Should I build whith one or two Turbos???

[Jocke]

Hello!

I´m gonna change the original Exhaust.

My question is:
Should I build the new Exhaust system whith a singel Turbo or maybee it´s better whith dubble Turbo´s.

Anywone who have done this, on the right side it´s seems like the Oil-tank is in the way...

This is what I gonna use: (I think it´s from an old Carrera)

[Jocke]

Ouups!

The car I´m building this on is a 930 -77

/J

[RarlyL8]

The stock configuration headers or heat exchangers from a N/A 911 engine exit too far back and too low for good turbo fit. You should modify them.
One or Two turbos? Is the cool factor worth twice the cost and three times the headache? A small displacement engine does not benefit much from twin turbos.
Your choice.

[WydRyd]

You could modify the outlets to point upwards between cylinders 1&2 and 4&5 and have the smaller turbo's mounted to the side of the engine. However, you'll need to move the oil tank slightly.

'Mike The Mechanic' is doing a TT conversion on his 3.2 Carrera, so maybe he'll offer some input here.

There WILL be a fair bit of fabrication work required and custom intercooling etc.

Good luck...

[Jocke]

Thanks for the information!!

It would really be great if someone happens to now about some webb-sites whith pictures on a conversion like this.

/Jocke

[WydRyd]

You could e-mail Stephen at ImagineAuto, or Todd at Protomotive. I'm sure they have some pictures they'd be willing to e-mail you.

I do recall something about the CIS Injection not being suitable for quick-spooling twin turbocharged applications, but you may want to clarify that with Stephen.

[JohnC]

try this:

[WydRyd]

Thanks for sharing JohnC

Imagine the flames and bumper melting heat from those turbos

[JohnC]

I say disregard RarlyL8's (Brian) comments,(remember he's OLD & Crotchety!)

I'm working on a similar project myself and have recently decided to go to two turbo chargers vs one.

One is the "cool" factor, the other is that the Garret t3 turbos are quite plentiful (at least in the US) and can be had in many different configurations.The fact that they're plentiful means that they are also less expensive. For the price of two new T3's you could get a new k27. I've decided to do this even after purchasing a used k27!

As for the suitability of using those exhaust manifolds well...IMHO the primary tubes are too long, unless you're running at 6500rpms on an oval track, otherwise spool time is gonna be a pain.

(see the 935 above) The primary tubes should be kept as short as possible and YES I KNOW what Indy car turbo manifolds look like!.....different animal entirely!.

It looks as though you probably got those for free or real cheap anyhow...... what the heck.... weld a suitable flange on them and try them out, if the car is a pig (takes forevever to spool up) you'll know why.


Of course I'm ignoring the proper size,trim etc...of the turbos.

All of those specs will affect spool up time so..... consult the appropriate proffesionals.

I vote TWO.....

[JohnC]

one of the things that is interesting about that picture, among other things, is the scavange pump is located on the back of the motor rather than the front (driven off the camshaft).

[WydRyd]

I agree JohnC. as long as you have properly matched turbo's and shorty headers, I don't see any issues relating to spool-up time.

If Jocke shortens the outlets and use an on-the-side turbo configuration, I think he'll get pretty good spool-up using a pair of T3's.

The beauty with the side configuration is that you don't need scavange pumps. If you mount the turbos slightly above the lower valve cover, you can use gravity drain. Works fine on my single turbo system and K27. I'm replacing the cracked rubber drain-back line to a braided stainless steel unit for reliability at the moment.

Of course, there'll have to be some creative work done to move the oil tank slightly, but it can be done.

Mike is doing a TT 3.2 (to 3.3) and I believe is going to use side mounted T3/T4 Hybrids.

[JohnC]

I think the time required to get those "rusty tubes" to work is probably not worth it now that I'm looking at his picture.

Those headers are designed to run very close to the motor hence the flat collector design. So squeezing a turbo "under the motor" is out of the question. The next idea is to utilize the extended tube from the collector to place the turbo "behind" the motor ala "935".

Or.... put the left header on the right bank and the right header on the left bank, backwards of course, then cut the tubes where they wind up in the same plane and place the flat collector there?.
Unfortunately the turbo will still end up under the motor with no space.


WydRyd: How did Mike size his tubos? His method I mean.....
I'll need to cross that bridge in the future too....

