Diesel350

Has anyone done this before? If so, how much HP is there expected to be with adding high flow cats?

jat0223

iTrader: (1)

After market high flow cats are usually not welded to the headers. They are welded to the exhaust. If you'd like to replace the stock cats on the stock headers I think you won't gain much for the amount of work involved

lolfunxion

iTrader: (25)

Next to nothing. The designs of the headers are restrictive more than the cats are. Maybe weight savings from a lighter wallet?

Diesel350

So gutting them out instead is the better option??

ISFPOWER

iTrader: (20)

its cheaper, more power. and passes any visual test. downsides are being loud.

lolfunxion

iTrader: (25)

No, buying PPE headers is the best option. I don't think you make hardly any power on gutted cats. Once again, the design is the flaw.

jat0223

iTrader: (1)

Even though I have headers I have to disagree with you here. Gutting the cats provides close to the gains of headers. You gain the most from getting rid of the cats.

tas02

iTrader: (2)

Before this thread spins out of control, you would only want to ADD high flow cats to the exhaust, not to the header itself.
FWIW, PPE sells their exhaust with high flow cats already installed.

Fsport2UR

That is only typical on other cars. Dyno results show similar gains for gutted cats on stock ISF headers compared to aftermarket headers. The stock cats are the restriction, not the header design.

flowrider

iTrader: (9)

^^^^I have not seen that proven anywhere The exhaust manifold design on the ISF is terrible IMO.

Lou

MileHIFcar

Can you please post up a link or a pic of a dyno run of someone with an aftermarket exhaust (Joe-Z/Borla/ISS etc....) with gutted primaries that is putting out the same numbers as PPE/Sikky headers gains???

Just curious, because I have never seen one posted here on CL of a dyno run with gutted primaries/aftermarket exhaust only......

Thx

nickj718

iTrader: (1)

Rafi and his race car has gutted cats and not headers. Has to be a reason for that because it sure isnt laziness

Sylvan

iTrader: (6)

There have been multiple threads about it, one was even a gutted cat car racing a header car and the race was so close no one would even admit losing.... Save yourself a pile of time and money and gut your cats.

Diesel350

And smelly?

ISFPOWER

iTrader: (20)

long tube headers are smelly too. deleting any catalytic converter on any headers, you will see power gains.