A brief conversation about the available options
Mid-mount is dead, RIP midmount. A handful of fabricators used to create this wonderful configuration. It was typically difficult to install, but once installed it provided a number of benefits:
easy to drain, easy downpipe, and most of the other typical bottom-mount benefits (temp, weight, invisibility, ac, etc) without any of the top-mount problems. It’s really a very high-mounted bottom-mount. One catch is that they sometimes required totally custom motor mounts.
On to stuff that’s still in production: Top mounts and bottom mounts.
The two most common top mount designs are the cheapest ones: The CX and the RSI and its twin, the knockoff RSI. Other options include PPF, k64, mint, doc race, ftwl, Cory Misko, vi engineering, Kangaroos team and certainly some others that were either forgotten or unknown. These are mostly stainless cast elbow construction- which is the handmade standard for high performance turbo manifolds. The PPF is unfortunately really limited to those with access to a diesel 20′ transmission. They make a lovely set of parts to go with that conversion. The Kangaroos team manifold is the first cast iron top mount for this platform.
Top mount pros:
- looks cool
- drains oil like a champ
- can typically run any turbo the manifold can support
Top mount cons:
- cooks valve cover gaskets
- cooks hood paint
- complicated downpipe
- complicated/impossible filter
- unpleasant heat locus
Bottom mounts are very much worth considering. They allow for AC without struggle. Center of weight of the kit is much lower and further back. It concentrates heat more or less where the cats are factory-mounted (a spot compliant with a lot of heat), not where the valve cover or hood are. Bottom mounts typically can’t house much more than an H-cover (4″/3″) and that’s not all manifolds. But that’s already pretty huge.
Bottom mount pros:
- Keeps the heat low and back like a stock exhaust system
- nearly invisible
- good weight distribution
Bottom mount cons:
- aftermarket or custom motor mount arm necessary
SPA makes the most beloved current production cast manifold for the m5x. The AA has been out of production for a while but is still available second-hand. The Steedspeed from CES is cast-like. It’s also a great deal. PPF also makes beautiful tubular bottom mounts that fit our factory 30′ slant. The cheap chinese ebay cast bottom mount has had a lot of reported issues from warping to manufacturing issues that prevent easy installation. The cheap ebay tubular bottom-mount doesn’t deserve this many lette…
Let your budget and tastes guide you.