Hey all, I have an '03 A4 Vert which is stock except for corsa pace car and xpipe, and a modified air box (stock box, hole cut open larger and K&N filter). I I'm thinking of doing headers, high flow cats and I know I'll have to replace the xpipe too so it mates up with the headers. What can I expect performance wise and will it drive me crazy from a sound point. I like the nice sound when you put your foot in it, but don't want to go crazy while in the 1500 -2k rpm cruse range. Then the next question is header size, (diameter) whats best and what do I give up with doing this over stock? Anything?? going to talk to some shops, but would like to get you're take on this. Thanks all.

 

Unless you plan on doing a heads / cam setup on the car, don't waste your money on headers. A set of headers (like Kooks or equal) will set you back a $1000 and you'll gain very little - in fact, you might lose if the exhaust pulse isn't right.

As for size, go 1-7/8" tubes, stay away from the 1-3/4" tubes as they will rob you of horsepower if you ever decide to do heads / cam.

With a proper set up on a heads / cam car you can typically expect around 25hp gain from headers, but only if the air intake matches up so the car can "breathe" easiser.

The "noise" is a factor of your exhaust system - if you have Corsa then you'll get some resonance with the headers at low RPM.

The rest is up to you.

 

If you have Corsas you wont have a problem with drone at any rpm.I am not a huge fan of just headers on the street.A good set will set you back at least $1000 for min gain.Perhaps headers and a good tune may make a difference for you.

 

I'm sorry, but I don't agree with much of this and want to see the OP make the right decisions based on his needs.

Longtube Headers on a C5 is one of the milestone first mods to do on any corvette reguardless the path you choose to go with the car unless you need a specific turbo manifold.

Size wise, Its up to your wallet and installation procedures. 1 7/8 is a great header for forced induction, and big NA displacement builds, you can always grow into them! However, I know MANY high power cars running 1 3/4 with no problems.. A few HP left on the table. The 1 7/8 headers also sit tighter to the AC lines and steering shaft, so its a tight install fit.

I dont find headers a waste of money in the least bit. Companies such as XS Power and Texas Speed offer great header systems for a FRACTIONAL price of the high end units. you can make good power on a budget, or go all in for excellent quality and craftsmanship with proven systems such as LG Kooks and American Racing...

The Corsa Indy's are great mufflers. The drone is rather minimal and should not be to big of an issue with your car. You can always swap out to Ti's if its too much for you.

 

thanks all for the information, I have some thinking/planning to do, thanks again, this helps.

 

Woooo!! You saved me a bunch of typing!! Could NOT have stated it better or agree more!!!.

I installed Stainless Works 1 3/4 headers and complete 3" mid pipe and muffler system and a vararam as my FIRST mods and couldnt have been happier!! Got 390 RWHP and 375 TQ in my 02 ZO6 with a tune. The sound was OUTSTANDING and the car performed fantastic!

The Corsa system doesnt drone so,, adding headers wont be an issue. Headers really dont change the sound that much. You will hear a little more valve moise but that really isnt something to even worry about.

When you change the heads and cam,,, well then THATS another story!!

 

ARH 1 3/4 headers, ARH catted X-pipe, Z06 ti catback or Corsa touring or sport. This is quality stuff and it's gonna cost a few bucks, but you'll get your moneys' worth in performance, quality and durability. With the catbacks listed above, it should sound crisp and noticeably better than stock. If you want to save a little, leave the original C5 catback in place, it won't hurt the systems' flow very much. Consider 1 7/8 primaries if you know that down the road you will build to 450rwhp or more.

 

Here too. I picked up a set of 1 3/4 American Racing Headers + X pipe with high flows from East Coast Supercharging. Chris said exactly the same thing, no need for 1 7/8 unless you're running something with big airflow and HP. BTW - I've had the GHL catbacks for a while now and love them. Not over the top but provide a great sound and look great.

 

I have an 02 A4. First mod I installed (myself) was a K&N CAI. No real improvement noticed (and none was expected). Next upgrade a month later included a Ti exhaust and LG SuperPro headers (1 3/4") and a tune, all performed by LG. After tuning the Dyno reported 333 rwhp and 347 rwt. Although I didn't get base readings (before any of the above mods), I suspect "base" is around 300 rwhp and 300 rwt. In any event the performance gain was very noticeable. Us A4 owners don't get as much of a performance gain from our engine mods as will the M6 guys. But still...

Next mods, added 6 months later, included AFR 210 heads and a mild cam, plus porting the intake manifold and throttle body. Post-install Dyno numbers were 401 rwhp and 391 rwt.

Your A4 should respond to performance upgrades about the same as mine did (my 2002 A4 has only 9K miles on the clock - still just breaking it in).

