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Wastegate Porting Observations

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Old 01-31-08, 03:49 PM
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Lightbulb Wastegate Porting Observations

This is mainly concerning those people who have decided to go non-sequential or just to port out their wastegate to limit boost creep.

While the benefits of waste gate porting are largely known and usually necessary when making more power the limits of power gained from porting just the waste gate hole are quite low meaning that by porting as much as you can will still only result in minimal increases in flow. The major design flaw of the factory turbos are not in the size of the wastegate hole but the small angle at which it is able to open.

when you disassemble the turbos to port the wastegate have look at the center housing that connects the two turbos together. then re-assemble everything and just play with the loose wastegate. it is limited by the center housing that actually prevents the wastegate from opening wider. i measure the opening and at its most open point the flap was only less than 8 mm open at its farthest point. before hitting the center housing.

upon further investigation the part of the center housing that prevents the wastegate from opening further is a flat cast with enormous amounts of spare material. porting this extra material out will allow the gate to open further and YES IT DOES. after re-assembling everything i hooked up the wastegate actuator and applied pressure to the nipple and the actuator has the ability to open the wastegate even to this much increased angle. just think the actuators movement was actually limited by not pressure but by the wastegate hitting the center housings surface.

I dont have a before pic but i will sure post some after ones tonight and the range of motion or the increase was astounding! the flap now can open 15 millimeters at its widest point, an increase of nearly double, and this combined with porting the hole will increase flow massively. for anyone to ignore removing this material on the center casting is missing out on the full benefits of a perfectly ported wastegate.

Last edited by cp1; 01-31-08 at 04:13 PM.
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Old 01-31-08, 04:58 PM
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interesting...if you can post some pictures, it would benefit greatly along with your detailed description. Nice observation non-the-less.
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Old 01-31-08, 06:52 PM
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Ok a foreward it is very hard to see the limits of the wastegate when assembled but have a look at the pictures and the one with the red line i drew is where the surface of the casting extended out to. this "face" is what was stopping the wastegate, if someone has a pic of an un-altered one that would good for comparison but you can see how much material i have removed safely. the bolt hole is fine as that is for the downpipe and will be filled in of course the bolts dont actually thread that far into the housing even with all this porting so you could easily fill most of that hole with weld again. but the improvement is huge.
Attached Thumbnails Wastegate Porting Observations-b-031.jpg   Wastegate Porting Observations-b-032.jpg   Wastegate Porting Observations-b-033.jpg   Wastegate Porting Observations-b-034.jpg   Wastegate Porting Observations-b-035.jpg  

Wastegate Porting Observations-b-036.jpg  
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Old 01-31-08, 06:54 PM
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one more
Attached Thumbnails Wastegate Porting Observations-b-037.jpg  
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Old 02-01-08, 04:01 AM
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In my opinion this is a must for anyone about to port their waste gate and there really is no reason not too as long as you already have them apart.
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Old 02-01-08, 08:59 AM
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When I do the Rich Mans non seq modification I remove materal from the center casting so the gate opens more than stock . This is nothing new , if I do it I guess everyone knows about the need to do it .It is a must as you stated . Nice pics and write up for the non mechanics .
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