I'm one that can never leave a stock car alone. One of the first things I usually do is intake and exhaust. My question is this...

Do any of the aftermarket exhausts really increase hp by much? The stock exhaust on the G actually sound pretty damn good for a stock system. I'm not looking for advertisers claims (way overstated, expecially by Stillen) or "seat of the pants" responses, but instead dyno results if anyone has done a before and after.

Thanks.

 

DO a search, it has been discussed many many times.

 

He's got a G35X, so exhaust choice is limited to the Stillen. Kinda mean's you have that system to talk about and that's it. Somewhere on freshalloy their is a dyno of the Stillen on a sedan with before and after dyno's IIRC it made 10hp.

The oem system does have area's of opportunity that allow a good aftermarket system to make power. None of the aftermarket makers wild hp claims can be copied however and increased sound level's will come along for the ride, though the Stillen was recently redone to help quell noise.

 

nothing you will feel, bolt ons, from experience i've learned are not worth it imo. you might squeeze out 50 hp, but it's not worth the money. go FI if you wanna be goin fast. otherwise exhaust and intake are good for sound. ie if you want your car to be louder.

 

Thank you, Gsedan35.

On some cars, the stock exhausts are extremely restrictive. On others, they are fairly well done by the manufacturer. I picked up 35 RWHP with the aftermarket Camaro exhaust. On other cars, the gains are much less.

If Stillens exhaust only nets 10 hp, I'll probably skip it. My guess is some good hi-flow cats would net more. I might try a couple of Random Tech's. I've had very good luck with them in the past.

 

It appears the 2005 G35's are at the limits of the VQ motor. You might be able to squeeze an extra few hp out but nothing big. Some are arguing that certain mods actually decrease performance. It's hard to say because butt dyno's and the real dyno's are very subjective.

 

The '05 has a very good exhaust system. It is well balanced and the car performs its best with it. The only option that I would consider for the '05 would be the new Stillen catback, but I can't handle the increased noise levels.

I've had both the '03 and now the '05 Sedan (RWD). In the '03 after market exhausts + coupe mid pipe will help you a great deal. But the new redesigned '05 system works much better than its predecessors.

In my '05 I had the coupe midpipe first, and noticed absolutely no difference in sound and performance. Then I added the HKS rear section and again got no increase in HP but the sound is very, very nice. It is deeper and a bit louder than the stock OEM '05 system.

However, the increased sound and slight drone in the 1500 to 2000 rpm's plus the loss of back pressure, made me switch back to my OEM system last week. I have to honestly say that the car runs a lot smoother now and the back pressure is back. In fact it feels faster than before at the low end and top end. The sound is beautiful too. The only mod to it was the tips, they were replaced with full length tips eliminating the ugly bolts.

So, short of getting the Stillen catback that some like very much, I'd save my money for other mods.

JMHO.

 

I'm surprised none of you folks have mentioned the Cats of the "Y" Pipe. Those are the most restrictive part of the exhaust on a "G". For Cats, I like the Crawfords, for a "Y", find one with the steel mesh vibration isolators, nice smooth mandrel bends, and a 3" collector.

Lou

 

I was actually thinking of going that route. Getting cats and Y-pipe with OEM middy and rear section. But after my recent experience with the mid pipe + HKS, I don't feel like spending extra cash and then find I MIGHT end up losing HP or gaining just marginal power for the money spent.

I believe that replacing parts of the exhaust in the '05 is pointless. The OEM system seems to work at its optimum as it is. Any changes might actually be counter productive.

If I decide to change the exhaust again in the future, I'd go for the full cat back instead of playing around with other parts.

 

Thanks for the input, guys. That helps a lot.

My experience with exhausts on a N/A car is that the cats are usually the bottleneck. I have no experience with the Crawfords, but I will now research them. What I do have experience with is the Random Tech cats, which are incredibly flowing, near indestructable cats. They are not cheap, but are very good. When we tested exhausts in our F-Body club, we put Random Techs on a 650+ twin turbo LS1 and thrashed them beyond belief. When we were done, they were perfect. I have read magazines that have used them on a number of cars and have described them as "bulletproof".

Does anyone have a link to Crawford's website? Thanks.

 

I agree with you 100%. I owned 5L Mustangs and Camaros and the exhaust was the first thing I did and got my money's worth. But with our Infinitis it's different ball game.

Here is the link you need: http://www.crawfordzcar.com/

 

Thanks, Chico. I appreciate it.