| skipjack |
08 November 2002 10:21 AM |
Just found this on the IWOC site about the new WRX 03: if true, does this mark the end of the beloved burble?
"In an effort to squeeze out more torque from the 2 litre STi engine, Subaru have changed the turbo to a twin scroll design along with some pretty nifty exhaust headers. The twin scroll term means that the fan bit of the turbo effectively has two inputs into which the exhaust gasses blow. The exhaust headers are required to get the relevant cylinders connected to the relevant side of the turbo inlet.
"The boxer engine employed within the Impreza has a 1-3-2-4 cylinder firing order where the cylinders adjacent to each other 1 & 3 fire in sequence and then wait until the two on the other bank 2 & 4 fire. This means that the exhaust gas pulses from those adjacent cylinders mix such that the second pulse sees a back pressure.
"The new headers take the gases away from the adjacent cylinders in two separate pipes and connect them to the cylinder which then fires 180deg from it on the opposing bank (1 with 2 and 3 with 4). Thus there are pulses flowing down the pipe at equal intervals. The gases are kept separated up and into the turbo because of the twin scroll design.
"As people who have fitted equal length headers know, you lose the distinctive Boxer beat. Now that would be a bit of a bombshell."
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