How badly will cat affect HP
Thread Starter
Joined: Mar 2003
Posts: 1,224
Likes: 2
From: Hamilton Ontario
How badly will cat affect HP First trip to the dyno without cats and a 90/90 intake 85mm maf and a poor exhaust, stock over the axle pipe and then to cutout. Those were the numbers shown below. Well there was a restriction in the intake so pulled the maf off and went to a 102/102 fast intake and TB also added a 4"pipe and dump after the flowmaster merge but I was tired of smelling raw gas to I added a set of 3" magnaflow mini cats.
I have also added a GZ vacum pump.
So just curious what everyone thinks the cats are going to hold back.
I was hoping for 600 rw from going mafless better exhaust and the GZ pump but now Im not so sure.
I have also added a GZ vacum pump.
So just curious what everyone thinks the cats are going to hold back.
I was hoping for 600 rw from going mafless better exhaust and the GZ pump but now Im not so sure.
Depends on the cats and motor output, some will choke out a stock cube ls1, others like goose caddy had good enough ones his 418 didnt lose anything. I know when you really get up there in the power, there arent any cats to sufficiently flow your motors needs, high boost gt500s it really becomes an issue with building up heat/pressure in the cylinders and they typically lose 1-2 psi removing them but gain power simotaneously from better breathing
If it's a really overweight cat, it will affect it a lot, but if it's one of those skinny hairless csts, not so much. 
In all seriousness, it is going to depend on how much airflow the setup makes. Cats are going to be a restriction when that air is trying to escape through the exhaust, but can't fully do so with the force needed because of the cats. Either don't run them or put hollowed ones one there if the visual appearance is all you need.
In all seriousness, it is going to depend on how much airflow the setup makes. Cats are going to be a restriction when that air is trying to escape through the exhaust, but can't fully do so with the force needed because of the cats. Either don't run them or put hollowed ones one there if the visual appearance is all you need. 
