Mt. Washington Turbo Restrictor Q's

Mt. Washington Turbo Restrictor Q's

Postby linc44 » Thu Nov 21, 2013 3:06 pm

So after looking through the posted competition classes for Mt. Washington, it looks like the only thing I need to change to my Subaru is adding a 40mm restrictor. Where did people buy/make/borrow a restrictor from for the 2011 event? I understand this question is being asked farrr in advance, but I'm in the sourcing parts mode since I will be doing some major maintenance (clutch, engine gaskets, suspension bushings, etc.) this winter and figured it would be a good idea to do the restrictor addition while it's all apart.

Also, I'm assuming that I will need a retune once the restrictor is installed correct? The car will otherwise be a completely stock 2004 STI, I'm just looking to verify if this should be another addition to the "to-do" list.

Thanks all!
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Re: Mt. Washington Turbo Restrictor Q's

Postby agrabau » Tue Mar 08, 2016 9:18 pm

http://climbtotheclouds.com/141-2/

"If the engine is turbocharged or supercharged and the displacement is under 2,501 cc it must have a turbocharger restrictor of 40 mm or smaller. If the engine displacement is over 2,501cc it must have a 36 mm restrictor or smaller. Any engine equipped with twin turbo chargers must utilize 28.8 mm restrictors in both turbo chargers. All turbocharger restrictors will maintain the required opening for at least 3 mm and the specified opening must be positioned no further than 50mm from the impeller. The restrictor must be pressed or bolted to the turbocharger and may not allow any additional air to enter the turbo except through the specified opening."

The best way to get this done is to remove the compressor housing from your turbo (or better yet, buy a spare housing) and bring it to a machine shop. Have them machine the compressor inlet nozzle flat and drill/tap three holes at 120 degrees apart on that newly created face to mount the restrictor. Show them a photo of a rally car restrictor and do your best to create a drawing for them based on the above info. Have them make the actual step to max diameter 39mm (or however large you feel safe) because it will expand with heat and will likely be expanded when tested. If you make it 40 on the nose and it's warm, it will fail.

Lots to consider.
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Re: Mt. Washington Turbo Restrictor Q's

Postby agrabau » Tue Mar 08, 2016 9:32 pm

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