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Old 05-31-2018, 07:48 PM   #1
Tfrasca
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Default T3/T4e 50 trim, .48 or .63?

I want a 300 whp B23ft, and I'm realizing that my 19t is going to be beyond its limits trying to get there. This is my set up:

B23ft with squirters, ET pistons (9.3:1)
405 head
IPD cam
Deka 60 lb injectors
3" thick, pretty big eBay intercooler
Custom intake manifold
3" turbo back
LH 2.4, eventually MS

At first, I was dead set on a GT2871r, but now I'm less sure I need a $1300 turbo. I've been looking at a Garrett T3/T4e 50 trim instead. I'm pretty sure the .48 turbine housing will get me to my goal, but will I miss the top end punch of the .63? I figure my higher compression should help with spool, so maybe that's less of a concern?
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Old 05-31-2018, 07:58 PM   #2
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Maybe buy the complete turbo, and then find a used housing in .48 or .63, whichever you don't get?
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Old 05-31-2018, 08:02 PM   #3
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Originally Posted by centason View Post
Maybe buy the complete turbo, and then find a used housing in .48 or .63, whichever you don't get?
Funny you should mention that, as I just talked to a friend with a spare .63 housing. Good call.
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Old 05-31-2018, 09:30 PM   #4
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When I bought my T3/T4e 50 trim, the housing size and style (external/internal wastegate) was a no cost option, maybe ask the supplier about that?
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Old 05-31-2018, 09:40 PM   #5
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Originally Posted by 2turbotoys View Post
When I bought my T3/T4e 50 trim, the housing size and style (external/internal wastegate) was a no cost option, maybe ask the supplier about that?
housing A/R is a no-cost option, yes. Which size did you get?
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Old 06-01-2018, 02:54 AM   #6
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That T3/T04E 50-trim is a fair bit larger on both ends than a GT2871R.
Fun fact: the real model name is TA34 (although no one calls it that).

Compressor is 76mm exducer (vs 71mm) and turbine is 65mm inducer (vs 54mm).

0.48 A/R on the turbine end is tiny for that wheel, and will choke around the same flow rate as the 0.63 A/R housing on the GT28 (about 17 lb/min corrected). For 2.3L and 300whp you are looking at around 350 bhp at the flywheel, which is going to require a very large wastegate to bypass enough flow around that 0.48 A/R turbine housing.

I'd go with the 0.63 A/R, but then again, I don't have a lot of firsthand experience with these late '80s wheel designs, so best to check with others who've done it.
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Old 06-01-2018, 03:42 AM   #7
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I had to port the piss out of my .63 housing to eliminate boost creep. If a .82 housing was available I would have taken it.

Definitely get the .63 over the .48
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Old 06-01-2018, 07:05 AM   #8
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Quote:
Originally Posted by TurboDenny View Post
I had to port the piss out of my .63 housing to eliminate boost creep. If a .82 housing was available I would have taken it.

Definitely get the .63 over the .48
Your 0.48 t3/t4 is still sitting in my turbo pile
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Old 06-01-2018, 08:52 AM   #9
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Depends,

What transmission are you using?
What stage turbine wheel are you using?
300whp all you want?
Stock cylinder head?
ATP Ultimate wastegate?
etc.
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Old 06-01-2018, 10:08 AM   #10
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Originally Posted by tryingbe View Post
Depends,

What transmission are you using?
What stage turbine wheel are you using?
300whp all you want?
Stock cylinder head?
ATP Ultimate wastegate?
etc.
Good questions. I have a t5, and am trying to upgrade to a T5z, but the gear ratios I want are not available for the foreseeable future.

The 50 trim turbo I'm looking at is a Stage III wheel.

300 whp is all I want for now, but you probably know how that goes.

Stock 405, but I would like to build a big valve head, even I don't necessarily need it for the current goal. Just seems like it would be fun.

Yes, the ATP Ultimate wastegate is currently in my shopping cart.

Another perhaps useful bit of information is that I have a 4.30 rear axle.
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Old 06-01-2018, 10:11 AM   #11
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Originally Posted by Duder View Post
That T3/T04E 50-trim is a fair bit larger on both ends than a GT2871R.
Fun fact: the real model name is TA34 (although no one calls it that).

