Is there a way to tell the difference between s4 and s5 t2 irons?

 

I had to ask Kevin L. when trying to confirm my rear plate was S4 and he said-

Easy way to identify s4 vs s5 rear irons.

At the oil filter pedestal, on s4's you can see the 2 "tubes" running up to
it, they come down perpindicular to the dowel landing area. ON s5's, there
is a triangular reinforcement added here, that goes from the top of the oil
pedestal, to the front corner of the dowel landing area. You may have heard,
but s4 turbo engines are notorious for cracking the dowel landing area under
stress such as high power, leaking oil, and requiring a rebuild. This is why
the s5 reinforcement was added.

Also note that s5 housings have slightly larger intake ports than s4.

You can identify s5 FRONT irons by the oil o-ring casting size, the s4 has
the small one, the s5 the large one. The INT housings are the same thing, to
my knowledge.

 

To add to that, the s5 INT housing has a slightly SMALLER intake port on the inside than an s4.

The port difference on the front and rear irons I discussed is on the manifold side, not the inside. The difference is about 1/8" in width and height. The ports inside the engine appear to be identical on teh F and R irons.

 

Yep, Kouki primary port open 10-degrees later - thus, the smaller (narrower) port.



-Ted