07-09-2014, 01:40 PM
This is surge ON the throttle... Nothing to do with lifting off the throttle - that's why it's damaging.
This is happening due to the fact that the turbo is moving too much air at too lower shaft speed - the air pressure is going up due to increased airflow rates, but the flow becomes unstable in the compressor - the turbo eventually gets to the point where the air starts tumbling on the tips of the compressor blades and starts effectively returning back through the housing, causing that massive chirp...
I've seen compressors do this ONCE and snap the shaft clean in half...
https://www.youtube.com/watch?v=nCj6Spwl1CU
Notice it's ON the throttle making those horrific noises. This is generally due to poorly sized or older turbochargers, older generation turbos that are used in larger applications that generally aren't designed for high pressure ratios, rather higher airflow rates... This is why I've harped on so many times about the GTB2056VK on the basis it's compressor geometry is designed for high pressure ratios, making it very resistant to surge. Same goes for the new GTX2860RS Rally turbo:
![[Image: GTX2860R_rally_map.jpg]](http://www.owendevelopments.co.uk/uploads/products/GTX2860R_rally_map.jpg)
Notice the pressure ratio goes to PR4.5!!!
![[Image: gt28rscompress.gif]](http://www.atpturbo.com/root/maps/images/gt28rscompress.gif)
Versus the older GT2860RS - only goes to 2.5 before it runs out of puff...
But all of this bollocks is irrelevant because apparently it sounds awesome.
This is happening due to the fact that the turbo is moving too much air at too lower shaft speed - the air pressure is going up due to increased airflow rates, but the flow becomes unstable in the compressor - the turbo eventually gets to the point where the air starts tumbling on the tips of the compressor blades and starts effectively returning back through the housing, causing that massive chirp...
I've seen compressors do this ONCE and snap the shaft clean in half...
https://www.youtube.com/watch?v=nCj6Spwl1CU
Notice it's ON the throttle making those horrific noises. This is generally due to poorly sized or older turbochargers, older generation turbos that are used in larger applications that generally aren't designed for high pressure ratios, rather higher airflow rates... This is why I've harped on so many times about the GTB2056VK on the basis it's compressor geometry is designed for high pressure ratios, making it very resistant to surge. Same goes for the new GTX2860RS Rally turbo:
Notice the pressure ratio goes to PR4.5!!!
Versus the older GT2860RS - only goes to 2.5 before it runs out of puff...
But all of this bollocks is irrelevant because apparently it sounds awesome.
