Been looking through the forums and doing research.
Have a Stockport 12a I'm converting to EFI and turbo.
This is what my plan is.
Engine was rebuilt by previous owner. Compression numbers are solid. These are the things im planning to add
17 mm oil pump from late model 12a for more flow
FD rear regulator with FD front regulator spring and 2 washer from Atkins to increase oil pressure.
650 cc primary injectors 1000 cc secondaries ( have not purchased these yet ( recommendations for sizing are welcome)
Garrett GT2860RS w/ .82 A/R T3 DIVIDED oil and coolant cooled
Turbo manifold I ordered from Australia has a 50mm wastegate hole.
FuelTech FT450
This build is for a fun project for a weekend car. Not trying to blow the thing up. This is going into a 74 RX4 wagon.
Question : Any issues with that turbo Sizing for a stock port 12a ? any other recommendation for the build and plan /sizing in general are very welcomed. I appreciate any input.
It's definitely bigger than a factory turbo but even on a motor with stock NA porting it will choke the top end. Most people would probably start at a minimum with something around SXE257 or GT30 or largest turbine housing on a G25 for a 12a.
Doesn't hurt to try it and see if you would prefer more top end.
Sorry if this is a silly question. But isn't the A/R most important when it comes to flow/size? the car wont be making a lot of horsepower so why would I need something rated for more horsepower if the physical size is similar? Thought the A/R determine the size and flow , is that not correct? Are you saying those higher horsepower turbos will simply flow better by design on a rotary?
Sorry if this is a silly question. But isn't the A/R most important when it comes to flow/size? the car wont be making a lot of horsepower so why would I need something rated for more horsepower if the physical size is similar? Thought the A/R determine the size and flow , is that not correct? Are you saying those higher horsepower turbos will simply flow better by design on a rotary?
Download a garrett catalogue or open a few tabs of different frame size turbos, they list turbine flow graphs. There is usually some overlap between frame sizes and A/Rs but fundamentally rotaries have a lot of overlap and like relatively larger turbine wheels and ARs for compressor size compared to piston engines.
A turbine that size will chop the top of the power curve even at very low boost. Being divided is good for response however.
You may find you like the power curve it gives you, just don't expect it to peak power at 7500rpm.
the 2860RS flows about 35lbs per minute, for reference a stock T2 Hitachi HT-18 flows about 31lbs feet, so it should perform a little better than that
interesting choice, should be pretty much instant spool and lots of mid range, and then probably fall off up top
What are your thoughts on this turbo ? They also have a one year warranty . Again this is going to be a low boost build . Is this junk ? Reading online some people are saying they use Garrett stuff. SPA have any sort of good reputation ?
That sounds like a modernised to4b compressor wheel on a P trim /GT38 turbine with an AR that probably suits a 12A, split pulse is definitely desirable.
If you are making a divided T3 manifold anyway you can start with the GT28 and step up to something like that if you want more top end. The only rework would be dump pipe if you are careful the the exhaust manifold design.
I owned / daily drove 1982 era 12A RX-7 for roughly a decade before I got my FD. I had all manner of setups on it, factory nikki carby, 50mm ida injection, series 5 turbo intake adapted onto the 12a.
What you want at a minimum is a turbo with 55mm/55mm turbo, 1.0 A/R.
Ideally the absolute smallest would be a gt30 gtx30 g30-660/770 or series 5 (1990 T2 13BT) turbo all with a housing in the 1.0 to 1.06 range.
The best setup I found was the series 5 intake manifold with ask adaptor plate. It had good drive ability, anything without staged primaries and secondaries does not drive nicely.
anything 4x800 to 4x1000 will work on petrol, if you want to run E85 you'll want secondary injectors at least as big as 1600
Thank you for the info Jobro. Very helpful. I got a really good deal for a brand New Garrett GT3076R .82 A/R. Size is below. I can always change exhaust housing if needed. See any complications with that?
the old old yellow FEED FC ran a turbo like that. i'm not sure how much HP they claim, it kind of depends on when you ask,
in 1999 they were running an HKS GT3040, which is a GT30 turbine wheel in a 1.12 a/r housing (the biggest one)
compressor on that is 58/82mm, which i haven't had time to run down yet, but its like a smaller GT35
