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So I recently picked up a new Turbonetics 57 trim with a .63 A/R stage III turbine housing for stupid cheap. It isn't the 50 trim that I had been looking for my MR2 but it is pretty close. I've noticed that many people complain about surging issues with this turbo so I've been trying to find a way to fix it and make the turbo perform better below 20 psi.

So here goes....


Below you will see a cut away of the inlet of the turbo. The blue line represents the top of primary fins while the purple is the top of the secondary fins. The black holes in center and to the left are a width enhancement grooves (WEG). To the right is how the turbo inlet looks when it is not modified.

My general theory and hope is that by placing the inlet to the WEG at the transitioning point from the bell mouth to the vertical side wall, I will allow the slower moving laminar air around the walls of the inlet to be sucked into the holes and supply more air to the secondary fins. My main concerns are the effect this will have on the region just below the holes. I don't know how these low pressure regions will effect the performance of the primary fins. My other concern is at higher speeds if the WEG system starts working in reverse and air is bled out of the region between the primary and secondary fins and exits out the inlet of the WEG holes. In theory however, air should only be exiting the inlet of the WEG holes during events just prior to surge, otherwise they are "supposed" to aid in making the compressor more efficient. Properly tuned WEG systems can also decrease spool time as well. Holset's WEG system is very efficient and is part of the reason why they are such robust units when it comes to flow and spool.

This flow model gives only a very basic idea into what will be happening. I unfortunately cannot run a flow simulation with a spinning object inside so take this model with a grain of salt. It may turn out to be completely useless and not representative of reality.



Now I've done similar modifications to 3 other turbos so this isn't my first time doing this. My issue is the only difference in this situation is that there was a lot more room on the other turbo inlets to put the WEG hole inlets much higher up, away from the compressor. This new setup has the potential to be more effective but I thought that I'd get some feedback first.
 
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