968 Turbo

[corsair944]

I just bought a totaled 968 and I want to turbo it and drop it in my 944. This will be a long project due to time and $$$. Im leaning towards the 16 valve head and I know I will have to have Manifolds made..
My first set of questions is.
1)I know I need a larger turbo than the K26. What are my options..
2) Transmission: will the 6 speed be geared right for turbo or will I have to use the 951 tranny. Or can the 6 spd be regeared..
3) Injectors: larger Im sure..
And anything else anyone would like to throw out will be appreciated..
Thanks Patrik

[rage2]

1) What power goals are you looking for? Are you looking to run only pump gas or are you looking to run race gas as well?
2) 6 speed works and is geared well.
3) Depends on your power goals. I suggest getting the biggest you can get so you don't have to replace them when power goals change.

You'll need a lot more than those items. In addition to manifold, turbo and injectors, you'll need:

- Custom Exhaust
- Wastegate
- Boost controller
- Standalone EFI system
- Intercooler
- Custom charge piping
- Variocam delete (I'm not an expert on 968 16v turbos but I remember reading that variocam doesn't work well with forced induction)
- A lot of tuning

Good luck with the project.

[legion]

Wouldn't an S2 head take care of the Variocam delete?

He could probably trade straight up.

[corsair944]

Im really intereste in a street toy. So Id be running pump gas.
What uses the bigger turbo.. Is it a K28 ????

[AaronM]

Originally posted by corsair944
Im really intereste in a street toy. So Id be running pump gas.
What uses the bigger turbo.. Is it a K28 ????

The bigger turbo is a K26/8 instead of a K26/6. The difference is on the compressor side (8mm vs 6mm), the driven side is the same. The K26/8 is slightly more laggy but doesn't have the boost falloff at higher RPMs that the K26/6 does, IMO it's a worthwhile tradeoff. Singe you'll have more displacement, I'd say that the k26/8 is as small as you'd want to consider, I'd go a little larger for track use, but for street use the K26/8 should be more than adequate.

Aaron

[corsair944]

What uses or used the /8 .. ??
Whats the problem with the varicam head & turbo??

[AaronM]

Originally posted by corsair944
What uses or used the /8 .. ??
Whats the problem with the varicam head & turbo??

The 1988 944 Turbo S and all 1989 944 Turbo models used the K26/8. It is physically a bolt-in replacement for the K26/6.

Aaron

[corsair944]

Okay, Got the turbo figured out..LOL
Now will I need to change the pistons ??

[J1NX3D]

http://www.fitz-racing.com.au/sub-6.htm

[rage2]

Originally posted by AaronM
The bigger turbo is a K26/8 instead of a K26/6. The difference is on the compressor side (8mm vs 6mm), the driven side is the same. The K26/8 is slightly more laggy but doesn't have the boost falloff at higher RPMs that the K26/6 does, IMO it's a worthwhile tradeoff. Singe you'll have more displacement, I'd say that the k26/8 is as small as you'd want to consider, I'd go a little larger for track use, but for street use the K26/8 should be more than adequate.

Aaron

Wrong, the K26/8 has a bigger turbine, compressor side is the same. It doesn't flow more air than the K26/6 since the compressor is the same, but it does have less exhaust backpressure, therefore it'll be more laggy but make more power overall due to lower pumping losses.

However, that turbo is way to small on a 2.5L, let alone on a 3.0L. You would want a custom T04 turbo or a GT series turbo for a 3.0L setup. Something like a GT30R would fit the bill nicely, or a T04E 60 trim compressor.

Finally, you don't just change pistons on a 3.0L motor. They have to be Alusil compatible pistons. So if you're looking for stronger pistons and lower compression, you will have to sleeve the block and use forged pistons like I had to do on my block.

[AaronM]

Originally posted by rage2
Wrong, the K26/8 has a bigger turbine, compressor side is the same. It doesn't flow more air than the K26/6 since the compressor is the same, but it does have less exhaust backpressure, therefore it'll be more laggy but make more power overall due to lower pumping losses.

However, that turbo is way to small on a 2.5L, let alone on a 3.0L. You would want a custom T04 turbo or a GT series turbo for a 3.0L setup. Something like a GT30R would fit the bill nicely, or a T04E 60 trim compressor.

Finally, you don't just change pistons on a 3.0L motor. They have to be Alusil compatible pistons. So if you're looking for stronger pistons and lower compression, you will have to sleeve the block and use forged pistons like I had to do on my block.

Oops. Sorry, transposed the sides of the turbo.

