What turbo

[sk8ercbs]

I currently have an old isr(isis) t25/t28 replacement turbo, but also an older isis rs3871, that i plan on rebuilding and putting in instead. Are the power gains worth it? Whats the difference in lag? What numbers have people gotten with each? Need to know before going to martin for a tune.

Ty for any feedback

My supporting mods
BC springs and retainers
ISR M spec intercooler
555cc injectors
z32 maf

[derass]

First off, both of those turbos are doo-doo.

Secondly, your engine in it's current state will make about 300whp. You should be looking for an OEM T28, S15 turbo, or a GT(X)286xR.

A GT(X)2871R would be more appropriate if you had cams, metal headgasket and 740cc injectors, and were gunning for 400whp.

[sk8ercbs]

Originally Posted by derass

First off, both of those turbos are doo-doo.

Secondly, your engine in it's current state will make about 300whp. You should be looking for an OEM T28, S15 turbo, or a GT(X)286xR.

A GT(X)2871R would be more appropriate if you had cams, metal headgasket and 740cc injectors, and were gunning for 400whp.

Thank you for the trivial information, they might be doodoo, but that's what I've got. I don't have 1000 bucks to spend on a temporary set up.

[S14DB]

The RS3871 is basically a 2871 with a journal bearing center. I would rebuild that. It's going to be a little laggy but worth it over a t25/28 clone.

Originally Posted by sk8ercbs

Thank you for the trivial information, they might be doodoo, but that's what I've got. I don't have 1000 bucks to spend on a temporary set up.

Naw man, you got to drop a stroker kit in there, 280 cams, solid lifters, 1000cc injectors and a efr9180. Then you can save up to swap in a real motor... /s

[derass]

Originally Posted by sk8ercbs

Thank you for the trivial information, they might be doodoo, but that's what I've got. I don't have 1000 bucks to spend on a temporary set up.

Well, then this whole thing's trivial isn't it?

But I guess to answer your question, the 3871 can make more boost, but will spool more slowly. But at the same time, your motor isn't ready for high boost. It's pretty much a standard 15psi setup. The car will be quicker overall with a smaller turbo at that power level. Have you tried turning the T28/T28 replacement up to 15psi?

[sk8ercbs]

Originally Posted by derass

Well, then this whole thing's trivial isn't it?

But I guess to answer your question, the 3871 can make more boost, but will spool more slowly. But at the same time, your motor isn't ready for high boost. It's pretty much a standard 15psi setup. The car will be quicker overall with a smaller turbo at that power level. Have you tried turning the T28/T28 replacement up to 15psi?

Yeah the guy that had the car was running 15 pounds on it and i drove it just like 5 pulls before i pulled everything apart, but that was with a smaller intercooler and just a shitty set up in general. The car has a metal gasket, why do you think i should run the 3871.

[sk8ercbs]

Originally Posted by S14DB

The RS3871 is basically a 2871 with a journal bearing center. I would rebuild that. It's going to be a little laggy but worth it over a t25/28 clone.




Naw man, you got to drop a stroker kit in there, 280 cams, solid lifters, 1000cc injectors and a efr9180. Then you can save up to swap in a real motor... /s

Do you think the power is worth the lag, i personally have no idea, ive literally driven my car 6 times a year ago before i pulled it apart and started replacing everything, idk if losing XXX rpm of boost is worth it or not to much XXX more hp

[derass]

Originally Posted by sk8ercbs

Yeah the guy that had the car was running 15 pounds on it and i drove it just like 5 pulls before i pulled everything apart, but that was with a smaller intercooler and just a shitty set up in general. The car has a metal gasket, why do you think i should run the 3871.

If the T25/T28 holds 15psi to redline then that's going to be quicker / faster than the 3871 at the same boost.

The metal headgasket is good, you can start turning up the boost. But you're quickly running out of injector. Your 550's can support about 320-340whp. But that's kind of a weird power level: the T25/T28 can't make that much, and it's not really optimizing the 3871. You'd be running it really low.

To me, it only makes sense to switch to the 3871 if you swap to 740cc injectors, grab some 256 or 260 cams, and turn it up to 20 psi for 350-400whp.

[derass]

Originally Posted by sk8ercbs

Do you think the power is worth the lag, i personally have no idea, ive literally driven my car 6 times a year ago before i pulled it apart and started replacing everything, idk if losing XXX rpm of boost is worth it or not to much XXX more hp

That's exactly it. Unless you drag race everywhere, a smaller, better utilized turbo will be quicker everywhere else in the powerband.

You're talking about gaining 20-40whp with 1000 RPM slower spool time. I think that sort of trade-off is only worth it if you're gaining 50-100whp.

[sk8ercbs]

Originally Posted by derass

If the T25/T28 holds 15psi to redline then that's going to be quicker / faster than the 3871 at the same boost.

The metal headgasket is good, you can start turning up the boost. But you're quickly running out of injector. Your 550's can support about 320-340whp. But that's kind of a weird power level: the T25/T28 can't make that much, and it's not really optimizing the 3871. You'd be running it really low.

To me, it only makes sense to switch to the 3871 if you swap to 740cc injectors, grab some 256 or 260 cams, and turn it up to 20 psi for 350-400whp.

Yeah i mean i emailed martin for his opinion on it all too, and i mean id be perfectly happy with 330 to 360 with the 3871, but as for the injectors i literally just bought these after wasting my money on some more 370s, so im not really trying to buy more and feel like im wasting the ones i just bought. And cams are a possibility i just haven't found any for a decent deal, i don't want to pay retail, because i m on a budget.

[derass]

The 550's will make 330-340. Maybe 350. No way they hit 360.

[sk8ercbs]

Originally Posted by derass

The 550's will make 330-340. Maybe 350. No way they hit 360.

Okay, i guess itll all just be the decision on whether or not the t25/t28 at 300 will be worth it over the 3871 at 340-350. Its just a daily so idk...