Twin Turbo???

[GenX Porsche]

After being inspired by the twin turbo dream conversion in Waynes book I had to ask the question, is it really possible? I guess that needs to be elaborated on...is that possible for me? You may ask, why? For some reason the philosophy behind the newer twin turbo setups that alleviate turbo lag by allowing a pull throughout the RPM range really has me hooked. In addition I have recently looking at the CTR as if it were the hottest girl I have ever seen in my life. So the question is not "if" it is "how"? In Waynes book you see a 993 based engine with GT2 twin turbos, what I propose is a 930 3.3 based engine with a similar twin turbo setup. Is this feasible? I would assume the 930 itself would be able to handle the twin turbo. I guess the question after that is fabrication of the exhaust and routing of the turbo system. Any idea about either of these? And the last question that might be to much is the idea of the individual intercoolers of the ctr and the feasibility about creating something along these lines. And finally is if anyone knows where I might find the turbos for something like this. If anyone has any ideas about concepts for this project I would love to hear them. I am in the research stage of this project and am trying to get as much information about this as possible. My initial plan is to attempt to use my 1977 911S for the body unless I can find anything more appealing. Thanks for all your input.
David

[Wayne 962]

First question - what's your budget? The motor in the photos cost about $50K or so...

-Wayne

[89turbocabmike]

GENX, I wonder if stock 993tt turbo's might work. I know they are for a 3.6L motor, but alot of 993tt guys upgrade their stock K16's for K24's so you might pic up the turbos at a decent price.

[GenX Porsche]

Wayne you are very right in your suttle assumption in that 50K is a little out of the current budget. This is also my dream setup and would appreciate humoring the thoughts of a twin turbo setup and begining to do some research on the subject. I have no experience with turbos. I however did watch an older 911 turbo take off recently and I was amazed and wanted that kind of power plant in my car. Thanks for the idea of running twin stock 993 turbos...will have to keep my eyes open.
David

[emcon5]

Well, I was pondering this this a while back, and you could do it fairly economicly, probably in the $10-12K range if you do your own work.

You start by finding a core 3.2. Get the heads modified for twin plug, send the cylinders to EBS to get bored out to 98mm (for 3.4 liter), with a new set of JE pistons, at about 8:1, with at minimum 964 cams. You need to relocate the oil tank forward like on a 72 (or Yellowbird), to make room for the right side turbo.

For exhaust start with Bursch headers and move the flange back toward the collector and fabricate a short pipe to the turbos, with the exhaust continuing to a custom flowmaster (or similar). Or try and adapt 993 TT headers, but they would probably cost more.

I don't know enough about turbos to know which ones to use, but there are certainly off the shelf components that will work, off any number of different cars. I wouldn't limit myself to Porsche turbos. There is a lot of turbo knowledge with the import guys. Who knows, Supra twin turbos may bolt right up.

For induction, use the stock 3.2 manafold with a aftermarket EFI (Motec, Haltech, etc). You would still need to come up with a boost controller of some sort, oiling for the turbos, ARP hardware, and probably a bunch of stuff I haven't thought of. The hardest part would be mapping the EFI.

Of if you are really talented like Mark Hargett, you can fabricate the whole thing from scratch.

Coffee Table or Put It In The Car?

Tom

[Wayne 962]

Originally posted by emcon5
[B]Well, I was pondering this this a while back, and you could do it fairly economicly, probably in the $10-12K range if you do your own work.

Hmm, that would be at least $12K, not including the cost of the core motor. There are some very expensive items needed like a TEC-3 system with custom manifolds for a turbo (probably about $6K min). Flat-top low compression pistons, custom exhaust, the turbos itself.

I would break it down like this:

Core engine, 3.2 in need of rebuilding $5000

Engine Management and intake system to run the engine with two turbos $8K

Rebuild of the engine itself to your 'turbo-ready' specs $8K - standard cost for an engine rebuild.

All the turbo stuff (exhaust, turbos, etc.) $5K

That adds up to about $25K in parts alone, and I think my estimates are pretty reasonable.

But it would be a cool project!