Unless you're going for a monster though, I don't think the K26/8 is too small for the 2.5 litre. It's capable of more than 300 RWHP on a 2.5 litre. People get 18 PSI out of the K26/8. Should make a nice, low-stressed, powerful 3.0 litre.

[schnellfahrer]

There's a guy over here with turbo'ed S2 engine running a 27/6 turbo. It makes for killer spoolup. He sees 367lbs@2250rpm!

[corsair944]

What about the head. I want to run the vario cam. Is this possible, or just impractable.
What are ther problems with turbo'ing the 968 head..
I know the intake & exhaust will need to be fabricated, but what are the performance pro's & cons..

[sca037]

From what I gathered at 944Fest, the hot setup is to get the big-valved 8V head from the 1989 NA 2.7L to use on a S2 / 968 block. They are few and far between so finding a good one is tough, but they're much simpler to get working right and make xlnt power. This is similar to the path Porsche took in building the mighty racing 968 RS turbos (which ran 8V heads):

http://www.968turbo.homestead.com/

Also (for further inspiration ;-) have a look at what packages Powerhaus builds:

http://www.powerhaus.com/968t.htm

....and especially this parts list (Turbo S Conversion Details):

http://www.powerhaus.com/968t.htm#968

Just my 2 cents,
Brian

[legion]

It was always my opinion that Porsche made the 968 RS an 8 valve so as not to embarass the 911 Turbo.

[corsair944]

Can anyone run these #'s and see what this one is ??
http://cgi.ebay.com/ebaymotors/Porsche-turbocharger-944-turbo-charger_W0QQcmdZViewItemQQcategoryZ33742QQitemZ798 9117813QQrdZ1

& this one ??
I hate asking so many ???.. But how will I ever learn ???
http://cgi.ebay.com/ebaymotors/Porsche-944-Turbo-951S-turbocharger-K27DR-Audi-Quattro_W0QQcmdZViewItemQQcategoryZ33742QQitemZ798 9610271QQrdZ1

[corsair944]

Ive decided to go with the 8V head. Does it have to be an 89, or will any 2.7 head work??
Thanks again..

[sca037]

In the US at least, the 2.7 was only available in the 1989 model year 944 since the 3.0L 16V replaced it in the subsequent S2.
If you find a head from a 2.7 then you're good to go.

Brian

[x3m944]

My 2 cents - stand alone would be nice - but piggy back would work as would a Additional injector controler that auto compensates for boost. Not expensive. But very do able.

Exhaust for the under 400 hp should not be bigger than 2.75.

If build a custom manifold dont limit yourself to the KKK - their are other options - but since you have that decided - go for it.

You need either a stand alone oil delivery system for the turbo -not expensive and easy to use to keep running the oil for cool down after engine is off.
Or you need to tap oil supply and return to pan.

Internal wastegate is a nice option - but if not - lots of choices and easy to incorporate into exhaust design.

Not mentioned was a blow off valve - again lots of choices.

Heat shield is a good option for turbo and if you are not going to run forged pistons or sleeve - then coat the pistons - swain is a good choice. You can run low boost with high compression but timing will be ultra important.

Also spark plugs - important to change those.

Basic low boost - 6 psi is cake - more is doable depending on your configuration. You can dial in wastegate to dump above 6 and tune with 6, then increase boost as you sort out each level.

Very rewarding and fast car will result from proper execution.

For the turbo manifold either cross over config like the 951 or a log or collector on the passanger side.

Never ever support the turbo completely by the pipe on a cross over - use a support bracket to support weight off the engine.

For a log or collector style setup - relief cut the flange to handle stress of expansion and contraction. Thermal coating on the manifold is a good idea.

If you are swapping heads - send heads and pistons both out for coating - lots of fantastic thermal coating options. With stainless valves.

Originally posted by rage2
You'll need a lot more than those items. In addition to manifold, turbo and injectors, you'll need:

- Custom Exhaust
- Wastegate
- Boost controller
- Standalone EFI system
- Intercooler
- Custom charge piping
- Variocam delete (I'm not an expert on 968 16v turbos but I remember reading that variocam doesn't work well with forced induction)
- A lot of tuning

Good luck with the project.

[Porsche-O-Phile]

IMHO a k27 anything would be vastly undersized for a seriously boosted 3.0L 16V machine. Were it my project and I was putting all that work into it, I'd look at a Garrett GT-35 at a minimum.

Failing that, pick up a copy of the PET and emulate the 968 Turbo-S in selecting your components, and build on that.

Keep us posted - sounds like if you stick it out to completion this will be one hell of a machine!