Does the overpipe really make a difference?
 

I'm looking at getting the Perrin exhaust system and I'm weighing up whether to get it with the over pipe, or to just get the catted front pipe and the cat back components.

My question is, does the overpipe really do anything? Perrin quotes a 3rwhp gain but that's pretty negligible on a dyno and wouldn't even be noticed when driving. How does it increase flow being such a small part of the system?

Does anyone have any experience comparing these two setups?

the stock one is 2.16" and has some bumps and dents in it. its probably the biggest restriction in the exhaust system as far as piping goes. the overpipe is definitely worth it! there are a few threads about it already just do a search.

absolutely... nameless has an incredible op?downpipe combo piece that I am strongly considering. What it does is combine the two exhaust pieces together and reduce some of the arc or degress that the op into the downpipe with otherwise create stock.. this improves flow and increases power.

the op is so damn close to the headers.. improving this piece will absolutely create power power than say changing your muffler or midpipe.

It won't add you even 2 hp. Not worth to spend money on snake oil. If you want to mod exhaust, you have to go with high flow cat or just straight pipe. Though it wont be streat legal in most states.

Im in the same boat. I PM'd Nameless and they said it will make a difference but when i PM'd FA20Club about theirs they said no not really, don't worry about it until you do headers. Im currently waiting on JDL to see what they say about it.

Haha thanks for the responses guys. Seems like opinions are divided here.

I wasn't planning on doing headers for awhile. My initial plan was just to do Header back + intake + tune.

dood,
i am not sure what you have on your car or what your planning to purchase 1st but its a waste of your efforts, money and time to just get an OP alone

either do a header/OP combo or the nameless OP/downpipe combo and headers later. this will get you a bang for your buck.. if you do just the headers alone (no OP) your still going to get nice gains but your choking the flow with a stock OP

while the OP is a crucial part of the exhaust system.. being so close to the engine and an intriquite piece.. it accounts for like 8% of the length of the entire exhaust piece and is nothing more than a single flow pipe.

Skip the intake. Here is what I would do in this order:

Tune
Header
Exhaust(sound purposes only)

Everything else can stay stock. The front and overpipe won't get you much.

I've already got a Takeda Intake installed on the car.

So do you think Perrin Cat Back + Borla UEL headers would be a better option than just Perrin Header Back?

I want to keep at least one of the cats in the car and not be too loud. I was thinking of getting the resonated catback.

Its a good idea and common plan but then you have to deal w/ the repercussions of the CEL.

Start on the engine side of your exhaust and work backwards. Muffler is mostly for sound change but doing headers and/or OP/FP will change your sound anyway.

Plus a tune to maximize benefits and fix torque dip/cel if you can.

Is the cel a prevalent issue with changing the headers or is it only isolated cases?

Get the revworks. Better quality. I would get the tune first before you get the header. Tune is what will unlock the most from any header. Also it will help and disable the CEL from removing the cat in the header where the main O2 senzors are. Keep the stock front pipe with the cat.

Yes. Headers first. Then over pipe. Then front pipe. Then catback.

The ideal thing would be to do it all at once and tune right then. That way you're not driving around with all this without a tune, or trying to tune your stock car before you get all this stuff.