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Old 04-10-2001, 06:14 PM   #1
Kcz
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Post Pics of my new Turbo setup

I got my car back last week, and finaly found time to get some pics. This is a custom setup built by Cobb Tuning. The turbo is a Garrett GT25 hybrid ball bearing unit. Custom up and down pipes. The intercooler is from Rallispec with a Greddy Type-S BOV. Trey had it laying around, so I went with it to save him some time. Overall I am very happy with it. It's a good clean 7 lbs. of boost. Hope you enjoy the pictures!

Click on the thumbs to enlarge.

<A HREF="http://imagehost.auctionwatch.com/preview/kc/kcz/engine1.jpg" TARGET=_blank><IMG SRC="http://imagehost.auctionwatch.com/preview/kc/kcz/.thumbs/engine1.jpg" border=0></A>

<A HREF="http://imagehost.auctionwatch.com/preview/kc/kcz/engside.jpg" TARGET=_blank><IMG SRC="http://imagehost.auctionwatch.com/preview/kc/kcz/.thumbs/engside.jpg" border=0></A>

<A HREF="http://imagehost.auctionwatch.com/preview/kc/kcz/GT25.jpg" TARGET=_blank><IMG SRC="http://imagehost.auctionwatch.com/preview/kc/kcz/.thumbs/GT25.jpg" border=0></A>

<A HREF="http://imagehost.auctionwatch.com/preview/kc/kcz/IC2.jpg" TARGET=_blank><IMG SRC="http://imagehost.auctionwatch.com/preview/kc/kcz/.thumbs/IC2.jpg" border=0></A>

<A HREF="http://imagehost.auctionwatch.com/preview/kc/kcz/Intercool.jpg" TARGET=_blank><IMG SRC="http://imagehost.auctionwatch.com/preview/kc/kcz/.thumbs/Intercool.jpg" border=0></A>

<A HREF="http://imagehost.auctionwatch.com/preview/kc/kcz/turbo.jpg" TARGET=_blank><IMG SRC="http://imagehost.auctionwatch.com/preview/kc/kcz/.thumbs/turbo.jpg" border=0></A>

<A HREF="http://imagehost.auctionwatch.com/preview/kc/kcz/turbobov.jpg" TARGET=_blank><IMG SRC="http://imagehost.auctionwatch.com/preview/kc/kcz/.thumbs/turbobov.jpg" border=0></A>
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Old 04-10-2001, 06:39 PM   #2
ColinL
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Very nice. What rpm do you make 7psi at?
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Old 04-10-2001, 06:45 PM   #3
stimpy
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Looks like you are using a RRFPR? What rate are you using and what type is it?

Overall, it looks like a nice setup.

-Jon
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Old 04-10-2001, 07:17 PM   #4
scubypoo
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Dude I gotta ask, I see that your BOV bleed into the atmosphere, how is drivability?-Poo.
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Old 04-10-2001, 07:36 PM   #5
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Dude! Did you know your IC is crooked (sp)? j/k

Looks nice!
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Old 04-10-2001, 08:43 PM   #6
Kcz
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I hit full boost around 2500. The RRFPR is made by Cartech, Trey has done all the tuning so far, so I don't know what rate it's at. This is a very streetable setup. The only problem I have is the clutch. It just can't handle to power. I will be upgrading the clutch very soon.
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Old 04-10-2001, 09:19 PM   #7
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pm'd ya had a question...
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Old 04-10-2001, 10:56 PM   #8
TiltedKilt
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Uh...call me a rookie if you want to, and I don't know much about turbos, but assuming my engineering degree is more than a piece of paper I'd have to say that your I/C is a (tad) bit on the inefficient side of life just by looking at its geometry. Also, why would you want full boost at less than half of your redline RPM? That just about gives you nothing left at the high end.
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Old 04-10-2001, 11:27 PM   #9
kaos200
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actually Tilted I can see how that intercooler works well (given theory always is the same in real life, although we know it isn't always so)...
If slanted, the air is entering more of the vertical "columns" of fins in the inside of the I/C (if it wasn't slanted, they would be truly vertical, but you get my drift)...
Therefore going through more surface area of metal, dissipating more heat...
and having full boost lower on means you accelerate much quicker! It doesn't sacrifice your top end at all since you would still have full boost at top end...

