T3/T4e 50 trim, .48 or .63?

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.

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.

thelostartof said:

What is the peak HP flow on a gt28? 350whp or so right at the limit?

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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).

thelostartof said:

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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This is an excellent point to keep in mind, especially with an 8-valve.

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?

Tfrasca said:

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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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

SlowRide said:

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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Don't worry, I'll change my mind 10 times before I pull the trigger.

I got the .63, .82 housing was available, and I ran an external wastegate, but used the internal wastegate housing. I got the turbo from Blouch Turbo