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Just check out the torque curve with 350 Nm between 1250-5000 rpm. Yummy!
And in case no one noted the bore of 84 mm is bang on the GRE center spec. Expect to see derivatives of this engine in DTM, Rally and GT cars. I would not even exclude F1 mid term.
Ulrich Baretzky wrote:Source
We looked at the block, and decided it was 84 mm bore for example + or - 3 mm, so you could start with an 82 mm bore or you could go up to 87 mm bore.
Todd DeMeza, Modified Mag wrote:So what makes this twin-scroll turbo so special?
After searching for a long, in depth article on the subject of twin-scroll turbos, the best one was found over at Modified magazine written by David Pratte titled Twin Scroll Turbo System Design - Divide And Conquer?
For those who don’t know what a turbocharger is, it is a supercharger driven by the exhaust gases of the engine. The more air you can get into an engine, the better the combustion, power and so forth. The Turbocharger is the most efficient supercharging system because it uses the exhaust (waste) gases created by combustion.
The key to having an efficient motor, turbocharged or naturally aspirated, the exhaust gases need to leave the combustion chamber completely and smoothly. In a perfect system, the exhaust gas leaving the exhaust manifold will leave a low pressure pulse. The exhaust gases are being pushed out of the combustion chamber is in a state of high pressure, and is attracted to this low pressure area. This is known as exhaust scavenging.
In a single-scroll turbo system, especially one with an unequal length exhaust manifold, all cylinders exhaust gases interact with the flow of each other. Just as the exhaust gases have left one cylinder, it is just leaving another. The low pressure pulse isn’t there.
This can cause the opposite of scavenging called reversion, where the exhaust gases go back into the combustion chamber which creates higher temperatures, less power, and more NOx emissions. To remedy this manufacturers have the exhaust valve open as long as possible before reversion occurs.
The a twin-turbo setup, especially on an inline six like the N54, has a better scavenging effect because the six cylinder exhaust system is split in two, with three cylinders for every turbo. This split creates the opportunity for low pressure pulse to occur in the exhaust manifold. But twin-turbo systems are complex and have a higher weight than a single-turbo system.
A twin-scroll turbo allows for the benefits of the twin-turbo system’s exhaust without the weight and complexity. The exhaust housing of the twin-scroll turbo is split in two, one path for three of the N55’s cylinders, allowing exhaust scavenging to happen. The exhaust is also coming in twice as often than a twin turbo setup, which had to be split up. This then spins the compressor side more consistently.
According to Pratte, “With its greater volumetric efficiency and stronger scavenging effect, higher ignition delay can be used, which helps keep peak temperature in the cylinders down. Since cooler cylinder temperatures and lower exhaust gas temperatures allows for a leaner air/fuel ratio, twin-scroll turbo design has been shown to increase turbine efficiency by 7-8 percent and result in fuel efficiency improvements as high as 5 percent.”