The Full Bolt on SR20 Engine, Part One, The Basics

The GTX2863R with a 3mm bigger compressor wheel has slightly more inertial mass than the Disco Potato’s 60mm wheel but we believe that the improved efficiency of the GTX2863R will come close to canceling this out when it comes to turbo lag.  The newer turbo is vastly better in all parts of the compressor map except the very bottom at really low-pressure ratios.  We feel that the newer turbo will spool right through this area in the blink of the eye and it will not be perceived by the driver.

What can be better, spool as fast as one of the fastest more responsive turbos on the market with the ability to make 80 more hp and to deliver the air at our target power levels much cooler with low lag and less backpressure.  It is big win all around!

The GTX2863R uses a floating dual ball-bearing center section.  Ball bearings are mechanically much more efficient than plain sleeve bearings and can improve transient spooling by as much as 20%.  They can also spool about 500-800 rpm quicker when coming on boost.  Garrett’s floating bearing cartridge damps high-order vibrations which improves turbo life.

For mechanical simplicity and compatibility with many options of manifolds as well as the stock exhaust manifold, we decided to stick with an internal wastegate.  You can see .86 cast into the turbine housing which indicates that it is the large .86 A/R housing.

For an exhaust manifold, we chose the tubular stock location header/exhaust manifold made by ISR. Let us go on record as saying we are very impressed with this manifold and we are amazed that ISR can bring this much quality at such a low price point.

The ISR manifold is constructed of tig welded thick wall stainless steel and features close to equal-length primary tubes. It can be interchanged with the stock manifold and is compatible with stuff like downpipes and O2 sensor housings designed for the stock turbo.

The flanges are thick, warp-resistant stainless that looks to be CNC Plasma cut.  Every primary tube is reinforced to prevent cracking at the flange.  Stainless steel has half of the thermal conductivity of regular steel and cast iron.  This means more heat energy to drive your turbo and less heat is going to get radiated into your engine compartment.