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Has Anyone upgraded their Turbo, seeing gains without a boost increase?

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Has Anyone upgraded their Turbo, seeing gains without a boost increase?

 
Old 01-04-2019, 02:16 PM
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Default Has Anyone upgraded their Turbo, seeing gains without a boost increase?

I have searched and found some light discussion on this matter but I am hoping to hear some more thoughts and opinions on the matter.

It's winter and time for upgrades. On the list of potential upgrades is a new turbo. Will upgrading from my current BW S475 T6 1.32 to a S480 Billet (or something similar from forced inductions) yield any positive benefits (reduced backpressure?) if I keep the boost levels the same? I currently like where/how the car spools/drives.

The car sees three-ish track trips a year, otherwise it's a street/fun cruising car. As such, I keep the "street tune" limited to 10lbs of boost (550ish WHP). Naturally, I would like "more" when I visit the track... maybe 17-20lbs of boost if the SBE will stay together for a hero pass. FWIW I run race gas in place of pump gas for track trips (for the added insurance).

Next year's track goals are a 1.2 - 1.3 60ft and hopefully a low(er) 9 sec slip. Best 60ft so far was a 1.52. I plan to tighten up the 60ft before considering adding more boost.
Long(er) term goals are a forged shortblock for more power and faster times...with the hopes of an 8 second slip someday.

The Current setup: 6.0 SBE, LJMS cam, etc., BW S475-T6 1.32, 2.5" hotside, 4" fender exit exhaust, 4L80E, Jakes converter, pump gas + Meth, Goldbox EFI, Drag Radials, 3400lb car (1966 Nova - ladder bar).

The Current "best" time: 9.89 @139mph with a 15lb PSI spike, settling in at 13.7 psi, footbraked leaving at 7lbs of boost around 3k. The Wallace calculator estimates roughly 700WHP from both ET and MPH...which aligns with the dyno tune on 14lbs. 1.6 60ft.

Other winter upgrades include a transbrake, backpressure transducer setup and datalogging, and bracing the 9" rearend.

Last edited by liquidmx; 01-04-2019 at 02:29 PM.
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Old 01-04-2019, 02:58 PM
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Yes despite some here that think going twin turbo instead of a GT55 is pointless... I went to smaller twin turbos from a single, dropped 15psi and went faster.

Want an easy gain, add head flow. Boost goes down but you make more power.
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Old 01-04-2019, 05:40 PM
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Slow Sedan: 15psi drop in backpressure I assume? How much faster?
With 700whp through a 4l80e and 9" I suspect i may be nearing the limits of the S475 on my 6.0...and suspect I may have very high backpressure.
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Old 01-04-2019, 06:10 PM
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Originally Posted by liquidmx View Post
I have searched and found some light discussion on this matter but I am hoping to hear some more thoughts and opinions on the matter.

It's winter and time for upgrades. On the list of potential upgrades is a new turbo. Will upgrading from my current BW S475 T6 1.32 to a S480 Billet (or something similar from forced inductions) yield any positive benefits (reduced backpressure?) if I keep the boost levels the same? I currently like where/how the car spools/drives.

The car sees three-ish track trips a year, otherwise it's a street/fun cruising car. As such, I keep the "street tune" limited to 10lbs of boost (550ish WHP). Naturally, I would like "more" when I visit the track... maybe 17-20lbs of boost if the SBE will stay together for a hero pass. FWIW I run race gas in place of pump gas for track trips (for the added insurance).

Next year's track goals are a 1.2 - 1.3 60ft and hopefully a low(er) 9 sec slip. Best 60ft so far was a 1.52. I plan to tighten up the 60ft before considering adding more boost.
Long(er) term goals are a forged shortblock for more power and faster times...with the hopes of an 8 second slip someday.

The Current setup: 6.0 SBE, LJMS cam, etc., BW S475-T6 1.32, 2.5" hotside, 4" fender exit exhaust, 4L80E, Jakes converter, pump gas + Meth, Goldbox EFI, Drag Radials, 3400lb car (1966 Nova - ladder bar).

The Current "best" time: 9.89 @139mph with a 15lb PSI spike, settling in at 13.7 psi, footbraked leaving at 7lbs of boost around 3k. The Wallace calculator estimates roughly 700WHP from both ET and MPH...which aligns with the dyno tune on 14lbs. 1.6 60ft.

Other winter upgrades include a transbrake, backpressure transducer setup and datalogging, and bracing the 9" rearend.
The big change going from a S475 t6 1.32 A/R to a S480 T6 1.32A/R is really just the compressor wheel. I would guess that back pressure would actually go up slightly, given a bigger (maybe heavier?) compressor wheel to spin; it will likely take more drive pressure to get it moving. They have the same Turbine Housing, Same size Turbine Wheel (I'm assuming both 96mm). The advantage to the billet S480 in this situation is that the compressor can produce so much more flow (more PSI).