[This message has been edited by kaos200 (edited April 10, 2001).]
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Old 04-10-2001, 11:46 PM   #10
the Dabbler
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Kcz --

Looks great! Thanks for the post -- always nice to see clean installs. May I ask what it cost you? The turbo unit alone must have been considerable, not to mention the custom fabrication, install, tuning, etc. If you'd prefer not to say, I totally understand. I was just curious. It seems GT-25 setups are fairly rare in our circles, so I don't have many people to ask.


TiltedKilt --

Please clarify your post. Assuming the turbo could support the flow (and assuming a typical mechanical wastegate), the boost level would be unchanged at high rpm, would it not? And certainly max boost at such a low rpm is a good thing (again, assuming it can be sustained).

Or are you suggesting that the GT-25 would not be able to sustain that level to redline? This does seem to be at the high end of the GT-25 scale, but in Kcz' original post, he identified this as a "hybrid". This being the case, I don't think you can make judgements as to efficacy without actually seeing the compressor map for this particular turbo combination. Given that Cobb Tuning designed the system, I'm assuming it's fine, within the design goals.

Re the intercooler, the end tank design does seem a bit odd. Perhaps it was a packaging issue. But I'm no expert. And again, if Cobb Tuning and Rallispec are involved, I'm willing to assume they know better than me.
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Old 04-11-2001, 12:03 AM   #11
Kcz
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Guys, I'm going to steer clear of the cost ?'s. I don't think Trey is going to make any more kit's, but if he does I don't want him to be tied down to a price. I will say that if you take the cost of one of the kits that are out there now, and figure in the cost of a ball bearing turbo, you would probally be in the range of what it cost me.

-Kris
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Old 04-11-2001, 12:13 AM   #12
Kcz
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TiltedKilt, I'm sure you could give Rallispec a call and they would be happy to fill you in on why they designed the intercooler that way. I agree that it is a very strange design, but I'm sure a lot of R&D went into it, and it seems to work just fine.

Oh, and I have full boost all the way to redline.

[This message has been edited by Kcz (edited April 11, 2001).]
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Old 04-11-2001, 08:25 AM   #13
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I have read this thread more than once and I would tend to agree with TiltedKilt...but before I get flamed let me explain. Everyone is correct in their own right.

1) I/C: While I believe that the flow direction of the I/C channels are in the correct orientation, I seriously doubt that "efficiency" of the design is optimized (which coincidentally is what Tilted was referring to). The inlet side of the tank looks to be ok but the outlet is in the wrong spot if you want your fluid dynamics to be correct. Instead of the air making it smoothly into the throttle body, about 2/3 of the air has to fight its way past edge effects, sharp corners, and changes in flow direction. A cardinal sin of fluid flow and pressure losses.

2) A turbo spooling up on the low end and providing full boost at 2500 is ok if you can live with it. I think what Tilted was getting at was that a turbo is designed to pump a certain amount (cfm) of air for its given design. If your turbo pumps all the air it can pump at 2500rpm then thats all it can do. You will have full boost until redline but you have maxed out the capacity of the turbo to supply air to the engine. Any increase in demand for air and your turbo will fall short of the engine's intake needs. (when something reaches its peak it has nowhere to go but down...down in this case is compressor efficiency). So any upgrade you do requiring the engine to consume more air, the farther behind the turbo will fall with its supply. I am sure that COBB designed this system to have a "limit" for obvious street driving reasons. Nothing necessarily wrong with it but certainly a few shortcomings (and thats not to say a full race turbo set up isn't without shortcomings either).

