Turbo gurus, guide my cash
 

What would be the best turbo for an engine with a ported head, ITB's and 11:1 CR? I'm planning on running it in conjunction with water injection if necessary, but my goals are
- not a ton of boost, 12psi with WI at the very top
-quick spool
-response response response
-torque

I'm thinking I could run a pretty big turbo at low boost for my needs, since the head and plenumed ITB's should flow pretty damn well.

What say you?

You did not mention the most important number... HOW MUCH POWER DO YOU WANT? Are we talking 150whp/200/300??? The most popular turbo below 250whp is the GT2554r. Between 250-300whp, GT2560. Above 300whp, you're looking at a GT2860/71. Once you hit 350whp, we're talking GT30+.

Your setup for 250whp is a GT2560. Quick spool, huge midrange torque, top-end for 300whp. End thread.

thanks! what would be a step up from that, something that could handle 300-350? i wouldn't mind rocking something with a little spool on it at 250hp until I can get tranny gears that won't fly off :D Should I consider the sizes of the intake and exhaust sides of the turbo, or should the regular setup be alright? Edit: edited numbers

edit: The main reason I'm asking instead of just buying a gt2560 to begin with is basically because I feel like my system could spool the crap out of one of those, so I wouldn't mind rocking something that on a stock miata would have a sort of crappy spool. Not a huge ass one like a T30 though.

Edit2: I was thinking something like a T28?

Edit3: when I was talking about 'the size of the intake and exhaust sides of the turbo' i meant the compressor and turbine sizes, and the A/R. I'm not a turbo guy, so I have no real experience with changing that stuff around for different purposes

imho 12psi on a big turbo on a high comp motor is A LOT of boost.

hehe. yeah. :D Edit: 12psi would be max, and thats on aftermarket rods and WI.

I think a GT2860 is what I want. any advice on A/R though? Can you find exhaust manifolds for miatas that mate up to T28s? Edit: I like that the t28 maxes out at around 360hp

with a CR as high as that you will have such a huge dependency on octane it wont be funny
you will need a proper aftermarket ECU and a very smart tuner to handle off boost response (ie high timing values) to on boost behaviour - perfectly possible but the transitions are going to be close - if you get it wrong detonation will be your companion

I vote for a T3 50 trim on an equal length rams horn style manifold with a 3inch downpipe

The T28 is the exact same thing as the Gt2560R.

T28 = Journal Bearing
GT2560r= Ball Bearing

Are you having a custom plenum built for the ITB's? You have to be a little more realistic with power goals man. 350hp on a high-compressed motor is goin to be a tuning nightmare.

did we already kick you out of here for being a ------? I really don't want to read a bunch of ITB garbage. I also don't really give a fuck for the high-compression / FI crap that anyone with an engineering background thinks is garbage.

Basically, you fucked up and you've spent all this money on a slow, NA, ITB queen ride because you wanted to be cool and JDM. Now look at you, you're a bitch. You're also one of those morons who doesn't understand that "12psi of boost" from a pea-shooter turbo is different from a gt45r.

Is this even english? Your girlfriend can spool my balls, rather than letting them sit on her chin.

What viperormiata is saying is with an 11.0 CR you cannot acheive the same boost or HP as a motor with an 8.5 CR on pump gas.

You will always be at a diadvantage to the guy with a lower CR, all other things being equal. That's freshmen class Turbo 101 information.

My guess is you'll probably never see 300HP on pump gas with that lousy CR even with WI, unless the WI gods are really good to you.

I don't know. I'm interested to see you get that working but I'll reiterate ITBs plus high compression plus turbo= tuning nightmare. That's a lot of variables to work with. Adding WI further complicates things and adds another place where a failure would cause catastrophic damage. Plus you're talking about big money now for a setup that might have slightly better response than a similar one without the hassle of ITBs or the danger of super high compression and significantly cheaper. Drop the compression down a point and I think you'll still have the response you want but with a better margin of safety...or get a v8.

My guess is about 220WHP. With any size turbo you pick. You can have it at 3500 RPM or at 7100 RPM depending on the turbo.

Maybe 230WHP.

-yes I'm building a plenum for the ITBs
- I'm not opposed to dropping CR, but only if its impossible to get 12psi, which I don't think it is impossible. I'm still researching though. I'll be happy with whatever HP 12psi gives me.
- the tuning doesn't really scare me. maybe it'll turn out to be impossible to tune the itbs on a turbo, but i'm gonna give it a shot first, and if it doesn't work I'll sell them and swap out a regular single throttle body style manifold
- yeah sorry about not knowing what a T28 is, I don't really know that much about turbo systems yet.

the biggest reason I'm doing what seems like a complicated setup is that I'm working with what I already have, and I think it might just turn out awesome.

Hustler, eat a dick.

Still though, the reason I started this whole thread is basically to ask, if you have a really high flowing motor, does that affect what turbine/compressor setup you should run, or A/R?

Edit:
Even if the number is low, I think the dyno curve will look mighty interesting. I'm fine with those kinds of numbers. I know you guys don't like the idea really, but give me a chance to do it and see what happens, I think it might turn out pretty fucking mean.

why 12psi? Why did you choose this magical #?

You need to sell the motor and ITB set-up and buy a stock motor. 230whp is easy on a stock motor, almost impossible on yours.

so thats a "no" on whether or not I should worry about A/R and turbine/compressor housings?

Edit: Just noticed this
This is what I was looking for. Thank you. I'm tempted to run 10:1 because this is tried and true on NB's, but 11:1 doesn't seem impossible, people just seem scared of it.

static compression all depends on power goals. and the trade-off with output and spark angle. As for turbo sizing, its basically been beaten to death over the last 20-years on our old-ass motors and old ass turbo systems. Its not rocket science anymore, pick your output goals, determine where you want those targets, then buy that turbo. If you want 230, that's a gt2554 or gt2560 (where do you want the power) on a stock-ish motor. You probably have a fairly bad-ass NA motor, but its a waste of time and money to change directions on that motor. Sell it and buy a stock-ish motor, or build a motor like mine for $2k.

do you have a plan for this car? Street? Autox? Road Racing?

uhmm, yeah, but its not anything anyone wants to hear about on this forum, lets just say the most important things are responsiveness and midrange torque
hustler, I have to say, i really appreciate your civilized and intelligent answer. I think I'm gonna run a season on it non-turbo at least, but in the meantime I'm gonna start stockpiling turbo parts and figuring out what I want to do.

here's a perfect guide for your cash: send it to me:)

lets say I run a gt2554; it seems to me like that thing would be damn near insta-spool on my setup, so the wastegate would open pretty fast. Would I need to run an external wastegate to not choke things up on the top end?