I wouldn't look at your setup and assume the drive pressure is really that high. You have a fairly large turbine, large turbine housing, and 4" exhaust out the fender. It's hard to guess a number; but I think a lot of similar setups are roughly a 1:1 ratio of boost pressure and drive pressure.

If you went to a Larger turbine you may gain some efficiency (more power, lower boost). Why the focus on less psi? All things being equal it's pretty easy to just raise the pressure assuming the compressor can supply the flow.
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Old 01-04-2019, 07:34 PM
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I donít measure back pressure but I did just swap my 475 to a billet 480 on the dyno 17lbs of boost and identical tune up the 75 made 845 and the billet 80 made 970 hope that helps
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Old 01-04-2019, 08:19 PM
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I wonít have numbers but I went from a VS cast 78/75 .96AR to a VS Billet 78/75 .96AR and will be hitting the road next spring. Iím not touching the tune and will leave the truboost alone, should be able to get you some injector duty cycle to compare outputs.
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Old 01-05-2019, 06:05 AM
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get that 60' down a tenth or so with your trans break and turn up the boost and let it eat. my nova ran 9.90 with a 1.50 60' at 13 psi boost. turned it up and my last pass was a 9.44 at 19-20 psi leaving harder. with 1.41 60'
our cars are close to the same. mine is 6.0 sbe, less cam than you. powerglide with break and 3.42 gear. 3510 lbs with me in it. ladder bar small tire 275 pro .and that was with my borg 80/83 turbo . I just upgraded to a 80/ 96 t6 and im hoping for a couple tenths.
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Old 01-05-2019, 08:11 AM
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Changing the compressor while using the same turbine/housing can still have a dramatic effect on drive pressure if the previous compressor is being pushed hard

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Old 01-05-2019, 08:16 AM
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Been from a cast 88 to a billet 94 on the same turbine and housing.

As you start taking the small compressor off the map we have to keep driving the turbine harder and harder to get output from the compressor .. but we aren't seeing the compressor output that could be there with a larger compressor

So drive pressure : boost starts running away and away until finally you can't make any more boost no matter how hard you drive the turbine


Swap to the larger compressor and bam .....drive : boost is right back in line
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Old 01-05-2019, 01:25 PM
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Thanks for the feedback guys, it was all very helpful. I am planning on calling Jose and FI as well to get his .02 and go from there...but it sounds like i am headed/thinking in the right direction.

Yenkomike: Yes, the goal is a 1.2 or 1.3 60ft. I am planning on meeting that goal before running the car out the big end.
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Old 01-05-2019, 08:23 PM
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Originally Posted by liquidmx View Post
I currently like where/how the car spools/drives.


So why change anything ? If you're only at 15psi now...or less. You've still plenty to go.
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Old 01-05-2019, 08:27 PM
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Originally Posted by stevieturbo View Post
So why change anything ? If you're only at 15psi now...or less. You've still plenty to go.
seems like the 475 on a 6.0 runs out of turbine at 17ish lb give or take depending on setup according to the other threads I’ve read.... like Stevieturbo says maybe leave it be and max it out... still got some boost to go
Check this out:

https://ls1tech.com/forums/forced-in...ast-475-a.html
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Old 01-05-2019, 08:38 PM
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Originally Posted by 47ford View Post


seems like the 475 on a 6.0 runs out of turbine at 17ish lb give or take depending on setup according to the other threads Iíve read.... like Stevieturbo says maybe leave it be and max it out... still got some boost to go
Check this out:

https://ls1tech.com/forums/forced-in...ast-475-a.html

Compressor ..... Not turbine
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Old 01-06-2019, 06:32 AM
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send yours to f.i get there etr ho billet 76 mm compressor wheel and race cover. it will spool the same but have about 3 to 400 more hp in the compresser than you have now. that wheel flows about the same as a cast 80.mm. your turbine and housing is fine.
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Old 01-06-2019, 08:35 AM
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Originally Posted by rotary1307cc View Post
Compressor ..... Not turbine
yeah what he said lol
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Old 01-07-2019, 12:36 PM
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Originally Posted by liquidmx View Post
Slow Sedan: 15psi drop in backpressure I assume? How much faster?
With 700whp through a 4l80e and 9" I suspect i may be nearing the limits of the S475 on my 6.0...and suspect I may have very high backpressure.
Not backpressure boost, twins went 10+mph faster on 15psi less boost. I've seen close to 1000 through an auto with an S476 so I think you have a bit more room to go with that turbo before needing to upgrade.
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Old 01-07-2019, 03:49 PM
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Not quite the same but I went from a cast wheel Turbonetics TC7868 to a cast wheel Turbonetics T7875 and had to add an additional fuel pump at the same boost level so needless to say it made a bit more power.
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