Need input on Turbo size For a Build I'm Planning

[mikedsilva]

My current setup, is a 3.0SC engine with efi, single plug, 3.2 carrera intakes, stock heat exchangers, j pipe, 3076R turbo with 0.63 housing, 0.6 Bar.

I'm in the planning stages to rebuild the engine. Main change is
3.6 crank and 98mm pistons aiming for 8.5:1 compression.

Using the 3.2 carrera intake, staying single plug.
Will use 1&5/8 Headers.

The plan is to increase the capacity to 3.45litres to fill in the bottom end due to the lower compression.

I'm not intending to build the worlds biggest HP monster!

Will my current turbo (3076r 0.63) be ok or should I be looking to upgrade and if so, to what? (i dont really understand teh 0.63 etc)

What boost should be safe? 1 Bar?

[kamaro]

Hi Mike,

Last year I upgraded my engine to 3.4 using Mahle P&Cs and I use a GT3584 turbo with .82 A/R, with a 7.7 C/R and with that turbo I was expecting a sluggish low end but I was surprised with a very responsive and very early boost (I could feel and see the boost take-off as low as 2000 rpm), it seems the 3.4 has enough air to move that turbo quickly! .. One of the big tuners here drove my car and he told me to go for GT40 turbo because he feels the 35 is small for it. I'm using a 3.2 carrera intake but a very cheap (OBX) chinese exhaust with big muffler.

[911TT33]

You would want a 0.82 A/R hot housing for sure. Anything smaller will choke up your engine, unless you’re running twin turbos.

Compressor flow capacity depends on what your HP goals are.

When I was running a single turbo setup, I found the Garrett GT35R ball bearing turbo to be more than enough. Quick boost onset/response and great top end.

What’s your use case? Drags? Track? Fast street?

[quattrorunner]

I had an off the shelf 3076 garrett that was perfect for your starting spec. But as you increase displacement and lower compression I was told by many smarter than me that the gt30r was too small and would create too much heat for that bigger engine. Currently I have 3.3l and a gt35r. A newer garrett revision or other brand would also have great more current design efficiency updates. I'd like to upgrade to gt40 sizing even with 3.3l when I do more engine upgrades.

[flat6pilot]

Probably GT35 at least.

I have a GT30r on my 3.0l build. Moving to 3.2, but was told it should be fine...for now. Keeping hp levels around 400-450.
7.5:1 compression, expecting about 1 bar or so of boost.

[mikedsilva]

Depending on the speed at which I can get parts ordered, i may just use the existing turbo, then upgrade at a later date. But I am leaning toward a 3584 with 0.82 a/r housing.

[1979-930]

I’ve got a GT35R twin scroll, ceramic coated hot housing and heat shield with matched RarlyL8 ceramic coated headers with heat boxes I don’t need anymore.
I pulled them off my 79 930 and put the stock parts back on.

PM if interested. I need to start selling stuff I don’t need.


Sent from my iPhone using Tapatalk

[Leoo]

Hey,

Your planned engine build sounds impressive! With the increased displacement to 3.45 liters and an 8.5:1 compression ratio, you’re setting up for a robust performance.

[Leoo]

The Garrett GT3076R with a 0.63 A/R turbine housing is a well-regarded turbocharger, typically supporting engines between 2.0L and 3.5L and capable of producing 310-525 horsepower.  However, with your planned increase in engine displacement to 3.45L, this turbo may become a limiting factor, especially at higher RPMs. The smaller 0.63 A/R housing provides quick spool and excellent low-end response but might restrict top-end power due to its size.

[Leoo]

Upgrading to a larger A/R housing, such as 0.82 or 1.06, can improve exhaust flow and support higher horsepower, though it may introduce more turbo lag.  Alternatively, considering a turbocharger like the GTX3076R Gen II, which offers enhanced performance and efficiency, could provide a balance between spool time and increased power capacity.