Originally Posted by 007 Vantage

Hey guys,

Still have a few more tech things to post even though the Aston is gone, but I will just post them here to save time. I purchased a set of stock cats a while back just to see exactly what was inside them. It was very surprising to find out they are not a normal single set of cats.

It turns out our stock OEM cats are actually not one pair of cats but TWO pair of cats. Obvioulsy Aston has to comply with strict european & american emissions standards, but the stock exhaust system simply did not leave much room for emissions equipment in the mid-pipes. Therefore, they actually shoved both the Primary & Secondary cats into ONE housing. From the outside it appears to be just one cat per bank, but if you look more closely it becomes evident this is not the case.

The OEM Primary section of the cat is a 600-cell ceramic core cat. Immediately after the Primary portion there is a secondary O2 Chamber roughly 1" wide where the secondary O2 sensor sits (you can clearly see this area in attached picture from the outside by the "heat signature ring" all the way around in the middle of the cat). Immediately after this chamber is another 400-cell ceramic core secondary cat to further clean up the emissions.

This design allows for the maximum amount of emissions scrubbing in the shortest possible distance. However, it also means the cats get extremely hot and the secondary O2 sensors are subject to extreme heat/pressures in that secondary O2 chamber (which is probably why they fail relatively quickly compared to most O2 sensors). This is also probably why the cats fail so quickly (on top of the horrible rich condition the car exhibits)

When you upgrade to high flow cats what you are actually doing is a secondary cat delete + a high flow primary. It is for this reason why the cat upgrades on the aston make the car so much louder compared to other applications where the sound difference may not be as drastic. Is 15-20 HP realistic for such a drastic change in restriction, sure .... but I probably wouldn't bet much more than than that since the rest of the exhaust system is pretty much just straight pipes and a catback at the end.

Ultimately the real place to unlock more power (besides the cats) will be the headers. The stock headers, although tubular in design, have a very restrictive pair of squeezed downpipes which give it the camel toe shape.

To unlock the absolute maximum amount of power, you will have to run a long tube set of tubular headers with a full 3" merge pipe coming to a specially matched 3" inlet on the cat (exit still being the same diameter). You can run a 2.75" pipe leading to the regular aftermarket 2.75" cat inlet, but you will be leaving HP on the table. However, its only recommended to run larger than 2.75" once a set of high performance headers is developed, until then it would be a waste of time and money. For now though until such a set is developed, the 2.75" high flow cats are more than enough improvement in flow for the stock system.

Based on the restriction of the headers I would not be shocked if another 15-20HP at the crank could be picked up from a proper set of long tube headers.

Anyways, just thought I would share that as it appears nobody has ever mentioned any of this before

Hope that helps,
007

Originally Posted by 007 Vantage

I don't think anybody knew frankly, then again nobody chopped up a set of OEM cats to find out lol. If you look closely at a picture of cats blown through you can see the two separate cat cores. What is shocking is that not a single actual real world dyno graph exists of the gains ... Just claims