Intake Options
11-01-2010, 05:22 PM
#21
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Maximum vacuum is at idle. Opening the throttle plate reduces the vacuum in the manifold.
On an old NA engine one can have manifold vacuum (max at idle) & venturi port vacuum (max at max airflow).
On an old NA engine one can have manifold vacuum (max at idle) & venturi port vacuum (max at max airflow).
Last edited by m444; 11-01-2010 at 05:25 PM.
11-02-2010, 05:44 AM
#22
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Maximum vacuum in the manifold, yes, but in the airbox?
I doubt the airbox is ever significantly under- or over-pressured at all (it's not even air-tight).
I doubt the airbox is ever significantly under- or over-pressured at all (it's not even air-tight).
11-02-2010, 08:04 AM
#24
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No No, No, This only refers to vacuum lines that might run up to a vacuum operated actuator air vane. There is not enough vacuum in the air box to drive anything.
11-02-2010, 10:14 AM
#25
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Exactly - So I go back to: I don't see any way this flap is opened by vacuum - and it doesn't have any electrical connections, so . . . ?
11-02-2010, 10:18 AM
#26
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And in that case, did it have a power connection, and a connection to the ECU to convey RPM data? This flap has no wiring, tubing . . . no nothing connected to it in any way that I can tell, but there is a mechanism that seems to act against a spring that holds it closed, somehow . . .
11-02-2010, 10:52 AM
#27
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I would not expect wires to run vacuum, but vacuum lines would. The earlier statement mentioned no wires, but that does not preclude having a vacuum lines running to the flap. It could be just a thermostatic valve that opens when temperature rises above some preset temp.
11-02-2010, 12:03 PM
#28
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There's no vacuum line to the mechanism, either.
I believe actuation of this flap is temperature-driven as well, as I think its function is emissions-related. This point is what makes this conversation not a total thread hijack - this flap and its function, whatever that may be, are lost with any aftermarket intake that doesn't retain the factory airbox.
What I don't understand is where the motive force comes from to open this flap against a spring. Are you suggesting that there exists a completely unpowered mechanism that could react to a temperature change and do this? (That would be neat, and seems to me to be exactly what's happening).
I believe actuation of this flap is temperature-driven as well, as I think its function is emissions-related. This point is what makes this conversation not a total thread hijack - this flap and its function, whatever that may be, are lost with any aftermarket intake that doesn't retain the factory airbox.
What I don't understand is where the motive force comes from to open this flap against a spring. Are you suggesting that there exists a completely unpowered mechanism that could react to a temperature change and do this? (That would be neat, and seems to me to be exactly what's happening).
11-02-2010, 12:22 PM
#29
AudiWorld Super User
Yes, thermostatic springs have been around for a long time. On the old domestic cars, there was heat riser on the exhaust, that was activated by a thermostatic wound spring. It would be closed, when cold, but would open, when the exhaust heated it up. Some old carburetor chokes used this type of control for cold start.
Metals contract and expand with temperature. Depending on the alloy & physical implementation this can be used to create a temperature sensitive valve or switch.
If you look at an old wall thermostat inside is generally a thermostatic wound spring with a mercury switch hanging off the end. Rotating the spring mount, will change the position of the spring end relative to temperature. The mercury switch contacts control current in a circuit to activate a heater of cooling system.
Metals contract and expand with temperature. Depending on the alloy & physical implementation this can be used to create a temperature sensitive valve or switch.
If you look at an old wall thermostat inside is generally a thermostatic wound spring with a mercury switch hanging off the end. Rotating the spring mount, will change the position of the spring end relative to temperature. The mercury switch contacts control current in a circuit to activate a heater of cooling system.
11-02-2010, 01:07 PM
#30
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Very cool. Most likely then the brass cylinder that I thought was a battery actually does something like you descibe here. [Must resist the urge to tear the thing apart in a fit of curiosity . . .]
Yes, thermostatic springs have been around for a long time. On the old domestic cars, there was heat riser on the exhaust, that was activated by a thermostatic wound spring. It would be closed, when cold, but would open, when the exhaust heated it up. Some old carburetor chokes used this type of control for cold start.
Metals contract and expand with temperature. Depending on the alloy & physical implementation this can be used to create a temperature sensitive valve or switch.
If you look at an old wall thermostat inside is generally a thermostatic wound spring with a mercury switch hanging off the end. Rotating the spring mount, will change the position of the spring end relative to temperature. The mercury switch contacts control current in a circuit to activate a heater of cooling system.
Metals contract and expand with temperature. Depending on the alloy & physical implementation this can be used to create a temperature sensitive valve or switch.
If you look at an old wall thermostat inside is generally a thermostatic wound spring with a mercury switch hanging off the end. Rotating the spring mount, will change the position of the spring end relative to temperature. The mercury switch contacts control current in a circuit to activate a heater of cooling system.