A catch 22 for all turbo lovers...too small a turbo, not enough capacity...too large a turbo, increased lag and poor low end performance. My Buick Grand National (3.8L V6 turbo Regal for those who don't know) has a monster turbo on it and suffers from the low boost / poor low end problem... Then again it needs 25psi to "run".

have a good day scooby lovers!

....and guys, don't be so sure that all companies do their homework. R&D costs lots of money and often times many small shops can't afford the development time/costs. A little thing called "time to market" comes to mind. Meaning that its better to have a product available before anyone else does....its a fact of business and unfortunately our "must have" American way compromises product readiness for product availability.



[This message has been edited by mgmetalworks (edited April 11, 2001).]
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Old 04-11-2001, 09:02 AM   #14
ColinL
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Gentlemen, the GT25 is by no means undersized for this application. I am sure it is set to 7psi out of a desire to limit power with respect to the fueling ability of the engine as it currently sits and the power level desired, and not out of compressor flow concern.

Hitting 7psi at 2500rpm allows for an exceptionally broad torque curve, and its small size allows it to make boost very quickly.

Kcz, if you are crusing on the highway at 60MPH in 5th will full vacuum (you have a boost gauge, right?) and you floor it, how long before you see 7psi?
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Old 04-11-2001, 09:28 AM   #15
the Dabbler
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mgmetalworks:

I'm not sure I agree with your assessment of the turbo efficiency. Again, without actually seeing the compressor map for that turbo, it is impossible to determine if a particular flow can be sustained at a particular pressure, and at what efficiency. You are assuming the turbo is maxed out at 7psi/2500rpm. You could be right (and it is relatively small turbo family), but I guess I'm saying you can't make that assumption without more information. Remember also that this turbo was identified as a "hybrid", which may have substantially different characteristics than a "standard" GT25.

As far as the intercooler is concerned, like I said, the design of the endtanks do look a bit odd (i.e., inefficient), for the issues you cite, but I'm assuming they had their reasons. As mentioned before, perhaps it was a packaging constraint. With this endtank design, a larger core is accomodated, given the space it occupies. Perhaps they felt this increased cooling area offset the drop in efficiency from non-ideal flow. Then again, maybe it was a design that Rallispec tried and rejected that found it's way into Cobb's shop by some means, that was "good enough" for this application.

In general, I agree with your caution in not assuming everyone knows what they are doing. However, Rallispec is a respected name in Subaru circles, and some would say deserve the benefit of the doubt in the absence of more detail. And I don't know if Rallispec would necessarily be slaves to time-to-market concerns, given the nature and size of the Subaru aftermarket. Time-to-market concerns are exacerbated with "commoditized" products or cutting edge products, neither of which describe an intercooler.

No flame intended. Just looking for some discussion.

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Old 04-11-2001, 10:30 AM   #16
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Smile

i will take a stab and say that is the only way the IC piping would connect with the turbo and the IC. I have seem piping for a GT-25 in our car before and the piping in the pics looks like it was for a regular T turbo. just taking a stab at it here.
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Old 04-11-2001, 10:33 AM   #17
NickSTi
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ooops i just saw the close up pic of the ic. i dont get it either
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Old 04-11-2001, 10:46 AM   #18
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The tapered inlet tank is a more efficient design - that's what is recommended in Maximum Boost.

The tapered outlet tank seems to be a packaging issue, as the space there is sort of rectangular, so making the IC into a rectangle makes the most sense.

I guess a more ideal shape for that would be to have the top taper as is, then have a symmetrically tapered outlet tank coming to the center outlet to the TB. However, in order to do that, either the top to bottom length of the cooling channels (the core) would have to be less, or you get a less optimal taper on the outlet.

On some of the previous WRX intercoolers, the IC is mounted a little slant wise on the TB.

