Deciding on turbos, Advise?

[JosiahP]

So my goal for hopefully the spring is 450whp in my 1991 GTR.

As of now I have a trust intercooler, Greddy 3in hard piping, Trust oilcooler, a Greddy 3in turbo back exhaust, un known brand twinplate clutch currently installed on the car. I have purchased a Apexi Power FC, and will be getting z32 MAF's and 800cc injectors (is that good? should I go bigger or smaller? not 100% sure) also a larger fuel pump (walbro 255 should be enough) and fpr, Tomei pon cams, adjustable cam gears, and new valve springs. From what I have read that should be all I should need to hit 450whp probably more.

Now I am just stuck on the turbos. At first I was thinking about taking the N1 turbo route, but after talking to some other GTR guys they suggested ether Hks 2530 or Hks GT-SS. I do not mind spending a little more money to have a good quality set of turbos that can get me to my goal.

So can anyone offer me some advise on which route to go with the turbos?

[bobbo]

I've got N1s and I'm happy with them. I also strongly considered the GT-SS turbos but the N-1s at the time were to good of a deal to pass up.
I'm using stock MAFs, stock FP and FPR and made 426.7 WHP on 91. Make sure you have Datalogit to go with your PFC or whoever does your tuning will hate you. The PFC is almost useless without it. Also have a very good boost controller. The PFC controller works but isn't as consistant and doesn't have the versatility of some other kits.
With the other parts you have and with a good tune you'll have no issues reaching your goal.
Regarding your question pertaining to injector size. Rule of thumb is 1cc for every HP. What you have is much bigger than you need but I think will work fine. You'll certainly never max out your duty cycle.

[LittleDevilCRX]

I would say go HKS2530's the response of them is wicked if tuned correctly. I currently rock them and make 525whp.
N1's would be a solid choice as well.

[cobrAA]

gt-ss by far the best turbo setup for response and 500-530whp.

However, if you were to go -5, i would try to go for the new gtx28 turbos. should flow the same but make about 60whp more. Of course, you need custom downpipe and relocate by 2 inch the power steering reservoir but for the ''ultimate'' twin setup, i think its worth it.

[Bruizer]

The Ultimate twin setup thus far is 2 borg warner EFRs but run near $8k with hardware and hoses/pipes I hear... That would be beastly. Twin 6758!! Something like 850whp lol

[JosiahP]

Im trying to over build for reliability, thus the larger then needed injectors as well as upgraded fuel pump and FPR. I will also be buying a Datalogit.

So going the 2530 route is a good option? but they would have to be used turbos, the GT-SS route i can buy new turbos, does anyone have experience with these two options at this power level? how was the response? id like something that spools similarly to the turbos on the car now (full boost at 4krpm).

[Bruizer]

Im trying to over build for reliability, thus the larger then needed injectors as well as upgraded fuel pump and FPR. I will also be buying a Datalogit.

So going the 2530 route is a good option? but they would have to be used turbos, the GT-SS route i can buy new turbos, does anyone have experience with these two options at this power level? how was the response? id like something that spools similarly to the turbos on the car now (full boost at 4krpm).

Full boost by 4k is definitely doable for lots of power but I don't know about the 2530 unless you have serious headwork and support mods. I THINK the average on those was around 5000rpm?
Thing is, the more power, the more lag (generally speaking) but it depends what you're after. Like more guys with badass singles (cause twins suck, even ford has twin turbos now yuck), they'll tell you you just don't know how to drive if you're lagging. I just don't enjoy triple downshifting to pass someone in the fat of the boost.

GT-SS will get you 4000 rpm full boost for sure and could reach a sick 450whp if you want a road course car.
I smaller intercooler (like stock R34) will get you better response, along with hard pipes and a modified Y pipe, good flowing exhaust.

[r33_gtst]

So my goal for hopefully the spring is 450whp in my 1991 GTR.

As of now I have a trust intercooler, Greddy 3in hard piping, Trust oilcooler, a Greddy 3in turbo back exhaust, un known brand twinplate clutch currently installed on the car. I have purchased a Apexi Power FC, and will be getting z32 MAF's and 800cc injectors (is that good? should I go bigger or smaller? not 100% sure) also a larger fuel pump (walbro 255 should be enough) and fpr, Tomei pon cams, adjustable cam gears, and new valve springs. From what I have read that should be all I should need to hit 450whp probably more.

Now I am just stuck on the turbos. At first I was thinking about taking the N1 turbo route, but after talking to some other GTR guys they suggested ether Hks 2530 or Hks GT-SS. I do not mind spending a little more money to have a good quality set of turbos that can get me to my goal.

So can anyone offer me some advise on which route to go with the turbos?

Keeping the oem turbo manifolds?
Your supporting mods sound good. I think tomei supreme manifolds and N1's will flow good and get you where you want to be

[NismoS-tune]

I used to run tomei manifolds and outlets and they made no difference compared to ported R34 cast manifolds that won't crack like the Tomei ones over time. I'd spent the $1200 elsewhere and either port your stock manifold/dumps or get R34 sets.

[cobrAA]

So I just read like for 2 hours about those efr 6258... sound cool, but seems to have a problem with production which scare me to be honest.

But still.. same response as -5 but seems to make like 100whp,150whp more!! Amazing isnt ? but then you think these cost about 7k-8k and nothing is fitted. unless your a pro welder, you could easily figures another 1 or 2k to make it fit. so your down to 10k........

10K for 100whp isnt really that good if you think about it. thats like 1k for 10whp/15whp. I would rather spend the money on a rb28/30 or on tracking class. Sound awsome when you consider just the turbos and what they do but when you think outside the box, i couldn't call these turbos the ultimate setup for response/twins.

[gtrte37]

if your doing vavle springs might as well to head studs/gasket.

[Bruizer]

So I just read like for 2 hours about those efr 6258... sound cool, but seems to have a problem with production which scare me to be honest.

But still.. same response as -5 but seems to make like 100whp,150whp more!! Amazing isnt ? but then you think these cost about 7k-8k and nothing is fitted. unless your a pro welder, you could easily figures another 1 or 2k to make it fit. so your down to 10k........

10K for 100whp isnt really that good if you think about it. thats like 1k for 10whp/15whp. I would rather spend the money on a rb28/30 or on tracking class. Sound awsome when you consider just the turbos and what they do but when you think outside the box, i couldn't call these turbos the ultimate setup for response/twins.

Think your over thinking it...

What I should have said was, when someone wants ultimate, cost isn't important, and no matter what setup, those twins can spool 1000 rpm faster than -5 and make more top end than -10 without any shuffle. Though if go 6758 twins on an rb30. They aren't 10k installed, maybe 7?

As for failures, that was a casing issue with a manufacturer that went bankrupt (Borg Warner hires out the casings). Those inverstment castings were weak. Now they have sand casting.
Indy car uses the twin 6758 and they're that unreal that its very possible the new z07 will run these or the 6258 on their twin turbo v8 coming in the next year or 2

As for the turbo cost, they aren't more expensive than say precision (Honeywell -5's (aka Garrett Mexico are cheaper) as they include a boost controller, bov and wastegate so at $1600, it seems
Fair. Main reason you don't see many EFR on GTRs in Canada is because most are hooked on tried and true dinosaurs, too sacred to try the newest turbo technology or plain out can't afford em.
My -5 twins with tomei manifolds/outlets, fittings, hoses and hardpipes cost just under 5k (less than msrp for the parts.

[JosiahP]

Hmm thats all good info, i will definitely have alot to think about! It looks like i may end up going with GT-SS turbos, and @gtrte37 I will also be doing head studs and head gasket, forgot to add that