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Accelerating From engines to gearboxes--tuning the parts that make your car go.

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Old 01-17-2014, 02:18 PM
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Default Back pressure

Is back pressure a big concern on turbo exhausted systems? On a NA car you would lose torque when you open up the exhaust too big, but on turbos do you lose or gain with the different sizes?

I understand that if you have a smaller diameter exhaust than what was engineered for the car you would have unnecessary pressured on the turbo. I'm more getting at do you really need a 3" turbo back to gain power? Is there a balance where have this size and you get more toque and this size would give you more top end?
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Old 01-17-2014, 03:38 PM
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I'm no turbo expert, but Id say pack pressure will be the same regardless of pipe diameter after the turbo. The larger the pipe after the turbo the faster it spool, but not necessarily the more it will flow. Your exhaust is only as big as the narrowest part. Like on the r53 a cat back won't really do any thing significant unless you get rid of the ridiculously pointless bottleneck in between the pre cat and cat.
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Old 01-17-2014, 03:52 PM
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So the outlet of the turbo dictates the size of the exhaust? You look at a 3" turbo back system, does the opening of the turbo need to be that size or because it's the source it doesn't need to be? Last time I looked at a turbo, after the exhaust has spun the turbo turbine it just kinda flows out of the side which is where the downpipe attached.
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Old 01-18-2014, 09:12 AM
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For the size of turbo that is on the R56 2.5in dp is just right. You shouldn't go to a 3in dp until you have more displacement and a bigger turbo.
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