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max boost for 2871 around 22-24psi really. after that efficiency starts dropping off
Turns101 ran 28psi on 2871. I ran 30psi on my 3071. He had more power and held boost to redline because he had a tubular manifold. I had a log manifold.
And yes you will probably need to boost 24psi or so.
BTW I recommend a Borg S200SX. MUCH CHEAPER and as good.
Well, of course you can run more, but then you starting to overspin the turbo and get it out of its efficiency area... IMO if you're planning on running more than 22-24psi, then look for 3071 or something with a lil more compressor flow, so you can do it more efficiently.
2.5 PR = 22psi
2.75 PR = 25.7psi
Looking at it a lil closer then I'd say yeah...about 24psi max is what I would do.
If 325 is your power goal, 2871 can def get you there. Probably closer to 20psi with a typical setup.
Another question, since I'm looking into the 2867. How signifigantly different would this turbo spool from the .64 A/R tial housing to the .86 A/R tial housing? Also, what could I expect as far as differences on the top end power?
You may find the GT2860RS with the small housing will choke flow too much. The big housing is the way to go. You can make 16psi at 4500rpm on a log manifold with good tuning, that is about 255wtq on a mustang at 4500rpm. The compressor or cams will run out of steam above 6500rpm. Something runs out of steam up there, I'm not sure what.
The GT2860RS was made for the big housing, use it. I think it works very well on my car, which delivers power like no other turbo Miata I've driven, just don't expect more than 300whp on a Mustang.
First off, yes I know this thread is old as hell. However, this is the only thread i could find with people discussing the 48 trim gt2871 so for the sake of anyone else who decides to use a "legacy turbo" on their build i figured i would provide some actual feedback. I picked up a very lightly used 48 trim gt2871r off some guy on craigslist for pretty cheap so figured I would give it a try. The turbo I was running before was a gt2560. I bought the 2560 new from Nissan (S15 spec r turbo). So far I have been very happy with the 48 trim 2871. It spools extremely well.
I datalogged a pull from 2k RPM in 5th gear tonight (6 speed 3.9 rear) and I made my set wastegate pressure (15psi currently) at 3350 RPM. This is on a built 99 motor running 83.5 mm supertech 8.6:1 pistons, a taco taco manifold, Artech 2.5 divorced wastegate downpipe to 2.5 inch exhaust with no cat.
Transient response feels great too and i can tell no significant difference between how the turbo spools up compared to my 2560. However, after spool up this turbo just pulls so much harder than the 2560 did. Keep in mind this all seat of the pants data aside from the spool data which was datalogged. I can post the log if needed
Anyway, if anyone else comes across a great deal on a gt2781r 48 trim turbo and they are curious for some actual feedback based on use, I'm extremely happy with how its performing so far and it does not exhibit any feelings of slower response compared to my 2560.
Alright here are some results to go along with my initial impressions/thoughts. Still very please with its performance, spool isn't far off of my GT2560R. In colder weather it will make 17 lbs at 3450RPM. Full list of supporting mods in the dyno and timesheet section (https://www.miataturbo.net/dynos-tim...5/#post1554585)
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