Drop-in overpipe replacements
 

Am looking to replace the stock overpipe with an aftermarket one. I'm on stock headers and front pipe, which I'm looking to document the changes before and after.

If the overpipe is sold separately, I would assume the overpipe would fit?

Thanks!

Yes, headers, overpipe, and front pipe are all typically sold individually and will bolt up to stock versions of the others. There are some exceptions like Ace headers but those are uncommon.

You will probably need new gaskets each time you replace exhaust parts so if you plan to do more, you may want to do it all at once.

Upgrading the overpipe is not going to give you any performance improvement by the way, and may cause your sway bar bushings to melt without a heat shield.

FWIW: Nameless makes a one piece overpipe/frontpipe It eliminates the extra joint.

Thanks. I'm fully aware of the potential no-gains from swapping the overpipe, just find it odd that there is no gain despite having the smallest diameter section from the rest of the exhaust.

The main bottlenecks on the stock exhaust are the catalytic converters because they add a lot of surface area which causes drag in the flow. Next would be the muffler because it dumps flowing gasses into relatively stationary chamber and then relies on the increased pressure to re-accelerate the gasses out the tailpipes. Minor changes in pipe diameter like the overpipe or resonator and curved direction changes are a distant third cause of lowered efficiency.

the one bend in the stock overpipe is horrible for restriction. I bought my overpipe to match my header thinking it couldn't really do much, but looking at the stock overpipe, that one bend(front one IIRC) is just grossly restricted

Basically get zero difference with overpipe alone. I think it probably matters more when you add a header with merge close to the OP.

I logged a bit with Gruppe-s UEL header and everything stock, then added the matching brand OP and saw no difference in fueling adjustment at wide open with OFT OTS tune at the time.

My current setup with JDL 4-2-1, Catted resonated FP and CSG touring I logged with my tuner using 2.36" Gruppe-s OP then swapped a 2.5" OP and no difference in logs. My whole system is now 2.5".

Did see a bit of a difference when I briefly tried a Cattless front pipe in logs. Air fuel went roughly half point leaner from stock FP would shows some flow improvement. Catted front pipe maybe restricted flow ever so slightly but zero difference in perceivable power.

don't waste your money. tune + catless header basically only need to be changed for power.

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