Subaru Enthusiasts Car Club of the Sierras - View Single Post - OEM catless vs. aftermarket up pipe DEBATE

GrimmSpeed · 2010-03-10, 10:06 PM

There seems to be an on going debate whether or not it makes sense to add an aftermarket up pipe to a car that already has a catless oem up pipe(ie, All sti and 06+ wrx). we’ve cut apart the oem catless and found some pretty nasty ridges around the oem flex joint which definitely aren’t good for flow. We’ve seen dyno comparisons on nasioc but I don’t recall seeing actual flow comparisons. Over the next few days we will be running some comparison tests on the flow bench to get some hard data for you guys.

CONSOLIDATED RESULTS FROM THREAD:

UP PIPE

Subaru OEM Cat'd Up Pipe at 28" - 164.7 CFM <--- BOOOO!
Subaru Gutted OEM Up Pipe at 28" - 216.1 CFM
Subaru OEM Catless Up Pipe at 28" - 244.6 CFM
Grimmspeed Up Pipe at 28" - 292.6 CFM

CFM increase of 20% or 48 CFM at 28" of water

I am honestly quite shocked by the difference between the catless oem and an aftermarket up pipe. My initial thought was that the aftermarket version would flow better but not by this much. I can only imagine what the difference is between an aftermarket and a cat'd oem.

Remember, this isnt max flow, this is just the flow at the industry standard of 28" of water...it is used for comparison, not determining max flow.

Subaru OEM Catless Up Pipe

GrimmSpeed Up Pipe

Ok here are the Cat'd OEM Up Pipe results
Subaru OEM Cat'd Up Pipe at 28" - 164.7 CFM <--- BOOOO!
CFM increase of 78% or 127.9 CFM at 28" of water vs. an aftermarket up pipe.

OEM Catted Up Pipe

Here is a graph of all three tests:

Subaru Gutted OEM Up Pipe at 28" - 216.1 CFM

I was rather shocked by this number compared to the oem catless up pipe. The oem catless is still about 30cfm more than a gutted oem.

Subaru Gutted OEM Up Pipe

CROSSPIPE

Subaru OEM Crosspipe at 28" - 230.4 CFM
Grimmspeed Crosspipe at 28" - 315.5 CFM

Subaru OEM Crosspipe

GrimmSpeed Crosspipe
CFM increase of 37% or 85.1 CFM at 28" of water vs. oem crosspipe.

Justin

2010-03-10, 10:06 PM	#1
GrimmSpeed EJ22 Join Date: May 2008 Posts: 244	OEM catless vs. aftermarket up pipe DEBATE There seems to be an on going debate whether or not it makes sense to add an aftermarket up pipe to a car that already has a catless oem up pipe(ie, All sti and 06+ wrx). we’ve cut apart the oem catless and found some pretty nasty ridges around the oem flex joint which definitely aren’t good for flow. We’ve seen dyno comparisons on nasioc but I don’t recall seeing actual flow comparisons. Over the next few days we will be running some comparison tests on the flow bench to get some hard data for you guys. CONSOLIDATED RESULTS FROM THREAD: UP PIPE Subaru OEM Cat'd Up Pipe at 28" - 164.7 CFM <--- BOOOO! Subaru Gutted OEM Up Pipe at 28" - 216.1 CFM Subaru OEM Catless Up Pipe at 28" - 244.6 CFM Grimmspeed Up Pipe at 28" - 292.6 CFM CFM increase of 20% or 48 CFM at 28" of water I am honestly quite shocked by the difference between the catless oem and an aftermarket up pipe. My initial thought was that the aftermarket version would flow better but not by this much. I can only imagine what the difference is between an aftermarket and a cat'd oem. Remember, this isnt max flow, this is just the flow at the industry standard of 28" of water...it is used for comparison, not determining max flow. Subaru OEM Catless Up Pipe GrimmSpeed Up Pipe Ok here are the Cat'd OEM Up Pipe results Subaru OEM Cat'd Up Pipe at 28" - 164.7 CFM <--- BOOOO! CFM increase of 78% or 127.9 CFM at 28" of water vs. an aftermarket up pipe. OEM Catted Up Pipe Here is a graph of all three tests: Subaru Gutted OEM Up Pipe at 28" - 216.1 CFM I was rather shocked by this number compared to the oem catless up pipe. The oem catless is still about 30cfm more than a gutted oem. Subaru Gutted OEM Up Pipe CROSSPIPE Subaru OEM Crosspipe at 28" - 230.4 CFM Grimmspeed Crosspipe at 28" - 315.5 CFM Subaru OEM Crosspipe GrimmSpeed Crosspipe CFM increase of 37% or 85.1 CFM at 28" of water vs. oem crosspipe. Justin Last edited by GrimmSpeed; 2010-04-30 at 11:12 AM.