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Anti-Surge/Ported Shroud Compressor Housing - Is it worth it?

Hey guys,

I've started to look at turbo options for "phase 2" of my turbo conversion, and I see that Garrett offers an Anti-Surge or Ported Shroud compressor housing to ensure that the intake manifold doesn't get overloaded under boost. It's only a $70 upgrade, but I'm wondering - is it worth for our cars? Most of us are running well under 2 BAR of boost with our air cooled engines. Plus our intake manifolds tend to be much larger than those of 4-bangers.

Thoughts?

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Old 06-21-2011, 09:25 AM
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I wouldn't buy it, same goes for ball bearings.
Old 06-21-2011, 10:56 AM
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It's for compressor stall between shifts... Why would you skip it for only $70 if you have room or it?
Old 06-21-2011, 01:10 PM
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Quote:
Originally Posted by E-man930 View Post
It's for compressor stall between shifts...
Isn't that what the BOV addresses?
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Old 06-21-2011, 01:26 PM
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Quote:
Originally Posted by polizei View Post
Isn't that what the BOV addresses?
Yes.
Old 06-21-2011, 01:31 PM
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BOV is to release pressure from closed throttle surge, between shifts, anti surge housings release excess pressure from compressor surge within the turbo. They're 2 very different issues.

Interestingly, if you look at the maps, well the ones I have seen it also increases the efficiency.

The bigger 40 series GT turbos have anti surge housings standard I'm pretty sure.

Andy, compare the maps of the turbo you're looking at with and without anti surge and base your opinions there, I have heard it adds lag but I'm not sure. As you mentioned, at low boost levels I don't think this is a factor.

Would love to hear Turbocraft's opinion on this as they use and spec their own Garretts.
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Old 06-21-2011, 03:47 PM
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Thanks Spence88mph - I didn't have the energy to type an explanation - my German Shepherd pup is wearing me out. Sometimes I feel 930 owners have become stuck in the turbocharging stone age. Wake up guys or the world of turbo cars will pass you by.
Old 06-21-2011, 04:58 PM
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polizei, if by BOV you are talking of the recirculation valve that connects the compressor discharge to the compressor intake tubes you are correct. The function of this valve is to prevent compressor surge when the throttle is closed and the air flow is instantly restricted.
Old 06-21-2011, 05:08 PM
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Stone age? Fancy slots cut in the housing and ball bearings are now state of the art? Maybe for a Honda. Twin VNT's are state of the art for Porsche.
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Old 06-21-2011, 06:20 PM
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Quote:
Originally Posted by spence88mph View Post
Andy, compare the maps of the turbo you're looking at with and without anti surge and base your opinions there, I have heard it adds lag but I'm not sure. As you mentioned, at low boost levels I don't think this is a factor.
Thanks as always for pitching in. I pulled the compressor maps for the two Garrett compressor housings I'm considering. The one on the left has a ported shroud and the one on the right does not. Otherwise, they appear identical. I'm not sure how to read these graphs. Thoughts?

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Old 06-21-2011, 06:36 PM
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I'm not an expert in turbo graphs but as you can see the graph on the left has more effeciency range (i.e. fatter area within the curves). Also, surge happens when the turbo operates to the left of the most left curve. So, the surge is less likely to happen on the left graph at the same air flow for a given pressure ratio. This can happen when the turbo is too large for a given engine dispacement under certain condition such as when the turbo starts to build boost at low engine rpm creating a phenomena where more boost builds than the engine can ingest. I'm sure this happens rarely on our 930 since our engine is relatively large for typical turbos used on these cars. I hope my lame explanation helps.
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Old 06-22-2011, 02:52 AM
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Quote:
Originally Posted by MikeD94 View Post
I'm not an expert in turbo graphs but as you can see the graph on the left has more effeciency range (i.e. fatter area within the curves). Also, surge happens when the turbo operates to the left of the most left curve. So, the surge is less likely to happen on the left graph at the same air flow for a given pressure ratio. This can happen when the turbo is too large for a given engine dispacement under certain condition such as when the turbo starts to build boost at low engine rpm creating a phenomena where more boost builds than the engine can ingest. I'm sure this happens rarely on our 930 since our engine is relatively large for typical turbos used on these cars. I hope my lame explanation helps.
A spot-on explanation.
The more developed a 930 engine, the less necessary the ported shroud is because the engine is more efficient at lower revs and can consume all the airflow generated by the turbocharger.
On a more stock engine -- 7:1 pistons, stock ports, stock cams -- we have had surge on the dyno and on the road. The turbos boost up quickly and produce more airflow than the engine can use, thus the surge. It makes a real distinct shhh-shhh-shhh sound, and a honking or chirping sound in really bad instances. It's really hard on the turbocharger.

