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The noise created with the turbo discharge silencer removed is minor, no big deal. HOT and later models don't have one. Between the turbo compressor and the intercooler is a 2" aluminum pipe. The silencer is pressed into it and is made of plastic and fabric. It comes out in pieces with the help of long nose pliers and other implements of destruction. It will be wet with oil, some from the engine blow by gasses that enter the intake upstream of the turbo, some from turbo sealss... which is normal.
The turbo noise is more easily heard with a K&N and a modified air box.
To remove the transistion casting, remove the plastic cover by lifting up at the back, the moving backwards to slide pins out of rubber gromlets at the front. Remove 2 10mm head hex bolts that go into the throttle body, and slacken two hose clamps. Remove wire harness socket from the intake air temerature sensor. Lift the big end of the casting and pull out of the rubber coupling sleeve with one motion.
Note that the outside diameters of the casting and the rubber coupling sleeve are the same. Note that the 2" - 50mm aliminum pipe is thin walled, and the casting thickness varies from 3/16 to 5/16 inch, depending on how the casting was 'balanced' when mounted to get the outside diameter machined to accept the rubber coupling sleeve. This thick wall of the casting creates the inside diameter step reduction. To eliminate this you need to grind and polish off a great amount of aluminum to get a thin lip at this point in the casting, and transistion this as far up into the casting as you can. The bend in the casting does limit what you can do.
If you do not see this thick wall at the casting end, then the casting was reworked by someone else. This engineering goof in in all NG900's from 1994 to 1999 production.
The casting rework produces more power and makes the engine smoother at the same time. Seemingly contradictory. The stock situation creates such turbulance and surging that the fueling and cylinder charging is uneven. Reworking the casting fixes that situation. Power comes on faster and torque holds better up to the red line. Removal of the turbo compressor discharge silencer also removes a significant restriction that will allow faster boost onset and better power when heading for the red line. These two changes will complement each other, and the sum is greater then the parts. Ditto for the air box and low restriction eshaust. That is the way that things are with turbos.
Further details and pictures are in my posts from last fall, and a few links to these were posted since then.
Keep everything clean. Brush off dirt from clamps before opening things up. Wash what you can before refitting. Use a light dressing of silicone grease on the large o-ring for the casting before refitting.
, Wed, 14 Mar 2001 08:56:17, Wed, 14 Mar 2001 11:00:37
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