Compressor is 76mm exducer (vs 71mm) and turbine is 65mm inducer (vs 54mm).

0.48 A/R on the turbine end is tiny for that wheel, and will choke around the same flow rate as the 0.63 A/R housing on the GT28 (about 17 lb/min corrected). For 2.3L and 300whp you are looking at around 350 bhp at the flywheel, which is going to require a very large wastegate to bypass enough flow around that 0.48 A/R turbine housing.

I'd go with the 0.63 A/R, but then again, I don't have a lot of firsthand experience with these late '80s wheel designs, so best to check with others who've done it.
Interesting, about the comparable AR on the GT28. I'll admit that I have only a cursory knowledge of all this stuff. I keep starting to read through the tech pages on Garrett's site, but I need some time to absorb it all.

I take it that your vote would be to get the GT2871r?
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Old 06-01-2018, 10:13 AM   #12
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Originally Posted by TurboDenny View Post
I had to port the piss out of my .63 housing to eliminate boost creep. If a .82 housing was available I would have taken it.

Definitely get the .63 over the .48
You mean you had to port the wastegate hole? Were you running an internal wastegate.

I think I forgot to mention that I'd really prefer to run an internal.
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Old 06-01-2018, 10:40 AM   #13
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Quote:
Originally Posted by Tfrasca View Post
You mean you had to port the wastegate hole? Were you running an internal wastegate.

I think I forgot to mention that I'd really prefer to run an internal.
If you get the ultimate wastegate housing, you'll be able to port a good bit of the wastegate hole out. Here it is on a .48 housing:

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Old 06-01-2018, 10:46 AM   #14
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Originally Posted by SlowRide View Post
If you get the ultimate wastegate housing, you'll be able to port a good bit of the wastegate hole out. Here it is on a .48 housing:

Wow, that's a ton of material. Once you matched those ports a bit better, you were able to prevent boost creep, right?

And even so, you still would have gone with a .63?
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Old 06-01-2018, 10:56 AM   #15
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Originally Posted by Tfrasca View Post
Wow, that's a ton of material. Once you matched those ports a bit better, you were able to prevent boost creep, right?

And even so, you still would have gone with a .63?
I haven't actually done it yet, babies eat time and money. But that's the plan. I have a .63 on standby, though, and it will receive the same treatment. Gotta do the LH3.1/2.4 conversion first.
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Old 06-01-2018, 10:56 AM   #16
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Mostly stop light to stop light? .48 housing would be more fun.

Mostly 80MPH+ pull? .63 would be more fun.


I got a .63 turbine with stage III on my GLH, lots of top end, not to much lower end. I would agree, port that turbine wastegate hole! I ported it a little, but not enough!

My Dyno.
HP VS boost,

Red line starts at 9.5 psi and creep to 13psi and 250whp
Blue lines spike to 26psi and settle at 23.5psi and 350whp


Last edited by tryingbe; 06-01-2018 at 11:02 AM..
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Old 06-01-2018, 11:17 AM   #17
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Originally Posted by tryingbe View Post
Mostly stop light to stop light? .48 housing would be more fun.

Mostly 80MPH+ pull? .63 would be more fun.


I got a .63 turbine with stage III on my GLH, lots of top end, not to much lower end. I would agree, port that turbine wastegate hole! I ported it a little, but not enough!

My Dyno.
HP VS boost,

Red line starts at 9.5 psi and creep to 13psi and 250whp
Blue lines spike to 26psi and settle at 23.5psi and 350whp

Yeah, I hate to admit it, but "stop light to stop light" more accurately describes my car. Actually, mostly spirited backroad driving and twisty roads, but the same powerband idea. I like the idea of more top end power for high speed pulls, but an old 140 just isn't the best vehicle for that stuff.

Nice dyno sheet, by the way.
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Old 06-01-2018, 12:33 PM   #18
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Originally Posted by Tfrasca View Post
Interesting, about the comparable AR on the GT28. I'll admit that I have only a cursory knowledge of all this stuff. I keep starting to read through the tech pages on Garrett's site, but I need some time to absorb it all.

