Disco Potato or T3 Super 60? - Page 3 - Miata Turbo Forum - Boost cars, acquire cats.

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DIY Turbo Discussion greddy on a 1.8? homebrew kit?

View Poll Results: Which turbo for my 1.8 swap?
GT2860RS (Disco Potato) 13 54.17%
t3 Super 60 11 45.83%
Voters: 24. You may not vote on this poll

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Old 11-21-2007, 01:27 PM   #41
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Mark, Tim

I am new to turbos, but my research is telling me you guys have those turbine inducer/exducer labels backwards.

smaller


Consequently, I did run the numbers and your calcs appear correct, only the labels are backwards.

As a side note...

Why in the heck does Garrett make everyone jump through hoops to figure out their turbine specs? It took me forever to confirm that Garrett's turbine "wheel diameter" is actually the turbine inducer just so I could do the algebra.

The only clue Garrett provides on their website is this snippet from the GT Basics / Nomenclature page (sixth paragraph):
"...units which utilize a 53mm turbine wheel (as measured at the inducer) are now referred to as "GT25" frame size..."

http://www.turbobygarrett.com/turbob...gt_basics.html

If you look at Garrett's specs for any GT25XX turbo, indeed the provided "wheel diameter" is 53mm.
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Old 11-21-2007, 01:39 PM   #42
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Quote:
Originally Posted by Loki047 View Post
Nope, GTs are riskier cause they can not be rebuilt
399 for brand new CHRAs with wheels though.

But yah... no normal rebuilds for them.
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Old 11-21-2007, 02:00 PM   #43
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Originally Posted by Loki047 View Post
Part of me wants to buy one then have Garrett replace the cartridge for whatever cheap price that is.
yay me
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Old 11-21-2007, 02:03 PM   #44
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Quote:
Originally Posted by MazDilla View Post
Mark, Tim

I am new to turbos, but my research is telling me you guys have those turbine inducer/exducer labels backwards.
yes indeed you are correct, sorry.

Quote:
Originally Posted by Loki047 View Post
Nope, GTs are riskier cause they can not be rebuilt
how often do you expect to rebuilt a GT-R turbo? I'm pretty sure they last a very long time assuming proper maintainence/tune/etc.

If something goes thru the turbine, that's another story.
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Old 11-21-2007, 02:06 PM   #45
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They are backwards because I have been not getting enough sleep. We all know the small side is the exducer... It all depends on which way you are blowing though.

Mark
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Old 11-21-2007, 03:55 PM   #46
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I'm also considering a T3/TO4E 50 trim as an option now. I like that I could run it external wastegate where I would have to weld the flapper shut on a GT2871R or potato to do that and then I would be paying for something I'm not using. Also knowing that I can rebuild it cheaply is a plus. So now I'm down to a GT2860RS, GT2871R, or T3/TO4E 50. Now just to find one cheap enough to make me pull the trigger. I have at least a couple of months to find one, so used (read cheap) is better.
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Old 11-21-2007, 04:06 PM   #47
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well if you wanna go new, this price looks reasonable:

http://www.rogueusa.com/Garrett-T3-T...t-t3to4e50.htm
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Old 11-21-2007, 04:21 PM   #48
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I'm also considering a T3/TO4E 50 trim as an option now. I like that I could run it external wastegate where I would have to weld the flapper shut on a GT2871R or potato to do that and then I would be paying for something I'm not using. Also knowing that I can rebuild it cheaply is a plus. So now I'm down to a GT2860RS, GT2871R, or T3/TO4E 50. Now just to find one cheap enough to make me pull the trigger. I have at least a couple of months to find one, so used (read cheap) is better.
Don't buy used, at $575 for a brand new one, it's just not worth going with someones used turbo. I would still take my chinacharger over a used turbo for the $200 I paid for it shipped to my door.

