Twin Scroll on a Miata, anyone else do it?
09-02-2009 | 05:37 PM
#25
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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09-02-2009 | 07:11 PM
#26
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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09-03-2009 | 12:20 AM
#29
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:
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-up…
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...
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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09-03-2009 | 01:25 AM
#31
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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