will a s5 turbo fit on a s4 manifold?

 

no

 

i have a ht18 turbo and it doesnt look like my s4 turbo and the wastegate doesnt have the two port thing?
what kind of turbo is it?

 

The s5 turbo to manifold bolt pattern differs. Wont really bolt right up. Should get the s5 manifold anyhow. Then you dont have to worry about the twin scroll.

I'm not sure what you mean by the second question. The s5 turbo looks almost the same. Easy way to tell is the wastegate actuator rod has a crook in it as apposed to the s4's straight rod. Looks a bit different on the exhaust end as well.

got pics?

 

The S4 and S5 compressor sections are the same however they each differ in the exhaust. The S5 has a larger turbine for a little better flow. The S4 turbo has in a sense a dual a/r ratio which is determined by the flapper door that is closed at low rpm's. However even though the housing is divided both a/r's (left and right) are not the same. The smaller of the two holes has the larger a/r ratio although you wouldn't think it by just looking at it. If you somehow adapted the S4 turbo to an S5 manifold or even built a custom divided manifold each side of the engine would breathe differently. The back rotor would be restricted more through the turbo than the front. The divided housing on the S5 turbo is of equal capacity on both sides and therefore each rotor flows the same through the turbo. I hope this description isn't too complicated to understand.

 

You can easily bolt a s5 turbine housing to the center and compressor of a s4 turbo. Not sure if it would work the other way around from what he just said...

 

Actually when I think about it, the exhaust wheels might be the same between the two turbos but the exhaust housings different between them. I'm thinking too hard and can't remember. It'll hit me later...

 

will a s4 turbo fit on a s5 manifold?

 

and is the j spec turbo different from the us?

 

No the S4 and S5 turbos are not interchangable with the opposite style manifolds. The J-spec turbos are the same year for year.

 

just buy a T78