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I was curious if anything would be affected by changing the length of a vacuum hose on the 3SGTE engine (or, I guess, any engine).
I had purchased some silicone hose in the hopes of rerouting some of the vacuum hosing to 'tidy up' the engine bay a bit
 

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I was curious if anything would be affected by changing the length of a vacuum hose on the 3SGTE engine (or, I guess, any engine).
I had purchased some silicone hose in the hopes of rerouting some of the vacuum hosing to 'tidy up' the engine bay a bit
I'd say it wouldn't affect things enough to worry. What hoses were you planning to adjust?
Running a hose from the engine to the cabin for a boost gauge/controller can affect things due to it being so long but if it's just engine bay stuff from manifold to sensor or actuator then the affect will not be enough to worry.
 

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Don't forget there is a vacuum pipe that runs from the intake manifold to the brake booster.

I think you'll be just fine.
 

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The longer the vacuum line, the longer the lag will be between changes in pressure at either end of the line. Long lines are ok for things like brake boosters or AC idle up solenoids, but their lengths should be kept short for things boost controllers, map sensors, etc.

Sent from my SM-G973U using Tapatalk
 

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The longer the vacuum line, the longer the lag will be between changes in pressure at either end of the line. Long lines are ok for things like brake boosters or AC idle up solenoids, but their lengths should be kept short for things boost controllers, map sensors, etc.

Sent from my SM-G973U using Tapatalk
Have you seen how long the vacuum piping is on a stock GEN4/5 3SGTE? It's very long and also has a vacuum damper tank in line unlike the GEN2 and 3. Not sure about the GEN1 in the ST165 Celica.

But your points are valid.

AC idle up is just an air bypass valve. Not really an issue for length as it's quite long already.
 

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You can definitely get a resonance in the pressure signal, which is more likely with longer line lengths. This is only a problem on MAP sensors really.

Keep in mind the pressure inside the intake manifold is fluctuating, and the air in a vacuum line has a mass and stiffness, just like a spring. At a certain RPM, you can definitely get the air in the vacuum line to “bounce” more than the actual signal is changing now the intake plenum.

So don’t go longer than 12” on your MAP sensor line unless you know what you’re doing.
 
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