Nismo OEM exhaust compared to aftermarket...

Lenny

there are two cats; one per header

in most exhaust layouts, the catalic converters are where a lot of back-pressure builds up due to the setup, hfcs free up that pressure and allow for a briskier throttle response, though often at the expense of some high-end power (loss of back-pressure in high rpms tends to lose hp, tho i'm not sure if thats the case with the Z)

370Zsteve

It's not the case:

Run Details

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SOLD MY Z MARCH 2018 - another Core OG moves on - new ride 2019 Z Corvette Grand Sport - no mods necessary but already have eyes on HFC and intakes LOL IT NEVER ENDS.

Jordo!

Generally, without raming more air in, a less restrictive exhaust will often lose some low end power while picking up some high end power -- this is because optimal cylinder filling tends to happen higher in the rev range, at which point, smaller diameter piping or cats may be somewhat of a restriction.

However, at low speed, when there is less cylinder filling, those "restrictions" are closer to approximating optimal exhaust flow under those running conditions.

So... in short, extra exhaust flow is only helpful when/if you are sucking in enough air to take advantge of it.

In real life, you end up with some sort of compromise, and then tune around that.

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Enjoy it. Destroy it.