Ok, I just got out of an 04 Cobra making over 460 RWHP, so this is a whole new world to me. Does a cat-back exhaust on a 05 6 MT add any substantial amount of HP/TQ, or is it mostly for sound? I want an exhasut that is louder and deeper, but not obnoxiously loud or a droning exhaust at highway speeds. It seems that the new generation of Stillen is quite popular. Is the G exhaust composed of three parts? Cat-back, mid pipe, and manifolds? The Stillen cat-back seems to incluide a mid pipe as well? What about Borla? I like Borla products and have seen several people here using them, but their site does not list a specific system for 05 G sedan's? I searched, but did not find all the info needed. What about fit and finish? I had a Borla on my Cobra, but they never bolt up like factory systems do and do nit fit very well, you always have to bend hangers, and all that.

 

By the way, the mid pipe on a Cobra is an H, but several people change it to an X pipe, which would cause some low end torque loss, but a gain in HP in the upper RPM's. The X would also make sound higher pitched more exotic sounding as compared to a more deeper sound with an H. It appears that the Stillen Cat-back has an X pipe, instead of a Y?

 

Anyone???

 

I own a coupe so I can really say in strict regards to a sedan. However, in the coupe configuration there is an exhaust manifold, which bolts to a catalytic converter which then bolts to a Y-pipe which then seperates and goes into 2 mufflers.

A cat back system in this config would replace all the piping after the catalytic converters hence "cat back." Most AM cat backs are Y-pipe configurations, however there are some H-pipes (HKS hi-power for one) that are true dual.

Headers will void your warranty but you should be fine with hi-flow cats and/or cat-backs. Cat backs are the cheapest and most effective HP increase for the G.

For the most part you will hear a louder exhaust. From what I've read in the forum Fujitsubo and Borla are generally quieter but don't give you the most HP gain.

 

Thanks, what about the new Stillen Gen 2? They claim 23 RWHP and quieter than their first one? IS the HP claim real?

 

Hmmmm.... didn't know about that one. Funny too, cause I'm on the Stillen website almost every day. 23 RWHP is insane and being that my local perf shop is an auth Stillen installer, you could pretty much count on me getting one right away if that claim is anywhere near true. Time to go Google for "Stillen Gen 2!"

 

Ok, care to share where you heard about this "Stillen Gen2" and it's 23 rwhp increase? Can't find anything on it.

 

The quote below was taken directly from everythingg35.com, which sells Stillen. The new series for 05's claim the same HP level, but with a quieter tone:

"The Infiniti G35 Sedan gets a big boost in performance with the addition of STILLEN's new Cat-back Exhaust System. This Stainless Steel cat-back exhaust system will increase your Sedan's performance by 21-23 hp and 21-23-lbs ft. of torque - at the rear wheels! Twin resonators ensure that the exhaust note is powerful and yet remains responsible for adult use. This is a dual path, single muffler system that uses Stillen's distinctive X pipe to promote exhaust scavenging as well as balancing pressure. With only 4 pieces to install this system weighs in at 13 lbs. less than the stock exhaust and offers a precise fit. Polished pieces include the twin resonators & muffler while twin polished Stainless tips finish off the system for a great look."

 

The quote below directly from Stillen's website:

**NEW AND IMPROVED - SAME GREAT POWER NOW WITH QUIETER TONE** The Infiniti G35 Sedan gets a big boost in performance with the addition of STILLEN's Cat-back Exhaust System. This latest design will fit any 2003-2005 G35 Sedan, RWD or AWD. The original system yielded tremendous power but at a higher sound level than we normally look for. Our tireless R & D team has refined the exhaust to come up with one that is quieter than its predecessor without reducing any performance gains. This stainless steel cat-back exhaust system will increase your sedan's performance by 21-23 hp and 21-23 lbs ft. of torque - at the rear wheels! Twin resonators are employed. This is a 100% Stainless Steel system with dual path piping and a, single muffler system that uses Stillen's distinctive X pipe to promote exhaust scavenging as well as balancing pressure. With only 4 pieces to install this system weighs in at 13 lbs. less than the stock exhaust and offers a precise fit on any Sedan trim level. Polished pieces include the twin resonators & muffler while twin polished Stainless tips finish off the system for a great look. Please note, ships in two boxes SHIPPING AS SHOWN IS TOO LOW! Call for a more accurate shipping quote!

 

Ok, must be a sedan only exhaust system.

 

It is.
& if NE1 believes those HP claims;
I've got this bridge........

 

Yeah, I hear ya. Stillen makes good $hit but they ought spend more time backing up their claims. Post some dyno sheets and explain their testing procedures -- for example, year model make of car, number of miles on odometer, any other mods, etc. etc. It may not make a believer out of everyone, but it would certainly help. On a good number of their perf mods they list on their website, they don't even tell you if the HP increase is at the crank or wheels! I'm like c'mon... can't you at least specify that?

 

I find it hard to believe, especially since the 05 exhaust is suppost to be less restrictive. Can I expect 10 - 15 RWHP realisticaly? If not, $1000 is a lot to spend. How about the Borla system?

 

Hey Brasil, I'm a fellow mustang owner as well. I have the injen on my 04 and the gains are quite minimal albeit a louder tone (almost unbearable sometimes at lower rpms). I would look at Stillen claims with a very skeptical eye. None of the exhausts on our cars would offer that much power imo. Ultimately you are paying for the sound factor.

 

I think half of that 23 rwhp is realistic. Actually, $1000 although not pocket change, is not that much to spend for 15hp at the wheels. I can't believe Borla would give you more. Generally from what I've read, Stillen cat backs produce the most hp of most systems out there. Perhaps you can find someone that posted some before/after dyno numbers?

Many don't go with Stillen b/c they supposedly are also one of the noisier systems and most guys that are buying Infiniti's want to balance civility with their performance, right? I mean, maybe that's why you sold your Cobra.

But it boils down to simple physics. You can't muffle air too much without restricting the flow hence losing HP. HKS gets around it a little bit with their Hi-Power Ti series for 350z/G35c by adding resonators, but I have yet to see a noise comparo between HKS and the Stillens. (Those resonators look cool though! )

I mean to cut to the chase, I think you'll be pretty happy with the Stillen although their HP claims are a bit exagerrated. If you're pretty serious about it, I would call or email them and ask for some test results.