9bells

Seriously, going nuts. I know this is honda-tech, but honestly some of the folks in the knuckle-dragging world **** me off...
Anyway, 2011 camaro. Want to build twin turbo kit. Want instant spool, and about 700crank hp. I'm going blind on maps and math. Done it all plotted it on every map I can find.
The problem is, the v8 guys are always trying to go huge turbos for 1000hp. Anything smaller needs a purse...blah blah.
I want 700hp, so 350hp/turbo. I'm sorry, but plotting that with 10lbs of boost tells me gtx2867r is the killer set-up. Everybody and their dog is saying too much backpressure, not top end,etc.
Issue is, I'm pretty sure those guys are referencing the 30psi graphs where the turbo falls off hard early. I want 10-12psi, and the graph says that will be great around 35lbs/min each turbo.I'll be at 74% at the top, but in the midrange the thing will be in the best parts of the graph.
So, my question is am I missing something with all this math? As mentioned, done all the reading and math I can find to do this right, and yet nobody agrees. I don't always care, but HT has some of the best FI tech and builds I've ever seen, so I figure I'll ask here as a final effort.

Turbo-LS

iTrader: (4)

Well in my opinion with a larger displacement motor your going to want something with a higher flowing exhaust wheel. i would think minimum on this would be twin gtx3076 with .82 housings or twin gtx3676 with .63 housings. Or look into precision turbos twin 5858 or twin 6262.

Hopefully Mac aka TheShodan will chime in here with a good matching setup

9bells

I hope so too. I couldn't find precision maps, and I really want to be able to have v-band housing to package these bad boys.
I mean maybe a gtx30xx with a small A/R will get me the spool I want, but it just seems like overkill for 550whp or so. Spool by 3000 and area under the curve matter more to me than peak hp. It's a driver, and it has to maintain it's current "grunt" attitude.

TheShodan

iTrader: (14)

Yes, you're missing 3 other sides to the equation. Turbine exhaust wheel efficiency (shown in a turbine map), turbine housing size in conjunction of that exhaust wheel based upon that map, volumetric efficiency of the engine application you're using it on, as well as static compression that the engine has to reach a specific dynamic compression. ALL that can't be found on a standard compressor map.

3 + 4 = 7.... But 3 + ? = ** doesn't mean that ** is lying. It just means you need the ? to figure it out.

Muckman

iTrader: (2)

Compressor maps dont lie. Problem is they only tell you half the story. Turbine side plays an equally important role. I think the GT28 turbine is too small for 3.1L (x2).

TheShodan

iTrader: (14)

I think that for 750whp on good compression LSX, GT2860RS and GT2871Rs actually do quite well. we do those for a lot of Older 2001 Camaros and Corvettes.

Muckman

iTrader: (2)

Ill admit I dont have any large discplacement experience. A GT28 series is considered "small" for Honda boys with 1.6 and 1.8L engines. I couldnt imagine it on something twice that size. Seems like you'd need alot more turbine for all that exhaust energy.

TheShodan

iTrader: (14)

not as much as you'd think on two banks of cylinders with such large stroke. On paper, it seems crazy. But when most Camaro guys use T76 (not a typo) at only 9psi (13% efficiency for about 58-60lbs/min) to make 650whp and higher, it actually makes sense to use 2 smaller units. They are actually really responsive to great power.

rich7777

It's all about experience, I believe in when it come to stuff like this. You're always best off speaking to someone that does know, than trying to work things out for yourself if you're not sure (unless you're made of money lol).

OneBadTurboCRV

Without even remotely thinking about it, basic math is simple to figure out.

B-Series + GT2860RS = 350whp

350whp x 2 = 700whp

Obviously this is just like saying, "Hey your car is puke green, why is it faster than my red car?", but why would it be so far fetched GT28 turbo might work in a twin setting?

People need to realize the engine differences and characteristics. If you read some of the compressor maps and solely live by them, people would never be putting anything bigger than a GT35R on a Honda. Twin charging a V8 doesn't even compare to a Honda. Honda's have the best (well, at least used to haha) flowing heads from the factory in relation to engine size. This coupled with their excellent efficiency, these little turds can do some amazing things.

