Ok, so Ive got my 4-2-1 Headers in and its badass (Deleted Pre-Cat)
I noticed more torque right away, and the cat back was 2.5" piping (I know most o' you do 2.25" but I figured I shoot for the middle, for that Turbo install later on)...
Today since Im moving to Florida and theres no inspection/emmissions, I said "To hell with it, I want more power!" and deleted the main Cat as well as upgraded the rest of the Exhaust to 2.5".

So now I have a Headers and a 2.5" exhaust all the way, w/ no Cats, only I dont really notice anything, I feel like I may have lost power, cus I dont feel that boost I got when I first had the Headers put on (w/ cat and stock pipe). Its just louder. Thats it, it seems.

Whats the deal, is it just me? Is it prolly just gonna show at higher revs instead of low revs now? Dont tell me that lil' 1/4 inch makes so serious a differance and reduces backpressure like that... thats like Night and Day differance from a 1/4", C'mon! ???

(Tho I will say, I have a tiny leak where the Header meets the Downpipe, I just need to put 2nd gasket in there.)

Can I do sumtin' about this?

This is really fu(kin' with me...

 

Did you get rid of the cat underneath your car?
If so put the old one back on.

 

There are 0 Cats.
Hmmm, so you think that (the Cats) pressure being gone is whats causin' this?
Thats actually makes some sense, I didnt think about that...

 

put a high flow 2.5 on there and you should be fine... and were did you get a 421 header from?

your exhaust is pretty much what mine is... i just wish i had gotten the rpw header instead of RRM.. but then when i got mine there was hardly any rpw presence on here

 

The 4-2-1 Header is actually a Mirage Header from OBX.
Its better than the RMR or RRM, and looks nicer too.
Oh! and is half the price.
(Their a beautiful Chrome/Stainless Steel, but wont stay like that. They'll turn Gold due to the heat. I think its cool lookin' actually.
Yeah... its the smart way to go. A couple people on here did this, so it can be attested to.
Thanx to Alchemist I got it put on the right way (theres a small downpipe issue with the Mirage Headers), he was a big help

 

Nice job but without a cam you are probably not gonna push enough air to get the backpressure you need with a 2.5 exhaust.

I've got 2.25 and have no real complaints. Maybe throw in a resonator instead of the cat if you choose and it should add a little back pressure while quieting things down considerably.
I had to get one installed as the noise at 80 on the highway was unbearable. Driving around town though on short trips it didn't affect me.

WADAD

 

Agreed, you have lost some torque with the lack of back pressure.

Also, have you changed your DP?

 

Can you explain in details how is it better than RRM header? I'm really curious!

 

From what I've heard the rpw headers have some kind of long tube shape so there is no loss in torque, perhaps even a gain. there was a thread a while back that has people arguing about it for 20 pages or so but the rpw guy on the boards is confident his design gives you more gains in a broader range (they are more expensive though). this is interesting though cause i'm doing my exhaust next week and am wondering if i should buy a header and do it all the same time. if i go with magnaflow muffler, resonator, stock cat, and rrm header should i only be seeing nice gains or am i gonna loose torque like poor cityknight?

-cityknight you definitely lost pressure. other people on the boards with your setup noticed no gains, and even some torque losses when everything was opened up. look into a highflow cat or stock cat. 2.5 is supposed to be a little too big as well but hopefully cat will solve it

 

oh woops i forgot he was using mirage header. ignore my comments earlier

 

<--- my rpw race headers due in this week! I'm giggling like a little schoolboy!

 

unless you are turbo, you need some kind of backpressure or your torque will suffer. put a hi-flow cat in place of your stocker.

 

your lack of backpressure is what killed your power. Combination of 2.5' exhaust and no cat equals no torque on a naturally aspirated lancer. Even with turbo 2.25 flows fine. you don't need anything bigger unless u are making like a 300whp lancer, and the majority aren't

put in a cat to get back some backpressure, if you are still missing lowend put in a resonator. Pulley and tuning will help give you some good low end torque.

 

Ask Alchemist he can explain it better than me.
It has to do with the fact that its a 4-2-1 rather than just a 4-1.
Dont everybody start PMS'in on me now, just cus I said somethings better than RRM...

 

Aright question tho... I High Flow Cat, is meant to be less restrictive.
The impeadance is what creates back pressure however... Therefore, with a 2.5" exhaust would it be wiser to use the Stock Cat or no?