OK turbo guys. How do you size a turbocharger. I need one for the current project. The last turbo setup I basically guessed. It worked, but that was a draw through carb setup pushing 5psi, high tech it wasn't.
The engine in question is a 3.4L V6 with a base CR of 9.5:1. I'm looking for 10-15 pounds of boost and 350hp.
How do you pick the right turbocharger.
This is a HUGE subject, one not easily answered in a couple of sentences. That said, I'll vote GT3076R, or maybe the next size up. Depends if you want top-end only, mid-range, or a wide torque curve.
I strongly suggest getting some books on the topic rather than looking for a quick answer.
Are you going with a single turbo or a twin set up?
Single turbo, street driven so a wide torque curve is preferred. I would rather sacrifice some top end power, than have an engine that only pulls over 4K rpms.
I've read Maximum Boost, but that was years ago. What are some other must read books.
Oooh! can I play too?
Which cheap and easy to find in the junkyard turbo for a 2.8 or 3.3 6 cylinder?. Low power goals of 200 to 250hp.
Chinese T70 with a T4 flange?
GT2871 or 3076?
Read "Maximum Boost," by Corky Bell again. Here it is in PDF: http://www.fusca.net/wp-content/uploads/Maximum_boost.pdf
I also have found this site helpful, has a pretty decent selection of popular compressor maps. http://www.squirrelpf.com/turbocalc/
Garrett has a pretty good primer on turbo selection:
really good calc to plot some compressor map points: http://www.not2fast.com/turbo/glossary/turbo_calc.shtml
Amateur turbo sizing generally gets hung up on compressor sizing because that's what's most easily understood with charts and math. The side effect is that people recommend turbos with turbine sections that are horribly mismatched to the intended application because they happen to be attached to a compressor section that more or less works on paper.
A gt28 or 30 turbine is comically undersized for a 3.4L engine. A gt35 turbine would be considered small for a 3.4.
How heavy is the car? Auto or manual? Where does the engine make power on its own? Where do you want the power?
Vigo wrote: Amateur turbo sizing generally gets hung up on compressor sizing because that's what's most easily understood with charts and math.
That and the lack of generally available turbine maps.
Yeah, turbine maps are a lot trickier than compressor maps not just to find but to make and get any use out of. I can understand why companies catering to the aftermarket dont bother even trying. It's sort of a case of "if you have to ask, i wont make any money off you" kind of thing.
I guess i can infer the 3.4 and vehicle we're talking about based on Toyman's other thread and get to work. Mid-90s camaro/firebird ohv/2v gm 60* v6 and an 83 rx7.
In that app you probably don't want a midrange monster because it won't have any problems exceeding its traction to begin with while turning. I'm assuming this is supposed to be a turning car.
So, go for something that's not going to spool until ~3000 something rpm. A later spooling turbo is coincidentally also going to ramp boost up more gradually (although gradually may not be a good term) which will make the car a little easier to drive. It'll flow more because it's larger, which also means that it will make more power on the same boost and compressor side than a smaller turbine because of decreased pumping losses to run it. So big-ish is good.
I'd avoid anything with a garrett t3-based turbine section. That's what's easiest to find used due to the proliferation of t3/t4 hybrids for the 4 cylinder crowd, but the hot side is too small for a 3.4L. Garrett P trim T4 turbines would be good. Turbonetics F1-62 and -65 would be good. Mitsu TD06h turbine..Holset HX-35..Garrett GT35, maybe gt37...
A lot of times manufacturers will sell a turbo that doesnt tell you anything about the turbine from the name. Those you just have to go looking.
Ready. Here is my horrible quick and dirty turbo sizing.
If it works on a 6 liter diesel at 3000 rpm it should work ok at 6000 rpm on a 3 literish gas motor.
It's all about the gas flow. And I don't mean uncle morty after a bowl of chili and two natty lights.
Playing with the turbo finder tool on Garrett's website, the GT3776R sounded like a viable option.
Honestly, I think I'd just call Garrett customer support, unless you're looking for a used turbo to keep costs down.
U looking new or used? I say a nice holset from a dodge. Maybe even something mitsu and used for cheap. if its too small get 2. The evo had a nive twin scroll that everyone seems to upgrade and sell cheap.
I'd say a hx35 would be kinda small. also they are designed with divided housings so unless you're willing to build headers with that in mind, you'll lose spool. Maybe a hx35/40 hybrid would work.
Forced performance is selling an MHI TD05H 20g for $540... Or their FP Black turbo for $800.
EFR6758. Will make 400hp on 93 octane with ease, should hit full boost by 2000 rpm on that displacement engine, make stupid stupid torque. match bot
Based on the match bot you'll probably need an external wastegate since the turbo is a bit small, 350hp is Bob Costas E36 M3 on a 3.4 liter. So you'll notice I picked an under sized turbo and am struggling to keep it under 500hp, I hate displacement.
FWIW, the gt30 sizes will be fine. Your engine won't flow enough to make the others viable options.
In other words, displacement means nothing if your engine sucks at flowing CFM's.
Some of our sho guys are using the gt3076 and doing OK.....with 3-3.2L displacements, and we probably outflow your engine by a third again.
A ct26 or hx35 would probably be fine for your application and they're easy enough to find for cheap.
Keep in mind this car doesnt really need a turbo. That frees up turbo sizing quite a bit because it lets you get a turbo that doesnt have to be spooled by 2000 rpm to get the car moving.
IMO, putting a gt30 on a 3.4L is going to be counterproductive because this thing is not going to hook to begin with and having a turbo that spools at 2000 rpm is just going to make that worse. Even if you dont make ANY more peak power (which is unlikely, but for the sake of argument here...), having a bigger turbine section that spools slower is going to make the car faster in the real world.
But, if you've never had a huge-torque all-midrange turbo setup, it's still fun. After a while you just realize it's more novelty than performance when you finally gain traction because the powerband is dropping like a rock at 5000 rpm and you shift and start spinning again. 
I'm down with a t3 flange hx35 or hx40 in this case if you're looking cheap.
3076 will do your requirements but Vigo has a good point.
Vigo wrote: Keep in mind this car doesnt really need a turbo. That frees up turbo sizing quite a bit because it lets you get a turbo that doesnt have to be spooled by 2000 rpm to get the car moving. IMO, putting a gt30 on a 3.4L is going to be counterproductive because this thing is not going to hook to begin with and having a turbo that spools at 2000 rpm is just going to make that worse. Even if you dont make ANY more peak power (which is unlikely, but for the sake of argument here...), having a bigger turbine section that spools slower is going to make the car faster in the real world. But, if you've never had a huge-torque all-midrange turbo setup, it's still fun. After a while you just realize it's more novelty than performance when you finally gain traction because the powerband is dropping like a rock at 5000 rpm and you shift and start spinning again.
I'd rather have the power under the curve and quicker throttle response. Stupid big torque is easy to manage if it responds quickly to inputs and you have properly setup boost control. I think a gt3076 would be more than enough to keep linear torque to a typical american v6 redline. Even the smaller efr 6758 would be able to.
Did I miss the drivetrain selection?
Can the moving bits in the gm 60deg v6 handle a turbo? What do the heads flow?
I really don't know much about this engine.
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