For 17000 miles now, I have been running a true dual exhaust, from the cat back on my 04 ram. Stock y pipe was removed. I have been happy with the set up, but have heard many conflicting thoughts on the subject....it was my understanding that less backpressure is better, considering i still have the 2 cats, i believe there is sufficient backpressure.......

point is.....with the HEMI engine, what truly is the best exhaust path to take? True dual, or keep the y-pipe and running 2 out from the muffler?

 

From what ive read on many forums the hemi comes pretty well tuned from the factory. So unless you are doing something up front i.e.; TB, supercharger or somethin lilke that, it would probably be best to leave the factory y-pipe.

*2 cents

 

Hi, I'm led to believe it is of benefit to have a "balance pipe" between both of the banks in a V8.
It has a lot to do with low to mid range torque benefits.
I don't know exactly why, something to do with the back pressure.
My friend has just completed a build of an Ultima c/w a small block Chev pushing out 535 hp on the dyno. He made a bespoke exhaust system including this balance pipe for that reason.
I'll try and find a more technical explanation and PM it later for you.
Hope this helps and please see enclosed pic of my buds Ultima.
It's a little dirty..........we had just finished "playing" when I took the picture.
Regards,
Al.



[IMG]local://upfiles/24099/B409AB120822469881FE7CC1C9BE44EA.jpg[/IMG]

 

Makes sense, equalling out the output from the exhaust.....i am just contemplating installing a y-pipe again, in order to balance things out...just was wanting some tech info, or where to find this info, on this subject.....

 

skaarew.....

Look at answer #6.hope this helps you? I've also enclosed a few other bits of info on exhausts. The mention of larger isn't better in ref to exhaust pipe sizes is a little surprising eh?


FAQ - FREQUENTLY ASKED QUESTIONS

1. How is a Jaguar TT exhaust system different to a big bore one.

A big bore exhaust system merely relieves any restrictions to flow that might exist. As the main restriction on most Jaguars takes place in the 1st silencer boxes, replacing these with our Silencer Substitute Pipes achieves a major part of the gain available from a Large Bore System. Our TT (Twin Tube) system consists of tuned length resonant pipes which play an active part in the scavenging process and help to draw exhaust gases out of the engine. A TT system can therefore increase performance much more than the big bore system and can do so even in the mid-range speeds. Really effective performance systems thrive on high gas velocities - which means pipe sizes do not actually need to be very big. It is instructive to look at the modest pipe sizes found on cars made by such as Ferrari - they are hardly forced to skimp on pipe size yet undoubtedly provide the necessary performance.

5. Can you supply an exhaust system with straight pipes running under the rear axle assembly to avoid the restriction of the bends around the drive-shafts?

Actually it is well known that bends in an exhaust system have no significant effect on performance. The bends around the axle typical of a Jaguar are hardly restrictive at all and there is nothing to be gained by having a straight pipe run.

6. Why don't you have a cross-over pipe between banks on your performance exhaust systems for the V12?

It is true that a crossover can be of benefit to conventional V8 engines (with two plane crank) but only because they have an uneven firing sequence along each cylinder bank, which creates the rather delightful V8 exhaust note. A consequence of having two cylinders firing consecutively on each bank is that the flow rate is briefly doubled, then later in the cycle the long gap between firing impulses halves it, compared to the average flow rate. The temporary high flow rate means the V8 can benefit from using larger exhaust pipe sizes than other engines and a cross-over pipe can help to even out the impulses. It is not obvious but the Jaguar V8 has such a balance pipe within the main silencer box.

A V12, on the other hand, has equally spaced firing impulses along each bank creating an even sequence of pulses. There is no flow variation to require a balance pipe and the system does not have to contend with brief periods of peak flow so pipe sizes can be smaller. The only reason the V12 E Type had a balance pipe was simply to tune the exhaust note.

Another item found on the web:- # What's a "Balance Tube"? Do I want one? -

IF YOU HAVE DUAL EXHAUST, AN "H" PIPE, OR BALANCE TUBE, can aid in reducing that resonance, or "drone", which plagues most short wheelbase vehicles. One about 1 1/4" in diameter is suitable for this application, and should be placed as far forward as possible, according to the literature. Within the past six months Hot Rod Magazine and Car Craft Magazine have done articles on exhaust systems, and addressed the issue of balance tubes. The consensus is that they 1) reduce noise and 2) improve low-end torque. Most people don't realize that dual exhaust with no downstream connection actually makes the V-8 function as two separate, slightly unbalanced, four-cylinder engines. A common misconception is that exhaust gases freely pass back and forth between the two exhaust systems if a balance tube is employed. This is not so. In operation, this short pipe serves mainly as a plenum, or type of resonance chamber. This compliments the plenum found in the intake manifold where both cylinder banks are already "connected". The resulting dynamic feedback balances the sound waves which pulse throughout the intake and exhaust tracts when the intake and exhaust valves open and close. This improves scavenging, and results in a smoother running, and quieter engine. The underlying physics and dynamics of the relationships between intake runner length, exhaust tube diameter, and length, are deep, but in a nutshell, it works for you in good ways.

Warm regards,
Al

 

thanks Al, good reading.....gonna go read again.....

just trying to make this dual exhaust worth it...i've been happy with it, but the engineer in me knows that things aren't 100% balanced, yet.....

 

I think a balance pipe is always suggested for a performance exhaust system. However, I really don't think much horsepower can be made from these motors by simple upgrading the exhaust. You would have to be stuffing more air in at the front end to realize a benefit. I think I lost a bit of low end with my Gibson exhaust.

 

well i do have the intake done, with free flow tube into throttle body. i had my duals long before the intake, and i believe i felt a loss of low end torque. with the addition of the intake mods, i gained low end torque, but really have noticed it has become more of a mid- higher RPM performer........really wanting to crack the code on this.....think i need to go reference those old fluid mechanics textbooks from college........

 

It's pretty simple - one can't have both. You can either modify the exhaust for higher rpm gains losing low rpm torque or vice-versa. Why do you think most systems come "cat back" not messing with the y pipe? You lose torque when you remove the y pipe. You have got to have back pressure for the engine - not too much - but a delicate balance. It all depends on what you want. Do you want to scream from the line or have better top end? Are you a 1/4 mile runner or a speeder? Either way either the torque management or governer is going to get you (LOL).

 

If you are that worried, go with an H pipe setup; ortherwise, just leave it alone and put the money in the gas tank.