Garrett Turbo Questions

[RhdHybrid]

I would imagine there are some very knowledgable people on here in this field. I have been doing a bit of research on what turbo's to go with. Now I'm sticking with the twins, not going big single. I want to swap out my perfectly good stockers for something with a steel exhaust wheels. I have a sour taste in my mouth because of ceramic wheels and a twin-charged project(B20Vtec using a Eaton M62 blower to spool twin 2JZ turbo's to 16psi at 2000rpm = Fins out exhaust). So on to my questions?

The turbo's in question are:

Garrett GT2860R - 707160-5 360HP
Garrett GT2860R - 707160-7 310HP
Garrett GT2871R - 707160-10 460HP

I have see alot of people using the -5's. The other two not so much. I have been looking at the Garrett Compressor/Turbine maps(Garrett website), but in reality I don't really understand them. So I don't really now what that information means, and how it relates to the drivability, response, and overall effiency of the motor.

So I guess I'm really wondering which of the above turbo's would provide the best combination of reponse and overall power. Why would one use the -5's over the -10's? That being said I would like to see 500hp this summer. A Modest number, but in reality I won't have the fuel system for much more this summer. But I want room to grow, as I'm not one to leave well enough alone.... LOL.

Thanks Ken.

EDIT* A Google search revealed a previous thread on GTRC that the search function didn't. So I have some of my answers. -5 will spool 500-600 earlier then the -10's, -10's may be abit laggy for street use, which is where I'll be using it. I still wouldn't mind someone explaining the compressor and turbine maps and how they apply to the real world.

[NismoS-tune]

The -7s will get you the 500hp and response you want. Or you could get some HKS GT-SS.

Honestly, figure out your budget first. Most guys making 500hp are spending near 10k with a built engine. From there it gets more expensive. Budget is no one else's business but some people get started and find out they cant' finish theirs cars due to lack of funds or take way longer to finish.

So, what's all done to your car now and what WILL be done by the time you're tuning for "500hp". That'll help the others point out which turbos are indeed the best.

[GTRADDICT]

Research the new Billet style turbo's... more power, less lag more $$

[cobrAA]

GTSS for the response. I seriously think they can't be beat in term of response. Actually, they are very close to the -9 which are rated 20hp more than the -7. so your looking at 600whp max.

but the -5 will give you a kick in the butt that the -7 -9 can't mimmict. However, some say that it's only 500-600rpm laggier but I could really feel the difference of 500rpm.. Like.. I was thinking : its coming.. it gonna pull..puuuuuuuulllllllllll lol when with the -7. you will only think 1 second and it will be pulling.

at the end, the -7s are more progessive. hence why you will less likely feel the kick in the butt. with the -5. it's a more brutal, so you get nothing.. and then at a certain RPM.. Boom it fly. Keep in mind, there's trick to make it more responsive but it can cost easily 3-4k lol

[NismoS-tune]

What's the trick to more responsive -5s? don't even say 2530 cause it's not true

[cobrAA]

Hard piping, tomei dump pipe, non-restrictive exhaust, divided twin turbo pipe or suction kit, head work. that's that I can think off in 1 minutes lol

[NismoS-tune]

Ah, those mods don't help that much... The modified OEM devided pipe is a start but the shape and flow is still gross. HKS racing chamber, greddy or custom intake kits is the real fix.

[RhdHybrid]

So, the -7's are the most responsive, but they will run out of lungs up top, the -5's got the lungs up top but I have to wait for them. So here is my general take on it, the main reason the -5 and -10's for that matter take longer to spool for two reasons,

1) Exhaust turbine pressures aren't equallized, causing them to fight each other. Which is a issue when you get into larger turbines. Not really that noticeable with smaller ones as they can over come this easier. Less Kenetic energy required. Solutions, Equalization tube(modified Stainless manifolds), Anti-reversion valves( also going to have to be added to the stainless manifolds. Bench test and Calibrate adjustable wastegate actuators to open and close at exactly the same pressures.

2) Poorly designed intake charge tubing. Fix - HKS, Greddy, ETC, Intake piping kit.

I also understand that head work plays a part in the spool time as well. But lets just focus on using a stock head and cams for now. Upgrades will come but I figure by the math that my turbo setup will cost me 3-4 at this point. I guess it will be another trip offshore in the new year....

My mod list thus for:
Mine's Downpipe
Cat Delete Pipe
HKS Exhaust
Mine's ECU
Apexi Intakes and Filters
Splitfire Coils
HKS EVC Boost controller
Blitz BOV's

That's it for the motor. Just the basic Bolt ons. Parts on the way, Bee R Power Builder and for Christmas I'm sending my old ecu for NISTUNE and some 850cc Injectors, maybe even some Z32 MAF's. And of course the necessary turbo components.

What is your take on my spool issues and solutions?

[cobrAA]

Ah, those mods don't help that much... The modified OEM devided pipe is a start but the shape and flow is still gross. HKS racing chamber, greddy or custom intake kits is the real fix.

Please show me a dyno-graph that say so lol? Never found a single dyno sheet that proves that the 500-900$ intake piping is better than the divided pipe. Both gives about 10whp and help spool 200-300rpm sooner.

Let say for the sake, one gives 20whp. would you say paying 400-800$ more is worth 10whp ?