Turbo response/range question for the Turbo Dodge guys

My collection of Internet links for Turbo Dodge is long long gone. So let me lay it out in a nutshell.

I have this engine that looks a lot like a 2.2/2.5 Mopar in breathability and is about that displacement. I also may be able to get a Super 60-sized turbo. I would like to use this instead of the KKK K26 that I've currently got bolted up.

What I'm curious of is what the spool characteristics and powerband range were like with the old Mopar Performance Super 60 turbo setup on a 2.2 or 2.5. Boost onset, how far it would pull, etc.

Back of envelope math says the turbo should be a good match for what I want the car to drive like but I'm curious if my back of envelope SWAGing has basis in reality.

There are a bunch of dynos on The Dodge Garage and may be somewhat helpful. In the "Turbo database" #43.

I didn't see anything useful there.

A stock 2.2 with an S60-ish turbo (there are several variations) and a 3" exhaust behind it should be making boost around 2000 rpm in the higher gears. Sooner with a 2.5. One guy claims that his 2.2 with ported top end parts was making boost starting at 1300rpm.

The s60 term comes from a 'super 60 trim' t3 compressor wheel, but generally in the turbo dodge world a 'real s60' has a larger compressor housing and larger A/R turbine housing (.63 vs .48) compared to the stock t3 that came on most of them.

Thank you, that's the kind of info I was trying to find

The turbo I'm considering is Grand National turbo, which as far as I've ever been able to ascertain is a Super 60. Goofy inlet flange, but that's fine since part of wanting a different turbo is making a header.

The GN turbo is still a t3 with the same 'stg1' turbine wheel, but it has a larger compressor wheel than any 'standard' t3-family compressor wheel. It's sort of a t3-t4 hybrid before those were a thing. The compressor wheel has about the same inlet/inducer diameter as an s60, but the 'major'/exducer diameter is 10mm larger. The turbo dodge people call it an s70. Theoretically they are capable of around the same ultimate power, but the GN turbo is probably noticeably more adiabatically efficient (i.e. heat added) at higher pressure ratios. So if you make your 300hp with 17 psi, it may not work any better than an s60. If you make your 300hp at 32 psi, it might be noticeably better. Because the compressor wheel has that larger exducer diameter, it is going to spool slower than an s60. The turbo dodge community is full of a lot of mixed opinions on using the GN turbo (although all of it is old and from a time when people generally knew less). My opinion is that it's a perfectly decent turbo for a mild 2.2-2.5 if you can get it for next to nothing. Just so you know, since it is a stg1 t3 turbine, any turbine housing from anything that came stock with a t3 should go onto it if that ends up helping you somehow.

The dilly-o is, I may be able to buy it very inexpensively as a takeoff. If I were going to spend money buying a new turbine housing, I'd just as soon go with a V-band housing attached to a new Precision turbo. Which was kind of my plan before this came along

My power goals are... more than 300hp. I'm not certain that this turbo could take me right where I want, but the car it is currently attached to has been down the track deep in the 11s at 25 pounds of boost. My little 2.3 isn't going to flow nearly as much as a 3.8, of course, but mine also does rev a bit higher, and I'd prefer it if boost onset wasn't until much later anyway since it's a manual transmission.

I am planning on running 23-25psi, more if the engine can do it without having to pull a lot of timing. I'm on 7:1 compression so this should be not terribly difficult. The K26 is known to be out of breath at about 17psi, but it's mainly on the car as a stopgap measure so I could get the car running and sorted before going for the gold.

A GN turbo will make more than 300hp but it's not going to be as efficient as a newer turbo while being pushed that hard. It's also a pretty small turbine side to be flowing that much through. You may want to ask the owner if that 25psi is the 'all of it' setting because the same mass flow on a lower-flowing engine is going to be a higher boost number and it's possible that him pushing that much air through the turbine means he is experiencing uncontrollable boost creep and he's just ok with it because the rest of his setup can handle the turbos 'all of it' without blowing up. Pushing the same level of exhaust flow through the same turbo on a smaller engine may cause it to creep into the 30+psi range which may be dangerous for your motor since the charge air would be hotter at that pressure ratio. So if you plan on retaining stock internal wastegate that's something to think about.