Using hollowed out cats instead of delete pipes

Interesting. You may be the first to do it intentionally. I put test pipes on my F355. When taking the cats off the element inside had shrunk to the shape of a CIGAR! I could have dumped it out & put it back on.

 

This would be a good experiment. If you remove the ceramic matrix, also remove the metal strap across the inlet side. My 348 has the test pipes and tubi and sounds like a F1 car at high revs. Try it and report back to the group.

Jeff Pintler
89 348tb, 86tr

 

I've done this on a Porsche 928 and didn't like the results. It might be different on the 348 but a hollowed cat tends to produce a resonance chamber (resonator) such that at certain RPM's, their is an awkward and unplesant sound. For my car it was between 2000-2200 RPM and it sounded like the exhaust note was split into 2 distinct sounds with a delay between each (like a reverb). This sound went away when a straight cat by-pass was used. I dynoed before and after but changed more than just the cats but even so - the performance difference was minimal (less than 3% hollowed cats and s/st headers). I hope this helps you.

 

Jays post is what I was trying to warn you about and why I made the reccomendation I did. Scott

 

Be careful with the innards. Hazardous materials and all of that (mostly metals). Use gloves. There is value to the material inside if you care to try to find an outfit that will buy it.

 

I'm running gutted cats with Tubi. The sound is awesome, especially at WOT and redline. The sound is much deeper now under load and I enjoy it. The exhuast is still quieter than most Lambos and is quieter than my Corvette. The beauty is it looks like I have my cats in place. They are safe on a shelf and I'll bring them down and hook them up every two years.
Bee Jay

 

I have done this in the past. hollow cats are quieter than test pipes beause the hollow cat is a chamber and effects sound and you can gut the packing but the metal deflector tongue cannot be cut out so it changes the exhaust flow inside the hollwcat. BTW the best way to clean the guts is to use long nose pliers (really long) and grab some guts. Then shake the cat up/down like trying to flick a blue crab that got hold of your finger. If you just pull the guts out it is really hard. Shake/grab method gets the cats clean fast.

 

Got an '89 Euro pre-cat, which left the factory with hollow Cat pipes ! Sounds good with Tubi exhaust, and doubt there's much to gain by replacing with test pipes.