vforrest

I have a 05 M6 3lt that I had in a speed shop this March with 30k on it, put on an Edelbrock 554, ATI balancer, Catch can, 160 stat into Borla S Type II axle back...some new rims and skins because I'm weak. 5 lbs. boost, 13% air/fuel ratio 13 degree's of timing and has been running great. Dyno 492/467 so it is lot's of fun but everyone got on me because I left on the stock headers and cats.

So they say I'm losing 20-40 HP being stock but was PETRIFIED I would get DRONE so I'm easing into aftermarket headers and cats. I drive at highway speed and just would be so pissed if I get out on a road trip and my wife looks at me with that WTF look because of the drone.

So what I have learned is that I need 1 7/8 headers because it is FI and it will be tuned again with HP tuners and I really like my wrench he's sharp. So I'll lose a bit of boost maybe down to 3 lbs. which is OK by me as I hope my low boost idea also is easier on the engine longevity.

Questions:
LG, Kooks, Stainless Works (all with cats) have caught my attention with the last one at just under $1600. My shop sells LG and I don't mind them making a couple buck off product too but I think it's like $500 more. Any real difference here?

What's my sound change going to be? My wrench said if they are not to my liking he could put resonators in to tame it down.

I know it's going to breath better but my SC in one bolt on got me 150 HP at about $47 per HP. Now if I pick up lets say 30 HP it will cost me $69 per HP...not a bargain comparatively speaking. Doesn't seem like I'm getting much bang for my buck with headers. I'm not chasing some final number as it is what it is to me....much faster and much more fun with the SC. I already have surprised a number of challengers with my stealthy looking 05....

So far I love it...very clean...tight as a drum. So my last years winter project turned out great with all the decisions I had to make along the way I ended up with exactly with what I wanted. Great drivability with easy shifts at 3,000 rpm and no boost kick in. 2,000 mile road trip to NC and back and got 32.5 mpg cruising at 2,000 rpm and like 78-80...freaking loved that. And anytime I get a hair up my **** and jump on it, the low end grunt just pushes me back in my seat and puts a smile on my lips....

Thoughts....? Someone tell me I just got to do it because.....?

realcanuk

If you are happy with the car the way it is , don't put headers just because people are telling you too. Yes, you can make a bit more power, but if you don't care about that, then why bother. You mention 13% afr. I you mean 13 to 1 and that is at full throttle, it is too lean and you are risking damage to your motor. I would question your tuner on that number.

Streetk14

Agreed on 13:1 being way too lean. Hopefully that isn't where your engine is set for WOT operation. I tuned my own car to be in the 11.2-11.3 range, but I wouldn't go any leaner than 11.8:1. That's just me, though.

I don't see many downsides to headers if you buy a good brand and have the right axle-back. I would go with either ARH or Kooks. I would never buy a set of LG headers again. You can PM me if you want, but they wouldn't be high on my list after my experiences.

My car is just as quiet as stock on the highway, but I have NPP mufflers that are controlled via my DashLogic. When the flaps are closed it's as quiet as a mouse. I'm not sure how those Borlas will sound with headers.

My experience has been that headers really don't affect drone, but they will make the exhaust tone louder and more aggressive. A dual-mode system is priceless for those times you want it really quiet. Corsa is another option that is very quiet at cruise, but is always loud when you hammer it. Lots of options on mufflers.

I think I tried to steer you away from the Borla mufflers back when you were doing this build, but maybe I'm thinking of someone else.

Nosferatu

if by 13% you mean 13.1 AFR that's extremely bad.

With the level of boost you're running it's almost not worth running the boost.

The drone is really not even noticeable on my setup at all. I'm catless and supercharged. I do have mild to wild and never place it in mild mode. Here's a demo clip of me screwing with it when I first got headers (no supercharger).

It's fine on the highway. All you can hear is the tire noise. It sounds like a luxury car with the valves closed until you get over 3500rpms when it opens anyways to wild.

breecher_7

I live right down the road from you. Shoot me a PM with the name of the "speed shop" that did the work please... Also before you spend another dime let me know what you are looking for as far as power goals. My friend is probably the best tuner in the region and does the tuning for several of the local shops, its possible he did your car. If thats the case I assure everyone that the AFR is NOT 13.1 at WOT...

I would personally go with a set of American Racing 1 7/8" headers (best quality you will find and I can set you up with someone that will get you a VERY fair deal on these) and get the catless x-pipe. Even if you get "drone" it wont be that bad and your engine is much happier. I would also get a smaller pulley and crank that thing up a bit. That is VERY conservative and rediculous, your engine will live a long life at 10-12psi with the proper tune. 600+whp would probably be good for you.

