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Bypass Valve Block?

Sun Dec 02, 2018 9:10 pm

Hi! I was wondering how to block the bypass valve so i could get that "stututu" sound.
i tried blocking the hose where the boost air goes in return in the air intake, but the car wouldn't idle. it just died. And it wouldn't run clean...

help! is there somewhere else i can block it? maybe before the valve somewhere?
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Re: Bypass Valve Block?

Mon Dec 03, 2018 12:17 am

You want compressor surge? Generally you'll need to run high boost without a BOV or BPV. On a 185 that should just mean leaving it stock, on a 205 capping off both sides of the BPV should do it but I doubt you'd get surge at stockish boost levels.

Re: Bypass Valve Block?

Mon Dec 03, 2018 2:20 pm

i'm going to increase boost level soon, i have the parts for it.
planning on pushing the boost just below where the fuel cut happens.

but how do i get rid of or block the bypass valve to get that compressor surge sound?


Re: Bypass Valve Block?

Mon Dec 03, 2018 5:11 pm

I'm confused about this thread. On a stock st185 there is no bypass valve from the factory.

If there is a bypass valve just unplug the vacuum line going to it and it won't open when you let off the throttle.

To get the stutututu sound you just need an open air filter like a cone, pod, or mushroom type before the air flow meter.

Re: Bypass Valve Block?

Mon Dec 03, 2018 11:11 pm

Compressor surge is really hard on your turbo. And it won't last long with high boost. Maybe you're thinking of the sound a blow off valve makes.

Re: Bypass Valve Block?

Tue Dec 04, 2018 6:01 pm

no, i was thinking of the compressor surge sound, but if the ST185 dont have a bypass valve, then where doeas the air go when i let go of the gas? does the air go backwords thru the tutbo and out the air filter stock? :shrug:
Sorry if i seem stupid, but i recently bought this car, and it is my first turbo car... :) (really want to learn)

Re: Bypass Valve Block?

Tue Dec 04, 2018 7:59 pm

Sort of. A bypass valve and blow off valve are the same thing. It really just depends on where it sends the air. A bypass valve sends the back in front of the turbo and a blow off valve vents to atmophere. They are basically pressure release valves. The st165 and st185 don't have either. So when you let off the throttle and the throttle plate closes. The compressed air from the turbo has nowhere to go except try and go back through the turbo. But the turbo is still spinning and resists this. And since the turbo is still spinning it's still trying to compress the air. So now the turbo is fighting against all that compressed air and starts "chopping" through the air instead of flowing it. This chopping is what compressor surge is. Its also called turbo bark. This is really hard on the turbo bearings and will make your turbo not last long. Why Toyota didn't put bypass valves on I'm not sure. Maybe because the engines run such low boost maybe they thought it wasn't needed. But turning the boost up will make this problem worse.

Here is a good article explaining it better. http://www.themotorhood.com/themotorhoo ... 3njyfv84bn
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