LG told me, when I was thinking about headers, that they didn't make 1 7/8" headers for the C-5, and their website affirms this. They also told me that unless I was going to go crazy with my engine build, 1 7/8" headers were not going to be of much benefit.

Add this in to your other feedback and see where this takes you.

My $0.02 worth - headers were well worth it (although expensive) and teed me up for the heads/cam upgrade. Now I'm done (unless my retirement checks increase enough for me to do something radically different - i.e. supercharger).

 

Yeah headers are useless, not worth it. I trapped 109mph without headers, now im trapping 118mph with headers. Not much of a difference.

In all seriousness, expect 20-35rwhp with the addition of headers and a tune. The car will sound much better. I run the granatelli catback with xspower headers and its LOUD at WOT, yet tame/deep while cruising. People always say they can hear me coming from miles away, but the noise in the cabin isn't bad at all. The 1 3/4" headers are perfect for bolt-ons to h/c setups to moderate blower setups. Stepping up to the 1 7/8" is usually only necessary for BIG cubes or lots of boost or nitrous. If you can get some XS headers, get them. The TSP headers aren't made nearly as well. Kooks, LG, and ARH are the best in the business. If money wasn't an option, I would go ARH. Kooks put out great power, but a PITA to install.

 

I agree with most--- 1 3/4 is fine for N/A engines cammed or stock--The 1 7/8" headers are good for supercharged applications---Bigger cubic inch motors or engines that run mostly above 6500 RPM--Going to big on the hdr diameter will kill off bottom end TQ on a stock cubed engine--
Some headers offered even come in 1 5/8"--especially for camaros
Unless you get a tune you won't get the full potential of adding headers--with tuning 25 RWHP is easy--without maybe 10 or less---
And besides a tune will make your car quicker if it's an automatic with trans tuning alone--
Hi flow cats to me is a waste of $$$ maybe 5 rwhp for what $300 or more ??? not worth the trouble---However an X pipe will add some HP and make the exhaust not ehave more of a race car sound--Even may quiet it down some
PS: use the GM layered exhaust gaskets they seal the best and will never blow out--They are a crush to seal type and once used thrown away-

 

Again, thanks to all,couple of PM's sent. This helps with the process and opens up some options on vendors not considered before.

 

Saved some more typing.
This is the exact results I got with mine. I added the rear compartment divider and now I can hear my radio at low volume with the windows down.
I don't plan on changing heads or cam since the car is fast enough for me the way it is right now. That would be scary fast

 

Go with the 1 7/8" over the 1 3/4" they make more power and down the road if you go S/C you are already set up. As far as sound factor it enhanced the sounds of my exhaust by ALOT!!! I went with the Stainless Works 1 7/8" 3"X and no cats gained almost 40 rwhp with a dyno tune. I did a review a few weeks back couldn't be happier.

 

1 3/4" are fantastic for MOST applications. 1 7/8 are only beneficial if your engine has big inch displacement or FI.

 

pretty sure a vette magazine or one of the performance magazine/websites debunked this one. i dont really care enough to look, but im 99.99% sure that the conclusion was the bigger always is better in this case.

 

Negative why do people have this embeded in their head..
yup Texas Speed did the testing 1 7/8" doesn't loose anything and gains throughout. So yes in this case bigger is better.

 

Again thanks to all....you guys have all been great with a lot of things to think about.
The biggest questions I have are:
- noise at cruising speeds (have a vert and have the corasa pace cars - love them)
- heat - do I need to replace the tunnel with a insulated one
- any smell from the hi flow cats
I've pretty much made up my mind that air induction and exhaust are the limits on my car, no opening up the engine, nothing wrong with that, just not for me. Will do other upgrades like drilled/slotted rotors, wheels and such. So I want to be happy and not create a noisy ride and do it right one time. So if I'm doing this its headers, cats, xpipe (would have to sell my current corasa x), a tune. Am I making any sense?? What in your opinions wold be high end headers to low end, if you were doing it over again, what would do different if anything. Also in my "cost structure" I will have to pay for the install so there's that too. Thanks again guys.

 

You already have Corsa Pace and if you have their x-pipe you shouldnt need a replacement with headers. Atleast not with LG's. I cant speculate on smell with hi flow cats and headers. I have a cam with my setup and didnt do the hi flows until i did the cam. My car still smells. Doesnt bother me. When you smash the throttle with the pace system your gonna know you added headers but coupled with the hi flow cats will remain tame enough. By tunnel i assume you mean where the exhaust lies. No you dont need to replace anything there. However i would recommend some higher heat tolerance plug wires. Hope i have helped you out