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Need suggestions for finishing design on 911SC twin turbo conversion

I'm in the design phase for a hot rod build and would like some input. It won't be for a while, but it keeps me occupied. But more importantly I tend to just plow through projects once I start, which means initial planning is important for a project of this scale so that I can have it ready to go and just dive in.

The current setup I had in mind:
-Twin Turbo setup
-Rebuilt '78-'79 SC motor with 100mm Nickies/JE pistons (3.3l engine)
-EFI and twin plug
-Zork tubes with a 2 into 1 on the waste gate to give the 917 exhaust look

Typical driving:
-Mostly for fun on the weekends and ripping through back roads
-A handful of track days

The goal:
-400hp at the engine
-Good mid range (3k to 5.5k) with the ability to rev decently high (I would sacrifice some mid range performance for top end, but not all of it)

Advice needed:
-Cam profile (also for just good mid range, and just top end performance running between ~5k and ~8k)
-Boost level and compression ratio
-Is 8k red line realistic for this short stroke design
-Is short stroke ok, or should I instead go longer stroke and smaller bore

I'll state this now, I'm new to turbo charging. I've tried to read quite a bit, but obviously that is limited when it comes to designing specific setups. Any tips and suggestions are most welcome. If I'm way off base, just say so. That way I can step back and rethink things and come up with a more suitable setup or more appropriate goals.
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Jonathan

'79 Copper 911 SC
'88 911 Carrera
Old 02-20-2017, 05:32 PM
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Quote:
Originally Posted by jons911 View Post
I'm in the design phase for a hot rod build and would like some input. It won't be for a while, but it keeps me occupied. But more importantly I tend to just plow through projects once I start, which means initial planning is important for a project of this scale so that I can have it ready to go and just dive in.

The current setup I had in mind:
-Twin Turbo setup
-Rebuilt '78-'79 SC motor with 100mm Nickies/JE pistons (3.3l engine)
-EFI and twin plug
-Zork tubes with a 2 into 1 on the waste gate to give the 917 exhaust look

Typical driving:
-Mostly for fun on the weekends and ripping through back roads
-A handful of track days

The goal:
-400hp at the engine
-Good mid range (3k to 5.5k) with the ability to rev decently high (I would sacrifice some mid range performance for top end, but not all of it)

Advice needed:
-Cam profile (also for just good mid range, and just top end performance running between ~5k and ~8k)
Original SC camshafts, add scavenge pump drive to 1-3 camshaft

Quote:
Originally Posted by jons911 View Post
-Boost level and compression ratio
Can run between 8.0-9.0:1, boost of 0.8-1.2bar on 93-octane without issue. Tweak the CR vs. boost to get the kind of engine characteristics you are looking for... but you'll really be running less boost in order to keep the power level down to 400hp.
And over 400hp is will be the death of your transmission, sooner than later.

Quote:
Originally Posted by jons911 View Post
-Is 8k red line realistic for this short stroke design
No. Most intake manifolds stop being efficient long before that, camshafts that are still efficient at those revs doesn't work with factory manifolds (only with ITBs), and your pistons need to be very light weight.
ITBs -- good for 7,500rpm or higher
964/993 manifold -- good for high 6k rpm range
Carrera manifold -- good for mid 6k rpm range
930 flat manifold -- good for low 6k rpm range

Also bear in mind that generally RPMs are harder on engines than boost.

Quote:
Originally Posted by jons911 View Post
-Is short stroke ok, or should I instead go longer stroke and smaller bore
Depends how you want it to drive.
Lightweight car using revs like a naturally aspirated engine?
Short stroke engines are very responsive, but aren't usually high in torque. The heavier the cars got over the years, the longer the stroke used.


We've got small ball bearing turbos in stock that will work well on a build like this.
Can fabricate any exhaust and intercooler systems, EFI, etc.
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Old 02-21-2017, 10:02 AM
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Chris,

Thanks a lot for all the info. I love that this forum affords people like me the opportunity to get advice from people who actually work in industry. The lower red line being the only major issue is great news. I plan on doing a different short stroke NA engine, so I'll probably try to tune that one for a higher rev range then. For the short vs long stroke, I was wondering if there was a preferred setup for boost application. If the deciding factor is just torque (short having less, long having more), then that would come down to my driving preference.
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'79 Copper 911 SC
'88 911 Carrera
Old 02-23-2017, 05:07 PM
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Confused -- you'll be building 2 engines, one short-stroke and one with torque?

Maybe the best all-around combination on that engine case: 76.4 x 98mm, a stroker 3.5L.
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Chris Carroll
TurboKraft, Inc.
Tel. 480.969.0911
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Old 02-23-2017, 05:16 PM
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What EFI are you using?
Old 02-24-2017, 05:39 AM
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Chris, I am already planning a 3.2SS on the SC that I currently own. The twin turbo engine is for a hot rod project down the road. I wasn't sure what kind of rev range was ideal for a boosted engine, which is why I was asking about short vs long stroke.

