For performance and a more mellow sound a merge box is a good idea like Aston Martin did on the DB7 with the v12.



David Vizard pioneered the dissemination of this knowledge into the public domain here.

Auto Exhaust Science


This type of device needs to be of a specific volume relative to the engine. It allow exhaust pulses to coalesce. This a good thing if you like a more mellow and quiet exhaust becasue a baffled muffler flows more with an exhaust gas steam rather than a high velocity pulses. If you spread out the stream across two baffled performance mufflers you end up with a quieter exhaust with less loss.

Theoretically speaking, the engine sees the merge box as an open exhaust system so an X pipe ahead of the merge box may help scavenging if you've got the exhaust duration to take advantage of that effect.

 

Agreed Daim, if I were to aim for quiet when cruising and about town but loud (very) when really going for it, then I would go for a combination exhaust with straight through mufflers and low restriction cat coupled with a Y valve to bypass all mufflers when activated (with possibility of auto actuation when more than three quarter throttle

 

I did this on my SBC 406 convert, had a custom merge box made with the correct volume, one side is muffled, the other outlet is open to atmosphere and a vacuum operated valve snaps open with a solenoid controlled by the ECM. Result... Perfectly quiet when closed, when the valve opens it's loud and screams. Feels exactly like a 50 shot when the switch over takes place at 3500 RPM with TPS > 50%

 

Icsamerica,

thanks for the link to the great David Vizard article

 

Big pipes. That, in my opinion, is what mine needs. Not for flow, but for bass. Small displacement motors are making such remarkably low growls! Just dumping tiny tinny toots into a 3" pipe with cheep straight through mufflers.

Im currently planning stock manifolds and downpipes to a custom 3" collector straight back to an an H crossover before the front Borla Pro XSs. Duals out of that to squared pipes over the axle to fit, then another 3" collector into the rear Borla XR-1s.

Either of these mufflers alone would be too much to suit me. Both should be just enough! Looking for that deep burbling idle, ferocious deep growling, and banshee wail at high RPMs.

 

this an old pic 1985 about, car always sounded great , BUT! V12 engines always sound great, like my 1937 Lincoln V12 coupe.

i been around V12s for awhile!

 

Even just with some different tailpipes you'll get a deeper bass sound... You must have larger tips though!

Here a comparisson between my XJ8 with standard tailpipes and then with some 4" diameter pipes...

Standard pipes:

Larger pipes:

The rest of the exhaust is identical...

Then you rip it all out, refit some factory mufflers at the rear and then all piping incl. an X-pipe up front and you get this:


The XJ-S would profit just by ditching the resonators (infront of the rear axles). Removing the cats causes the areas to turn into some small resonators resulting in the tone changing not a bit. Larger piping can work, but then you get to that area "how large is large?" and "how large can the entire system be?"

 

I've played with pipes since way back. No science at all in my creations.


1. My first one. Slightly warmed up Ford T four banger in fenderless roadster.
I cut a hoe about 1 1/2' in the exhaust manifold at the front. So, now, the outlet at the back of the manifold and the new one up front. Stock pipe sans muffler at the back outlet. Flex pipe from the front all the way back. Dual straight pipes. T "chuckle" gone. A rather neat "roar" to my ears. Not so much to a cop and the neighbors!!!


2. Decades later, A T again. Diffrant theme. Speedster of the 20's. Single pipe, a bit larger. No muffler. But exiting into a larger pipe, open at both ends. Objective. Road draft to scavenge. Effective? who knows.


Carl

 

back around 1949/1951 we would take off center muffler, put in a glass pack, but the thing that gave it a good sound was called the ECHO CAN, 4" diam. at least 2 ft long!

yup echocan dual exhausts. i guess it was just that it made the exhaust pulses ECHO.

have heard it called echo chambers also, same effect.