Mark
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Old 11-21-2007, 04:57 PM   #49
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Originally Posted by Braineack View Post
well if you wanna go new, this price looks reasonable:

http://www.rogueusa.com/Garrett-T3-T...t-t3to4e50.htm
Wow, that is a good price, especially for the stage 3 wheel. Thanks for the link! Which do you think would be better on a stock 1.8 .48 or .63 a/r turbine?
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Old 11-21-2007, 05:41 PM   #50
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on that big of a turbo on a 1.8, dont **** around with the .48. Get the .63.
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Old 11-25-2007, 09:24 PM   #51
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Just so you all know those ebay turbos have and do work most of the time if used right. On our import engines where the oil pressure is most of the time double what american engines are the turbos tend to blow the seals out. If you put an oil restrictor inline of the oil feed line you will have much better luck.
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Old 11-26-2007, 12:49 AM   #52
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I have a new in original box from Garrett GT2871R 52 trim, with .48ar T3 turbine (equivalent in spool/flow to .64ar T25 housing, but external wastegate and T3 flange for improved boost control and turbine efficiency). Send me a PM if interested.
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Old 11-26-2007, 01:14 AM   #53
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Hit up Turbotim... hes got a GT2871R... best turbo in the world of Miata's.
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Old 11-27-2007, 01:10 PM   #54
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Originally Posted by PaKMaN View Post
Hit up Turbotim... hes got a GT2871R... best turbo in the world of Miata's.
Has anyone actually dynoed one on a Miata? Hard to make that statement with no evidence to back it up.

Frank
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Old 11-27-2007, 01:46 PM   #55
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I am considering it but like was said earlier in this thread, I'd loose a couple hundred as soon as I start the car. If I do do it, I'd probably sell the turbo with the manifold and downpipe too.

I'd much rather someone just buy the turbo though.
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Old 11-27-2007, 01:59 PM   #56
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Matt's 2876 dyno pulls should be enough, same turbo with a slightly larger compressor....

8psi?:



9.5psi:

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Old 11-27-2007, 03:06 PM   #57
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Matt has the .64 exhaust A/R, mine's the .86. But you're right about the compressor, his should take a little more oomph to spool. .64 turbine is $185.
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Old 11-28-2007, 12:57 AM   #58
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find a friendly shop and trade your .86 for a .64. that's how i got mine. drove down to ATP turbo and asked nicely. they're good guys. maybe WOT can swing something.
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Old 11-28-2007, 02:56 AM   #59
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Quote:
Originally Posted by Braineack View Post
Matt's 2876 dyno pulls should be enough, same turbo with a slightly larger compressor....
I respectfully disagree, the 2876 is a significantly different turbo than the 2871. My apologies for the long explanation, but I'm sure someone will wonder why, so here it is.

The 2876's TO4S compressor wheel is not a GT wheel, it was introduced in 1976, and is outdated compared to the modern GT wheels. The older design wheel has more blades, that are thicker and angled differently, making it heavier and less efficient. At 76mm on the exducer it is significantly larger, further adding intertia to the rotating mass.

Besides the compressor being older technology and over sized (50 lb/min, or roughly 500 crank hp), it is mated to the same tiny T25 turbine wheel from the 28RS; creating a size and shaft speed mismatch. The NS111 turbine wheel flows only 17-21 lb/min depending on housing option, and cannot generate the shaft torque required to efficiently spin up the large T4 compressor. Both turbine to compressor wheel size ratio, and shaft speeds must be well balanced for the turbo to operate efficiently.

The result of the mismatch is higher exhaust gas speeds to spin up the compressor (higher engine speed, more lag), and more exhaust restriction from the undersized turbine once it does spin up (higher backpressure and thermal load/EGT, ie more detonation prone, and limited power level). In other words, the potential flow capacity of the compressor is never realized, and the same power is produced that could be done with a smaller turbo, albeit with more lag.

Garrett has since phased out the 2876 as a performance turbo in favor of the newer 2860, 2871 and 3071, which all have increased turbine to compressor wheel ratios and better matching shaft speeds.

This information is stated in the catalog on the Garrett website:

"Best suited for unique applications such as asymmetric turbo installations"
"Not recommended for general performance applications"

http://www.turbobygarrett.com/turbob...R_705330_2.htm

This isn't to say that the 2876 doesn't work; it has been proven to make 400whp, just that it can be done more efficiently and with better spool.
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Old 11-28-2007, 10:53 AM   #60
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I was generalizing. It's the same turbine with a slightly larger compressor, it flows 50 lb/min vs 45 lb/min, otherwise the islands are very similar themselves, minus the RPM rates. You should expect better spoolup and possibly better hp-per-psi results with the 2871.

the purpose of me posting his dynos was simply to show what ballpark you'll be in.
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