NeverSatisfied02

iTrader: (12)

Ahh ha!! So it is a 3" collector on the OBX!! I thought so but when I heard it was 2.5", I had to look into it myself. Lol that makes me feel a lot better! Pretty headers BTW and thanks for posting the pics bud!!

I'll be staying OBX after all since they are indeed indentical to the kooks anyway and both have clearance issues with the steering shaft on the 1-7/8 headers. I'll just put a minor dent in my primary and be done with it.

NeverSatisfied02

iTrader: (12)

So now that I know the collectors are 3", is there an advantage to full 3" exhaust over the 2.5"?

Fuzzy_Wuzzy

iTrader: (8)

It looks like it does neck down to 2.5" right where the pipes merge then flares back up to 3" for the connector.

I think it is down to a cost per HP if you want to compare OBX vs Kooks, if comparing kooks to kooks it is probably worth going bigger for the smaller cost increase.

DMM

Not unless you're shooting for over 1200 hp.

vmapper

iTrader: (8)

Sorry, should have done this in the first place.
3" on smallest O.D. portion of the collector.
1 7/8 primaries, however, the I.D. near the head is 1.75" for some and others are 1.9" .. f*%k Looks like someone forgot to grind... (1st pic vs last pic)

NeverSatisfied02

iTrader: (12)

Thanks for the pics again bud!! Either way, the OBX look nice. I'd bet you'd find some minor flaws on the kooks if you looked that close as well. Im sure its hard to get them 100% perfect and flawless. And even if they do vary between 1-3/4 - 1-7/8 on the primaries, i can't see that hurting anymore than denting the primary for steering shaft clearance so i'm sure they are just fine. Still a major power upgrade over factory manifolds.

I was asking about the 2.5" vs. 3" because I just bought a cut up B&B catback. I have the 3" X pipe, 3" mufflers/tips and the 3" kooks connector pipes for the headers but everything in between was previously fabbed to fit the headers and around a 9" rear on another car so it was all useless from being formed differently than id need it so we cut it all apart. Debating on whether id be better off paying to have the exhaust shop put the 3" all back together on my car and run the B&B or just throw on the 2.5" magnaflow catback i have in the garage. Only reason im hesitant to use the magnaflow is because it has yet to be cut on yet and its perfect. Almost thinking since the B&B has been cut and i need to cut for headers anyway, maybe i should just have the exhaust shop fit it to my car and be done. Maybe throw some cutouts in later.

Fuzzy_Wuzzy

iTrader: (8)

one other thing to consider is that there is a difference in a very short neck down to 2.5" with a 3" exhaust behind it, and a 2.5" exhaust the entire way. (blow through a short section of straw then one much longer)

NeverSatisfied02

iTrader: (12)

If I go 3", it would all be 3" from the 3" collector back.

I get what youre saying though so which would be more beneficial?

vmapper

iTrader: (8)

FYI

Kooks connector AND the OBX resonator connector are 3" down to 2.5". The 3" side mate up to the header collector and the outlet back is 2.5"

NeverSatisfied02

iTrader: (12)

I know that but the looks connectors have been cut and made 100% 3" for the B&B. My obx is still the way it came but if I got B&B, I'll use the custom made kooks solid 3" connectors and if I run the magnaflow, I'll keep my obx 2.5" reducer connectors.

1989GTA

Does the OBX headers have the "spike" in them? How about the Kooks?

wcryan

iTrader: (2)

I had a very bad experience with OBX. But if I would have done what I tried the second time, it would have been easier (used a different shop the second time)

They had to cute one of the primaries and re-weld it.

It was bending my steering shaft...... That's how bad it was

NeverSatisfied02

iTrader: (12)

Damn... That sucks. I'd imagine that's pretty common if u just install the headers without clearancing for them by denting the primary or grinding on the steering shaft.

So is 2.5" or full 3" exhaust more beneficial on this car?

vmapper

iTrader: (8)

OBX does.

NeverSatisfied02

iTrader: (12)

Wtf is a spike? Lol

vmapper

iTrader: (8)

Its deceiving in the picture, but its a few inches in height. Part of the collector.


Here is a better illustration.
http://www.coneeng.com/ (bottom center of page)


Here is an article on it. Supposedly helps with velocity and air turbulence
http://www.carcraft.com/techarticles...rbs/index.html

Here is OBX

NeverSatisfied02

iTrader: (12)

Oh ok. Makes sense now! I remember seeing that on mine. I think my kooks had it too on my old car. Thanks for answering all my questions btw. The pics are def helpful!

itsslow98

iTrader: (18)

I highly doubt you would see anything gained by going full 3". I would imagine you could find similar gains just by going with a less restrictive set of mufflers on 2.5" exhaust.

NeverSatisfied02

iTrader: (12)

That's what I'm trying to figure out. I sold the corsa mufflers so I need to go early tomorrow to cut them off the car and either install the magnaflow or the B&B. Magnaflow is complete just like u would buy it. B&B is just mufflers/tips, 3" x-pipe and 3" connector pipes but the rest would need to be fabbed together. Not a big deal but it'll prob cost a little more. Just don't know which i'd rather run.

The corsa sounds great at idle but it's got a higher pitched scream than I like at WOT and it still has a little bit of that pingy raspy sound my car had when I had no mufflers because I'm running catless. I think the B&B and magnaflow will both sound deeper and more the way I want it to. Just gotta decide tonight which route to go. Main difference is 2.5" or 3". My main attraction to the B&B is the nice 4.25" tips! I'll prob add cutouts later regardless which one I decide to run.

Big Bu Bu

iTrader: (4)

Back to your original question, this debate rages on daily on forums everywhere. Like this one Same dyno, same brand, same vendor 1 3/4 vs 1 7/8. After reading countless threads, there is no real credible empirical evidence that one size is better than the other on a 346. That's a decision you need to make on your own from what you hear and read. I say do whatever you feel like without the worry you made a bad decision.