911 Turbo race motor (based on SC)

Cookie Porsche · 08-10-2005, 08:15 AM

I have read and searched before asking!

I am building a Turbo race engine from a 3.0SC (930/09) engine and would like a little input.

The goal is some 400-450bhp, max 7000rpm, small twin setup (less lag), no silencer, big twin intercooler. Car MUST be track-able and I am not after ultimate max bhp.

No worries about space, fit or looks - it's a race car!

1) What pistons (and supplier) do you recommend. First I was going with the 3.0 option, but now somebody recommended 98mm p/c? (must then fit 3.0 crank!). JE, Mahle, Andial?

2) Is the 74.4 crank a must or can I stay with the (like new) 70.4 I have?

3) We were planing on using a 964 PLASTIC intake manifold with adapters - securely fastened. Comments?

4) I am running twin-spark, 102.6 fuel, what is your suggested max compression?

5) Would a factory 964 cam be nice in this setup?

Any more ideas? Please chirp...

Regards
Tom

Oh... any competitor looking in here - BRACE YOURSELF.

air-cool-me · 08-10-2005, 10:00 AM

I can take a stab at two...

#2 corky bells book on turbocharging says that a longer throw crank is better for turbocharging. I cant remember why....

if you stay with the 70.4 you will have a SS 3.2 or with the 74.4 a 3.4. more displacement with a longer throw would be ideal... but 3.2 cranks are alot of $$$$

#5 I dont know if this helps... but Randy Blaylock wrote .
There was a debate about which cam profile to use, the more common ones being SC or 964, and others. SC cam profile gives better overall power than stock 930, with better low end than 964, but less overall. The application really determines the cam, and I used the car for 10% street and 90% track, so moving the power up the curve with 964 cams vs. SC cams made sense for my use.

camgrinder · 08-10-2005, 10:54 PM

Are you using EFI?
At what rpm would you like the turbo to spool up?

Cookie Porsche · 08-10-2005, 11:15 PM

John,

Yep, EFI (Wolf 3D V4 or our local G.T.S.). I was thinking that the 964 plastic intake manifold (42 ID) with 700cc Bosch injectors would be a nice setup. I would fit a larger throttlebody with TPS (for the EFI).

I suggested the 964 cam because I have a few sets in stock (budget consideration!) and would like power btw 4000-7000rpm. Turbo 'coming in' from 3500rpm ??

Nick,

Agree on the crank $, but will I find 98mm Turbo pistons for the 70.4 crank? - ANYONE?

Tom

air-cool-me · 08-11-2005, 01:52 AM

Quote:

98mm Turbo pistons for the 70.4 crank

If by turbo pistons you mean low comp ratio\flat-top.... i think JE pistons can build you a 98mm to any spec's you want..

i called them about 95mm at 8-1 ratio for an SC (turbo)
they said they could help me out...
its worth a call at least!

Porschekid962 · Porschekid962's Garage

Do you already have the 964 plastic intake? You need to buy adapters so they will bolt up to the 2 bolt sc heads versus the 3 bolt 964 and then later 993 heads it was designed for. A metal 3.2 intake will bolt right up and is stronger than the plastic so it can handle boost reliably. I believe it was StrohkerRacing on this board that wrapped his plastic 964 intake with kevlar to beef it up. Also the sc heads have a taller intake versus the 3.2 and later 3.6 heads so clearance in the engine bay may become a problem.

You say race engine so I would suggest the 964 cams. On your crank decision some reputable builders I have spoken with like the 3.0L rods better than the 3.2 simply because they have a larger, stronger rod bolt. You can always modify the 3.0 rods to work with a 3.2 crank but the crank is heavier than the 3.0. JE can make you pistons anyway you like them to fit any bore and rod size. Comes down to money, how you want the motor to perform and then more money.

Happy building!

camgrinder · 08-11-2005, 08:42 PM

The 964 cams will work, but I suspect you will outgrow them quickly.

Cookie Porsche · 08-11-2005, 09:37 PM

Gents,

Thanks for the input.

I like the 964 intake manifold because it apparently is more harmonic and flows a lot more air than the 3.2 manifold. The adaptors are easy (already have a 3.0SC with the same setup).

ANDIAL have a set of P/C 98mm (935 style) that may work - that would give us 3.2. Anyone know this setup?

John Camgrinder: I have considered the 964 cam limitations, but would like to have a broad powerband btw say 3500-6500 (max 7000) - revs cost money! What other options do I have? Africa is lovely but also far from retail US!

Tom

camgrinder · 08-11-2005, 10:56 PM

I think 3500 to 6500 rpms is reasonable with the 964 cams.
What turbos are you using?

I bet shipping to Africa is less than $100 U.S. Postal.

Cookie Porsche · 08-11-2005, 11:40 PM

John,
What's the time in CA now - aren't you meant to be sleeping?