I was looking at the bitz racing EFI for my 3.2SS. I haven't looked at whether or not that kit could work for a boosted engine.
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Jonathan

'79 Copper 911 SC
'88 911 Carrera
Old 02-24-2017, 03:36 PM
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Quote:
Originally Posted by jons911 View Post
I was looking at the bitz racing EFI for my 3.2SS. I haven't looked at whether or not that kit could work for a boosted engine.
No
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Old 02-24-2017, 03:43 PM
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Quote:
Originally Posted by jons911 View Post
...I was looking at the bitz racing EFI for my 3.2SS. I haven't looked at whether or not that kit could work for a boosted engine.
Yes, if you upgrade Tony's kit to an MSII.

Another 911sc Turbo Conversion

I was able to net ~420fwhp (360whp) on my stock 3.0 SC motor. 8.6:1. Carrera intake, Bitz MSII EFI system.

I've dialed it back to about .4 bar and still produce about 300whp.
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* 1980 911SC - 3.0l R.o.W 8.6:1 w/ Garrett 30R turbo conversion (.5 bar), Bitz MS-II EFI, Carerra intake, Zork tube, 2300lbs, 360whp
Old 02-24-2017, 11:01 PM
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Today I took delivery of the above mentioned project car. There was a slight change, and I was fortunate enough to get an '88 Carrera. The car looks pretty good and seems to be in pretty good shape. In a little while, I will probably be asking for some guidance on specific parts now that I know exactly what vehicle I'm going to be using. If you're interested, there will be a thread in the tech section as I start going through it.
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'79 Copper 911 SC
'88 911 Carrera
Old 05-30-2017, 05:46 PM
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I must be driving the wrong cars...I've never driven a 930/turbo with SC cams that I like.

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- 1965 911
- 1969 911S
- 1980 911SC Targa
- 1979 930
Old 05-30-2017, 06:23 PM
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Quote:
Originally Posted by kenikh View Post
I must be driving the wrong cars...I've never driven a 930/turbo with SC cams that I like.

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I agree. I have a set of sc cams in a box. They have about 2k miles on them. Posted them to sell a few times with no interest. Both my cars have 964 cams.
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89 Carrera
89 Turbo; K27, Turbokraft intercooler, 964 cams, Fabspeed exhaust.
87 Turbo; EFI project.
86 Turbo; Ruf wannabe, 3.4 liter twin plug, 964 cams, lots of Ruf parts.
Old 05-30-2017, 11:17 PM
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I spoke to Clewett about their 3.2 twin plug EFI kit. The kit uses the Tec 3R. Can anyone confirm that can run a twin turbo setup? I plan on swapping the P/C's for 97 or 98mm and I was told the carrera grind is good for 400hp at 1 bar (which would be fine for me), but maybe I should consider the 964 grind. Any thoughts/preferences on the cam? Also, are there any suggestions on which turbos to use (I would prefer external gate)? I'm trying not to spend a fortune as this is already a somewhat expensive build. I'm having a real difficult time figuring out how to size a turbo for this project. As always, I greatly appreciate the help. You guys are awesome.
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Jonathan

'79 Copper 911 SC
'88 911 Carrera
Old 06-23-2017, 07:44 PM
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Stupid question on the ECU. I looked up the Tec3R and TecGT and clearly they are up to the task. So the remaining questions are which cam/can the 3.2 be reground to 964 if that is the desired profile and which turbos. Reminder: I'm aiming for 400hp at the crank.
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Jonathan

'79 Copper 911 SC
'88 911 Carrera
Old 06-23-2017, 09:41 PM
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Regrind to 964 is easy. On the new pistons, up your compression to 8:1 and twin plug. If going electromotive, follow Richard's advice to the letter. FWIW, I'm in the process of removing my Tec3r to pursue FrankenCIS.

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Old 06-23-2017, 10:28 PM
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My car is a 3.1 with 9.5:1 compression single turbo. Single Plug heads, running 10lbs of boost on e85. Carrera intake, microsquirt, Ford EDIS with COP. Making a little over 400rwhp. The transmission exploded a few months ago, now using the bearing retainer plate to beef up the transmission a little. It runs awesome, and I think I could run a litttle bit more boost, since I am not really picking up any knock.
Don't waste your time with the bitz kit. If you are using a carrera intake, just use the stock carrera fuel rails, and lines(if they are in good shape). The MS1 is not a good platform to start your turbo setup with.. You would be a lot better off just buying from DIYautotune. MS2 or higher to control spark also.
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1979 911SC widebody conversion. 3.1 engine, 3.2 liter heads, carrera intake, Microsquirt V3 ECU, K27 7200 High flow turbo, Tial F41 wastegate, Ford EDIS. .7 bar. 402hp 360tq

Last edited by scottrx7tt; 06-24-2017 at 06:37 AM..
Old 06-24-2017, 06:33 AM
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Standard K16 turbos are fairly inexpensive and would hit your HP goals. We've coupled these with SC cams for an engine that is extremely responsive in the midrange with great drivability. Cams follow the turbo, if you want torque go SC, if you want power go 964 or 993SS. If using OEM Carrera intake and OEM Motronic there is an upgrade for turbos that is pretty impressive. We also have rear mount twin turbo headers for this application.
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 06-24-2017, 10:48 AM
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