Fed Up.
 

Alright.

I'm tired of looking at ridiculously expensive cat-back options for our cars.

My solution? The CorkSport 80mm "POWER SERIES" (heh) cat-back exhaust.

Secondary problem: It's a single outlet, and while I have no problem with the single outlet in theory, in practice my rear bumper still has two holes for exhaust.

Is there a plug-up piece for the holes? Or a way I could do it myself? For $289, 80mm (3 1/8") exhaust is a ridiculous deal, and everyone has had good luck with the 2.5" in terms of sound and reliability.

I've even done the math - a single 3" pipe has more volume inside than dual 2.5" pipes (sounds weird, but it's true), so really the 3" is the way to go.

Readers Digest Condensed Version:
Damnit! Somebody tell me how to make a bumper 'hole-filler".

Go to the junkyard, and cut a piece of bumper off. take it to a body shop, have it moulded in, and painted.

Its not brain surgery :)

ok, so it's not brain surgery, but it is early in the a-m, heh. (Couldn't you tell by me not being able to figure a better phrase than 'bumper hole filler'?)

:P

and oh yeah
would the piece i cut out need to be about the same size as the cutout, or do you think that a body shop would be able to do that?

I would just cut out a large piece from the center, and wittle it down till its about an inch bigger than the cutout on all sides, then take it to a shop and tell em what youd like them to do with it.

no man
dont take it to the shop
cut out the peice u need and do it yourself cuz the shop will rape you....hell if i can make my own hood you can make a baby buggy bumper butt pluggerhttps://www.rx7club.com/forum/attach...postid=1833592

k, its not hard, but you are going to have to repaint it...

get some fiberglass mat (small peice, enough to do like two layers), some spray adhesive (3m works best), some fiberglass resin/ hardener (small can of it), and a thing of bondo (fiberglass reinforced or regular, your preference)

first step, take a dremmel or something and cut out the inner lip inside the bumper around the arc for the exaust pipe.... after thats gone, spray the inside of that area with the spray adhesive and then press some fiberglass mat there on the back side of the bumper.... its going to want to cover the entire area that you want to fix... basicaly from the side its gonna look like an L shape, covering the hole and the lower lip of the bumper...

trim it down if its too big (not to critical as you have to do it later anyway, but make it fit preety close, you prolly want to go about an inch over.

once the spray adhesive sets, get a cardboard box that is as high as your bumper (like 5 inches or whatever), and and put some aluminum foil on top of it.

now wedge it under the bumper so that when you put the fiberglass resin on it it wont sag... now go and mix up some fiberglass resin/hardener (follow the instructions) and apply it to the mat using a brush (the brush will be destroyed (unless you clean it imediately with acetone) but it wont be good for much else as it will be really stiff, so id get a cheap brush for this)

you may need to put something on it to keep the upright peice from sagging... i leave this up to you, maybe some aluminum foil....

let that dry for a few hours, till its nice and hard, and pull the box out, pull off the aluminum foil, now put another layer or two of mat on, untill you think its thick enough...

then after that is dry, use some bondo on the front sides of it, to fill in any gaps (there will be some... its best to use a little too much bondo and go over, so you have something to sand off... make the bondo spill over onto the bumper a little so you dont get a seam

now comes sanding, sand sand and more sand, using progressively finer grades of emory paper and a sanding block, untill it is nice and smooth and you cant tell that there was ever a hole there....

now you just have to paint it (either get it painted, or paint it yourself) and you are set

asside from painting it shoudnt cost you more than 20 bucks for the supplies, especialy if you have some of them already

will probably take about 2 - 3 days since you have to wait for things to dry

get a mask (cheap paper one works fine) when you are sanding, or wet sand, cuz you dont want to breath that shit in... and get some gloves... fiberglass itches like hell, and the resin hardener will burn you if it gets on your skin

make sure they are latex gloves... ive had other types start melting on me ;)

haha, damn, its hard to realise how much you have typed into this little box :P

Re: Fed Up.
 

How do you figure a single 3" is bigger than two 2.5" pipes?

A single 3" has a volumn opening of 9.42"

Dual 2.5 have the total volumn opening of 15.7"

Diameter x Pi

very simple.

:D ICEMARK OWNAGE!


Santiago

That fiberglass idea is more work than you need to do. Just find someone with a plastic welder. (yes, there is such a thing) Then sand it and paint it.

Re: Re: Fed Up.
 

Diameter x Pi = circumfrence.

Area = Pi x (radius squared)

That means area of 2 2.5" pipes is about 9.81 sq inches.

A single 3" is about 7.07 sq inches.

A single 3.25" is about 8.29 sq inches.

Both of these are technically smaller in area than the dual 2.5" pipes... however, due to friction and turbulence (more surface area on the dual 2" pipes) the single 3" will flow better... and it's lighter.

I meant dual 2", since that's what's on my car now. I'd forgotten whether I'd calculated it with dual 2" or dual 2.5". Oh well. Whatever.

Thanks for all the help, guys. Now to find someone with a plastic welder :P

if u have to much flow wont u lose torque in the low end? isnt it better to have the 2.5inch so u get lil bit of pressure, so u get that torque?

uh oh I sense another 2309482309848 page thread on single vs. dual.

The backpressure doesn't matter on a turbo car, because it really only helps with exhaust scavenging, and since no exhaust scavenging occurs after the turbo, you want as little backpressure as possible.

Here we go again... :D Two 2.5" pipes have ~40% greater cross-sectional area than a single 3" pipe, but because of the increased surface area they only flow ~25% more. That's based on actual measured data, not just maths. You lose some of that advantage because of the Y, but if it's well made it's not the killer-of-airflow that some think it is. All things being equal (built quality, muffler design, etc), a dual 2.5" system should flow at least as well as a single 3", probably better. Yes it weighs more, but that extra 20lb is well under 1% of the car's entire weight. If you can tell the difference, perhaps McLaren have a test driver spot for you. ;)

BTW, if you do the same comparison with the 80mm pipe (10% bigger than 3") the results are quite different. It would probably flow a bit more than a dual 2.5" system. Of course you could always custom-build a dual 3" system... :eek:

Also, I second finky's idea of plastic welding. Since the bumper's made of plastic it makes sense. If you do all the cutting and shaping yourself, a bumper repair shop (logical really...) or anyone else who can weld this type of plastic (ABS I think) can weld the patch cut from another bumper to a matching section cut from your bumper where the exhaust cut-out is. Then just sand and paint. :)

i don't think you can weld plastic :)

Yes you can. Look up "plastic welders" in the yellow pages. You'll be surprised.