Turblown Engineering Investment Cast 347SS T4 Twinscroll FD3S Turbo Manifold


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These are now on back order for a 2 months as of 5/2/2024

 Turblown has developed the Ultimate FD3S T4 EWG ( external waste-gate) Turbo Manifold. This Investment Cast 347SS manifold is based on their proven welded design, but improved drastically. The improvements include tapered runners, 4X egt/emap ports, stronger build construction and higher flower transitions.

The welded version is proven to over 700rwhp, and has held boost pressure as low as 6 psi on road raced Rx7s. It was the first of its kind on the market.

How is the new cast version different from our welded version?

347SS vs 304SS
Tapered Main Runner Inside Diameter ( 2" I.D. tapering down to 1.687" I.D.) 
4x 1/8" 
NPT EGT or EMBP bungs standard
Every Flange is CNC Machined
Larger Inside Diameter Entrance Bore( 2" I.D.") compared to the traditional 1.5" schedule 10 weld els. 
Smoother transitions not just at the engine and t4 flange, but through out all runners.

Cast 347SS

This manifold is cast from 347SS which is far superior to 304SS. Not only does 347SS last longer at elevated temperatures , there are no welds like those found in traditional turbo manifolds. When a welded turbo manifolds fails, they almost always break at or next to the welds. A broken turbo manifold even if it features a life-time warranty can be a serious hassle to remove and send back in for repair, especially if you miss a race because of it. We have weighed our cast manifolds vs our welded units and they actually weigh a few ounces less! Since these manifolds are investment cast, they are less than 1/2 the thickness of your traditional cast iron turbo manifolds, and therefore do not retain as much heat as cast iron manifolds. There are zero downsides to this casting process vs welding. 

Tapered Main Runner Inside Diameter

This manifold's inside diameter slowly tapers down as it reaches the T4 flange. This process is only possible with a cast manifold. A traditional welded manifold does not change inside diameter. This tapering process is identical to the volute of a turbine housing. By tapering down it increasing velocity, and speeds up the exhaust flow and increases boost response.

CNC machined flanges

All flanges are CNC machined to be perfectly flat. Most turbo manifolds are just belt sanded flat, which is not as accurate as CNC machining. The wastegate flanges typically leak slightly on a welded manifold, even if the face is belt sanded flat. The outside vband flange, and inner wastegate seat dimensions do not stay true because of the welding process. 

Smoother transitions

Welded turbo manifolds require hours of hand porting with a die grinder, and sanding drums to contour the change in shape from a round tube to a square T4 flange. We have taken this step, just like the rest of the manifold, to an even higher level of quality. The investment casting process makes every transition seamless. Welded manifolds are made from short pieces of cast elbows. Every time there is a joint it is welded, there can be a slight disruption on the inside diameter if the pipe is not perfectly matched, or the weld penetrates all the way through. This disruption is eliminated with the casting process resulting in a better flowing turbo manifold. While billet collectors improve this, they only improve the collector area. 

Design and Fitment

This manifold has Proper Waste-Gate Placement for Proper Boost Control. Does your current turbo manifold overboost from poor wastegate placement? If so this unit is guaranteed to never boost creep! The entrances to the waste-gate runners are in the direct flow, and tear-dropped. The waste-gate runners are very short to disrupt the flow as little as possible. These manifolds are flanged for twin TurboSmart Comp40 genv waste-gates( both standard and motorsport models), but also fit Tial mvs(38mm) & Garrett 40mm with turbosmart inlet clamps. 

This manifold fits both LHD, RHD, Stock LIM, Xcessive LIM( some turbine housings might require an extra spacer or milling of LIM for excessive), and most Vmount Inter-Cooler Systems. It will accommodate any size down-pipe up to 4". It also clears the Pineapple Racing Idler Pulley( Except for GT42, or S472/475- we recommend our EWP kit here) Air pump, Air Pump Bracket, and EGR require removal. Heat Core Hardline Requires relocation or replacement with flexible line. Fits most popular turbo sizes like Garrett, GT35R, GT40R, GT42R(T4) Precision 6262,6265,6266,6765,6766,7175( H cover only for 7175), Borg Warner( standard airwerks and SXE) S360, S362, S366, S472, S475, EFR EWG 7670, 8374, 9174 and 9180. 

Zero modifications are needed for sheetmetal/frame. This unit is guaranteed to fit with good condition engine mounts/oem subframe. 

This unit will fit both 1st and 2nd gen Rx7s with re or rew swaps only( both LHD & RHD). 1st gens require FC subframe/steering rack swap or rear WG will bump 1st gen oem pitman arm assembly. 

T4 flange thread pitch is M10 x 1.5


Read more about this manifold on our blog posts here;

Cast VS Welded Turbo Manifolds

New Cast EWG Tapered Runner Rx7 Turbo Manifold

Install kit includes twin dump tubes, K&N air filter, heater core hardline, turbo cooling lines, oil drain block off plate, marmon downpipe clamp, 3" 2 bolt rear gasket/bolts/nuts, turbo manifold to turbo gaskets/bolts