I take it that your vote would be to get the GT2871r?
I would say GT3071R over GT2871R, if you're looking at older ball bearing options. A GTX3067R (67 not 76) would be even better. I'm not saying that in order to sell more turbos or anything; the reasoning is that overall turbocharger performance improves dramatically as you reduce compressor size.

For turbine/compressor matching, tribal knowledge (and consumer demand) for a long time was to downsize the turbine wheel in order to reduce inertia and "increase spool up" or "reduce turbo lag." Unfortunately the mass & inertia of a wheel is only part of the equation - turbine efficiency is the other side of the coin, and by creating a mis-matched turbo (large compressor / small turbine) the turbine wheel is forced to operate at a much slower than optimal shaft speed.

T / GT / GTX turbo nomenclature is a bit confusing because the size of the turbine wheel isn't explicitly stated in the model name but here's a short list:

GT28, GTX28: 54mm
GT30, GTX30: 60mm
T3/T4E "Stg 3": 65mm (the one you're considering)
GT35, GTX35: 68mm

These are all varying blade designs which does affect performance for sure, but they are all 76-trim turbines and therefore the inducer (major) diameter is a good yardstick for flow capacity.

I've done several matches that were close to being 1:1 on size between turbine & compressor, but those normally don't work out due to shaft speed limits. For example, a GT3060 would have 60mm compressor and turbine wheels and performance looks great on paper.

3063 has been the answer for me on several different projects which have done quite well (the red, white, and blue cars racing in IMSA GT and Le Mans for example).

With older compressors you had to go with something too large in order to get big airflow on a performance engine, but with aerodynamic design advancing steadily over the years, the size of compressor needed for a given airflow keeps getting smaller & smaller. It's now possible to come up with a good match between turbine & compressor without sacrificing performance in one way or another.

Anyway this is a roundabout way of saying that it's actually better to first choose a compressor that meets your requirement, and then pair a larger turbine wheel with that compressor. So if a GT2871R and GT3071R share the compressor stage, and therefore either would look good in terms of boost & airflow on the compressor side, I'd recommend the GT3071R because of the larger turbine wheel and better speed match to the compressor wheel. The efficiency gain on the turbine side is often big enough to offset any downsides that come with higher inertia from the bigger diameter. A twin-scroll turbine housing with equal length properly divided manifold would likely make boost response (lag) markedly better than a smaller GT28 with the same compressor.
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Old 06-01-2018, 12:36 PM   #19
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Also remember that an initially low power target and small turbine will force you to wastegate a ton of flow to prevent boost creep. Hence a large external gate or heavily ported internal. As you increase turbine wheel diameter, turbine housing A/R, and/or boost & power, you will need to wastegate less (more of your exhaust energy needs to power the turbine instead of flow through the wg), so boost creep becomes less of a concern.
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Old 06-01-2018, 01:04 PM   #20
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Originally Posted by Duder View Post
I would say GT3071R over GT2871R, if you're looking at older ball bearing options. A GTX3067R (67 not 76) would be even better. I'm not saying that in order to sell more turbos or anything; the reasoning is that overall turbocharger performance improves dramatically as you reduce compressor size.

For turbine/compressor matching, tribal knowledge (and consumer demand) for a long time was to downsize the turbine wheel in order to reduce inertia and "increase spool up" or "reduce turbo lag." Unfortunately the mass & inertia of a wheel is only part of the equation - turbine efficiency is the other side of the coin, and by creating a mis-matched turbo (large compressor / small turbine) the turbine wheel is forced to operate at a much slower than optimal shaft speed.

T / GT / GTX turbo nomenclature is a bit confusing because the size of the turbine wheel isn't explicitly stated in the model name but here's a short list:

GT28, GTX28: 54mm
GT30, GTX30: 60mm
T3/T4E "Stg 3": 65mm (the one you're considering)
GT35, GTX35: 68mm

These are all varying blade designs which does affect performance for sure, but they are all 76-trim turbines and therefore the inducer (major) diameter is a good yardstick for flow capacity.

I've done several matches that were close to being 1:1 on size between turbine & compressor, but those normally don't work out due to shaft speed limits. For example, a GT3060 would have 60mm compressor and turbine wheels and performance looks great on paper.

3063 has been the answer for me on several different projects which have done quite well (the red, white, and blue cars racing in IMSA GT and Le Mans for example).

