Review – Doc Race Turbo Manifold – SR20DET


A true twin scroll exhaust manifold separates the exhaust streams from pairs of cylinders all the way to the turbine housing which is also divided into two sections or “scrolls”. This prevents exhaust pulses from interfering with each other and enhancing cylinder scavenging for improved efficiency. Given the exhaust pulses now work together, the turbo will spool more quickly at lower engine speeds reducing lag and improving response, a perfect set up for drifting.

Building an efficient exhaust manifold to accomplish this effectively is an increased challenge for a manifold builder. Space limitations, placement of waste gates, geometry, runner size and length are but a few of the factors that must be considered.

DOC RACE built our true twin scroll manifold. This is the T3 flanged version. While DOC RACE offer v-band, it seems the flange may be the better way to go given complexity at the turbine inlet and waste gate ports.

The manifold delivered by DOC RACE is a work of art in that it is well designed to achieve performance and the workmanship is extraordinary. While we did have to make a slight adjustment of one wastegate flange for our configuration (twin scroll makes it a tight fit in the engine bay), the manifold is otherwise an excellent example of how it should be done. We expect that DOC RACE will incorporate our adjustment in their production design going forward.

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The manifold itself is exceptionally well built. The welds are all clean and smooth creating an excellent flow path for exhaust gasses.

The use of a twin scroll manifold will add some complexity, cost and time to the install. In a tight space, there are no more components fighting for space and plumbing becomes more a challenge. We found the one and only position to clock our turbo components. We did find space for everything although the turbo oil drain line did create some challenges to the install.

2015 turbo install-4

Performance results on the dyno confirm excellent spool up performance as well as excellent top end performance. While a brand new component for us, we very much like the overall quality and robustness of the manifold and expect that it will perform exceptionally well for many years. After the end of a pro-am series and a full Formula Drift Pro2 season, the manifold remains perfect.

We strongly recommend DOC RACE exhaust manifolds.