Compressor Surge, good or bad Options

[Tigawoods]

http://www.youtube.com/watch?v=LZUbo_mNDZM

ive read many debates of whether or not this is good for the turbo.
i first heard it on the ken nomuras blitz skyline and thought it was the blitz bov. i was wrong haha

i love the sound to death

[Rayme]

I thought about it...

under normal operation, you have the exhaust side of the turbo pushing the turbing, and on the other side, you have the impeller compressing air. That normal condition alone apply a twisting force to the shaft.

During "surge" you have the impeller being slowed down by air, and the exhaust side somewhat spinning freely because of lack of throttle plate opening..that also apply a twisting force to the shaft.

So..is it really that bad? Certainly for performance as it slows the turbo when the throttle plate closes but damage the turbo?
The 5th gen all-trac has no bypass valve, and alot more cars (mostly older ones) and turbos have been around for decades.

Myself I don't think compressor surge is all what it's cracked up to be. All turbos are going to die before the engines itself.

This post has been edited by Rayme: Apr 23, 2008 - 10:09 AM

[alltracman78]

I thought about it...

under normal operation, you have the exhaust side of the turbo pushing the turbing, and on the other side, you have the impeller compressing air. That normal condition alone apply a twisting force to the shaft.

During "surge" you have the impeller being slowed down by air, and the exhaust side somewhat spinning freely because of lack of throttle plate opening..that also apply a twisting force to the shaft.

So..is it really that bad? Certainly for performance as it slows the turbo when the throttle plate closes but damage the turbo?
The 5th gen all-trac has no bypass valve, and alot more cars (mostly older ones) and turbos have been around for decades.

Myself I don't think compressor surge is all what it's cracked up to be. All turbos are going to die before the engines itself.

Twisting isn't the big problem, that force is applied in the same direction, which isn't as bad.

You have the compressor spinning at somewhere near 100,000 RPMs [under high boost], when you have surge you have pressurized air shooting back at the compressor blades, trying to force them in the opposite direction.
This fatigues the compressor blades.
It works similar to how rod bolts stretch at higher RPMs, though that is a much more extreme example.

It's not going to break the turbo the first time it happens, or the tenth, or probably the hundredth, but it most definitely will weaken the turbo to some extent. How much depends on how bad the surge is and how often you do it.

It's never a good thing.