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Can someone answer my retarded turbo exhaust question?

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Can someone answer my retarded turbo exhaust question?

 
Old 01-21-2019, 11:24 PM
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Default Can someone answer my retarded turbo exhaust question?

I'm looking to turbo my Miata for under $20 and I also have a used condom to trade for the turbo if anyone is interested.

Ok but seriously, I've returbo'd my MSM and I'm in the process of building a 2003 VVT engine because any noob from the forums could tell you that a stock Miata block running at 267 horsepower is probably not long for this world.

It is pretty fun having that insane boost curve for straight road pulls and stuff, but I'm not spending a couple thousand on this VVT motor just to run this jank old T04E turbo. The spool characteristics are pretty abysmal and even if they improve with the new engine all bored out, it's still not going to be as good as a decent turbo.

That brings me to my question. The simple version is: "What turbo do I use that has a T3 flange?" The manifold I made uses a T3 flange and I don't want to **** with it. However, if a T25 or a Vband inlet gets me more power or a better turbine housing A/R, I wouldn't hesitate to change it.

The long version is: Does the Garrett GT2860RS with a T3 flange and a .82 Exhaust A/R have enough meat to make strong power up top? If not, Then the GT2871R has the same sized turbine, but looks more efficient at higher boost so it looks like a better option. On the other hand, the 3071 has the same sized compressor as the 2871 but with a bigger turbine, so if that is a better option, what exhaust A/R would be suited for a T3 inlet on a 1.9 Miata motor?

However, the 3071 is starting to get pretty large for a miata to spool quickly, so that means I need to look for something more efficient instead of more bigger. That basically means the Garrett GTX2860R, GTX2867R or the Borg Warner EFR 6258.

I just don't know how to choose a turbine housing for those GTX turbos, the GT3071 or even the EFR.

Is there a rule of thumb to look at the exhaust flow charts and tell that if a turbo flows 20 pounds a minute it'll make a certain amount of power or something?

Turbo Setup as it is now. Wastegate dumps into drivers side wheel well. Makes a nice noise at full whomp.

Terrible Torque curve there. It makes 6 psi at 4,000 RPM and doesn't hit peak boost (16.8 psi) until 5,600 RPM.

This timing map should explain how my rods are still intact. It is quite conservative for 93 octane and with intake temps only reaching around 14 degrees Celsius on that virtual dyno pull, I'm staying well away from knock. Or MBT for that matter.
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Old 01-22-2019, 06:05 AM
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Check the spool thread where everyone posts their real result data and pick a good one.

I have a gtx2867r with a t25 .86 and posted my data in that thread. Not a super quick spooling turbo but makes more power than your transmission can handle.
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Old 01-22-2019, 08:09 AM
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Also checkout the dynos thread to see actual torque curves.

efr 6258 is the holy grail of miata turbos. But you'll need to redo your whole hotside setup.
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Old 01-22-2019, 06:58 PM
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IMO you should look into the Precison 5128 , you can get it with a T3 48ar 5 bolts IWG

It's basicly a gt2871r with a billet compressor wheel .... in other words a cheaper GTX2871r . Spool should be pretty similar too from what I've seen.

Don't get me wrong the GTX2871 is a great turbo but it's pretty pricy for some medival technology
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Old 01-22-2019, 11:49 PM
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Ok I hope everyone doesn't kill me, but I'm just going with the GT3071 China Town edition. It has a T3 .63 A/R inlet and a 3" nicely tapered V-band turbine housing. $229 shipped.

I'll probably put it on the current engine to test it before sticking it on my nice expensive VVT build.

For those wondering, the compressor inducer is 2.5mm larger than my current turbo (China T04E .63AR), but the exducer is 5mm smaller. The turbine inducer is 5.5mm smaller with an exducer that is about the same size as the old turbo. The smaller OD of both wheels should help with spool since they have less inertia.

I've got plenty of datalogs with the T04E, and I'll keep everything on the engine and just swap out the turbo to do a datalog. The only thing is the downpipe will have to be remade with 3" piping to fit the turbo so that will skew the science a little bit.
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Old 01-23-2019, 12:07 AM
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so you're going from one shitty turbo to another shitty(er) knock off - off a too large turbo.

i guess you enjoy driving at 5k+ rpm to get any sort of real power.
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Old 01-23-2019, 12:22 AM
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Haha well basically. I just can't bring myself to spend $1400 onna turbo that'll pretty much make the same power.

I do disagree with the size though. I've been driving around with a turbo that I would never in a million years use on a Miata based on info I've seen on here for over a month now and I've got to say, it really isn't as bad as people make it out to be. I used to be under the impression that a GT2860R was big for a Miata, but after driving the MSM with a 38mm turbo, driving my last Miata with a 44mm T25 turbo and then this thing, I honestly have to say I like the big turbo.