With older compressors you had to go with something too large in order to get big airflow on a performance engine, but with aerodynamic design advancing steadily over the years, the size of compressor needed for a given airflow keeps getting smaller & smaller. It's now possible to come up with a good match between turbine & compressor without sacrificing performance in one way or another.

Anyway this is a roundabout way of saying that it's actually better to first choose a compressor that meets your requirement, and then pair a larger turbine wheel with that compressor. So if a GT2871R and GT3071R share the compressor stage, and therefore either would look good in terms of boost & airflow on the compressor side, I'd recommend the GT3071R because of the larger turbine wheel and better speed match to the compressor wheel. The efficiency gain on the turbine side is often big enough to offset any downsides that come with higher inertia from the bigger diameter. A twin-scroll turbine housing with equal length properly divided manifold would likely make boost response (lag) markedly better than a smaller GT28 with the same compressor.
Man. I'm glad you chimed in here. This is definitely the best explanation of all of this I've come across. I also emailed ATP about turbo selection and, not surprisingly, they're steering me toward a 2871 or 3071 also. They're telling me that the 28 will give better low and mid range response, while the 30 will need less boost to achieve the same power, but will spool a bit later. That's a concern (one that I may have been willing to ignore if I went with the cheaper 50 trim option), as I won't be building a twinscroll manifold anytime soon. The idea is to run whatever I get on my 90+.

Knowing that, would you still recommend the 30 over the 28?
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Old 06-01-2018, 01:11 PM   #21
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You can't go wrong with a 28 on a Redblock from what I've seen. I guess considering your stated use case and preference of stoplight-to-stoplight performance, you might prefer the 28 actually. ATP isn't wrong; they are using their massive experience to help guide your decision. Again a 3067 would be optimal but those are only available as a GTX; more expensive.

I remember talking with a 1.6 Miata guy at SEMA when the 3067 first came out - he did a proper twin scroll setup with fully divided wastegates and said that response and spool-up was massively improved over the smaller GT28 he had on the engine before. For a budget-minded setup with single scroll and lots of wastegate & turbine housing options, 2871 is a good choice.

The other factor is the turbine blade design on the 28 is a bit better than the 30, so it makes up for some of the gains you'd get with a larger wheel if it was apples to apples.
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Old 06-01-2018, 01:32 PM   #22
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What is the peak HP flow on a gt28? 350whp or so right at the limit?

I am sure there are many other factors but we have to remember that despite out engine being larger at 2.3L the heads just do not flow as much as some newer engines in stock form.

Because of that most here might not ever need or make more than 300-330whp without doing a lot of other upgrades so it makes the gt28 ideal also.
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Old 06-01-2018, 01:39 PM   #23
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What is the peak HP flow on a gt28? 350whp or so right at the limit?
Peak HP will depend on the engine & complete system of course. But there are 3 different GT2871R versions, different compressor trims. For the largest 56-trim compressor the choke flow limit is right around 45 lb/min. With the traditional 10:1 rule of thumb applied, you can expect to be able to make around 450 hp with that (flywheel not whp).

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I am sure there are many other factors but we have to remember that despite out engine being larger at 2.3L the heads just do not flow as much as some newer engines in stock form.

Because of that most here might not ever need or make more than 300-330whp without doing a lot of other upgrades so it makes the gt28 ideal also.
This is an excellent point to keep in mind, especially with an 8-valve.
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Old 06-01-2018, 02:04 PM   #24
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I agree about the poorly flowing head. Like I said, I may get into the head at some point down the line, but even then, it wouldn't be a really wild build.

At any rate, you and ATP may have talked me out of the 50 trim. The 28 is looking like a good call, I'm guessing with a .86 AR turbine housing?
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Old 06-01-2018, 02:09 PM   #25
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I agree about the poorly flowing head. Like I said, I may get into the head at some point down the line, but even then, it wouldn't be a really wild build.

At any rate, you and ATP may have talked me out of the 50 trim. The 28 is looking like a good call, I'm guessing with a .86 AR turbine housing?
Make sure to report back, because odds are at the rate I'm going, I won't even have completed the LH3.1/2.4 conversion before you're done breaking it in

Plenty of time to bail on the t3/t4
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