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Twin Scroll on a Miata, anyone else do it?

 
Old 09-02-2009, 01:23 PM
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Originally Posted by ctdrftna View Post
im kinda pissed i didnt look into twin scrolls, when i bought my turbo(3071r), they just wernt as popular with the tunner scene 2 years ago, now twin scroll housings are everywhere. i woulda had my manifold built for twin scroll and had a sick setup
Look into quad scrolls and be ahead of everyone now.
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Old 09-02-2009, 01:56 PM
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Twin scrolls do it sooner. Spool that is. And you should look into the new hot thing -quick spool valves for twin scrolls- if you've got money and really hate to wait for spool.


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Old 09-02-2009, 02:05 PM
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Originally Posted by sixshooter View Post
Twin scrolls do it sooner. Spool that is. And you should look into the new hot thing -quick spool valves for twin scrolls- if you've got money and really hate to wait for spool.

Hmm that actually makes a lot of fun sense. Closing off one "scroll" effectively makes the turbine much smaller, greatly helping spool. You'd need a non-twin-scroll manifold however, but that's easy & more common anyway.

What's the smallest twin scroll turbo?
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Old 09-02-2009, 05:06 PM
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Originally Posted by Midtenn View Post
There was a huge post over on MR2OC a few months ago about the benefits of twin scroll on a 4 cylinder. The general consensus was that there is very little to be gained because the exhaust pulses are just to far apart.
Subaru, Mitsubishi, and Porsche must not read MR2OC.
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Old 09-02-2009, 05:37 PM
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why do people think a small single turbo would have much lag. If you're worried about spool and lag just run a gt2554. Its not like its a vette and you cruise at like 1500-2000rpms. most likely you will already be in your "good spool" range while just driving around
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Old 09-02-2009, 07:11 PM
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Originally Posted by Sam Amporful View Post
why do people think a small single turbo would have much lag. If you're worried about spool and lag just run a gt2554. Its not like its a vette and you cruise at like 1500-2000rpms. most likely you will already be in your "good spool" range while just driving around

+ 1 .....60mph in 5th gear is more or less 3k rpm in most miatas
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Old 09-02-2009, 07:23 PM
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I farted while driving once and my gt2554r spooled. It's true.
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Old 09-02-2009, 07:30 PM
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Originally Posted by TurboTim View Post
Hmm that actually makes a lot of fun sense. Closing off one "scroll" effectively makes the turbine much smaller, greatly helping spool. You'd need a non-twin-scroll manifold however, but that's easy & more common anyway.

What's the smallest twin scroll turbo?
T3 housings come in twin scroll and they make those valves in T3, T4, and T6 if I read right. And that's not the only company now making them.
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Old 09-03-2009, 12:20 AM
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Originally Posted by Jike Spingleton View Post
Subaru, Mitsubishi, and Porsche must not read MR2OC.
There are other factors involved, but there was some testing done with the GT30 single scroll (SS) (.63 A/R) and GT30 twin scroll (TS) (.78 A/R) on MR2s and there was neglagiable spool gains (if any) from the TS. With the MR2 already being a TS turbo from the factory, many people assumed a twin scroll would react better. The TS did make better high end power, but that was general accepted as being due to the larger A/R. Most of the post discussed how to properly utilize a TS turbo in terms of the wastegate(s).

I am not saying there isn't gains to TS turbos, but there is a lot more to it than just slapping one on and expecting a monster spool gain.

I found the post w/ dyno plots:

Originally Posted by ATS Scott
Bruce, I now have an answer for you. But first a quick summary of set-upů
Oh and for those folks that have not read the whole thread:
SS=Single scroll
TS=Twin scroll

Both set-ups are re-routed, with 3" DP's. The SS was a .63 A/R exhaust housing, and a SS ATS adapter, and the TS was the .78 A/R with Divided adapter. Everything else remained the same. I used my EVC5 Boost controller, and used the peak hold feature for consistancy. I was shooting for 17 psi on all runs, as that is what I run on the street with 93 octane. All runs were done on 93 octane. One thing I noticed immediately, was the SS required lower settings on the BC to make 17.3 psi, where the TS needed higher settings to make 17.2 psi. That was the first clue. I got it tuned for just under 12.0:1 A/F and managed a 395 rwhp run. Dangerously Lean made more power (413 rwhp)

Next up was swapping back to my TS set-up and attempting to duplicate the results. This is as close as I could get. TS is run 58, SS is run 19:



I wanted to see if dangerously lean would pick up the power of the TS, it did, but nothing like the SS. TS is run 54, SS is run 16.



From my datalogs, the SS consistantly hit 1.0bar boost at 3900 RPM, and the TS at 4000 RPM, even though the TS was beating the SS to 200 ft/lb by 100 RPM. (3400 vs 3500 RPM) at the 3400 RPM mark the SS was consistently ahead at .6 bar vs the TS at .5 bar. So the SS was building boost faster than the TS, but the TS was still spooling slightly faster. After 4400 RPM the TS just falls behind.

So Bruce, I say TS advantages are a myth on a GT30 turbo. This makes me want to ditch my TS set-up...
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Old 09-03-2009, 12:59 AM
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Unless I'm reading it wrong, the twin scroll maybe spooled a tiny, tiny bit faster down low, but made less up top?

Besides the fact, they have different A/R's, which kind of makes the comparison irrelivant
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Old 09-03-2009, 01:25 AM
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You should rather want a slight, and I mean "slight" because it probably is, worse spool rate than making your turbo choke in higher rpms. Cruising in a miata your rpms arent low, racing your rpms shouldnt be that low. Theres not worth while difference especially if you lose some up top, but I guess its not common and still cool or whatever.
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