Properly sized turbo's on a V8 is exactly like installing a supercharger aside from having to build boost off the line to get any type of decent launch. There is a reason between 3 cars I have 5 GT2860RS turbos installed.

OP - For your goals a GT28 turbo or GTX28 will be perfectly fine. If you want a shift in power band and more power down the road a GT/X30 twin setup would be more ideal. I personally only use Garrett turbos, but to each his own. For a street car, a single large turbo is practically uncontrollable on a V8. When I say uncontrollable, I mean useless...

9bells

Thanks guys for all the posts. Yes, the disco is a great piece, and is likely a very good choice on the small side. It would spool up silly fast though.
I am for sure going to go with a 28 series. I wish I knew more about precision, as the cea wheels seem to work great.
You guys think the gtx wheels are worth the bucks in a modest boost application like mine?

9bells

Thinking about it that way will do that. Thinking about it like my rsx makes 2/3's the power of my camaro on the same dyno, with 1/3 the displacement, starts to give you an idea of flow.
This is where I think most are getting caught up,and why my choices seem so small.
Where do you find turbine maps to start completing the picture? The A/R is something that will make a difference too, but I have found some of those charts.

TheShodan

iTrader: (14)

I'm like N3V3A on this one. I use OEM manufacturing companies (Garrett, Borg-Warner, IHI, etc) for reliability, repeatability, and repair-ability. Until Precision gets their act together with their material usage program I wouldn't use a Precision yet, especially their air-cooled ceramic bearing system. (what am I in, a Carmengia? 70's Beetle?.. Nothing cools like water )

A couple of 41-48lbs/min twin babies would just great for it.. Hell, you don't even need the GTX series to do it.

9bells

Yes, the gtx2867 looks amazing all plotted out, but the 2871r is amazing too.
The increased adiabatic efficiency of the gtx wheels is likely going to sway me that way.
the disco looks good, but looks to make a fair bit of heat up top. On this motor, I think that's worth avoiding.
I think I can even get away with using the smaller A/R on the gtx2867, but still looking into that.

TheShodan

iTrader: (14)

The GTX2867R use the same turbine wheel in the same volute and turbine packages as the GT2860RS and GT2871R (53.90mm wheel diameter in either .86A/R or .64A/R). Again, you're only looking at one side of the coin.

9bells

I saw that, and that is what made me go that way. If the turbines in the 2860's are great for spool, and work on the combos I saw, but the compressor runs out of efficiency before it's all over rpm-wise, why not upgrade the compressor and make less heat for the same turbine?

TheShodan

iTrader: (14)

Because your calculations don't account for use of an intercooler, which lowers that IAT more efficiently. Again, I've used the disco potato on several G8s, vettes, and twin turbo mustangs. You won't gain any "heat" from it not being in an optimal efficiency island of the compressor map; it's your choice but for that application, its not worth the extra $600-$700 for the GTX units over the GT-R series.. That's up to your wallet.

9bells

Fair enough. Not going to debate you on it. If you have done it and it works good, then I'm going to give it a go. Thanks for the help.
I'm sure the 600ft/lbs will make me smile for quite some time.
Few other questions....
A/R? Is the bigger .8x going to kill it, or on a big motor with lots of exhaust will it still spool great? I'll go with TiAl stainless housings for packaging/weight.
38mm mvs or 44mm mvr gates?

riceball777

Don't a lot of the r35 gtr's in the 700+awhp range run twin gt28 turbos?

TheShodan

iTrader: (14)

38mm gates are fine. The higher the boost pressure, the less excess pressure need to bleed off e.g. use smaller gates.

.86A/R is going to be just fine for those banks (those are comparable to a .63A/R in a T3 package).

TiAL housings... good call on that one.

9bells

Thanks again.
Best place to buy all of this stuff?

TheShodan

iTrader: (14)

You're in Canada. Where in Canada?

9bells

Calgary, AB. Out west.

Yeah, saw some R35's are running the discos.

LightningTeg

I've got a buddy with a 5.3 junkyard motor on a Precision 6765? and that is very responsive.

9bells

I'd love to see an rpm-based dyno graph. If you've done a bunch with good results, hopefully you have a dyno or two to throw out there.