new user but long-time reader has turbo questions . . .

[95lstegman]

i've been a reader on here for quite a while, and i finally decided it was time to join.

okay, here's the deal. i have a 1989 240SX with redtop that i installed myself. also has Koyo radiator and full 3" stainless DP and exhaust, no cat. that's basically it for mods, not even an intake. stock turbo and i/c.

sometime in the near future (hopefully), i'll have enough money to pick up a nice turbo. i am of the mindset that i buy once, get exactly the right part, and never have to buy it again.

my choices are: GT28R/S15-R turbo, GT28RS, and GT2871R. any other good BB choices please chime in.

the GT28R is a huge savings over the others, which is nice. allows me to get a manifold or turbo outlet or both or maybe something else. i've heard many times from different people that the GT28RS provides much quicker spool but, more importantly, better control and response, which is why it tempts me. the GT2871R is the choice for best power.

goals: i can't imagine making over 350whp ever. when i do buy it i will run stock boost until i can support other mods. i do, however, have an ECU that i chipped and can tune as needed, along with wideband and some datalogging goodies. response is top on the list, and the GT28RS seems to be the best in that category, but i think ~275whp w/o cams, manifold, etc. may not be enough to quench my thirst for power. maybe it would, maybe it wouldn't, but if i buy a $1100 turbo and find out ~300whp isn't enough, i'll be pretty sad. i'd be a lot happier if i spend <$700 on a GT28R and can only make ~300whp, i won't be so sad, because i'll have saved a bunch of money.

so pretty much, two basic questions to deal with:1) is 300whp enough to keep you happy for a long time, or would i soon be feeling slow again (took about 2 weeks for the SR swap to feel slow)?2) can the GT28R match the GT28RS in response, spool, and easy moderation of boost w/ the throttle?

any turbo i get, an Apex'i AVC-R will follow. thanks for your time guys.

[95lstegman]

BTW, i would be considering standard GT28R/S15 Spec-R turbo vs. GT28RS w/ .86 a/r turbine housing vs. GT2871R with the smaller turbine housing (.64 a/r i think it is). i want full boost NO LATER than 3500. 3000 is better since i spend more time there on the street.

[Nismo_Freak]

GT2871R

Cooler boost temps, more potential.

[95lstegman]

i would really like to roll with the GT2871R w/ .64 a/r turbine housing. probably the reasons i would go with the GT28R are the following:1) much cheaper2) spools significantly later3) perhaps the slight mismatch of turbine and compressor would make it less responsivei've seen what looks to be a knock-off S4 turbo on eBay for about $575 or so. for that price i'd probably stick with that almost no matter what else i saw. a new turbo is my only choice unless somebody practically gives me something decent for next to nothing.

i'd really like some REALLY specific information about the spool of the GT2871R. when does it (w/ .64 a/r turbine housing) make positive pressure, when does it make 50% of target boost, when does it make full boost? and how does it respond to throttle inputs? i'm guessing the GT28R wins in all of these categories by a good amount except down by 50-75whp.

[95lstegman]

so nobody can tell me how a GT28R/S15 turbo compares to the DP as far as response and spool?

[Nismo_Freak]

so nobody can tell me how a GT28R/S15 turbo compares to the DP as far as response and spool?

More than likely it's a 300 - 400 RPM difference.

Go with a GT28RS, it's a happy medium. Although I still would go GT2871R.

[95lstegman]

am i missing something? isn't the GT28R = S15 turbo, only without the wastegate divider? the one i see on ebay looks to be a knock-off S14 BB turbo for like $550, versus potato for $1000 or 71R for $1050. i think i'll stick with one of the smaller turbos as opposed to the GT2871R b/c of the cost of supporting mods and the fact that it's a daily driver, and fuel cost is somewhat of an issue. i'd go crazy with that much boost . i'm kinda just trying to figure out whether i'd be better off with a DP or getting a standard nissan BB turbo (which i thought was identical to the GT28R). i think so far i've kinda ruled out the 71R, fun as ~375whp would be. i just don't think i need that much. of course i want it, but i think with positive pressure before 2000rpm i'll be a lot happier than with a larger turbo that leaves me sucking in the RPM range i spend the most time. and 275whp from GT28R or RS is still nice on the street.

[Nismo_Freak]

am i missing something? isn't the GT28R = S15 turbo, only without the wastegate divider? the one i see on ebay looks to be a knock-off S14 BB turbo for like $550, versus potato for $1000 or 71R for $1050. i think i'll stick with one of the smaller turbos as opposed to the GT2871R b/c of the cost of supporting mods and the fact that it's a daily driver, and fuel cost is somewhat of an issue. i'd go crazy with that much boost . i'm kinda just trying to figure out whether i'd be better off with a DP or getting a standard nissan BB turbo (which i thought was identical to the GT28R). i think so far i've kinda ruled out the 71R, fun as ~375whp would be. i just don't think i need that much. of course i want it, but i think with positive pressure before 2000rpm i'll be a lot happier than with a larger turbo that leaves me sucking in the RPM range i spend the most time. and 275whp from GT28R or RS is still nice on the street.

Positive pressure before 2000 RPM? No turbo is going to give you that without some serious timing issues. Besides that is undriveable with that much response (turbo lag IS beneficial), get full bolt-ons and you'll notice that with the T25, it spools retardedly fast on the highway which makes the car surge at partial throttle.

I would get the GT28R if you are concerned with cost.

[95lstegman]

heck if i open the throttle with the stock T25 at 1800 i'll go out of vacuum by 2000rpm. i've just never actually floored it below like 2500, and even at 2500 it's kind of a waste. i almost never actually floor it, come to think of it, unless i'm shifting up high. but i read in a few places the GT2871R won't start making boost until like 3000rpm and have full boost by 3500rpm . . . i guess due to a bit of a mismatch in wheels. is this true? or will it still make 0 vacuum around 2000rpm?

[Nismo_Freak]

heck if i open the throttle with the stock T25 at 1800 i'll go out of vacuum by 2000rpm. i've just never actually floored it below like 2500, and even at 2500 it's kind of a waste. i almost never actually floor it, come to think of it, unless i'm shifting up high. but i read in a few places the GT2871R won't start making boost until like 3000rpm and have full boost by 3500rpm . . . i guess due to a bit of a mismatch in wheels. is this true? or will it still make 0 vacuum around 2000rpm?

The GT2871R will begin to make positive pressure at about 3000 - 3300 RPM. It's by no means laggy, and you will barely notice a difference in performance driving.

Personally I'm tired of these threads, who cares if the turbo spools at 1800 RPM and makes 30 lbs. of boost by 2000. The engine has poor VE at that point and will not produce power. A turbo that produces full boost pressure between 3500 - 4000 RPM is not laggy, and does not FEEL laggy once you get used to it. I cant think of one point where I would drop below 3000 RPM on an engine that is capable of 8500.

God damn this crap annoys me. Just buy the damn turbo that produces the power you want. You aren't racing in JGTC next week.