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Holset velocity stack

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Old 11-19-10, 11:28 AM
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Holset velocity stack

It seemed like the inlet to my turbo wasn't really optimized for flow, so I decided to whip up a quick velocity stack ring for the anti-surge housing.. Not sure how much it helped but it's removable so I can do back to back testing at some point.


Drilling holes.


Ready to part.


Rough inlet angles cut.


After finishing inlet stack.


Backside machine work.


Ready to drop into housing.
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Old 11-20-10, 08:15 AM
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Nobody like a show-off Aaron, especially with your fancy machining tool!! ;-)

All kiddin aside, it looks very well-thoughout and just plain cool, so I'll await your furthering success stories.
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Old 11-20-10, 12:42 PM
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Very nice work, looks pretty, quality craftsmanship.

I am not sure if it will actually do anything as the opening on the Holset is pretty wide and short... FWIW though It looks like something I would obsess over and do if I had the time/tools .

You don't think the ring will be forced out when you let off the throttle from air coming back through the anti surge shroud do you? or is it pressed in there pretty tight?

+1 on wanting to see success stories!
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Old 11-20-10, 04:06 PM
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damn Aaron thats pretty win!
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Old 11-20-10, 10:06 PM
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Thanks guys! Yeah, I'm not too sure it'll do anything either, but I had an itch to make it, so I did..

It's basically pressed in so will require some major effort for when/if I decide to remove it.

I want to start taking more pictures of the little things I've been working on, so should hopefully have some more good stuff to post soon.
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Old 11-21-10, 12:08 AM
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wow. Definitely a thumbs up Aaron.
I'll be visiting you when I come back to Arizona next month.
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Old 11-21-10, 06:08 AM
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Originally Posted by 2a+RoN View Post
I want to start taking more pictures of the little things I've been working on, so should hopefully have some more good stuff to post soon.
You should do like all of us rotary-narcissist, and start you own <forgive the military term> "I Love Me" thread. I'll even throw out a title for your consideration: Aaron Innnovation Funhouse!
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Old 11-22-10, 12:10 PM
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Hahaha, I might just have to do that!
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Old 11-22-10, 01:47 PM
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AZ

Originally Posted by 2a+RoN View Post
Thanks guys! Yeah, I'm not too sure it'll do anything either, but I had an itch to make it, so I did..

It's basically pressed in so will require some major effort for when/if I decide to remove it.

I want to start taking more pictures of the little things I've been working on, so should hopefully have some more good stuff to post soon.

Looks good! What are the radii of the diameter and the opening?

I'm in Gilbert. Where is your shop?


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Old 11-24-10, 01:30 PM
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I'm not sure I know exactly what you mean...? The velocity stack radius I finished by hand, but I'm guessing somewhere around .75 to 1" radius. The inlet opening diameter is ~2.4", and the outer diameter of the ring is ~3.6". Hope that answers your question.

I work at YawPower/Injector Dynamics in Phoenix.
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Old 11-24-10, 08:06 PM
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what's the purpose of the drilled holes on the outside ?
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Old 11-24-10, 10:12 PM
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Originally Posted by dj55b View Post
what's the purpose of the drilled holes on the outside ?
Anti-surge...

Holsett turbos are built for diesel trucks, which do not use BOV's. So instead of air surging through the compressor putting unwanted force on the compressor possibly causing it to rotate the opposite way, it sneaks out through that area.
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Old 11-24-10, 10:16 PM
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Your idea is way better than mine. But here's what I did to my Holsett (not trying to thread jack, just bored)

Beveled and radius the inlet and removed as much material as possible. The intake attaches to just the main inlet with a velocity stack on the end of that.


Stock:









Modded:









Did this to a friends GT28, he noticed a faster spool up. Have not tested this one yet.
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Old 11-25-10, 09:33 AM
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Looks good! Unfortunately my lathe isn't large enough to get the entire housing chucked up.. I would've liked to taper further down on the inlet like you did, but I drove the car to the shop that day and was running out of time.
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Old 11-25-10, 01:15 PM
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I have done alot fo flow work where I used to work and we used exclusively "3-D " orifice nozzles. The length of the straight section is the diameter, and the radii is also the radius of the opening opening dimension.

That anti surge opening looks like it could kill a ton of velocity. Can you plug it off since you have the ability to install a BOV?

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Old 11-28-10, 12:37 AM
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On the trucks some of the turbos cams with a plate over the antisurge ports. Removing the plate made the turbos much louder but also spooled up a bit faster.
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