It drives like a decently powered naturally aspirated Miata until about 4,000 rpm, so you can accelerate normally in the city and shift nice and smooth but not have to short shift to avoid the boost.

When you want to smoke some kid in an SN95 mustang though, just drop a gear, brake boost a little, then ****** blast off. No let down as the torque falls off, because it doesn't. And when you use Megasquirts flat foot shifting, it maintains 6 psi of boost during shifts. Once it gets in boost, the only issue I've found is trying to maintain traction.

I just can't go back to a camel hump torque curve.

HOWEVER, if I lived anywhere that had curvy roads, I'd hate the big turbo. But unfortunately, Florida doesn't have those.
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Old 01-23-2019, 10:43 AM
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Peak HP wins dyno days.

Drivability and a usable power curve wins everything else.

Area under the curve for the win.
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Old 01-23-2019, 10:53 AM
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Good thing you asked us!
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Old 01-23-2019, 11:26 AM
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Avoiding boost is called throttle control. I can accelerate all the way to redline and not hit any boost.
No short shifting required.

It's your car, do as you wish. But most try to get as much low - mid range torque as possible, as that is what makes normal street driving fun.

My car becomes a rocket at 3k rpm. Yours at 5k. We might hit the same 300hp peak power, but mine much more enjoyable to drive.

You can get a real ball bearing Garrett 2871 from the 240sx Silvia guys for 600-800. And this will spool decently and much better than a China 3071.
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Old 01-23-2019, 11:45 AM
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He doesn't want any advice
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Old 01-23-2019, 09:47 PM
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Originally Posted by sixshooter View Post
He doesn't want any advice
No I do, I just don't know what a Miata with a 2871R feels like so I find it hard to spend l$1400 on a turbo I might be unhappy with.

What if I put it on there and it runs out of steam?

I can build my MSM head with cams and valves once that engine comes out, so 7500-8000 rpm Isn't out of the question and I hate the feeling of acceleration dropping off like a cliff up top.

Wouldn't a Garrett 3071R be perfect flowing for stuff like that?
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Old 01-24-2019, 02:15 AM
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It's really hard to be unhappy with 230lb/ft at 3,500rpm. That's what my 6258 with 0.64 A/R makes on 3" exhaust.

As far as high ripm flow goes, get a square top manifold if you haven't acquired it already. In combination with a good turbo it'll make wider powerband and better response than a knockoff turbo with built head.
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Old 01-24-2019, 06:53 AM
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I sympathize with your concerns related to your lack of experience with different size turbos. This is the very reason that compressor maps exist. They chart quantifiable, comparable data so you don't have to guess. The EFRs being touted and any of the Garretts larger than the 2560 will make more power than the Miata transmission can handle. Any falling off will be related to the breathing problems of the stock heads, cams, and intake tract, which are optimized for midrange torque.

I have a gtx2867r and know that the EFR makes more power everywhere. I ended up with it way back when the initial EFRs were having problems many years ago. The EFRs will make power all the way to redline and beyond so don't worry about that.
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Old 01-24-2019, 01:23 PM
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Unpopular opinion: No need to negcat the guy, unlike some of the n00bs on here it sounds like he has a decent understanding of what he's doing and is listening to the information ya'll are giving him, just that he doesn't use HIS car in the way that ya'll do.

EFR torque curves are amazing but not necessarily what everyone wants or needs (or can afford). If he isn't satisfied with his (admittedly large) turbo , he's only out $200 bux instead of $2000.

Just sayin'.
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Old 01-24-2019, 02:12 PM
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Originally Posted by cpierr03 View Post
Unpopular opinion: No need to negcat the guy, unlike some of the n00bs on here it sounds like he has a decent understanding of what he's doing and is listening to the information ya'll are giving him, just that he doesn't use HIS car in the way that ya'll do.

EFR torque curves are amazing but not necessarily what everyone wants or needs (or can afford). If he isn't satisfied with his (admittedly large) turbo , he's only out $200 bux instead of $2000.

Just sayin'.
That's basically where I'm at. If the knockoff turbo doesn't do what I want, I'll be satisfied knowing I tried and just spend the big money on the Borg. If it is exactly what I want, I'll just keep it and buy the genuine Garrett when I forget how much money I'm spending on this engine build.

At the end of the day, this isn't a race car, it's just the thing I use to commute to work and back.
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Old 01-24-2019, 04:15 PM
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Again, there are 6 and 7 hundred dollar non-chinese turbos on the market if you just want a quality turbo that is not Leading Edge
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