Hi, This is a fairly tricky question I have been dealing with for a while. This is one of the only forums that I've found that might be able to address it. The situation I am faced with is how to get two 2.5 inch exhaust pipes around a jaguars IRS in a jag XJ6. Over and around are out of the question so the only answer is under. I would like to maximize ground clearance as I've put alot of work into my TIG welded mandrel bent dual 2.5 inch exhaust up to this point. The car is a Jaguar XJ6 so the before axle turn downs aren't cutting it with the booming resonance in the passenger cabin.

The question: Can I construct a box for the exaust to pass through with smooth circular 2.5 inch inlets and out lets that fits to the bottom of the differential pan. It would be about 12in wide and 1 inch tall there would be more surface area than the two 2.5 inch pipes. My concern is the exhaust flow in this box. Should the two sides be joined? X'ed any baffles or anything? or just seperated. There is already an H-pipe in the system. Will square corners cause issues? what exactly would happen in this situation with the exhaust flow? Will there be any resonance or collison of the gasses??

Or should I just not worry and run the 2.5 inch exhaust with tubing under and not worry about the extra 1.5-2 inches it sticks down because its centered on the axle. I believe C4 corvettes do this...

Any insight or opinions would be greatly appreciated.

Thanks!
Conor Musgrave.

 

NASCAR 800 hp engines use wide flat "boom tubes". Look at this link for some ideas.

http://www.drgas.com/catalog_nascar.asp

They get as short as 1-1/4 inches. The flow dividers also are the support. I would use this idea if I were doing it, and probably start with 1-1/4 or 1-3/8 round tubing, slice it lengthwise and use it for the sides. If you needed a bend, start with a tube bend and go from there.

You could split the outlets into 2 tailpipes out to the rear corners or perhaps 4 round tailpipes out the center? You sound handy with the Tig, so this should be a piece of cake.

My $.02

 

Wow! thanks I didn't even think of that, that is a great idea for the tube for the sides, that'll make it much easier. Thanks!

 

You will likely have some resonance on the flat sides. Flat surfaces on silencers tend to "oil-can" and at certain frequencies will buzz. The larger the surface, the lower the vibration frequency. You add stiffening ribs to the outside and baffles inside to fix the problem.

 

make sure you REDUCE the backpressure. those things already have a huge tendancy to crack manifolds as soon as the cats become slightly clogged. Pretty big design flaw, along with a lot of other components.