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Tippy Tippy is offline
Chain fence eating turbo
Join Date: Dec 2008
Location: Austin, TX
Posts: 8,844
Hp/tq increase going to 4" exhaust?

After asking about a high-flowing, moderately quiet muffler, I thought about 4" mufflers/exhaust pipe post turbine housing (I know, counterproductive to suppressing sound).

Why I ask is the turbo I have on hand has a 4" v-band turbine housing and never remember seeing anyone run such a big exhaust. Diesels run extremely large down pipes with small turbine wheels/inducer/exducers respectively. For reference, the turbo I have has around a 63mm minor with a 102mm (4") v-band outlet. Maybe this aids quick spool?

Then thought, this could guarantee you never have a restriction for the quickest spooling, least backpressure post turbine you could have.

Anyone seen any results or pondered?

Too, and on the other end of the turbo, newer compressors run say a 102mm (4") inlet with say only a 60mm minor compressor wheel. Of course this is due to the area required for surge ports but I'd imagine this bellmouth would a minor supercharging effect. I know this is opposite of the turbine side regards to physics but it seems to help.

I imagine having lots of extra volume for the exhaust could help overall performance of a turbo and there is some potential benefits to adapting the 4" piping.

Old 05-23-2013, 12:42 PM
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