by gman07 » Thu Jul 26, 2007 4:17 pm
Here's the best picture I found on a quick Google Image search:
http://www.litchfieldimports.co.uk/imag ... r/may3.jpg
The MWE slot is on the inside of the shroud, just behind the leading edge of the blades on the compressor.
Here's part of a turbo I drew in Solidworks... you can see the MWE slot, though it's not quite as wide as I wanted.
http://www.dieseltruckresource.com/pics ... user=34373
The first part of this article describes it:
http://www.turbobygarrett.com/turbobyga ... ch103.html
The MWE slot decreases compressor efficiency, so under normal conditions
no MWE slot (or ported shroud, or whatever you feel like calling it) is best. However, at low RPM under high load, the compressor will tend to surge without it. This is basically the same thing as turbo bark; when, especially on an auto, you let off the throttle and RPM's drop, the turbo continues to spin and try to create the boost pressures it was before. As RPM's drop, the compressor moves off it's map to the left, past the surge line, and the turbo "barks". The MWE slot widens the map out to the left.
Disclaimer: I don't necessarily know anything.
1992.5 W250 pump tweaked, straight pipe, gauges, 3200 Gov. spring, AFC lever partially ground, timed at 1/8", Fuel pin ground, BHAF, HTT Stage IV H1C/E 60/12wg (ported), Transgo shift kit, KDP clothes-hangered, 202,000 miles - 36psi, 1250°