I have doing some research and it seems a surprisingly large amout of power can be had from this simple modification, if like me you already have the cats done. From what I remember both pipes only have a structural connection between them after they exit the cats. A connection afterwards can reap many benefits.

A general consensus is that an H connections allows better low end and mid torque (much needed in the Vantage) while the X connection is better higher up in the rev range. Reports of 10 bhp + and healthy doses of torque have been reported from V8 engines of similiar engine size!

The reason why the connection helps is so that the exhaust gases can exit quicker from both pipes while firing from the other bank. The scouraging of gases is improved as is gas flow. Furthermore there is a slight vacuum caused that allows further benefit.

The best position for the connector is supposed to be as far back as possible so that the gases are slightly less hot when transference is possible to the other pipe.

I think I will be booking my car in the the custom exhaust shop and see what they can do .

 

Interesting stuff.. Especially the potential for low end tq! Would be great to see the dyno once the project is done.

 

This one has been "under development" for over a year. Might be worth a call.
http://www.supersprint.com/en/IT/pro...velopment.aspx

 

I have either available. PM me Vergis if you're interested I'm sure we can work out an arrangement.

 

I discussed this years ago during my project on the previous 4.3 vantage. It's the main reason I chose the RPI catback exhaust because it was one of the only ones that had a true X-pipe in the exhaust system.

X-pipe is almost always better than H-pipe, also x-pipe helps smoothen out the exhaust pulses and improve high end HP as well. My RPI didn't make anything below 6000rpm, but made 13hp @ wheels at redline due to its improved scavenging effects. So yes they definitely work.

 

Interesting. Here is a comparison on a Ford Mustang 5 Litre V8 that I found which support better low end torque with an H pipe over an X pipe. For street driving which I do the most low end torque is really important:

 

Not sure what this mod would cost but I think it would need to be pretty cheap for me to do it if it only yielded me an additional 10 bhp. Just sayin'.

 

Hi Stuart,
will these work for the V12V as well?
If so PM me with some pricing & availability.
Thanks!
I added an X-pipe to my supercharged C5 corvette, and I gained 22hp at the wheels (back to back dyno). It also smoothed out the sound a little.
I would imagine the gains on my V12V would be less as my C5 was already running 512 rwhp. 10 hp sounds more realistic for the V12V.

 

It is. Using existing pipes my exhaust shop can make an H connector towards the rear of the car which is the best place for it.....for... $160 equivilant!

And yes they use aircraft grade steel and do great tig welds too. Cant wait to get it done. For me the low end torque benefits will be the most interesting.

 

A properly designed high flow X-pipe should still out perform and Hpipe, and it should sound better too as well due to X-pipes superior scavenging effects. h-pipes, just balance they pulses, they do nothing for scavenging. Many of the cars that I have had H-pipes from the factory, still benefitted from even more gains by switching over to an X-pipe. H-pipe is still better than nothing, but nobody does H-pipes anymore, everyone goes straight to X-pipes.

Also, you actually want the X-pipes to be closer to the headers as possible, preferably pre-cats if possible. But on the astons that is not easy to do due to space restrictions. The closer to the heads the X-pipe is, the greater the effects. I have a feeling that's why my X-pipe on the RPI only helped really on top end past 6000rpm and did little on low end, it's because the X was so far back in the system that it wasn't close enough to improve torque response in low end to mid range. Also, the X-pipe gains will be greater on car with high flow cats, versus stock cats which are just too restrictive.

Hope that helps

 

Thanks 007 Vantage some very interesting thoughts based on real world experience.

I may actually opt for X pipes that are well designed. Maybe having X pipes closer to the headers and H pipes at the back is the way to go

 

Guys, we're going to do some testing on X-pipe designs next week and see what the real-world gains are like on the AM. If they are good we'll put this into production, we can make these relatively inexpensively.

 

i'm in for an x-pipe if the price is right!

 

^^^^ If you can, please make before and after videos so we can get an idea of what it would sound like.

 

I delay if you can have the X-pipe either a part of the cats and make it a 1piece design, that would be the ideal place. Whether you do pre-cat or post-cat is up to you, I'm sure they're are pros/cons for both. Angle wise, it appears aging the cats merge at 45degree angles towards one another, then having x-pipe immediately after the cats will help the scavenging effect "pull" the air through the high flow cats at a higher velocity than would happen naturally otherwise. You have to make sure the X-pipe cross section is larger cross section. You do not want two pipes two merge into the space of one pipe otherwise it will actually becomes restrictive. Getting x-pipes perfect is an artwork, it's not as simple as it seems, but when done properly, they can do wonders to a powerband.

It's much cheaper to incorporate the X into the cats portion, then trying to replace the entire stock mid pipes (both expensive and unnecessary as the stock pipes are 100% free flowing.

Before/after for all different prototypes would be fantastic Stu if you can make it happen.
Godspeed!