Help me with my build sheet?

[JMA-RUF]

OK guys, I was going to do a simple bolt-on turbo conversion on my 3.2 Carrera, but am now thinking I might go down the rebuild path so I can run more boost.

Car will be mainly street, but also monthly track events.

After a LOT of reading and thinking, this is what I'm considering, so please feel free to throw in your advice/experiences as it would be much appreciated:

MOTOR :-

- ARP head/rod fasteners
- bore out my 95mm jugs to 98mm & replate in Nikasil
- slip in forged JE's with 7.5:1 C/R
- Nerosist cylinders and heads for aluminium sealing ring to handle big boost
- twin plug & port/polish the heads
- bigger piston squirters
- 930 turbo oil pump
- 993 crank to stroke it to 3.5L
- extrude hone Carrera intake for even flow across runners
- GT2 CAMs
- racing valve springs
- titanium retainers
- new turbo spec valve guides
- full bay 28" x 12" x 4" tube&fin intercooler

Exhaust/Turbo:

- modified OBX 321 s/steel headers with a Burns T4 collector & larger wastegate pipe for 60mm TiAL w/gate
- custom Borla XR1 muffler (v-band, single 4" in/outlet)
- Garrett GT40R ball-bearing turbo (maybe 0.95 or 1.06 A/R?). I'm thinking a stroked 3.5L with GT2 CAMs shouldn't be too lazy for this size turbo?

EFI/EMS:

- undecided as yet. Maybe Protomotive MAP ECU for ease, or an Autronic aftermarket system.

Clutch:

- I've heard good things about the KEP G50 HD kit.

Advice/opinions please?

[dewolf]

http://cgi.ebay.com.au/Porsche-911-Carrera-84-89-Turbo-Kit_W0QQitemZ250087826200QQihZ015QQcategoryZ102344 QQrdZ1QQcmdZViewItem

[JMA-RUF]

WHOA! Looks great... but I want to run over 1.3bar with my new build and the GT30R is not sufficient for the power levels I want to run. That is an impressive kit tho!

[NathanUK]

Mahle's are the best P&C's according to these boards.

Maybe consider going twin turbo for less lag as you are reducing the C/R alot.

[JMA-RUF]

Yeh, I considered twins, but the cost to have a custom set of 1 5/8" TT headers is too prohibitive. I prefer to stay with a big single and combat the lag factor with nice CAMs and fully programmed map sensing EFI and a ball-bearing turbo etc...

I decided on 7.5:1 because I want to run 1.3-1.4bar. A higher base C/R will limit my max boost somewhat. The stroked 3.5L should provide nice torque down low, so I'm told

Although, a pair of GT3071R BB units would be awesome

[oms930]

Nice build list! Since I am doing an exercise similar to yours I have a couple of thoughts:

Have you compared the 3.6 993 crank with a 3.6RS crank?
I was adviced that the 3.6RS crank would be the easiest to balance.
Although I have seen a 993 crank I no longer remember if the throws/counterbalances are as narrow as the 3.6RS crank, which are much narrower than the stock 930 crank's counterbalances. One also realizes a weight reduction of approx. 6-7 lb over the 930 crank. Not sure about the 993 crank.

For the low end torque the 76.4 stroke will be helpful I'm told, but I was also advised that a modded GT35R turbo with a small hotside A/R (~0.65-0.68) with a clipped Q-Trim wheel will be helpful in getting both low- and high end power.

Then just a question: I've noticed that everyone gets the titanium retainers. Are they really necessary? I know the racing springs are, but would the steel retainers be just as good, although slightly heavier?

[TimT]

Yeh, I considered twins, but the cost to have a custom set of 1 5/8" TT headers is too prohibitive

We took an existing set of B&Bs and modified them for twin turbo use. So they are not pure "one off" custom headers, and dont carry that price hit.

We cut them after the collectors, added a bit of pipe and the flanges for the turbos. The passenger side turbo needs to be re-clocked and some clearancing done on the motor mounts.

Look here for some pics of the install.

Id up the C/R to 8.5 with EFI you have much better control over your AFR so you can take advantage of higher boost levels, other than that your build sheet looks fine.

[JMA-RUF]

Olli, thanks for the tips. I'll research the RS3.6 crank. I'm just not sure how readily available those are. 993 cranks come up from time to time on EBay, so those are easier to source

As for the titanium retainers, everyone uses those and I guess if the car was going to see lots of track time, you might as well have that extra insurance. For a daily street motor, it's not worth it I'd say.

TimT, that is an awesome setup you have there! The problem I have with rear mounted turbos is placement of mufflers. We have very strict EPA laws down here and I need a properly muffled system. If the turbo's were mounted to the side of the motor (near #1 and #4 cylinders), I could use one of those oval Magaflow dual in/out muffler cans for ease.

I wonder if there are any NA headers with the collectors just before #1 and #4 cyl's?