# GT2052 Map Interpretation?



## Stealth_TDI (Nov 12, 2003)

Hello,

First, let me say this this is for a lower-revving TDI with a redline of only 4600-rpm. So you guys with the big power please think "smaller" for a sec.  This is also an older AHU wastegate turbodiesel. So not the VNT's you may have read about. I've read great reviews from a couple of AHU owners who have installed a GT2052 wastegated turbo. My question is about the compressor maps and how they're interpreted. I thought I understood how they work. But I'd like an education on what I may be missing on these graphs. 

What I've done is used a pretty cool turbo calculator at *Squirrel Performance* and enterred some values to get me to a desire for 22-24 psi from 2000-rpm to 5000-rpm (click "Refresh Maps" to populate the missing data). The red dots, from left to right, represent rpms of 1000, 1100, 1500, 2000, 3000, 4000, 4500, and 5000 (2000-5000 is along a straight line at 22). So check these out:

Stock GT15... easy to see it's ill-suited for high boost beyond 3800 rpm while 16-psi (P/R of 2.1) is just about perfect...









Here's the GT2052 a couple of AHU owners like (reported as a 52 trim)...









This is where I have a question. I've read this turbo spools very well and works great at over 22-psi (exact boost level escapes me). I don't want to discredit the reports of those who are using this turbo, even if they're using them in AHU-swapped MK2s (lighter than my MK3). The prospect of the 2052 being a better replacement than my current K03/K04 hybrid and much less expensive than a VNT conversion is exciting. I just want to learn from all of this.

My interpretation of the graphs above is that it won't spool to 21-psi until nearly 3000-rpm (second dot along straight line) and that 22-psi is beyond the turbo's effective range. However, owner reports do not support this. Why? What am I misunderstanding about these graphs? And why would the GT15 rated for up to 150hp be able to operate at 22-psi when the GT20 rated for up to 230-hp has a map that doesn't appear to support that high of a PR?

Wanting more data, I decided to look at the two other configurations of the 2052.

Here's the 48 trim... looks marginally quicker to spool and works better at higher boost?









Here's the 50 trim... spools faster, but runs out of breath earlier?









What do you experts have to say about all of this? Some have noticed the 52-trim turbo map stops at 160,000 rpm while the 48 and 50 go to 180k. Is Garrett holding something back? All three turbos feature a 52mm exducer while the inducer is 37.6mm (52 trim), 36.1mm (48 trim), and 36.8mm (50 trim). All three variants feature a 47mm turbine with 0.50 A/R and the same compressor A/R of 0.51.

In short, the turbos look insufficient for 22-psi across the entire 2000-5000 rpm TDI band on paper and appear to be slow spoolers in diesel terms where full boost is desired by 2000-2200 rpm. But real world reports say the 52 trim turbo is awesome. I believe the reports, but I want to wrap my brain around the specs and operate my turbo within design parameters. Can you help explain what I may be missing? Do you think the 48 trim or 50 trim may be a better choice? Why or why not? I also recognize that a GT2052 will likely move more dense air at 20-psi than a my K03/K04 moves at 23-psi.

I hope this isn't too boring for you pros.  Perhaps it's a tad different for you? My search didn't reveal any other GT2052 talk here. So I hope my questions serve to provide answers to others who may search the term "GT2052" here.

Thanks!

Scott


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## schmiesus (Jun 18, 2008)

I had 16psi at 2000 rpm and was at 31psi by 3200


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## masterqaz (Oct 5, 2007)

why are your plotted points mainly on the the wrong side of the surge line?


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## schmiesus (Jun 18, 2008)

my bad i just pulled my turbo out and it is a GT2056


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## Stealth_TDI (Nov 12, 2003)

Hello,



masterqaz said:


> why are your plotted points mainly on the the wrong side of the surge line?


I plotted "goals." At first, my goal was 20-psi by 2000 rpm so I could compare to a stock turbo. Then I moved the goal to the right by putting the 20-psi goal to 2300 rpm. So, rather than plot actual turbo performance, I was plotting where the turbo might fall short. The graphs which fall in the surge area indicate to me that the turbo would lag in these areas. On the other end, I can see where the turbos may not hold max boost beyond a certain RPM.

R,

Scott


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