Later spool up? We haven't seen it on these engines.
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Old 06-22-2011, 08:42 AM
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It's really hard on the turbocharger.
Thanks for your input Chris. So it sounds like at $70 this is cheap insurance. I'd rather a $1,500 turbo take a hit than a $15,000 engine. What type of engine damage have you seen when a surge occurs without an anti-surge compressor?
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Old 06-22-2011, 08:49 AM
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Sometimes I feel 930 owners have become stuck in the turbocharging stone age. Wake up guys or the world of turbo cars will pass you by.
I agree with you and I think these are the reasons why:

1. Peak hp cars are usually drag cars which Porsche's in general are not. Drag racing a motor is way easier than WOT for several seconds to minutes at a time sustaining high RPM's.
2. Blowing up a Civic motor is peanuts in money compared to a 911 hindering all the R&D that is needed to make huge 911 hp/tq.
3. The longevity of the triple-K is hard to beat but at the expense of a lot of hp. The "other" turbos just don't hang on in the long haul like the triple-K.
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Old 06-22-2011, 09:30 AM
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Quote:
Originally Posted by E-man930 View Post
Thanks Spence88mph - I didn't have the energy to type an explanation - my German Shepherd pup is wearing me out. Sometimes I feel 930 owners have become stuck in the turbocharging stone age. Wake up guys or the world of turbo cars will pass you by.
Hmmm. as for me, my stone aged 930 still made some modern rockets crying
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Old 06-22-2011, 11:23 PM
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Quote:
Originally Posted by TurboKraft View Post
On a more stock engine -- 7:1 pistons, stock ports, stock cams -- we have had surge on the dyno and on the road. The turbos boost up quickly and produce more airflow than the engine can use, thus the surge. It makes a real distinct shhh-shhh-shhh sound, and a honking or chirping sound in really bad instances. It's really hard on the turbocharger.
Just a point of clarification, have you found the GT3582 will not surge under load on basically stock 930 (3.0-3.3L) engines with the ported compressor housing?
Do you normally apply the same turbine A/R (?) for both stock and modified (400HP) engines?

Thanks
Old 06-23-2011, 03:37 AM
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Originally Posted by copbait73 View Post
Just a point of clarification, have you found the GT3582 will not surge under load on basically stock 930 (3.0-3.3L) engines with the ported compressor housing?
Do you normally apply the same turbine A/R (?) for both stock and modified (400HP) engines?
Thanks
Correct -- the more stock the engine, the less efficient the engine, so the less it is able to consume the greater airflow at lower rpms and the greater the need for the ported shroud to reduce or eliminate surge.

Ex: we had a 930 come to us for tuning on the dyno, only mods were aftermarket headers, 3" muffler, and a GT35R. Stock intercooler, stock boost, stock cams, stock P&Cs. It had compressor surge. The owner took our advice on getting a ported shroud intake and upgrading the intercooler. He didn't bring the car back, did it elsewhere, but the surge is gone. I wouldn't attribute that to the ebay intercooler he cobbled on.

Another 3.3L with stock heads and P&Cs, SC cams, GHL headers, 3" muffler, Andial intercooler. Compact "E" cover on the GT35R that some people claim causes the surge due to the smaller A/R. No surge on that car, on the dyno or road.

Quote:
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I wouldn't buy it, same goes for ball bearings.
Why?
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Old 06-23-2011, 10:53 AM
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So it sounds like at $70 this is cheap insurance. I'd rather a $1,500 turbo take a hit than a $15,000 engine. What type of engine damage have you seen when a surge occurs without an anti-surge compressor?
I think it's cheap insurance. I haven't seen engine damage from surge, just damage to the comp wheel on some higher boost engines, and inevitably damage to the bearings (CHRA).
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Old 06-23-2011, 10:55 AM
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Correct -- the more stock the engine, the less efficient the engine, so the less it is able to consume the greater airflow at lower rpms and the greater the need for the ported shroud to reduce or eliminate surge.

.... only mods were aftermarket headers.....
Innapropriate wastegate tubing and after market headers design is also a key point for this problem ....
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Old 06-23-2011, 11:31 AM
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Originally Posted by TurboKraft View Post
Correct -- the more stock the engine, the less efficient the engine, so the less it is able to consume the greater airflow at lower rpms and the greater the need for the ported shroud to reduce or eliminate surge.

Ex: we had a 930 come to us for tuning on the dyno, only mods were aftermarket headers, 3" muffler, and a GT35R. Stock intercooler, stock boost, stock cams, stock P&Cs. It had compressor surge. The owner took our advice on getting a ported shroud intake and upgrading the intercooler. He didn't bring the car back, did it elsewhere, but the surge is gone. I wouldn't attribute that to the ebay intercooler he cobbled on.

Another 3.3L with stock heads and P&Cs, SC cams, GHL headers, 3" muffler, Andial intercooler. Compact "E" cover on the GT35R that some people claim causes the surge due to the smaller A/R. No surge on that car, on the dyno or road.


Why?
There are many terms being thrown around here. My point is to go back to the first. Surge is surge. Surge can happen under load because the engine can not maintain the flow condition vs pressure generated to stay out of surge or closed throttle can cause the restriction and surge. The compressor doesn't know one from the other but its reaction is the same, in the same location.

Theory and maps are great but only guidance. Look closely and the two maps show the opposite of this discussion. The surge line of the unported compressor is generally lower in the critical area up to 2.0P.R.

I ask your real world experience because as a sage chief turbo engineer is quoted as saying "Surge is where the customer finds it." Thank you for your replies as it sounds like the GT35, ported or not, is a risky compressor selection for a basically stock 3.3L 930, therefore probably unacceptable for a 3.0L.

Regarding ballbearings I consider them acceptable for racing applications where any positive margin may mean the difference of winning or losing but they are not tolerant of the wide range of conditions in everyday usage.


Last edited by copbait73; 06-24-2011 at 05:00 AM..
Old 06-23-2011, 03:48 PM
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