I just took off my Stillen 304 Stainless Steel headers. While I committed the grievous error of failing to do a before/after dyno of the headers for their installation, I did for the removal and return to stock manifolds. You see, somewhere in the last year, it appears that I've lost 15-20whp. I have no idea where or how, but it happened. Convinced that the only variable that I didn't account for rested in the headers, I had them removed. Essentially, I wanted some proof that they lost power so I could push Stillen to give me a refund (I've only had them since January). Much to my chagrin, the removal of the headers and subsequent dyno proved my theory dead-wrong.

Returning to stock showed that the headers (w/ tune) gave me almost +11whp @ 6500rpm over the stock manifold. The dyno chart below speaks for itself.

My Dyno Chart:
Blue = w/headers
Red = stock manifold


In summation, they were obviously not the cause of any power loss I've experienced, and the gremlin lives on. However, I'm a fair guy, so I decided to post these results as proof positive of Stillen headers (at least with other bolt on mods and a tune) provide a real performance gain - even on the VQ35DE.

I present to you two things to learn from my mistakes:
1.) Always, ALWAYS conduct before/after dyno's on expensive performance modifications. You never know when you might need them.
2.) Stillen headers certainly CAN yield notable power gains on non-HR 350Z's.

Hopefully some good can come of my expensive mistake.
In case anyone is interested, the headers are now for sale in the classifieds.
EDIT: Classifieds thread is down until I can get pictures of the headers themselves posted...

 

wow thats pretty interesting. Does the butt dyno feel the 11 horsepower difference?

 

To be perfectly honest, not very much. It might be because I don't drive at those RPMs nearly as much as everywhere else in the powerband and because the weather here in Tulsa is constantly changing between hot and cold. Not entirely sure.

 

Interesting

 

The only problem I see is semantics. Is a 4 percent loss-gain in horsepower “significant?”

 

Edited. 'Substantial' = 'real'. 'Significant' = 'notable'.

Problem fixed.

 

With as hard as it is to get NA power out of these cars id say so.

 

LOL, sorry but i know it sucks but still i had to LOL.

 

Dude, I understand. I deserve it. I've been kicking myself all day.

At least the car sounds better, now; the headers were causing some nasty rasp with my Stillen exhaust.

 

please tell me you didnt pay them to take off your headers?

 

Roughly expected......the rev-up does better with aftermarket exhaust manifolds than non-rev. Waste of money on an 03-05 IMHO.

 

When you say Non-HR 350z, do you have legitimate info or proof that they don't work as well on HR350z? Reason I ask is because I've been looking forward to this header but I'm not sure if its really worth the hassel and money. Please share your comment on this. Thanks!

 

Oh no. I think you're misunderstanding me. There have been several dynos, if I'm not mistaken, that show definitive gains with the HR350z. The Non-HR 350z was the one in question.

 

Did you dyno with your headers tune? Would that account for anything? If you retuned for your stock manifolds, would it have produced anything significant?

 

The dyno tune for the headers came after an eTune, so the gains were actually fairly small. I do think I could see a small gain after a tune for my stock manifolds, as the car is running a tad rich right now.

 

sorry man,

Do you have sound clips w/art pipes set up now minus headers?

Also, how do you think the headers + ART pipes affected one another?

 

Good info. I would have expected the "headers on" curve to be below the stock manifold's curve on the lower end of the RPM scale.

 

As a matter of fact, I do:
http://www.youtube.com/watch?v=4x3Cb7WsgbA

As far as how it affected the other, I really don't have a reliable way to tell. If I were to say one way, it would be pure speculation. Sorry .

 

It's curious with the ART pipes. All the tests were said to be skewed w/headers?

Your Dyno's without the headers look pretty similar to a normal set-up of similarly modded cars(without ART pipes). Granted, im not sure about you being re-tuned post removal?


Is this a different dyno(location) from previous tests?

 

................