-Wayne

[lendaddy]

"Core engine, 3.2 in need of rebuilding $5000"

You gotta be kidding? Maybe not, havn't been looking for 3.2s, but daaaaaamn! Anyone wanna give me 5k for my 3.0L turbo with a broken head stud?

[emcon5]

Originally posted by Wayne at Pelican Parts
I would break it down like this:
Core engine, 3.2 in need of rebuilding $5000

Not unreasonable, but you can probably do better if you are patient. You can recoup some of this expense by selling off the parts you don't need (like the stock exhaust and DME).

Engine Management and intake system to run the engine with two turbos $8K

Clewett's 3.2 based Twin plug TEC-E with 3.2 manafold is $3200. Not sure if they would give a discount for a core induction system from a 3.2, but it isn't unreasonable that they would. I also don't know what else would be needed to adapt this to a turbo, but they list it as fitting a 930. Intercoolers would be interesting, and probably quite expensive, unless you could adapt an off the shelf part from a different application.

Rebuild of the engine itself to your 'turbo-ready' specs $8K - standard cost for an engine rebuild.

That sounds about right, probably at the high end of the range though. The valve job and machining for the second plug is ~$1100, I have in my rebuild notes that EBS will do their 98mm bore and replate for ~$2200 with JE pistons. It may be a little higher for flat top pistons, I don't really know. Using your catalog prices, Raceware head stud kit and case essentials kit are ~$1500. You could save money here by leaving it 3.2L and using the stock cylinders, assuming of course they are in spec.

All the turbo stuff (exhaust, turbos, etc.) $5K

I did a quick web search, rebuilt units from a Mitsubishi 3000GT/Dodge Stealth TT can be found for ~$2K for the pair. Probably less if you can find junkyard units and have them rebuilt. I couldn't find them in your catalog, but Bursch headers are ~$400 from one of your competitors. A compitent muffler shop could relocate the flange and do any plumbing needed. The oiling would be tricky, but I still think you could do the exhaust and turbos for ~$3K. Less if you know how to weld.

That adds up to about $25K in parts alone, and I think my estimates are pretty reasonable.

Well, My $10-12K was optomistic, but I am still well under your $25K figure for parts.

Of course getting a tranny that will survive the added power is a expensive problem that would need addressing (unless you started with a G50 Carrera)....plus bigger brakes. Not to mention the dyno time to get the fuel/timing map right.

But it would be a cool project!

-Wayne

Wouldn't it though? I'll get started as soon as I win the California Lottery.

Tom

[Wayne 962]

I'll see your $25K and counter!

I haven't seen any 3.2s under $5k recently. Good core 3.0s can be had in the $2500-$3000 range. $5K is a pretty standard price right now.

$8K is also very reasonable for the core rebuild, considering the upgrades you will have to perform in order to sure up the engine for twin turbos.

I think you're way off on the exhaust numbers - pre-fab single turbo exhausts are about a grand - you would have to spend hundreds of hours fabricating a custom exhaust.

I doubt you would be able to run the standard 3.2 manifolds with a system like this (although you never know). I was quoting trottle bodies, which are more expensive, and may or may not be needed...

-Wayne

[emcon5]

Originally posted by Wayne at Pelican Parts
I think you're way off on the exhaust numbers - pre-fab single turbo exhausts are about a grand - you would have to spend hundreds of hours fabricating a custom exhaust.

Just to clarify what I am talking about with the exhaust: If you start with an off the shelf Bursch header, and cut the pipe right after the collector, or better yet, move the collector back a bit. Let Bursch do all the difficult bends, all the modifications would be shortening straight sections of pipe. Stuff any muffler shop could do.


Start with this:


Cut and weld to turn it into this:


Weld the flange on right to the collector, and bolt on an 90° elbow going outboard (or skip the flange all together, and weld the elbow directly to the collector), to the flange for the hot side of the turbo. You would end up with the turbos sitting pretty much where Mark has his:



You could do it easier/cheaper by using the thermal reactor replacement shorty headers, and a straight section of pipe to each turbo.

The piping from the turbos to the muffler wouldn't be difficult either, muffler shops make custom exhausts all the time. 2 flanges, 2 bends, and an off the shelf muffler. It would end up like the one Mark made here:
Made My New Exhaust Today

Mark is also using a 3.2 manafold, it looks like. I don't know if it is the same one he modified by shortening the runners when he had the supercharger on it.

