IS350 throttle body
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lilbaeleaf (04-19-24)
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09-19-06, 04:46 PM
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09-19-06, 05:19 PM
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They are throttle by wire. Basically what that means is that the butterfly valve inside the throttlebody is controller by a motor or servo which is controlled by the computer instead of having a cable physically connecting the butterfly valve to the accelerator pedal.
09-19-06, 07:33 PM
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09-19-06, 07:39 PM
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Without the TB, you're taking out one of those ingrediants which is AIR.
since that is where the intake mates with.
09-19-06, 10:33 PM
#14
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Huh?
All the throttlebody does is restrict intake air to regulate engine airflow and thereby control engine power and speed. They only work on gasoline engines with spark ignition. A cable operated throttlebody has a wire attached to the accelerator and the throttle is directly controlled by the operator's foot. We have a "drive-by-wire" system where the ECM controls the throttle position based on operator input and operating parameters predetermined by Toyco when they wrote the code for the ECM. The throttle can actually be doing something quite different than what you think, and there are a LOT of good reasons for this.
Diesels have no throttlebody because they control engine speed and power by restricting fuel, not air. Compression ignition needs a full gulp of air just to develop enough heat to ignite the fuel.
The throttlebody only plays a tiny role in determining a/f, and TPS data is used for enrichment when the blade (butterfly valve) in the throttlebody opens quickly just like an accelerator pump on a carburetor.
Determining the actual amount of fuel the engine needs involves a number of sensors, some of which refer to base fuel maps and others providing correction factors to those base maps. There are also a number of types of fuel injection both with and without feedback sensors.
The only FI using the throttlebody data exclusively is called alpha-n, and it employs no feedback at all. It's a simple VE map with target fuel values based on rpm and throttle position. It is not used in modern emissions controlled automobiles at all because it can't be made to compensate for myriad variables in atmospheric conditions and still produce a good emissions profile. They are the "carburetor" of electronic fuel injection - simple, effective, but impossible to keep in sharp tune over a wide range of conditions and time.
There is obviously a LOT more to electronically controlled fuel injection and throttlebodies, but if you think this post is long, well, the post describing all those things would be ridiculously long and only interesting to a very few people.
All the throttlebody does is restrict intake air to regulate engine airflow and thereby control engine power and speed. They only work on gasoline engines with spark ignition. A cable operated throttlebody has a wire attached to the accelerator and the throttle is directly controlled by the operator's foot. We have a "drive-by-wire" system where the ECM controls the throttle position based on operator input and operating parameters predetermined by Toyco when they wrote the code for the ECM. The throttle can actually be doing something quite different than what you think, and there are a LOT of good reasons for this.
Diesels have no throttlebody because they control engine speed and power by restricting fuel, not air. Compression ignition needs a full gulp of air just to develop enough heat to ignite the fuel.
The throttlebody only plays a tiny role in determining a/f, and TPS data is used for enrichment when the blade (butterfly valve) in the throttlebody opens quickly just like an accelerator pump on a carburetor.
Determining the actual amount of fuel the engine needs involves a number of sensors, some of which refer to base fuel maps and others providing correction factors to those base maps. There are also a number of types of fuel injection both with and without feedback sensors.
The only FI using the throttlebody data exclusively is called alpha-n, and it employs no feedback at all. It's a simple VE map with target fuel values based on rpm and throttle position. It is not used in modern emissions controlled automobiles at all because it can't be made to compensate for myriad variables in atmospheric conditions and still produce a good emissions profile. They are the "carburetor" of electronic fuel injection - simple, effective, but impossible to keep in sharp tune over a wide range of conditions and time.
There is obviously a LOT more to electronically controlled fuel injection and throttlebodies, but if you think this post is long, well, the post describing all those things would be ridiculously long and only interesting to a very few people.
