After some research into different turbo upgrades available on the market, I decided to go with the BorgWarner EFR 6258-G Twin Scroll unit supplied by Van Der Lee Turbo systems (Jaap), to replace the Esprit’s single scroll turbo charger. One of the biggest limitations of most factory single-scroll turbo system is the restrictive nature of its log or compact unequal-length exhaust manifold.
The design characteristics of both Manifold and Turbo were honed with collaboration between both Van Der Lee Turbo systems and Alunox engineers. Bringing the two companies together allowed me to get a twin-scroll (pulse) turbocharger system yielding maximum efficiency.
Divided or “twin-scroll” turbos and manifolds have emerged as the preferred design of many of the top tuners and even OEMs. To list some of advantages of the twin-scroll (or two-pulse) verses the Single-scroll (or constant pressure) turbo systems:
- Superior scavenging effect
- Better pressure distribution in the exhaust ports and more efficient delivery of exhaust gas energy to the turbocharger’s turbine
- Allows for greater valve overlap
- Increased turbine efficiency
The engineers in BorgWarner’s Advanced Aftermarket Product group created a wish list of every notable design characteristic when designing the EFR (Engineered For Racing) Series. They used materials that had never been combined into an aftermarket turbocharger. They delivered quick boost response, powerful performance and reliable durability.
The EFR 6258-G has an Aspect Ratio (A/R) of 0.8 and a low inertia 58mm Gamma-Ti (Titanium Aluminide) turbine wheel weighing 50% less than typical units. The turbine wheel is optimally matched with the FMW compressor wheel for maximum response and fast spool up.
So effectively we have a twin scroll manifold matched to our twin scroll turbo, designed for flow and pulse tuning. For the Esprit the firing sequence is 1-3-4-2 and the conventional single-turbo arrangement has all exhaust manifolds connected together at the exhaust turbine. The twin-scroll turbo splits into two separate paths and exhaust flows hit the turbine blades independently.
This prevents the two exhaust streams to interfere with each other.
I found many Video references on YouTube for Twin Scroll Turbocharging but this one seemed to explain the principle.