Now if your thinking you dont want more power, let me take you for a ride in a 1000+hp C5 and maybe you will be hooked.

vforrest

I must have the air/fuel ratio number wrong I'll have to check my notes for the actual number....I was surprised at how lean the factory ratio was when we did the baseline pull and the post SC was much richer....time to go and hunt for that.

Love my Borla's so really there hasn't been a decision I have regretted (lucky me) so far. The note when I get on it is excellent and love the low hum when at cruising speed. I don't want that to change much which is why I wonder what headers will do.

So now I have to referee on opinions again which is no big deal as I had to do that when planning out my build to start with. People advising on both ends of the spectrum centri vs. roots...catch can or no catch can and on an on and I'm not complaining at all, it just reminds me that it takes many different people/opinions to make our world go around. CF has lots of information on it but you won't find many unanimous opinions or even consensus some times.

So some have said not to worry about cats and I like saving $300 and don't have them put back on including my speed shop which has figured out a way to keep the computer happy and the check engine light off. Another mechanic (not a speed shop) friend I also trust has a local 8-10 mechanic shop that does routine work for me on my other cars...also does state air emissions testing for the state to get your annual registration. He said definitely go with the cats or leave the OEM on as the states computer plug in system is suppose to pick up EVERYTHING that has been done to fool the car computer. And reminded me that there is a fine if they catch you. The data they get when plugging in goes right to the states database, not the local shops computer.

Thanks for the help on opinion on the LG and offering other ideas...that experience you guys have is really priceless.

I have the kit pulley on right now and with headers I certainly could go smaller but understand that at idle other accessories may get starved for power like the steering pump...my steering already groans when I'm cranking the wheel at idle leaving the driveway. I'll probably go smaller one size and see how that works.

I'm not really trying to chase a final power number but with the research I did before the SC went on was finding many wrenches saying with an 05 the line in the sand is 600 HP. I want to keep my stock clutch my stock everything and not push the limits too much...this is my one and only "go fast car" I'll ever own. So if I end up at 550 HP or 520 HP, etc. I'll still have a smile on my face.

Thanks for your thoughts.....

vforrest

No CATS = DRONE...that freakin DRONE! My S Type Borlas are great no drone but I could live with a little louder...just not the DRONE vib!!!

My SC would melt the high flow cats?

No cats equal...bad smell in cockpit?

My state emission computer will know someone has removed the cats when they plug in (they don't put a sniffer on it anymore, just a plug in)....$10,000 fine?

If CATS they will get plugged within a year from the SC?

If I have DRONE with no-CATS they can add Resonators no problem?

1sc334

I have corsa sport kooks 1 7/8 headers no cats n electronic cutouts I have no drone unless cutouts are open but I love the sound both ways cutouts give u the ability to have a straight racecar sound wen u want it n when you wanna talk on phone just close them lol ...so if u want more sound n need cats to pass inspection I'd go high flow cats n electronic cutouts.

Nosferatu

as I said earlier, no cats + NPP exhaust and you get best of both worlds

Loud, mean, and fun sounding

Since I supercharged my car the exhaust note became a LOT louder under load. NPP and it's uber quiet in those "drone RPMs." Sounds like a hybrid

vforrest

Streetk14

Maybe I'm not following you here...... did you end up installing a set of catless headers?

Like I told you before, a set of high-flow cats is well worth the extra cost. Minimal exhaust smell and no notable power loss at your power level. They'll also help reduce drone in most cases.

Unless you're really beating on the car hard or making a bunch if power, the cats hold up. I roasted a set of LG cats on one of my cars, but that was a 700 rwhp car that was getting run hard into 5th gear at some 1/2 mile events.

For a normal street driven C6 making sub-600 rwhp, I think a good quality set of cats will not be a problem.

schpenxel

Is there a particular brand that you've seen hold up? I've found everything from expensive familiar brand name ones to cheapo ebay ones

Streetk14

I had good luck with the cats Pfadt supplied with the headers on my '08. Did plenty of WOT street tuning and some 160+ MPH airstrip events with those at over 700 whp, and they were still fine when I sold that car.

So far my ARH cats have held up, but I haven't put too much abuse on them yet. If I ever have another cat failure, I'm going to try one of the newer high-end cats that are supposed to be designed for big power cars. Like the ones made by GESI : http://vibrantperformance.com/catalo...b9b56e6f9be9f9

Those are the cats that AMS uses on their Alpha GTR builds. I'd have to think they'll hold up better than the typical ~$200 cat that the aftermarket supplies.