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911 sc series twin-charging

Hey guys! After lurking for some time now, I decided to join this community to ask the question that has been eating away at me for a couple of months now. I hope that you can help.

The 911 sc is my dream car. It provides speed and nostalgia, but is still fairly decent price-wise. After wanting this car for a while, I started thinking about all of the upgrades that I would love to do to this car if I had all the money that I could ever need. I came across the idea of series twin-chargers. That is, running the compressed air of a supercharger into a turbocharger. This eliminates spool time, and yields great increases in pressure.

All practicality aside, my questions are:
Is it possible to twin charge a 911 sc (any year, the year doesn't matter too much to me as long as it works) without the engine exploding. The major challenges would be the immense pressure in the engine, and the high temps caused by the pressure increase.

If so, what upgrades would be needed to do this? (E.g. Intercooler, upgraded pistons, etc.)

What kind of psi gain could I expect?

What kind of horsepower gain could I expect?

Now the practical questions:
What would the immediate cost be?

Possible long term costs?

And finally, how long would the engine really last under these circumstances?


The supercharger that I was thinking about using: Whipple W140-AX Supercharger (2.3 liter) Direct-drive WSC-140AXB-DD (BLACK)

The turbocharger that I was thinking about using: https://www.moranmotorsports.com/product/garrett-gt3776-55mm-journal-bearing-turbocharger

Sorry about the wall of text, I just had to know.
Old 12-18-2013, 03:36 PM
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i'll leave specs on what kind of engine rebuild you'll need to posters who have done it, but i'd personally spend a good while sorting out space constraints/ducting and pipework perhaps - sounds like it could get crowded in a hurry?
Old 12-18-2013, 04:19 PM
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Oops, I guess that I didn't really realize that space would be such a large constraint, but it would definitely fill up fast in there. Assuming that I could overcome that, is it still possible?
Old 12-18-2013, 04:34 PM
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I'm starting to think that the GT4294 would be a better turbo. It has 74% efficiency instead of 68% and it still uses the journal bearing, which is the most durable kind. If I'm not mistaken, higher efficiency means the air being put into the engine is cooler, meaning that I could use a slightly smaller intercooler. Any thoughts on this?
Old 12-18-2013, 06:18 PM
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Sounds like a $40k engine to me.
Old 12-18-2013, 06:52 PM
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That's not worth the effort IMO. And a GT4294 is a huge turbo!

Read up on Garrett's websites regarding efficiency in their beginner, intermediate, and expert turbo tutorials. The one you spoke would not be efficient on a 3.0 since it's so big.
Old 12-18-2013, 07:48 PM
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Okay, so it's probably pretty obvious that I don't know a ton about turbos. Can you guys give me any recommendations? Ideally I would have one small and highly efficient supercharger running into one small and highly efficient turbocharger, total psi gain being somewhere between 10 and 20ish. The PSI's are multiplied when running in sequence (but must first be converted into pressure ratios if I remember correctly), as are the efficiencies, e.g. 50% x 50% = 25%. For more info check out this wiki article.

Twincharger - Wikipedia, the free encyclopedia

Thanks again guys.
Old 12-18-2013, 08:03 PM
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Quote:
Originally Posted by DanielF View Post
Oops, I guess that I didn't really realize that space would be such a large constraint, but it would definitely fill up fast in there. Assuming that I could overcome that, is it still possible?
i will say pretty much anything is possible if you throw enough money at it..
not to be a nay-sayer but it's going to be a pretty big and complex project!
Old 12-18-2013, 08:43 PM
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The SC has quite a few inherent limitations stock to increasing horsepower and torque with forced induction beginning with a relatively high compression ratio and air cooled heads which dramatically affect detonation sensitivity. You also don't have fine control over air fuel ratios and ignition timing with the stock induction/ignition systems. Then there is the inherent weakness of the stock 915 transmission in high torque applications which has been graphically demonstrated more than a few times on this board.
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Old 12-19-2013, 05:07 AM
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Kinda like this....I guess you could but why?

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Old 12-19-2013, 03:02 PM
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Old 12-19-2013, 03:27 PM
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+1 on k.i.s.s.
Have you driven a 911 with a properly built and tuned Turbo engine?
How about one with EFI?
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Old 12-19-2013, 05:15 PM
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rod, that car aint for a short guy but i would love to hear it driven in anger!!!!
Old 12-19-2013, 06:07 PM
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no need for wheeliebars on the Hotwheelsmobile

visibility = overrated!

would only need to see as far as the nearest gas station at least
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Old 12-20-2013, 04:39 AM
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And by the looks of the drive belts the blower housings are empty.
Maybe he adapted forward collision alert.
Old 12-20-2013, 08:43 AM
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No its fully functional. Both engines and all 4 blowers work. It was featured here.

1927 Ford Model T Dual Engined Quad Supercharged T Bucket - R&T DRIVE Videos - Road & Track
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Old 12-24-2013, 08:45 AM
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