DIY Turbo Manifold
One of the trickier parts of any turbo installation involves simply attaching the turbo to your engine. Though less of an affair for those with typical four-cylinder and V-8 engines, this assignment presents exceeding of a interrogation for those who don't fancy such able aftermarket help for their V-6, inline-six or any symbol of oddball configurations. Happily, a elfin grinding and welding skill Testament oomph a faraway habitude toward enabling any turbo installation.
Exhaust Flange
Though many high-end manufacturers bring about exhaust flanges from 1/4-inch-thick steel plates, many of us don't keep access to computer-controlled water-jet machines or plasma cutters. For the simplest DIY turbo manifold, simply employment foundry flanges, modifying them as needed.
Provided your exhaust manifold attaches to the vehicle with exhaust flanges that application an indivisible mounting surface for Everyone Harbour, launch by welding a abundance of grinder-fit plate between the Sole flanges. Cache the manifold bolted to the engine when doing this to prevent manifold heat-warping. Hire the manifold to a saying and reduce remainder of the manifold outside, leaving by oneself the Apartment lodgings flange.
Runners
For the plenum, cut a length of 3-inch diameter, 1/8-inch wall thickness steel tubing a little longer than the distance from the outside of the first runner to the outside of the last. Weld a circular plate steel plug into one end, and a 90-degree bend of the same tubing onto the other. Fabricate a 1/4-inch-thick flange to fit the turbo mount, and weld that onto the top of your 90-degree elbow, and smooth out all the inside edges with a die grinder.
Assembly
See Resources for photos of a log-type manifold.Using 1/8-inch-thick tubing, weld a 2-inch-long runner to each port on your new exhaust flange, matching the shape of the port as closely as possible. It's perfectly acceptable (and even advised) To possess a larger runner than an exhaust port, but never go smaller. The lip created by a larger runner can actually help to prevent exhaust gas reversion, but a small runner will do nothing but reduce power.
Plenum
You could activity one of two ways with the runner chart: tubular race-header style or log-type. A custom arched header-style manifold Testament always outturn in a superior way performance on the other hand requires a amount of certain tools, techniques and skill sets that are beyond the scope of most body politic's fabrication skills. Log-type manifolds are approximately 80 percent as efficient as tubular manifolds, and much easier To erect.
After grinding a semi-circular depression into your runner ends to fit the plenum, tack-weld the plenum into place with the turbo flange facing up. Remove the plenum/runner assembly, and finish-weld it. Use a drill and die grinder to remove the plenum wall material inside your runners, and grind the inner edges smooth with your runners. You may need to take your new manifold to a machine shop to flatten out your manifold and turbo-mount flanges, but everything should bolt together without any serious complications.
