electric motor controls the throttle linkages and the accelerator pedal connects not to the throttle body, but to a sensor, which sends the pedal position to the Engine Control Unit (ECU). The ECU determines the throttle opening based on accelerator pedal position and inputs from other engine sensors.
Throttle body showing throttle position sensor. The throttle cable attaches to the curved, black portion on the left. The copper-coloured coil visible next to this returns the throttle to its idle position when the pedal is released.

When the driver presses on the accelerator pedal, the throttle plate rotates within the throttle body, opening the throttle passage to allow more air into the intake manifold. Usually an airflow sensor measures this change and communicates with the ECU. The ECU then increases the amount of fuel being sent to the fuel injectors in order to obtain the desired air-fuel ratio. Often a throttle position sensor (TPS) is connected to the shaft of the throttle plate to provide the ECU with information on whether the throttle is in the idle position, wide-open throttle (WOT) position, or somewhere in between these extremes.

Throttle bodies may also contain valves and adjustments to control the minimum airflow during idle. Even in those units that are not "drive-by-wire", there will often be a small electric motor driven valve, the Idle Air Control Valve (IACV), that the ECU uses to control the amount of air that can bypass the main throttle opening.
Image of BMW S65 from the e92 BMW M3 showing eight individual throttle bodies

Many cars have a single throttle body. Others employ more than one, chained together by linkages to improve throttle response. At the extreme, high performance cars like the E92 BMW M3 and high performance motorcycles like the Yamaha R6 use a separate throttle body for each cylinder, often called "individual throttle bodies" or ITBs.

A throttle body is somewhat analogous to the carburetor in a non-injected engine. Carburetors combine the functionality of the throttle body and fuel injectors into one in order to modulate the amount of air flow and to combine air and fuel together. Cars with throttle body injection (called TBI by General Motors and CFI by Ford) locate the fuel injectors in the throttle body, thereby allowing an older engine to be converted from carburetor to fuel injection without significantly altering the engine design.

[FrenchToast]

Originally Posted by HawgRyder

ITB's are for injection systems.
All they regulate is the air flow.
Bob

They can be used with carburators too...... right?

Take care!

[Bob Kontak]

Originally Posted by FrenchToast

They can be used with carburators too...... right?

I may be speaking out of school but I believe ITB's require an engine management system and or EFI where carbs do not.

Porsche 911 - 3.2L PMO ITB - YouTube

[Tippy]

You've never seen throttle response until you've revved a motor with ITB's. A great example is the E46 M3. The throttlebodies are right in the cylinder head like a sportbike. Super fast throttle response.

Other benefit is peak hp due to not sharing a common plenum interrupting airflow by intake pulsing between cylinders.

[Bill Verburg]

the 3 barrel Weber setups are individual throttle body setups as are the MFI setups, RSR used a variation called 'high butterfly' MFI. These all utilize a separate butterfly for each cylinder, street setups all have low butterflies that are efficient at separating the pressure waves from the pistons of one cylinder from interfering w/ the adjacent cylinders

Current thinking is to use low mounted ITBs as used on the Webers and MFI setups w/ a plenum and electronic control via Motec or similar EFI controls.

Single throttle body setups w/ or w/o a plenum are subject to intake manifold pressure fluctuations from cam timing events where the pressure waves from one cylinder interfere w/ adjacent cylinders and have become common on modern smog motors which and to use very mild cams which minimize intake manifold pressure fluctuations.
MFI manifolds w/ low butterflies


964 w/ single TB and plenum


TWM 46mm aftermarket ITBs, low butterflies


964 3.8RSR w/ low butterflies and plenum


low butterfly ITB 964 w/ GT3 plenum

[procan]

So, I am planning to do a 3.2 swap on my '69 912 (which currently has a 2.0L '69 911E in it). Originally I thought I wanted to go with PMO carbs on the 3.2, but now having looked at ITB's with EFI, I am reconsidering my options. I thought putting carbs on the 3.2 would be much easier considering I have potential access to a 3.2 motor sans motronic and all its fuel injection components.

I like the old school vibe of carbs because they are in line with the old school vibe of my car, but ITB's with EFI are tempting. Can you do ITB's with carbs at all?

Thoughts?

[Bill Verburg]

Originally Posted by Bill Verburg

the 3 barrel Weber setups are individual throttle body setups as are the MFI setups,

3 barrel Webers or PMO's are ITBs

[procan]

i guess that answers my question.

[Canada Kev]

They're just not electronic. Or "injected" for that matter...

[equality72521]

Anyone done ITB's on an inter-cooled turbo with EFI?

[James Brown]

Originally Posted by equality72521

Anyone done ITB's on an inter-cooled turbo with EFI?

you can't really do that with a turbo in theory. As all the air goes into the turbo then the pressurized air goes to each cylinder. so it winds up being the same common plenum to each "throttle body". The air is being pushed in the cylinder vice being sucked in as with carbs or itb's. You can efi a turbo.

[Steve@Rennsport]

Originally Posted by James Brown

you can't really do that with a turbo in theory. As all the air goes into the turbo then the pressurized air goes to each cylinder. so it winds up being the same common plenum to each "throttle body". The air is being pushed in the cylinder vice being sucked in as with carbs or itb's. You can efi a turbo.

Porsche did this very successfully on the later 934's, 935's, 956's and 962's.

The plenum following the intercooler on the 934/935 cars fed 6 individual runners and butterflies. 956/962C water-cooled cars had the IC's positioned in front of 2 plenums; one for each cylinder bank over an ITB system.

[Tippy]

Anyone done ITB's on an inter-cooled turbo with EFI?

That's my ultimate goal.......but very far off.

[TimT]

Anyone done ITB's on an inter-cooled turbo with EFI?

This is one of ours, ITB's turbocharged, intercooled, 12 injectors staged, etc... We have built a number of other like it... in this pic the intercooler is not mounted as the powertrain is about to be stuffed back in the car.

Depending on traction loss on the dyno... this one is the far side of 700 hp, idles and drives beautifully for a fire breathing monster...

you can't really do that with a turbo in theory.

Hmmm, What?

See

Porsche did this very successfully on the later 934's, 935's, 956's and 962's.

We and many other engine builders have copied Porsches success building these type engines..

[Flieger]

Originally Posted by TimT

This is one of ours, ITB's turbocharged, intercooled, 12 injectors staged, etc... We have built a number of other like it... in this pic the intercooler is not mounted as the powertrain is about to be stuffed back in the car.

Depending on traction loss on the dyno... this one is the far side of 700 hp, idles and drives beautifully for a fire breathing monster...





Hmmm, What?

See



We and many other engine builders have copied Porsches success building these type engines..

The picture is not coming through for me.

[porterdog]

Originally Posted by Flieger

The picture is not coming through for me.

Me too, and now the kittens are sad.

[TimT]

The pic I linked shows up for me..

Pelican has been so friggin slow loading and refreshing for a week or two, hangs during searches, etc...

Anyway I found some pics of the ITBs that are on the engine pic I posted before,, and some pics of some hardware we used on another build..

[Tippy]

Pants are tight....