ive searched and read up on this topic quite a bit

i know there a plenty of options for you single cat guys but i havent been able to find many aftermarket header systems made for dual cat cars

ive seen a few edelbrocks but they dont come with a y-pipe

i know hooker 2055's are a popluar choice around here and i was just wondering what modifications to the y-pipe would have to be made to fit a dual cat system

thanks, brian




ps i dont really want to convert to a single cat system

 

The TES for dual cats, 68762 (68763 for Ti-Tech finish) comes with the pipes to the cats. http://www.edelbrock.com/automotive_...ular_app.shtml (Footnote A: "Requires cutting and welding for installation.")

Hedman 68491 (66491 for ceramic coated) come with the pipes to the cats. http://www.hedman.com/pages/hedmanmain.html (You'll have to click through a few choices, like street headers, passenger car, Chevrolet, etc., to get to the application chart and footnotes [145 is the dual-cat footnote].)

To modify the 2055's, cut off the "Y" and connect individual pipes to the cats.

(Technically, the "y-pipe" for a dual-cat system comes after the cats.)

 

any particular reason? my car was dual cat and i switched to a single cat to save on costs and save on headaches. personally i like the route i took. hedman shorties and y pipe, and a carsound cat from ebay (3 inch inlet/outlet) for $50 to go along with the rest of my 3 inch exhaust. it also opens up some options for suspension and chassis parts as well.

 

thanks guys i feel stupid after i just looked under my car again and seein the exhaust routing

 

Area of a 3" cat = 7.068 sqare inches

Area of a 2.25" cat = 3.976" x 2 = 7.952 square inches

You are losing almost a square inch of area when you force 8 cylinders to flow thru one larger cat instead of 4 cylinders thru two small cats. And if you upgrade the cats to dual 2.5" you get

Area of a 2.5" cat = 4.908" x 2 = 9.817 square inches.

That's more than two square inches of area for exhaust gasses to flow with an upgraded dual cat system.

But of course, this costs money. How fast can you afford?

 

i had the same problem with my 2055's....my car had 2 cats. i purchased 2 catco cats, intalled the headers/y pipe than took it to the local muffler shop to finish the job with 2 cats. they charged me about 2 hours labor, looks and runs good.

 

If I had dual cats, I'd lean towards keeping them. Whether they're worth converting to, questionable, but the factory got ~10 HP gain doing it with manifolds. Of course, the system goes back to a single pipe after the cats, so the full gain wouldn't be realized unless the cat back was increased or dualed as well.

Kevin, your calculations use pipe OD's, which doesn't reflect actual flow area. Duals will have more wall thickness to reduce the total flow area, but will still have more than a single system. However, you'll also get more boundry layer reduction from the dual pipes (more wall area), so the total gain is not a simple ratio of flow area.

Dual 2-1/4" are still slightly better than single 3". Especially with a carefully placed X-pipe (difficult to do with shorties and factory exhaust routing).

 

I saw on Ebay a while back a Hooker 2055-1 or some other number that was for dual cats... Anyone else seen this?

Rafael

 

Hey mods, wouldn't the dual cat y-pipe be the problem not the dual cats themselves? I'm thinkin that the exhaust goes from the headers into a 2 1/4 inch pipe AND THEN into the dual cat system. Hopefully I'm making sense.

 

With dual cats, each bank has a 2-1/4" or 2-1/2" pipe to its own cat. They are joined only after the cats.

 

I forgot that they don't join until after the cats, thanks.

 

Keep in mind the numbers are for factory cats. Those have dual beds in them while most aftermarket cats have a single bed. I'd guess a Catco three inch converter would easily outflow the factory dual setup. Not sure what you'd get with replacements for both in a dual setup though.