An additional 911SC conversion

[Hill3312]

Hello!

I will be adding to the many 911SC 3.0 turbo builds here on pelican over the next few weeks. I have been wanting to turbocharge a NA car for quite awhile, and I have decided that now is the time.

I plan to order nearly everything at once to reduce the time spent waiting around for parts to arrive. My Bitz Megasquirt kit should arrive in just a few days so my first update will be during install.

- I need some information cleared up before I begin ordering parts. WTH is the compression ratio on a US spec 1980 3.0SC. I have read many different figures from many different sources. Is the below information correct?

1978-1979 911 SC (european)
2994 cc
180 bhp @ 5500 rpm
265 NM @ 4200 rpm
compression: 8,5:1

1978-1979 911 SC (US)
2994 cc
180 bhp @ 5500 rpm
237 NM @ 4200 rpm
compression: 8,5:1


1980 911 SC (european)
2994 cc
180 bhp @ 5500 rpm
265 NM @ 4200 rpm
compression: 8,6:1

1980-1983 911 SC (US)
2994 cc
180 bhp @ 5500 rpm
244 NM @ 4200 rpm
compression: 8,5:1


1981-1983 911 SC (european)
2994 cc
204 bhp @ 5900 rpm
267 NM @ 4300 rpm
compression: 9,8:1

-- If this is the case, I can assume a CR of 8.5 which means that my intercooler won't need to be completely obnoxious and I can roll with a .5bar spring. If I could safely make 300bhp my thirst for forced induction will be satisfied.

[flat6pilot]

If you go with a TIAL wastegate, they are correct in saying that aftermarket headers will produce greater results (pressures) from their springs.

i.e. their .5 bar spring (7.25psi) will actually produce or peak around 9-10psi, or about .7 bar.

I'd suggest starting at a .3 bar spring, tune and go from there.

What injector size are you starting with?

You'll have your hands full for a bit until you get the MS tuned and smoothed out. While very good, the MAP Tony includes will be for an N/A engine.

[Hill3312]

Got some bad news from the shop today. Mechanic discovered two broken headstuds....

-- I was wondering if I have an opportunity to make the best out of a crappy situation. If I am going to spend a ton of money getting the studs replaced, do I have any options as far as lower compression pistons and other internal parts go?

What can I do while the motor is being taken apart to make my 3.0 more accepting of Boost?

* Kyle, I will be going with 44lb injectors.

[jpnovak]

What is the engine type stamped on the case? This will confirm what would be stock compression.

If you are tearing down then just replace the pistons with the early 8.5:1. Just make sure to match the diameter and height groups. Best to install matched set if you can find them.

Otherwise, you can get JE's assuming you have Nikasil cylinders. If you have Alusil they should be plated or replaced to run the JEs.

I would also replace the cams.

[Hill3312]

Fell right out when the first valve cover was pulled off.

So I guess this build is going to begin with a motor tear down. Are there any piston/cylinder kits that will bring CR below 8? Money is not really an issue here, I want to do things right.

[Tippy]

I'd stick with 8.5:1 and just get a really good intercooler.

[Rawknees'Turbo]

If you look in the Engine Rebuilding forum for Henry of Supertech, he probably has piston/cylinder kits in stock for just about any compression ratio you want. He also makes head studs that are considered most excellent (though I don't have any personal experience with them - have Raceware studs in my engine - bought and installed back in 2006 or so, before I had even heard of the Pelican forums - no problems with them).

I would not use 8.5:1 as I prefer the power characteristics of low static compression with higher boost (more room for tuning error that way, too), so it really comes down to what you want with your engine.

JE also will make pistons in about any size & compression ration that you want.

[Rawknees'Turbo]

Oh ya', forgot to mention that JustTheTIPpy, that posted directly above me, has a lot of experience with Megasquirt EFI tuning, so I am volunteering his South TexAss tuning assistance if you are in need at some point!!!

[Hill3312]

These car certainly favor those with access to cash... check out this suspension bill!

[boosted79]

Yeah, they're similar to a BOAT, Break Out Another Thou

[Hill3312]

I'm still working on locating low compression Pistons. I've found a set of 95mm, 3.0 turbo Pistons with a 7.0CR.

I know you can't use the Pistons out of a 3.2 turbo, but would the 3.0 turbo Pistons work?

[Tippy]

Originally Posted by Rawknees'Turbo

Oh ya', forgot to mention that JustTheTIPpy, that posted directly above me, has a lot of experience with Megasquirt EFI tuning, so I am volunteering his South TexAss tuning assistance if you are in need at some point!!!

Giving me too much credit

[Tippy]

Originally Posted by Tippy

I'd stick with 8.5:1 and just get a really good intercooler.

If you plan on never exceeding say, 0.7 or 0.8 bar, and never seriously tracking the car, I'd stick with 8.5:1 CR.

Off boost would be so much better.

If plan on greater than 1 bar and heavy track use, <8:1 CR would be safer.

Off boost torque will suffer.

Others can disagree, but that's my thoughts.

[patkeefe]

JE will make you any pistons you want for $1k.

[Hill3312]

Getting customs Pistons ordered through LN Engineering.

I'm using 95mm Mahl 930 cylinders. I'm thinking of going 8.0CR for the Pistons.

[scottrx7tt]

My SC engine is at 9.5:1 and it is handling the boost quite well. 8:1 is probably a great choice though. If I ever rebuild my engine, I will go 8:1 and run gobs of boost

[Hill3312]

I've heard a lot of bad things about JE Pistons in Mahl cylinders.

Should I be concerned?

[Hill3312]

Regardless of the lack of posting. A fair amount of progress has been made.

- Engine was dropped
- Stripped down to short block
- Head studs removed
- Heads sent off to be re-surfaced and ported
- Pistons being ordered from JE

..... You can watch all the progress on Youtube if you'd like starting here: https://www.youtube.com/watch?v=CIMnVMoJwYc

[Hill3312]

It's been a long time! I nearly forgot about this thread but I'm going to need some feedback and help soon so its a good time to drop an update!

Here's what happened:

--------------
Complete rebuild... extremely thorough.

New head studs
New timing chains
930 oil pump
964 gt3 main bearing shells
996 gt3 connecting rod bearing shells
Intermediate shaft bearings
Rod bushings
ARP rod bolts
Rebuilt and ported heads
JE pistons with custom compression at 8:1
Lightly honed stock cylinders (had the hone-able Mahl ones)
-------------

At this point the long block is complete and I'm beginning to set up the EFI/ Turbo bits. Going to be installing Bitz Megasquirt kit tomorrow.

We put a tractor turbo on it. It's a Holset hx35 from a farm tractor. Seems to fit great. I'll be posting soon with some questions but it's not long now.

[Tippy]

The HX35 is a great, solid turbo. They're made for higher boost, so it probably won't wake up until a bar or more of boost.

Great to hear you built a solid foundation. Enjoy the new found power.