Cats are definitely the most noticeable change on a V8V! Between the extra hp and exhaust sound, they're hard to beat.

Only thing jumping out at me is the catalyst material itself. I'm wondering if the extra material in the KH cats burns off or something. And if it does burn off, how will it affect performance of the catalyst? Here's a look at the catalyst material in my 200-cell cats with several thousand miles on them.

 

Has anyone smogged the cars with the HS high flows after thousands of miles? That will tell if the cats are still performing properly on the smog reduction side.

 

Awesome writeup PKS! I agree with all your statements, above 4krpm with the KH cats sounds absolutely epic. I alreayd dynoed the gians so I can assure you the low end to mid range torque boost is very significant. It makes the 4.3 feel like the 4.7 as far as torque goes.

Glad you are enjoying the new modification!

 

I had a chance to record a few audio files today for the Harrison Signature High Flow cats. There are three audio files:

1st one: Cold start with fuse 22 in place
2nd one: Warmed up with fuse 22 in place
3rd one: Warmed up with fuse 22 pulled out

Fuse 22 makes a big difference when IN and when OUT. With it IN, the car is much much quieter when up to speed and coasting. In my audio runs, I'll stab the throttle in several places and will hold the RPMs around 2500 to 3000 in one or two areas in the run.

You'll be able to hear the difference between the two "warmed up" audio files with and without fuse 22 in place. The mic was placed about 6 - 7 feet behind the car when the recording was made. With fuse 22 OUT, the exhaust is much more consistent in each gear - but it's pretty loud. With it IN, the aggressive exhaust note is only on take off and will quiet down pretty quickly once you're at speed and not pushing the throttle.

The cold start audio file shows how the cats can crackle a bit when cold. Also when the car is about to drop the idle back down after warming up a bit, you'll hear a much deeper exhaust note for about 10 seconds until the idle drops to the "warmed up" position around 800 RPMs.

Enjoy.

 

A few of you PM'd me and asked if I'd do some video footage, so here they are. I did four runs and they were two with fuse 22 in and two with fuse 22 out.

Video 1 and 2: Runs with fuse 22 IN and you can hear how the exhaust quiets down after 1st gear.

Video 3 and 4: Runs with fuse 22 OUT and you can definitely hear the difference with up shifting. The exhaust note is there in every gear.

I'm going to run the car with fuse 22 in for now as that's the best balance with windows down and up. With the fuse out, it's loud all the time, especially with the windows down.

 

If anyone is interested I have a slightly used set (~300 miles) I'd be willing to make someone a smoking deal on.

 

Interested. I PM'd you.

 

Any second hand cats still for sale? PM me

 

Sent you a PM.

 

Any cats for 4.7L?

 

If you have a 2009 or 2010, the KH cats you're reading about will fit fine. Just like these:
http://www.velocityap.com/Aston-Mart...mv8200cell.htm

If you have a 2011-on, you can replace the secondaries with these:
http://www.velocityap.com/Aston-Mart...mv8100cell.htm

Or These:
http://www.velocityap.com/Aston-Mart...8decatpipe.htm

Or if you fit headers at the same time you can fit the KH or the first ones I listed as long as you do both together!

 

Has anyone gone catless, either the Harrison signature test pipe or AP Velocity test pipe? If they HFC can yield a significant increase in power & sound, I would image going catless would be even better! Shouldn't be too hard to swap in the cats every 2 years for emissions testing. Anyone gone catless please chime in.

Thanks!

 

From my experience on another car (Lotus Esprit V8), going from OEM cat to high flow cat adds about 25 HP, going from high flow cat to catless adds another 5 HP, these were dyno numbers, the noise level will increase about 30-50% from high flow cats to catless

 

Great! thanks for sharing. Will going catless on the Vantage be livable on a day to day basis? Keeping the OEM exhaust to quiet thing down. I love to hear more sounds from the Vantage but don't want a headache or my ears ringing at the end of a drive.

 

It's an X-pipe you seek, then. It smooths out the exhaust sound, and quiets it down, particularly in the residential driving range. Still more than enough wail at full chat.