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Old 11-05-2009, 08:12 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #21 (permalink)
OFF THE BOOST PIPE NOW...
 
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What's that black round thing ? The engine?



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Old 11-06-2009, 01:20 AM
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Quote:
Originally Posted by Miguel Antonett View Post
Forgive my ignorance, but what do the holes on the one on left do?
Sooooo, nobody knows?
Old 11-06-2009, 04:02 AM
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Quote:
Originally Posted by Miguel Antonett View Post
Forgive my ignorance, but what do the holes on the one on left do?
In theory, they should enable dilithium matrix realignment which in's turn will make vortex into turbo stronger.

In practice, they don't do anything. It's like polishing the compressor.

This "blinging" of turbo with holes not-going anywhere should not be compared to proper "ported shroud" intake present on Garrett and some other suppliers turbos. In "ported shroud" there is an extra air path to compressor which extends surge limit.
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Last edited by beepbeep; 11-07-2009 at 06:14 AM..
Old 11-06-2009, 05:11 AM
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That's exactly what I thought.............. just kidding.

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Old 11-06-2009, 05:16 AM
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Gtk series From Turbonetics


(A quote form Turbonetics Inc. home page). The GTK turbo units feature special "Map Enhancement Porting" to allow the compressor wheel to operate @ it's effiency accross a vary broad R.P.M. range This design has precisely placed slots machined into the comperssor housing to limit the effects of surge as well and provides additional air flow to make maximum H.P. @ high boost pressure levels and accross the entire R.P.M. range. All I can say is it works for me. And with what I have saw from thier products I have no need to question their engineering expertice. I get 1.2 bar @ 2900 r.p.m. in 3rd gear in a 92 3.3 with stock header,no cat and g-pipe fab speed air intake utcis w.u.r. ngk afr meter blltit bov stock waste gate w/gutted cat on it.
Old 11-06-2009, 05:54 AM
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As long as those holes actually lead to slit underneath the compressor, the trick will work.

But if you only have bunch of dead-end holes drilled into compressor intake, there is no gain.

This is how it works:
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Old 11-06-2009, 06:28 AM
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The holes do lead to the compressor. Benefit? I think it is mostly marketing.
Many turbos will hit full boost before 3000rpm, I would consider them a lag monster if boost comes later than that.
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Old 11-06-2009, 09:31 AM
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ok
Old 11-06-2009, 12:22 PM
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Quote:
Originally Posted by RarlyL8 View Post
The holes do lead to the compressor. Benefit? I think it is mostly marketing.
Many turbos will hit full boost before 3000rpm, I would consider them a lag monster if boost comes later than that.

The real ported-shroud does indeed offer benefits. But it doesn't have home-made holes. it looks like this:




And this is the difference:



If there are any old pilots here they might remember old 707's with "blow-in" doors on engines which were sucked open at takeoff. Ported shroud works in similar way but it's constantly "open" so you loose litte bit of efficiency to lower surge margins.

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Last edited by beepbeep; 11-06-2009 at 05:09 PM..
Old 11-06-2009, 04:52 PM
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Very cool information Goran. Thanks for sharing.
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Old 11-06-2009, 08:10 PM
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As always, devil is in the details. If you read the map above, it looks like ported shroud indeed gives better efficiency on boost threshold. But if you peek further, you see that shroud will actually give higher boost threshold (worse response) at low loads and boosts up to 1.2 bar (!). Once you start hitting 1.6 bar (which you probably never will in 930), ported shroud starts to shine.

Thus, ported shroud isn't always better. It depends on application. It's mostly used on very high boost diesel applications. But for moderate boost, it might actually make things worse.

Compressor map is needed in order to chose optimal turbocharger. Just drilling holes without actual map can easily make things worse.
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Last edited by beepbeep; 11-07-2009 at 04:08 AM..
Old 11-07-2009, 03:02 AM
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Quote:
Originally Posted by beepbeep View Post
As always, devil is in the details. If you read the map above, it looks like ported shroud indeed gives better efficiency on boost threshold. But if you peek further, you see that shroud will actually give higher boost threshold (worse response) at low loads and boosts up to 1.2 bar (!). Once you start hitting 1.6 bar (which you probably never will in 930), ported shroud starts to shine.

Thus, ported shroud isn't always better. It depends on application. It's mostly used on very high boost diesel applications. But for moderate boost, it might actually make things worse.

Compressor map is needed in order to chose optimal turbocharger. Just drilling holes without actual map can easily make things worse.
Goran,
Thanks for your invaluable input. What I'm most concerned about regards to shrouding are the benefits of such a design when the throttle body is suddenly closed under full boost (i.e. changing gears).
Does a design such as shrouding help reduce those stresses on the turbo?

Thanks,
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Old 11-07-2009, 06:05 AM
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Quote:
Originally Posted by WERK-I View Post
Goran,
Thanks for your invaluable input. What I'm most concerned about regards to shrouding are the benefits of such a design when the throttle body is suddenly closed under full boost (i.e. changing gears).
Does a design such as shrouding help reduce those stresses on the turbo?

Thanks,

Well I believe that BOV will take care of boost peaks. So abrupt throttle closing is not really the turbo problem but BOV problem. They might react differently if BOV is malfunctioning but as long BOV works, there should be no issues.

On the other hand, different low-load surge lines on ported/non-ported shroud designs will give you different boost buildup characteristics after you shift and get on the gas again, depending on boost you run.

Turbo depicted above will have "low boost" buildup slightly delayed and high-boost sped up. But I bet differences would be quite small and in <1 bar boost scenario, non-ported turbo would be wiser choice.
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Old 11-07-2009, 06:14 AM
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Quote:
Originally Posted by beepbeep View Post
Well I believe that BOV will take care of boost peaks. So abrupt throttle closing is not really the turbo problem but BOV problem. They might react differently if BOV is malfunctioning but as long BOV works, there should be no issues............................................ .
Agreed. Doing some primitive math in my head, I'm thinking of a high horsepower engine pulling some 900CFM at 6000RPM and then having the TB close for shift. It seems there may not be enough volume capability built into the typical BOV.
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Old 11-07-2009, 06:30 AM
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