You press down on the accelerator pedal, waiting. Waiting. Waiting. Your car is moving, but you wait a little longer, and the burst of power hits. Your BMW surges forward. Spool time equals how long it takes your BMW N55 turbo to generate usable pressure as you accelerate from a low speed to higher RPMs. Shorter spool times mean quicker acceleration. How can you improve your turbo’s spool time?
Spool Time vs. Higher Top-End Power
There is often a trade-off between the speed and power a turbo delivers. A twin-scroll turbo will have fast spool time, getting you up to high speeds faster, but it lacks power once it reaches that high end. An N55 turbo upgrade from a twin scroll to a single turbo means longer spool time, often called turbo lag due to the delay. However, that comes with higher-end power that can help your car achieve better half-mile trap speeds. Parts can help mitigate turbo lag, and it’s a careful balance of power and spool time that you need to figure out for your specific build and preferences.
Parts and Upgrades That Affect Spool Time
If you are going to upgrade BMW N55 turbo parts, which ones do you need to improve spool time? A lighter, better-designed billet compressor wheel can help, and even keep the stock spool time when increasing power. Because it’s lighter, it accelerates faster, reducing spool time. Upgraded inlet pipes help reduce airflow restriction. In the same vein, high-flow downpipes and exhausts let gases escape more quickly, reducing backpressure. A turbo blanket and exhaust manifold insulation can also keep gases hotter, increasing turbine speed. All these considerations play a role in what you might look for in a turbo upgrade.
How Your Exhaust Flow Drives Your Boost Response
Finally, you’ll want to think about exhaust flow as well. Exhaust flow reduces turbine backpressure while increasing gas velocity. In short, higher exhaust flow can significantly reduce lag time by speeding up the spool time. As mentioned, high-flow exhaust pipes and downpipes are excellent for letting gases escape. This reduces the pressure differential, spinning the wheel more efficiently. Gas velocity matters in the manifold, before it hits the turbo, as it spins the turbine faster. Even having pipes with too many bends can affect exhaust flow, so a smoother exhaust flow helps turbos spool faster.
About Vargas Turbocharger Technologies
Based in Hayward, CA, Vargas Turbocharger Technologies specializes in designing and engineering turbocharger upgrades and components. VTT™ offers a range of brand-new turbos for several vehicle makes, including BMW. They also offer a range of expertly rebuilt OEM turbos for select vehicles. Whether you’re searching for a comprehensive turbo kit for your high-performance BMW, you want to upgrade other systems (engine, fuel, drivetrain, etc.), or you need service on your turbo system, VTT™ has the solution for you.
Find the custom-designed turbos and parts to reduce spool times at https://vargasturbo.com/
This article was originally published on vargasturbo.com’s blog here.
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