Surge ports less effecient

[GST Kidd]

"A Ported Shroud compressor (see Fig. 2) is a feature that is incorporated into the compressor housing. It functions to move the surge line further to the left (see Fig. 3) by allowing some airflow to exit the wheel through the port to keep surge from occurring. This provides additional useable range and allows a larger compressor to be used for higher flow requirements without risking running the compressor into a dangerous surge condition. The presence of the ported shroud usually has a minor negative impact on compressor efficiency."
I got this info straight from garret. So this means a none surge port housing is better. But I read on one of the rx7 forums where somebody did a comparisson with a surge port and none surge port housing and the surg port housing made like 21 more horses than the none surge ported housing.

 

[turbo addict]

ported shroud flows less than a non-PS. But if you get surge then it is better to have it. The supraguys have been getting inserts and/or custom intake bellmouths that get rid of the PS for more top end.