[b924]

Hello

I am a little new to this - especially choosing a replacement turbo and was hoping someone may be able to help. I have a 1979 Porsche 924 that has an old aftermarket bae kit attached that uses a rajay 300 or 301e series turbo that has 4 bolts to the manifold. ( the factory 924 turbo uses a k26) The engine is otherwise stock.
A little about the car and goals. It is a 2.0L 4cyl (121cid) that uses a bosch cis injection system. Normally the car could produce around 110-115hp. I am hoping to improve that to around 160-180(at least for now). I do not have an intercooler or water injection now but I am looking into both to see which would work optimally for me.
If some of my other calculations were correct along the way, the pressure ratio that I was looking at @8psi is 1.54 with a flow rate of 23lbs/299cfm. that would be at 6500rpm - I do not think that I would run it that high - more like 5500-6000. I am not sure if that helps.
The car is primarily street driven but with the hope of seeing some track time eventually. I have looked at numerous maps and types of turbos but quite honestly they all start to run together after a while.

Any help that anyone can give would be most appreciated.

thanks

[Robert]

Before we get too deep into this I need to check with the team on Monday as I'm not sure if the K26 housing is still available through Turbonetics. I know the Rajay units aren't anymore

[b924]

thank you

I was not sure how that related even to some of the t3 sizes or there about size turbos that you have. I had heard about the rayjay being defunct.

thanks - I look forward to hearing what you find out

[Robert]

Well I talked with the sales manager and there are no K26 or Rajay parts left at Turbonetics. Unfortunately that would mean a new manifold before we could talk turbo sizing. Is that something you still want to pursue? If the base kit has a standard T3 turbine housing there are parts for that we could discsuss.

[b924]

thanks Robert for checking.

I wonder if we can use an adapter to transition from manifold to turbo? I was already thinking that I might do that to allow for a wastegate - unless the upgrade comes with an internal unit. I do not know if it is the best solution at this time but if it works that may be an alternative.
the current opening on the rayjay to the manifold is 2"x3" with a 4 bolt flange (if that helps).
Does any of this sound like anything we can work with?

Again, thanks for your help and patience with this

[Robert]

Originally Posted by b924

thanks Robert for checking.

I wonder if we can use an adapter to transition from manifold to turbo? I was already thinking that I might do that to allow for a wastegate - unless the upgrade comes with an internal unit. I do not know if it is the best solution at this time but if it works that may be an alternative.
the current opening on the rayjay to the manifold is 2"x3" with a 4 bolt flange (if that helps).
Does any of this sound like anything we can work with?

Again, thanks for your help and patience with this

Take a look at this thread:

:: View topic - Turbo flange dimensions?

Does your flange match up to either of those?

[b924]

Hi Robert

neither of those matched however I used the same idea and searched the google image bank and found that a t04 inlet flange appears to match. It has a 2.940(W) x 1.940(H) opening with 4 bolts that measure 3.25(W) x 2.750 (H) center to center. If that is the case perhaps a t04 might work? could something like that work with mine? I was not sure if that might be too big and lag too much in the lower rpm's.(?)

thanks again
Sean

[Robert]

Originally Posted by b924

Hi Robert

neither of those matched however I used the same idea and searched the google image bank and found that a t04 inlet flange appears to match. It has a 2.940(W) x 1.940(H) opening with 4 bolts that measure 3.25(W) x 2.750 (H) center to center. If that is the case perhaps a t04 might work? could something like that work with mine? I was not sure if that might be too big and lag too much in the lower rpm's.(?)

thanks again
Sean

I'm shocked its such a big turbine flange but yeah a T4 could technically work. You'd need to size the turbine A/R pretty small with your displacement to make decent power. For a 2.0 liter engine looking to make 200 HP or less I you could run something like a GT-K 325 which would spool up pretty nicely and make the power you are looking for. I just can't believe that is a T4 turbine flange on there. That's just way to big for that motor. Can you post some pictures for me?

[b924]

Robert
Thanks - yes I was surprised as well - especially after finding a comparison between the t04 and the k26 - the k26 appears to be half the size. The only thing I could think of was that the kit was designed a while ago - and they may have been concerned about heat?

I do not know how to post pictures on here - I think I have a few of the kit before installation and I should have some of some other peoples kits that they sent me - if I cannot post would you like me to email them to you?

How does the gtk325 relate to the k26?

thanks
Sean

[Robert]

Originally Posted by b924

Robert
Thanks - yes I was surprised as well - especially after finding a comparison between the t04 and the k26 - the k26 appears to be half the size. The only thing I could think of was that the kit was designed a while ago - and they may have been concerned about heat?

I do not know how to post pictures on here - I think I have a few of the kit before installation and I should have some of some other peoples kits that they sent me - if I cannot post would you like me to email them to you?

How does the gtk325 relate to the k26?

thanks
Sean

You can use the Manage Attachments button at the bottom to attach jpegs id you like. The GT-K 325 is a T04E 46 trim compressor with a an F1-54 turbine wheel (T3). It's good out to 325 HP if you ever wanted to go there and the ported compressor shroud will make responsiveness at the low end REALLY nice. The problem is its a T3 turbine. I don't think I've ever seen a 2.0L engine with a T4 turbine unless it was fully build and pushing 600+ HP. I'd like to see the pictures of your car before we go to far though.