I picked up a '91 RX7 recently, and it has the FD HKS Cast manifold with a GT3582r with an undivided 1.06 a/r housing. I have seen that this manifold is divided, but when I had the turbo off to look at moving to a divided housing I noticed a notch in the dividing wall. Is this manifold actually considered divided, or does that notch make a difference?

Here's the manifold I'm speaking about: HKS Cast Log Turbo Exhaust Manifold FD Mazda RX7 DISCONTINUED [G17141-Z60020] - $551.00 : Himni Racing, Turbocharger, Turbo, Garrett, Turbo Kit, GReddy, Mazda RX-7, HKS, Apexi, TiAL, TurboXS, TurboSmart, Flange, Turbonetics, Exhaust, Intercooler, ACT

 

Revisiting this almost 2 years later. Any input on this?

 

The notch could just be for equalization between the 2 runners.... it's all I can think of

 

I'd expect it's just to allow expansion.

Typically the continuous bridges crack/erode with use in that area. It's probably made in some form of Ni-resist, and better than "normal", but very common on fabbed manifolds to fail there - and on the HKS stainless ones too.

 

As mentioned its just so help with cracking, as its not an investment piece, and this is one of the weakest areas on every manifold.

 

OK, that makes sense. Going for maximum spool on my GT35, so divided housing definitely on my short-term list. I would LOVE to get an EFR (or even a TDX), but its just not in the cards right now.