ibgoatin

iTrader: (1)

Hi guys...just wanting to get everyone's opinion about my turbo selection.

First, I'll give you the run down...car is an '04 GTO, motor will be a forged 346 w/a built set of 6.0 liter heads. I'd love to make around 800 whp.

Current set up is a bone stock motor with a pair of GT3071R T25 turbos...car made 510/570 on 93/meth, but those small turbines put a cork in it just north of 5000 rpm...power falls off sharply up top. I've since gotten rid of the smaller turbos and now I'm in the market for something with higher flow capabilities.

I honestly don't think I'll be able to fit a pair of full T4 turbos and still retain all of my factory accesories (something that's important to me) so it looks like T3/T4's are my only options. I've got my sights set on a pair of Precision SC61's but am also considering the SC63. My only concern would be compressor surge with the higher flowing '63...heck I'm not even sure if the '61 would be immune to it with the T3 housings?

So, what do you guys think a pair of T3 flanged units could flow on a 346...perhaps there are some of you here with a similar set up...do you think my horsepower goals are out of reach?

Thanks, guys!

JZ 97 SS 1500

iTrader: (2)

Twin 91's .

IF you go SC61's go with the P-trim since you are sticking with the T3's. You need to stuff the largest wheel you can in there with that flange. Stay away from the stage wheels..

JZ

onfire

iTrader: (17)

Somethings wrong with the set-up if you maxed out at 510rwhp with GT3071R's.....I'd recheck it before tearing it apart...LPE is making 850rwhp with those turbos....making 750rwhp with the smaller GT28R's...both with 346ci/mn6 and 16-18psi.

braap

iTrader: (4)

Are you sure they're using the T25 exhaust housings? I have no doubt that those were causing the problem on this car...boost would come on instantly...peak torque was at around 3300-3400 rpm and would slowly fall from there to about 5000 were it would fall off pretty quick.

ibgoatin

iTrader: (1)

Twin 91's

I have'nt made my mind up yet as to which turbo's to get, it's still kind of up in the air, but I want whatever I choose to work this time, well at least for a little while.

onfire

iTrader: (17)

Had one in my hand...no doubts...the Incon base kits used them also...cablebandit dyno'd around 750rwhp through an automatic with them in an fbod. PM him for details.

Zombie

iTrader: (2)

What valve springs are you running? 5000 rpms is the magic number for valve float under boost it seems.

MadBoost

We're at 550rwhp on a pair of gt2871r (.86 A/R T25/28 turbine housing) at only 9psi currently on an automatic '05 LS2 SSR we built. As soon as we screw with the tuning and boost some more I'm sure we'll see in excess of 650whp with the auto tranny at around 13 psi which will just about max out these turbos. They may reach 700whp but our target was 650 with a "HUGE" power band. Like 'Onfire' said, it's not the turbos holding it back.

gametech

iTrader: (1)

I think zombie is right on this one. I have a couple of dyno graphs from my gto with stock valvesprings where the valves float before 5000 at 10-12 psi boost. Comp 918's did the trick, but I don't know how high they will go when I up the boost more.

ibgoatin

iTrader: (1)

I appreciate all of the help, the motor is all stock and the valve float was probably the issue, but I went ahead and ordered a pair of MP T-70's I think they will be better for me in the long run.

I think they will make more power effciently-we'll see

2000 Tran Zam

iTrader: (2)

I would just suggest maybe using a smaller A/R ratio with those size turbos on a 350 cubed motor, unless you decide to go bigger, otherwise Lag will be an issue.