Just some thoughts....

Tom

[Wayne 962]

Good thoughts there. I guess the key is getting someone at the muffler shop who knows what they're doing, and won't charge you an arm and a leg...

-Wayne

[dean]

Those plain steel header wouldn't last very long in a turbo. I think it would be very hard to do a TT for $12K if you did it right. And you can use the Carrera manifold in a turbo app. Mark Hargett did a very nice job doing all the work himself and that would be the only way to get close to a $12k budget

[Britwrench]

And don't forget to add into the equation; better brakes/wheels/tires/suspension/body mods for bigger rear wheels/changing gear ratios for new engine/all the other little bits to do it properly so you can actually use the power and drive the car..........Probably cheaper to buy a 930 and start from there.

[RarlyL8]

I have been gathering parts for a twin turbo 930 engine for some time now.

If you start with a good 930 engine I believe it is possible to do a "budget" twin turbo conversion.

First, and this is VERY financially important, you use the stock CIS system. Good for 400-450hp. That's plenty of usable power for a low-lag twin turbo.

So now all you have to do is exhaust fab, oiling mods (modify the stock system), and buy a couple of appropriately sized turbos.

Simple, no?

[911pcars]

I concur with RarlyL8 and Tom on their suggestions. If budget is a consideration, start with known factors (base turbo engine), then convert from single to twin turbos using as many off-the-shelf parts you can. You're not necessarily doubling the boost, just using two, smaller turbos to eliminate lag and broaden the torque curve. Thus, your budget centers around two turbos, wastegate, associated lubrication and drainage needs, exhaust and intake system fabrication and an intercooler. You'll have to research the turbo size for your configuration, HP/torque @ ? rpm objectives, but there are plenty of books and sources to assist.

Once you have your TT working the way you want and you haven't yet grenaded the engine by experimenting at 1.5 bar, then you can assess how far the change in your wallet will go toward upgrading the inside of your engine. In other words, you might want to tackle this in steps.

As so many projects end up, you may tire of this idea at some point (or run out of money) and decide to cut your losses. This is not nearly so ruiness as building the ultimate long block (relatively easy but expensive), then having to finish with fabricating the rest of the system (not so easy, could be more expensive) that may not even work as designed.

A big difference will be how much you can't do versus farming it out to someone who can do. Because of this factor, I wouldn't even hazard a guess as to a realistic budget.

Sherwood
http://members.rennlist.org/911pcars

[snowman]

Another idea,

Get a second job, save, save, and buy one from Porsche.

[beepbeep]

The very cheapest method of doing a TT would be, as Rarly said, installing twin turbos on 930 engine and kepping CIS.

You could pick up two second-hand Garrett T3's for 300$ a pop, sell your wastegate for 300$ (T3's have internal wastegates), buy some tubing (maybe 600$) and get trigger-happy with TIG.

That way you could get your beloved TT-setup under 2000$ (including oil-piping etc.) but you'll need to fabricate lot's of stuff yourself and use OEM intercooler which isn't the best.

Of course, we are talking modifying 930 here, modifying 911S would be price-prohibitive....everything would need to be replaced: Pistons, intake, injection, brakes, transmission etc. etc.

Blown: ordinary steel can be used in turbo, no problems...what do you think OEM 930 exchangers are made of?

[dean]

SS

[Porsche_monkey]

Why not scrap CIS and make a programmable EFI like mega-squirt. In the grand scheme of things it is not a lot more work.

[project935]

PBH,
I'm going there ... not there yet ... won't be for awhile (just starting my project - chassis first).
My thoughts are to convert a crappy set of carbs I have to t-bodies, Megasquirt controller, FIs in the base of the manifold, and custom air-to-air intercoolers on top. Nothing fancy, mostly OEM production stuff (not necessarily Porsche) that is easy to get and work into the system. I have the vision in my head and it looks 934/5ish - I hope to CAD it soon.

The plan/story will unfold over the next few years ... I'm just now (last weekend) turning wrenches on my project - official kick-off website and links coming soon. Should be fun ... and I'll be asking many questions and sharing whatever I come up with along the way.