i originally ordered the hks 2.65'' or so downpipe... i thought it was 3''... but i found out it wasnt... so i decided to go with the altered atmosphere 3'' testpipe/downpipe.... few questions though... wat would be better the hks 2.65 or aam 3'' for low end power.... does the testpipe make a dramatic noise increase and if so does it sound smooth/good still or rumbly ****ty?

 

I had the same question when I was about to purchase the HKS Down Pipe, I thought it was 3 inch instead of 65mm. Anway. get the HKS one, as I don't believe would produce bad stuff especially for EVOs. I had mine fitted along with the HKS Hi Power catback and it goes alright. My friend EVO7 lose power after he got his 3 inch down pipe fitted.

 

u cant go wrong with hks

 

I got the RMR 3" downpipe (with the exhaust to follow after payday...) and their intake. I gained 30hp on the dyno. After reflashing my ECU with them, I gained another 30hp. Not much loss there. I think that the downpipe will depend on each mfg. Get a baseline dyno pull and then dyno mods as you add them. That way if it loses power, you send it back. I have to agree with the other posts - I can't picture you going wrong with anything from HKS. Just letting you know that the RMR 3" pipe works.

 

hey chris.. You have a 3inch dp and the 3inch catback with the stock cat, and you gained 30? and you gained another 30 with the Chip? so what your pushing like about 330hp? i also have the 3inch dp and the 3inch catback, and my test pipe is sitting in the garage.. I was wondeirng if i should get the flash

 

reflash = ? sorry i dont kno much about ecu stuff

 

An excerpt from Vishnu Performance's Technical discussions located at : http://www.vishnutuning.com/news_pvnrt.htm

So what exactly constitutes a properly-designed turbo exhaust system?

Many things. Among them being controlled management of exhaust gas boundry layer, minimal exhaust back-pressure at the turbine outlet, an absence of exhaust diameter changes/steps and the minimizing of exhaust gas turbulence and friction. In a perfect world (that is, one without sound level, practicality, emissions or packaging concerns), an exhaust system for a turbocharged engine would be nothing more than a short, horn-shaped exhaust pipe that extended outward from turbine discharge. Think of a horn speaker or a megaphone and you’ll get the picture. This will make maximum horsepower.

That’s right, the ideal turbo exhaust system would smoothly taper in the other direction- from smaller diameter (the same size of the turbine discharge outlet) to larger diameter over a short pipe length. The length of the exhaust system would be short enough to minimize exhaust gas friction while long enough to incorporate a suitable horn-shape with a diameter rate-of-change aggressive enough to minimize exhaust back-pressure while gradual enough to keep from inducing boundary layer disruption (when the exhaust flow no longer smoothly flows along the surface of the pipe but instead separates from it and becomes turbulent).

Turbo exhaust systems are not impacted by exhaust reversion and back pressure the way NA applications are. If you are losing low end power following the installation of a 3" DP I would suggest that the power loss is probably attributable to leaner A/F ratios resulting from the less restrictive exhaust. Tuning would alleviate the problem and realize the full performance benefits of the 3" DP.

 

thx jfh