Is there a verdict on if replacing the OEM overpipe is worth it?
 

I have been researching this for days and cannot get a consensus with any data. Some people say the stock overpipe is fine unless your are looking at FI. Others say it is too small and matters. I’m talking strictly HP gains, not sound.

I have Tomei header I installed and adding a Corsa catback this weekend (hopefully; please FedEx). I bought a Tomei expreme overpipe, but the stock over pipe is so fkn hard to get out, I am thinking about leaving it, if the HP gain isn’t there.

So, is it worth it to go through jacking up the engine to get the overpipe out (pulling it from the back of the car)?

In some 4-2-1 designs the overpipe becomes an extension of the collecter/merge pipes. I know this holds true for both the ACE and the JDL header. For such a small/inexpensive part so close to the header I would replace it for continuity sake.

For your Tomei header, it won't hurt. The cost/time/effort justification is up to you.

Thanks for the reply. Do I actually have to jack up the motor? I have heard you can just remove the heat shield, but conflicting info there, as well.

I googled around and the best I can find is that the stock overpipe diameter is 2.118". I also have the Tomei UEL header and a DC sports overpipe. When I installed the header, i measured both diameters and they matched (within a mm). The would be the biggest thing I would think that could have a positive/negative effect.. If you were stepping down in diameter from the header collector to the overpipe, that might not increase gains? Now I would assume as you go back toward the rear if the diameter was consistent throughout (or at least didnt step down) you'd be looking at potential gains? Just thinking out loud here.

Jacking the engine up an inch from undoing the motor mount makes swapping out the over-pipe a 30sec job. Much less headache than removing heat shields.

Great reply, thank you.

I am seeing the Tomei front pipe is 60.5mm (2.38189"). That seems pretty negligible of a change over the stock 2.118".

Was it difficult to get your OEM overpipe out?

X1000 on jacking up the engine. It is so simple you'll kick your self for not doing it sooner.

Unbolt right side engine mount bolt which is easily accessible, stick a piece of wood(or in my case a hockey puck) on your jack and lift the engine up via the oil pan.

Lift until you can slide it out. About an inch is all you need.

Ps good luck with that exhaust setup. I uninstalled my Corsa before adding gruppe-s header.

I saw drift offices dyno video with that setup and seemed too loud for me.
Upload some clips once you get it installed.

The stock overpipe is much smaller in its bends.Jacking the engine sounds easier though i removed the heat shield and jiggled it out PITA.

Just jack the engine. It's easy

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The overpipe and the old aftermarket header were on there when I bought it. The old header was trash so I got a Tomei UEL. I cleaned all mating surfaces (collector flange and block side with one of those green scrub pads - new) and with the Tomei gaskets, i had ZERO issues mating up to the DC sports overpipe that was already there, nice and tight fitment but minor manipulation to get it and the gasket and header set to the overpipe.. My exhaust wrap went two layers at the flanges but even then i was able to get an open wrench on the nut side and my torque wrench on the bolt (rear) side and tighten every thing down easily.. FWIW, i used a crows foot 14 and an extension to get the one bolt on the drivers side block flange.. super easy install. but yea i measured them both before i put the new header on.

I will for sure. Only the Tomei UEL is installed now and it's still to subdued (and I do not like super loud exhausts). I am keeping the stock front pipe for the cat in it

Okay, good to know. I am going to have the car up on a lift, so I would rather go the heatshield-removal-route. I am pulling it out the back because I do not want to remove the header again. Which way did you pull out the overpipe?


Did you jack up the engine or just remove the heat shield?

https://www.youtube.com/watch?v=a9jGtvmtflA

This video actually makes it look very easy to jack the motor up. It's just one bolt

The aftermarket overpipe was already installed prior to me buying the car.