[RarlyL8]

You becha I'm grouchy. Try waiting TWO WEEKS for a friggin $3 acorn nut to finish a swap you've been anticipating for two years!

God only knows the pain you'd go through if TWO turbos were involved.

Complexity, cost, and weight aside, the cool factor of twin turbos is irresistable. Did I mension weight? 930 engines weigh over 500 pounds. Now strap on another turbo, another wastegate, and all the added plumbing. Better get out the 35mm t-bars for this pig.

Now with all that said, I've toyed with the idea of twin turbocharging the 3.3t many many times. Got lots of ideas down on paper. The look is just too cool, but I see no real power gain for the big dollars it would cost to do it right. There would also be a real loss in durability given the fact that you cannot use tuff factory parts (a tiny aftermarket oil line causes a world of hurt if it blows a hundred miles from home).
My car is a driver not afraid of long distant hauls. This is important to me. A real hotrod weekend warrior would be pretty cool though.

[WydRyd]

To be honest, the rubber oil line actually lasted quite a while before giving way. Nearly 10,000 km's aint too bad considering it sits right below the hot housing! It would have lasted longer if they hadn't used any damn clamps which tear away at silicone, like Protomotive suggested.

Anyway, the braided stainless steel line will be much more durable It's one of those things that you need to suck'n'see.

Agree tho, if the rubber line went bung on a long trip, it'd certainly hurt

JohnC, Mike would have to answer that question for you. All I know is that he spotted them on EBay (a pair of Hybrids) and they were the exact A/R's he was looking for. How he got to those A/R's is beyond me

[JohnC]

Tsk Tsk Tsk...Rarly..... I think you're Arthritis is acting up.....
but I understand about the acorn nut.....

The additional weight is minimal (one turbo)...and...
some of the T3 turbo's come with a built in wastegate.

I think the basic Philosophical(sp?) idea is to build it as mean as you can afford....'cause you'll get used to the HP and you'll be wanting more...they all do.

[RarlyL8]

Why you snot nosed little phlegm wad! See how long it takes to get my arthritic foot outta your ass!

Ha! All kidding aside, I've been hording a few "choice" parts for a possible future twin turbo venture. While we're on the subject of exhausts I'll share my ideas on the subject.
Remeber back "in the day" when folks were replacing there thremol reactors with shorty headers?
Well I got a couple of those - they look perfect a for dual side mounted turbo application.
Just a thought.

[Wayne 962]

"A small displacement engine does not benefit much from twin turbos. "

Hmmm, perhaps this is a good time to bring up the twin-turbo 959, with a mere 2.85L and a whopping 450 HP?

-Wayne

[WydRyd]

Agree Wayne

What about the little 2.0 litre Twin (Sequential) Turbo Subaru B4's? 190kW in factory trim from a 4 banger is quite respectable

[RarlyL8]

You missed the point.

A small displacement engine does not benefit much from twin turbos VS A SINGLE TURBO.

You're not going to get much more power adding a second turbo to a little engine.

[beepbeep]

Well at first i tried to convince Jocke to use T3's as well...

Good part is that T3 is a turbocharger used on early Saab 9000's, and here in sweden you could pick up two of them for peanuts at every junkyard...and they are oilcooled as well.

But on the other hand there are some issues:

First, let's ask ourselfs why dual turbos? If we forget "coolnes factor" for a moment, people use dual setup to minimize turbo-lag. (two small turbos spin up faster than single large one)

Unfortunately, Garrett T3's, despite being dirt cheap, realiable and better dezigned than those awful 3DLZ's are a tad too big for 3.0-liter engine. I had one of those on my 2-liter SAAB (with A/R of 0.47), and despite having "headers" that were very short(10-15 cm at most), boost started to build up around 2700 RPM.

So 3L 930 with a pair of T3's would probably be pretty laggy from bottom. But as somebody mentioned, T3's have built in wastegates, rendering those external lumps useless and saving weight...


So answer is (in my opinion):

Yeah, it's a matter of taste. Properly sized and executed, dual turbos reduce lag (993 and 996 use dual turbos). Cheapskate approach with T3's won't reduce lag but will be able to return some decent power (approx. 400 HP with A/R 0.47 or ~500 HP with A/R 0.60) ... beeing cool to boot.

If you have time and tools, why not?