Project 240SX Land Speed Racer: Better Living through Volumetric Efficiency


Borg Warner EFR 8374 Turbo Twin Scroll Design

The twin scroll design cleans up the exhaust stream by separating and strategically timing the exhaust pulses, ultimately improving turbo response.  This is done with a specifically designed Full Race Motorsports' EFR turbo manifold, which properly pairs the cylinders by firing order into the two divided turbo housing scrolls.
Full Race Motorsports EFR turbo manifold

Specifically, the Full Race Motorsports manifold merges cylinders one and four into one half of the turbine housing and cylinders two and three into the other half.  This configuration ensures that the exhaust pulses have a clean, unimpeded pathway while the equal length runners strategically time the arrival of the exhaust pulses to promote exhaust scavenging.

Full Race Motorsports applied a thermal coating to the outside of the manifold in an attempt to keep engine compartment temperatures in check.  In addition, 5523 Motorsports, swapped out all of our exhaust studs with Inconel studs from a Nissan GTR.

Borg Warner EFR 8374 Turbine wheel

The key player behind the EFR turbo is the gamma-ti (titanium aluminide) turbine wheel. Your average run of the mill Inconel turbine wheel weighs about twice as much as Borg Warner's gamma-ti wheel.  It's absolutely crazy to hold one of Borg Warner's gamma-ti turbine wheels in your hands while holding an Iinconel wheel in the other.  The difference in mass results in a large reduction in rotational inertia which equals kick ass spool response and overall power.

Borg Warner EFR 8374 Turbo diagramOriginally we were planning to use an internally wastegated version of the EFR 8374 to maintain a tidy, easily serviceable package.  The Borg Warner engineers spent a lot of time optimizing the internal wastegate set up of the EFR series turbos.  In the diagram above, you can see how the wastegate port is split in two to ensure that excess exhaust from each scroll is diverted.  This is to maintain equal balance on each side of the turbine wheel.

Leave a Reply

Your email address will not be published. Required fields are marked *