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What Would Happen If...

rbee25

By rbee25,
in Engines & Forced Induction

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fLhayabusa Enthusiast

fLhayabusa

Posted
Posted

it would most likely wear a standard turbo out quicker due to backspin.. not straight away. the car would still be drivable though it'll wear quicker the harder you drive/boost it.

Im currently running an aftermarket turbo with no bov. And have not seen any signs of problems or wear to the turbo'.

gt-ahhh! Proficient

gt-ahhh!

Posted
Posted

no expert, but my hypothesis would be that you would suffer boost spikes everytime you changed gears, or got off the loud pedal after boost. invariably there is nowhere else for this air to go but your engine. and remember the throttle is never fully closed, it remains slightly ajar to allow idle. so the pressurised air would find its way into the chambers and create an extremely lean mixture, and possibly result in detonation.

thats just my theory. i want to see how close i am to the truth.

mitchy_ Grand Master

mitchy_

Posted
Posted

the butterfly does close, the idle control valve at the back of the plenum is used to idle the engine.

the air that is usually supposed to go out the bov is just sent back to the turbo and tries to spin it the opposite way.

MBS206 Grand Master

MBS206

Posted
Posted (edited)
the butterfly does close, the idle control valve at the back of the plenum is used to idle the engine.

the air that is usually supposed to go out the bov is just sent back to the turbo and tries to spin it the opposite way.

IT DOES NOT TRY AND SPIN IT THE OPPOSITE WAY!!!

Turbo fins are setup uni directional.

Spin the compressor one direction, air will move through it. Spin it the opposite, the air doesn't get moved through it.

The same applies if you blow air through it, it'll spin one way, blow it the opposite, it won't.

The issue of turbos slowing down, is you get a large pressure build up between the turbo and throttle, if your pressure source, for your wastegate, is pre-throttle body, the wastegate remains open, but your turbo has less gas flowing through it, and the majority of what exits the motor, is headed down the wastegate anyway, so the turbo slows down that way.

Take the pressure source post-throttle, and you're fine.

edit: On a motor running an AFM, you will get "double counts" of air as it reverts through the intake, and you'll get double the amount of fuel, On an aftermarket ECU, you can tune this issue out to a fair degree, on a factory car ecu car, you'll have stalling issues.

Throw an ECU on that makes the AFM just a piece of pipe (IE, convert to MAP) you won't have an issue.

Edited by MBS206
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