Throttle bodies
Discussion
Pretty much all cars have throttle bodies. One, usually- which contains a butterfly valve to regulate airflow through the inlet duct and into the inlet manifold, which splits the flow into the cylinders. On a SPI (single point injection) engine, the injector is also integrated into the throttle body.
Putting a mini-throttle body on each cylinder shortens the inlet tract (from about two feet to about six inches) Which is supposed to improve flow characteristics and therefore response, the flow of the head (increased cf/m) etc. Having a throttle body on each cylinder also increases tunability and facilitates accurate syncronisation of gas flow through all the cylinders (making them even in gas flow to improve power delivery etc)
Depending on the engine configuration, Throttle bodies can have injectors built in same as an SPI set up only multiplied for the number of cylinders.
Putting a mini-throttle body on each cylinder shortens the inlet tract (from about two feet to about six inches) Which is supposed to improve flow characteristics and therefore response, the flow of the head (increased cf/m) etc. Having a throttle body on each cylinder also increases tunability and facilitates accurate syncronisation of gas flow through all the cylinders (making them even in gas flow to improve power delivery etc)
Depending on the engine configuration, Throttle bodies can have injectors built in same as an SPI set up only multiplied for the number of cylinders.
Carby131 said:
Hi all
Quick question that will probably get a long answer...
I cannot see the logic or how throttle bodies on cars work.
In trumpet form where is the air filter?
lots of questions would aprechiate someone to explain it to me
Thanks all
Erm, all injection engines use a throttle body. I think you are wanting to ask a different question to the one you have.Quick question that will probably get a long answer...
I cannot see the logic or how throttle bodies on cars work.
In trumpet form where is the air filter?
lots of questions would aprechiate someone to explain it to me
Thanks all

The logic... on how they work is simple.
Normally aspirated engines (rather than forced induction engines, turbo, supercharger, nitrous) need a way of encouraging air to enter the cylinders. Part of the solution is to suck air in while the inlet valve is open and the piston is moving down in the cylinder. The other parts are to tune the exhaust, cams and intake. On some engines for some purposes you can open the exhaust valves at the same time as the inlet valves (overlap) which can help draw more air into the cylinders. If you eliminate the additional unnecessary parts of the intake tract by fitting individual throttle bodies directly to the side of the cylinder head you are making it easier for the cylinders to draw in more air. Ram-air does something similar. None of these things really work if you can't reconfigure the engine management though.
With variable valve timing you can play all sorts of funny tricks like bouncing air off closed valves and back into a one-way intake tract so the air is then forced to rebound and enter the combustion chamber at a higher rate when the valves open again.
Normally aspirated engines (rather than forced induction engines, turbo, supercharger, nitrous) need a way of encouraging air to enter the cylinders. Part of the solution is to suck air in while the inlet valve is open and the piston is moving down in the cylinder. The other parts are to tune the exhaust, cams and intake. On some engines for some purposes you can open the exhaust valves at the same time as the inlet valves (overlap) which can help draw more air into the cylinders. If you eliminate the additional unnecessary parts of the intake tract by fitting individual throttle bodies directly to the side of the cylinder head you are making it easier for the cylinders to draw in more air. Ram-air does something similar. None of these things really work if you can't reconfigure the engine management though.
With variable valve timing you can play all sorts of funny tricks like bouncing air off closed valves and back into a one-way intake tract so the air is then forced to rebound and enter the combustion chamber at a higher rate when the valves open again.
All injection cars have a throttle body. As standard you have a hose connecting the TB to the air filter. The air from the single TB is distributed via the inlet manifold.
ITB's is a throttle body for each cyclinder.
You can still have an air filter (as an example, most ///M engines use ITB's) but some crazy people just have open trumpets with no air filter.
Theoretically you can run a standard car with its single TB with no air filter.
ITB's is a throttle body for each cyclinder.
You can still have an air filter (as an example, most ///M engines use ITB's) but some crazy people just have open trumpets with no air filter.
Theoretically you can run a standard car with its single TB with no air filter.
i was talking about individual throttle bodies sorry, someone i know is putting them on a KA.
i have never had much experiance with them and people were confusing me saying they are only used with carbs and that it increases the cf/m, this confused me as if the ITB's were connected using adaptor plates between the manifold and head it cannot happen as it is not forcing air in and air can only flow at the same speed as through the manifold... if that makes sence
i just wanted to know the Pistonheads explination :P
i have never had much experiance with them and people were confusing me saying they are only used with carbs and that it increases the cf/m, this confused me as if the ITB's were connected using adaptor plates between the manifold and head it cannot happen as it is not forcing air in and air can only flow at the same speed as through the manifold... if that makes sence
i just wanted to know the Pistonheads explination :P
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