then why is there cat back 3" it dont make sence?

 

I love my AMS. The fit and finish is awesome. Talk about quality. I did have to bend the back arm brace but it was super minor. I would buy it again if I had a second chance. The welds and flanges are most impressive.

 

What doesn't make sense is that Espelir's catback is 80mm (3.15") and tapers to the stock cat 2.5". HKS does the same. So the JDM setup appears to be 2.75" DP, 2.5" stock cat, and 3-3.15" catback. The neck down in the JDM catbacks is what keeps me from buying a JDM system.

 

With that said, i can understand why most think a 2.75 dp is dumb....



what are my options for a high flow cat

is there a 2.75 or can i use a 3"?

 

+1

 

Check my signature for your answer.

 

i have the HKS Ti catback exhaust so what size Dp do i get ? a 2.75" ????? a 3" Dp will not fit correct?

 

Do a serach on DP's that fit 05's. There are both 2.75" and 3" that fit. But there is no point in a 3" if you keep the cat flange neck down on your HKS setup. 2.75" (70mm) or the HKS 60mm DP will be fine. My current setup is 70mm Espelir DP to HFC to Tanabe catback with necksdown to 72mm at the cat flange. So my piping is 70-72-80mm. You just don't want to go big to small. It's bad for flow.

 

wow...you really did a lot of research...good stuff!

 

thanks shadow1. i will be ordering a 70 mm DP very soon. thanks for your help

 

what is a catback? it's the part of the exhaust that goes from the cat back.... so it's not a matter of your dp fitting to your catback... it's a matter of your cat fitting to your dp and then to you catback.

 

Catback: exhaust system from the back of the cat to the tail pipe.
TBE (Turbo Back Exhaust): from the turbo all the way to the tail pipe

most manufacturers neck down the system so that the inner diameter is equal to the cat inner diameter (read stock exhaust diameter) . they do this so there is no major step down (90deg step) from say 3" to 2.5" at the cat. it is a more gradual reduction in diameter.

Mike

 

First and foremost, I would just like to say that I am brand new to the evolutionm forum and that I have been coming here often before I became a member for a lot of my research before buying mods for my evo. With that being said, I know this has probably been butchered to death already, but I was wondering what is everyone's thoughts on a down pipe and high flow cat (can't go with test pipe, illegal in Cali) with an already installed HSK hi-Flow Catback exhaust setup. I was thinking about going with either a Megan or Helix DP with the UR HFC, but I wanted to know wut y'all think. All replies are apreciated and thank you for taking the time to read this awfully long post. LOL.

 

uhm... hfc are also illegal in california. the hks catback tapers at the cat... whcih would make your biggie dp and hfc pointless. the only hks exhaust that is 3" is the one from rnr and they're like givin' 'em away right now apparently

 

I would recommend Works stealth HFC. They use the factory cat but weld on larger flanges for better flow. But should still pass CA emissions. Changing the DP is easy and could be accomplished every 2 years to pass emissions. HKS tapers at the cat flange. I would not go with a 3" DP - waste of time. HKS DP is 60mm and pretty much matches the catback you have.