[Gmecm] 305/350 Swap 10-month Progress Report...

[Mike Frels]

I don't plan on gutting any more cats anytime soon. The only reason the one that *was* on my car was gutted was due to the bricks inside it loosening, rattling, and clogging my exhaust 14-15 years ago. I just never needed to replace it due to my locale not having smog screening. I have come to understand during the past several years how some back pressure will increase torque if the engine is cam'd accordingly such as the OEM one in my car. 

I also like how a cat present in the exhaust stream makes for a quieter and smoother exhaust note.

Mike

-----Original Message-----
From: David Haggard <david at newcovenant.com>
Sent: Mar 16, 2005 8:49 PM
To: Mike Frels <mfrels at ix.netcom.com>, gmecm at diy-efi.org, diy_efi at diy-efi.org, 
	third-gen at lists.f-body.org
Subject: RE: [Gmecm] 305/350 Swap 10-month Progress Report...

> finally broke down and installed a new cat. Car passed 15mph with NOx 10%
> below max allowable. Strange though that the 25mph test remained virtally
> unchanged from when I had it tested with the gutted cat.

About cats--
CarCraft magazine has been doing a bunch of dyno tests with and without cats. They have discovered that a properly installed hi-performance cat INCREASES torque and horsepower, usually 5-10 ft-lbs increase in torque and 5-7 more horsepower.

Don't be too quick to gut out or eliminate the cat. Instead, replace it with a CatCo or Random Technologies hi-performance cat. Random is the best, but danged expensive. CatCo is a very, very close second place, and usually costs under a hundred bucks.

Dave Haggard