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Old 04-11-2001, 10:52 AM   #19
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let me start off by saying, I don't know anything about the GT-25, but here's a point some of you seem to have overlooked...
maximum boost is NOT maximum efficiency.
for example, the say a T3 is capable of 1bar.. you can have a car set up to reach max boost at 2000rpm w/ a T3... this is not necessarily 1bar... it could be 5psi... that's what the wastegate and BOV are for... so if a turbo can put out 7psi at 2500, as the engine spins faster and takes on more air, the wastegate can close and you can still have 7psi at 6250... it's possible that the turbo was capable of 1bar at 2500rpm, but the rest of the system slows it down...
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Old 04-11-2001, 11:06 AM   #20
the Dabbler
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mrbell:

Very true. I had assumed this was understood and what was actually being questioned was turbo efficiency and/or capacity. I.e., that the GT25 was actually incapable of sustaining maximum flow at redline at 7psi (again, we need a compressor map or lots of measurements to be certain).

If not, then the answer would've been much simpler: this is what the wastegate is set at.
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Old 04-11-2001, 11:17 AM   #21
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Note this photo of a pre 97 WRX IC from stimpy's site:


<IMG SRC="http://www.susogi.net/stimpy/images/mods/thumbs/th_IC_4.jpg" border=0>

If you see the outlet, it is canted off to the side, and the IC would be at an angle. The outlet portion of the tank is tapered not dissimilar to the Rallispec design. It has a more symmetric inlet tank because the inlet pipe comes up from underneath near the center.

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Old 04-11-2001, 11:52 AM   #22
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Hey guys,

I think the point about the intercooler was missed....

From a fluid dynamics stand point, the intercooler design is not optimal. Take a few engineering classes and it will be obvious. The point that TiltedKilt brought up was just that...fluid dynamic theory suggests (with no calculations necessary) that certain designs will have certain behaviors...the design in question will have certain inherent problems based solely on fluid flow and pressure losses cause by edge effects, entry and exit effects, rapid expansion/contraction effects...etc.

I don't believe for a minute that the fluidic calculations took precedence over the space constraints or manufacturability of this intercooler....and I will debate that with the manufacturer if they so desire. There is a way to accomodate both the fluids theory and space constraints but I won't post that in any forum...too long of an explanation.

without further information I won't touch the turbo capacity/efficiency issue. I know how to set up a turbo system for my car and my customer's cars, no need to give away secrets.


mg
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Old 04-11-2001, 01:42 PM   #23
the Dabbler
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mgmetalworks:

I think you should assume that most people here understand that the flow path appears to be suboptimal (your comment about "take a few engineering classes" is uncalled for, as many of us here are actually engineers). I will put this comment down to the impersonality of e-communication, and take no offense by it. The point is that optimal flow may have been sacrificed for a reason, possibly packaging. Nearly everything in engineering is a trade-off, and sometimes the trade-off isn't obvious at first glance. From your previous posts, I see that you understand that. So basically, I think we're in agreement. Your point is that the flow appears to be suboptimal. Agreed. I'm saying it might be that way for a reason. I hope you can agree that without asking Rallispec, we may never know for sure.


Trey:

Thank you. I was hoping you'd jump in with some first hand information. Speculation is fun, but ultimately, meaningless.

I'm glad to see you cleared up the turbo efficiency/capacity question. It's almost pointless to speculate about this without having very specific information on the actual turbo used, especially if it's a "hybrid".

Would you care to comment on the intercooler design? Or is this already getting out of hand?

Thanks.


[This message has been edited by the Dabbler (edited April 11, 2001).]
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Old 04-11-2001, 02:25 PM   #24
zaidallas
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nice nice , i went by the shop to do some more tunning on my car and i saw your car with an IC through the vent and i was like hey , more people in dallas are getting turbos cool . trey mentioned it was a pain so you got the only one hah ? looks good i'll have to check it out closely.
zaidoun
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Old 04-11-2001, 02:29 PM   #25
the Dabbler
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zaidallas:

Thank you for getting the original thread back on track!

Kcz, that is a nice install. I envy you, and I'm glad you're happy with it!
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