Catalytic Converter Bypass Valve

[zman]

Has anyone out there thought about bypassing the catalytic converter after the car has warmed up. How much power and milage gain would potentially be gained from bypassing it.

I did a quick sketch of possible bypass system with a shutoff valve. It seems to me it would be fairly easy to implement. The operator will be responsible for turning the system ON and OFF

[Daox]

You wouldn't gain anything. Modern cats really aren't restrictions.

[vtec-e]

It also wouldn't be an "EcoMod"

[dremd]

I'm with everyone on this, But I can tell you that I have been around a few Ferraris that did exactly what you are talking about.

[Peter7307]

Yep I have to agree about modern cats being efficient.
Bypassing them would result in virtually zero gain for either performance or fuel savings.

Just my 2c worth , Pete.

[Frank Lee]

Seems bass-ackwards on several levels.

For one, the cat doesn't work very well when it's cold. So you're going to run gases through it when it doesn't work, then when it's warm enough to work you bypass it??? I'd say with that logic just tear it out... but as noted, the cat isn't the biggest restriction and even if it was, tearing it out doesn't help fe.

[Domman56]

if you take it out it will gain 5.3 HP on a dyno on a 1985 Ferrari 308 GTS quattrovalve Not that i would know

Just winds up giving you more throttle response but not very good eco wise

[tasdrouille]

I can see how this could help at 7k rpm at WOT, but cruising along at 1700 rpm? Gains would be slim to none, and surely not noticeable. Plus it's totally illegal on roads.

[Domman56]

Originally Posted by tasdrouille

I can see how this could help at 7k rpm at WOT, but cruising along at 1700 rpm? Gains would be slim to none, and surely not noticeable. Plus it's totally illegal on roads.

Well not places that don't have emissions laws

[Daox]

Hes in the US, you need a CAT to be legal.