Yep - courier is not too bad, but then customs add 20-40% duty and then the Receiver add 14% VAT. All of this on the goods AND the freight! Adding customs to freight and VAT to duty is great!

I used to ship all goods to a 'central' source in CA and from there send bulk to Darkest Africa. Unfortunately 9/11 and your state tax sort of spoiled that.

The main reason was that I have some four sets of 964 cams in stock.

I'll mail you a little later when I decide on piston/compression choice.

Thanks for all the help.

Tom

dean · 08-12-2005, 05:05 AM

Does it have to be 3.0L for the rules? If not I would get some JE pistons and make it 3.2L with maybe 8.0 to 1 CR. I think that will give you the power that you want.

Here is a data point. I have an early 930 with stock pistons. 6.5 to 1 or so CR. I am running SC cams, shorty headers, a K27-7200 turbo, EFI and a big intercooler. I got 352 RWHP on a DynoDynamic dyno. The motor runs very strong and has a fairly low boost theshold and hardly any lag.

Here is the chart

Dean

dean · 08-12-2005, 05:08 AM

Oh yea,

I would also post turbo questions on other sites.

http://www.c2turbo.com/forums/index.php?

http://www.turbo911.com/

Dean

Cookie Porsche · 08-12-2005, 05:25 AM

Dean,

It can be a 8.0 ltr as long as it remains a 911 flat-6! I'm gunning for class AA unlimited so I need some wooma.

Your power curve is very nice and linear - a bonus to me. What do you mean by 'shorty' headers?

Is your intercooler OE?

Tom

camgrinder · 08-12-2005, 08:27 AM

Quote:

John, What's the time in CA now - aren't you meant to be sleeping?

It was kinda late. I have twins, and are out of the crib and sleeping in beds. First time last night. Its a lot of fun

dean · 08-12-2005, 04:17 PM

Tom,

Shorty headers are not equal length. They are a short as possibe to get the turbo to spool faster.

Here is a pic of my intercooler. It is not OE. I built it.

I think you will have no problem meeting your goals. You could also look into GT2 Evo cams. I know some people running them and they all like the cams.

Oh yea that dyno chart was running just under 1 bar of boost.

Cookie Porsche · 08-12-2005, 11:08 PM

Another Q.

I have a 993RS oil pump in stock. Will it fit into my 930 case?
Is this pump better than my SC pump? Worthwhile?

Dean,
That's not an intercooler - it's a family size braai (barbeque, grill...).

Does anyone sell the short header and twin-turbo setup as a bolt-on kit for a 911 race motor? Would save some time.

Thanks. Tom

Walt Fricke · 08-16-2005, 10:10 AM

Tom

I have a GT3 oil pump fitted to my early 930 case. It required clearancing of the relevant main bearing webs (I used a cutoff wheel and then a die grinder). I don't know the pump you are referring to, but it can't be larger than the GT3 pump with its extra scavange inlet. Just lay the pump in your case and you'll see where you need to whittle.

My early sandcast case accomodates a 930 turbo pump (with clearancing) with no problems.

If this pump is as long as the GT3 or 930 pumps, you will need the short splined coupling tube (I think there are only two lengths for this - long and short).

Is this RSR pump a separate part, or is it just the "964" pump?

Walt Fricke

Cookie Porsche · 08-17-2005, 07:25 AM

Walt'

Hrmph... just checked the oil pump. '964.xxx.so forth'. Came out of a 993RS 3.8.

Is this pump bigger than the 930 3.3T ?

Why did you use the GT3 pump?

BTW, my car uses GT3 brakes - so I'm already in the family!

Regards, Tom

Walt Fricke · 08-17-2005, 01:37 PM

Tom

I bought a GT3 pump because it cost a bit less than the 3.3 turbo pump (the turbo pump I have in my existing, at some time to be spare, engine I got before the GT3 was made and as a good deal swap of some other parts). I think it may not cost more (or at least not much more) than the 964 pump you have.

I just rembered that you will have to clearance a 930 case to fit the 964 also. A friend had both a 964 and a turbo pump in his private stock, and we held them up side by side to see what apparent differences there were. I don't recall anything of significance in terms of the lengths of the internal gears as best one could tell from the outside.

The spiel on the 930 pump was that because it was all cast iron it changed less when hot and was better for racing than the 964. My suspicions are that the 964 pump is probably just as good, but that is just a guess. If I had one I'd probably be using it for my 2.8 project motor.

Walt Fricke

Cookie Porsche · 08-19-2005, 06:55 AM

Walt

Quote:

If this pump is as long as the GT3 or 930 pumps, you will need the short splined coupling tube (I think there are only two lengths for this - long and short).

Just 'plugged' the 964 pump in. I see I have the long coupler tube - what model/engine used the shorter tube?

Otherwise I'll just shorten my tube - have a good engineer.

Thanks for all the help. Enjoy your weekend.
Tom