custom high flow cat for c36
08-30-2010, 01:38 PM
#1
Junior Member
Thread Starter
Join Date: Jun 2010
Posts: 22
Likes: 0
Received 0 Likes
on
0 Posts
c36AMG
custom high flow cat for c36
for the c36, the original catalyst is like this :
2'5 pipe from header
divided in 2 pipe of 1'75
the 2 cats
the exit of cats is 2' (compared to the 1'75 entry)
and finally a Y pipe to finish with a 2'5 pipe
this is not "optimised" for the low
I like to change that and use a metallic high flow cat (magnaflow sames good) and do a single pipe with only 1 cat
I hesitate between the 2'5 or 3' cat (I suppose flow is better with the 3')
It's hard to find correct informations for the CFM values
magnaflow claim 600 CFM for the 3' metal cat
theorical value for the c36 (max CFM) is :
(3.6 x 7000)/2 x 0.8 = 10080 liters --> 356 CFM
I suppose I'm not the first one to do this, is it a good idea ?
2'5 pipe from header
divided in 2 pipe of 1'75
the 2 cats
the exit of cats is 2' (compared to the 1'75 entry)
and finally a Y pipe to finish with a 2'5 pipe
this is not "optimised" for the low
I like to change that and use a metallic high flow cat (magnaflow sames good) and do a single pipe with only 1 cat
I hesitate between the 2'5 or 3' cat (I suppose flow is better with the 3')
It's hard to find correct informations for the CFM values
magnaflow claim 600 CFM for the 3' metal cat
theorical value for the c36 (max CFM) is :
(3.6 x 7000)/2 x 0.8 = 10080 liters --> 356 CFM
I suppose I'm not the first one to do this, is it a good idea ?
08-30-2010, 03:45 PM
#2
If you are going to improve power out of the C36 exhaust you will have to start from scratch and remove everything except the headers. Running a single 2.5" or 3.0" cat would be more ideal than trying to run two. You can run a single pipe 3.0" exhaust system but in order to do that you really need to make sure you get the y-pipe done perfectly otherwise it could kill low end torque.
Realistically though, the most you will get out of an entire exhaust system (excluding headers) is probably 12-15HP at crank ... and that's probably being generous. With custom long tube headers.... that's a different story. But without long tube headers, you aren't going to make much more than 15 at most (so keep your expectations realistic). It should sound amazing though and weigh significantly less than stock (you can usually cut the exhaust system weight by 30-50% by switching to aftermarket setup).
The only way you are going to free up low end acceleration is by removing mass off the crank pulley. It really is the only way to get these cars accelerating significantly quicker. We have a few "OEM+" crank pulleys for $299 but normally we don't even advertise these just b/c its such a low volume product, its really done on a one-off basis.
Realistically though, the most you will get out of an entire exhaust system (excluding headers) is probably 12-15HP at crank ... and that's probably being generous. With custom long tube headers.... that's a different story. But without long tube headers, you aren't going to make much more than 15 at most (so keep your expectations realistic). It should sound amazing though and weigh significantly less than stock (you can usually cut the exhaust system weight by 30-50% by switching to aftermarket setup).
The only way you are going to free up low end acceleration is by removing mass off the crank pulley. It really is the only way to get these cars accelerating significantly quicker. We have a few "OEM+" crank pulleys for $299 but normally we don't even advertise these just b/c its such a low volume product, its really done on a one-off basis.
09-01-2010, 02:06 AM
#3
MBWorld Fanatic!
Your car flows less than 400 CFM. If the 3" flows 600 CFM and the 2.5" flows 500 CFM, the 3" will not flow better. Depending on the shape, it may in fact actually flow less. If you are dead set on designing your own exhaust, you may want to read as much as you can about "exhaust velocity". Otherwise, you may want to consider copying someone else’s work.
