Magnaflow makes a 5" diameter high flow catalytic converter that should flow as good as no converter. I believe they will fit in the forward space where the headers join the X pipe if the header was designed to fit. Anybody know if any of the current headers would have the necessary clearance and length to fit these cats? Assuming current headers are designed for 4" cats then they would have to be extended down 1/2" and stop close enough to the engine to mount in this forward space.

Here's a link to this cat: http://www.car-sound.com/02product/displayuniversal.asp?universal=59559

Magnaflow makes a 5" diameter high flow catalytic converter that should flow as good as no converter. I believe they will fit in the forward space where the headers join the X pipe if the header was designed to fit. Anybody know if any of the current headers would have the necessary clearance and length to fit these cats? Assuming current headers are designed for 4" cats then they would have to be extended down 1/2" and stop close enough to the engine to mount in this forward space.

Here's a link to this cat: http://www.car-sound.com/02product/displayuniversal.asp?universal=59559

Several thoughts here... In order of importance...

- How much power are you making? Even at my power level, 600HP at the tires, removing the cats had virtually ZERO effect on engine power and torque (tested on a Dynojet with several runs). Modern high flow cats are simply not that restrictive; unless you are trying to make enormous power, you just won't see much gains by putting bigger cats in. IF you were going to huge power, then those big cats will melt because very high HP FI cars run rich and eat catalytic converters for lunch.

- Any time you go up or down in pipe diameter you introduce turbulence into the flow. The 5" cat will certainly flow more than a smaller cat, but the 5" cat assembly, with its dramatic step up and step down in diameter, most likely will not.

- I don't think it will fit:
http://www.powerlabs.org/images/c6/dualcats.JPG

At least not with adequate clearances so nothing melts around them.

Interesting Powerlabs and very informative!

I'm only making 409hp/409tq on a Mustang dyno. Right now I have the Z06 manifolds, cats and H pipe into my NPP mufflers. My future plans was to add headers but looking at the aftermarket cats being smaller than what I have had me wondering. The factory Z06 cats are 4 1/2" diameter. At my power level even headers may not even help unless I add a cam along with the headers.

Thanks for sharing.

Interesting Powerlabs and very informative!

I'm only making 409hp/409tq on a Mustang dyno. Right now I have the Z06 manifolds, cats and H pipe into my NPP mufflers. My future plans was to add headers but looking at the aftermarket cats being smaller than what I have had me wondering. The factory Z06 cats are 4 1/2" diameter. At my power level even headers may not even help unless I add a cam along with the headers.

Thanks for sharing.

You have to remember that aftermarket high flow cats are MUCH, MUCH less dense... You can actually see right through them if you hold them up to the light ;)

As a general rule running C6Z06 manifolds will give you at least 85% of the power you could get from aftermarket long tube headers. The long tubes will give you a lot more low end torque though (much better scavenging).

I installed Magnaflow 3" spun converters in mine with LT headers. They're about the same size as powerlabs. They work great IMO. Anything bigger might give you clearance problems i think.

I still plan to work towards headers eventually. I'm sure they will make more power than the Z06 set up. Not sure they are worth the extra $ until I have more flow as in cam.

I agree the aftermarket cats do have a much more course pattern than my Z06. My Z06 are dense just as my factory C6 cats were.

Another question, I've seen headers where the X is upstream of the cats and some downstream. Which would flow best and make most power? Maybe it doesn't make any difference. Yours, Powerlabs, have the X aft of the cats from your pic.

I still plan to work towards headers eventually. I'm sure they will make more power than the Z06 set up. Not sure they are worth the extra $ until I have more flow as in cam.

I agree the aftermarket cats do have a much more course pattern than my Z06. My Z06 are dense just as my factory C6 cats were.

Another question, I've seen headers where the X is upstream of the cats and some downstream. Which would flow best and make most power? Maybe it doesn't make any difference. Yours, Powerlabs, have the X aft of the cats from your pic.

I've had both. I originally had my car dyno tuned with a VaraRam CAI, a 160F thermostat, and the Kooks 1 3/4" headers you see there with a catted 3x2.5" X-Pipe and GHL exhaust. It made 395RWHP/389ft-lbs toque on 91 octane (LS2 manual car).
I swapped out the midpipe for a 3x3" pipe and started running C6 Z06 exhaust, also added a ported intake and throttle body. I removed the VaraRam and installed an A&A Supercharger kit with a Vortech V2 Si-Trim with a 3.8" pulley, making 10.5PSI peak boost. This combo made 597RWHP/518ft-lbs torque through those Kooks 1 3/4" headers with the cats you see there.
I the swapped the kooks for American Racing 1 7/8" headers with the cats located behind the X-Pipe, and did a before and after dyno; same car same fuel same day same dyno, 4 runs 4 hours apart.
The power difference had zero statistical significance.

Here: Please take a look at this post where I detail the back to back comparison with dynos:

http://www.smokinvette.com/corvetteforum/showthread.php?t=27860

Based on your tests might as well go with the 1 3/4" primaries. Easier to get to the plugs most likely, little cheaper maybe even easier to install.

Have any idea about my other question of X pipe placement? Before or after the cats? I've seen headers both ways.