Yeah I have the ATR. No fitment issues at all, but I removed all the studs and used bolts instead. Makes it much easier

 

Its and ATR I believe.
I used Allen Heads so its much easier to take on and off.

 

So the M2 doesn't require removing the studs, right? Are there any other problems with the M2?

 

No real problems with the M2. Get the M2 or Jet coat the HKS (so no problem with the mild steel, AND u get all the other benefits of JetHot).

 

I installed my Pettit DP without removing ANY studs. I did not have to jack up the engine either. I just used one of the nuts that come with the pipe to put on the stud that almost hits the pipe. If you start to put that nut on BEFORE you get the pipe all the way over the studs it fits fine. Use PB Blaster on the studs the night before you start the DP install.

 

no they don't. that cobra head peice is not their for space limitations it's there for more hp. it's designed to allow the turbulent flow coming fromt the turbine to smooth into laminar flow. they didn't just randomly put that crimp there, it's designed to be there. they will make more hp than american ones, though i admit not much. if anyone disagrees i'd like to make an even trade w/ my ss american dp (no crimp) w/ someone who has a ss japanese one(crimp).

 

I thought about that after being under the car and noticing that the exhaust hole is rectangular and the US DP's are circular. It made me think of a rectangular funnel.

 

yeah that's exactly what the cobra head is, it transitions the rectangular hole to the 3" circular piping while funneling air into smooth laminar flow.

 

So why do people bother with the Pettit instead of just getting the M2, which seems to be easier to install? Both are 3" polished 304, and they cost about the same.

 

www.jt-imports.com the TOPFUEL section has a SS downpipe for about $500 with shipping.

I dont know the quality, but im sure Jason at JT-imports does..

Matt

 

Pettit: went on good with some patience and time, lots of time.

 

Because it takes about 3 years to get any products from M2.

 

ok.. so hks=best performance-wise?

 

When I was doing a search for mine....everyone I talked to said Pettit was the way to go. For fit its supposed to be the best

 

"Because it takes about 3 years to get any products from M2."

That's what I figured. I'm new to this game, and I'm learning that if you want something, you better order 6 months in advance.

 

Knightsports (squished Cobra Head) JDM type in SS. This is very similar to Mazdaspeeds 2-into-1 header style version.

 

i have the HKS, pretty happy with itt

 

Why would anyone want to spend $500 on a DP. Especially one that doesnt flow as well.

Jason

 

With two 2.5" pipes and a 2-into-1 design, i'd imagine they flow excellent but at a price that isn't worth the gain unless you race professionaly and need an edge at any cost. The Mazdaspeed version is $1,000.00

 

I was refering to the Topfuel DP. None of the Jspec DP's are mandrel bent which means shitty exhaust flow and less HP gains. Plus they cost 3X's as much.

Jason

 

Could some one explain to me why this "knightsports" or "Mazdaspeed" two into one DP is better then one 3" tube???
Im a little confused. To me it is like having a little more restrictive "Y" split exhaust system like on the FC, then just one on the FD. Most peeps convert there FC to a single exhaust for better flow.....so why would you make the "DP" two into one?

 

the 2 pipes should in theory increase low end torque. they serve to increase exhaust velocity while maintaining the same cross sectional area that a single 3" dp would, by dividing the exhaust amongst two smaller tubes. at that price it's definitely not worth it though for the small amount of extra torque.

seriously, if anyone has a ss jdm dp w/ the cobra head and you don't like it, i'd like to trade my us style ss dp w/ you. i'm open to the hks dp as well w/ some cash for my dp, considering the hks is mild steel.

 

very true.. it'sl like blowing or sucking water/air through one big straw or two smaller straws... you have more velocity with the two smaller straws then one of bigger or equal size.. would be better for low end.

I had a FEED dp when i had stock twins. lil over 3 inches.. and the cobra neck does not hurt flow... It still has the same if not more surface area then a 3" circular dp. Installation is a breeze compared to any other us dp design out there.. flawless fit. I didn't realize it was goign for 600.. sold it for 230... oh wellz.. single turbo now anywayz... good luck on your descision.

 

NO, if the AREA is the same the VELOCITY is the same for a given FLOW

Flow = Velocity x Area

but with two pipes the surface area will be greater and thus there will be greater friction losses in the split pipe giving lower velocity and flow for a given pressure differential.

The reason a split DP may flow better is that 2 2.5" pipes have MUCH greater area than 1 3" pipe (36sqin vs 28sqin) but if the split pipe is made with 2" pipes it will have less area (25sqin) and flow less at a given pressure differential.