This is why I believe most after market exhaust dont work, especially poorly engineered if any. You cant just paste some parts together and tell us the consumer they work.......just add other parts and my exhaust will shine.
This is for the performance geeks.......long shot, but SRT8Jeep emailed me and asked if I thought reversion thru the X Pipe could be causing the horsepower drop.....compared to the stock muffler dyno runs. So I started thinking....looking in archives..... doing some research and found that first of all H,Y and X pipes were primarily developed in Nascar, F1, etc and later adopted to street/race cars. All applications require that the exhaust be of equal lengths starting at the headers or exhaust manifold running down just past the transmission and at that point the X pipe is installed then the exhaust continues. Most street applications from current manufacturers using dual exhaust and some type of "balance tube" is GM on the GTO, Corvette and Cadillac.......Ford uses it on the Mustang.....and Chrysler uses it on the SRT8 300 and Charger/Magnum. They all have one thing in common.........equal exhaust tube size and equal length dual exhaust, typically down the center of the vehicle.
Problem.......the Jeep! Designed as a single exhaust vehicle with the gas tank in the way. SRT8 comes along and installs an engine that requires dual exhaust. So they engineer it the best they can.......duals (2.75") with a longer length on one side. The driver side is longer starting at the manifold and coming over to join the shorter (passenger) side. Then they criss cross it into one muffler.....(inside the stock muffler)...the longer side exits at the flow thru chamber but wait, you will have uneven pulse waves at the muffler SO...they install a short metal block to slow down the shorter side but chamber them together in the first 1/4 of the muffler. My humble opinion.........they quieted it down from being raspy, but more importantly they attempted to tune the muffler by equalizing the pressure, but also allowing the (longer) flow thru side to "pull" on the shorter side (vacuum) with no pulse back to the exhaust valve........and us technoids know this disturbs the incoming charge and depending on the cam overlap.......could cause some reversion......loss of power......bottom line they tuned the stock exhaust to compromise an uneven exhaust length........and in my humble opinion that is why the the driver side rear resonator pipe has the loop, to equal the total length of the exhaust system.
Question??? When have you ever seen a performance vehicle with one side of the exhaust longer (total length) than the other???
We come along.......wanting more power.......rip off the stock system or portions of it, not fully understanding. The BIGGEST mistake is from cat back installing an X pipe, where an X pipe has no business......and installing a exhaust system that does not take into account an existing system of unequal length and a tube size of 2.75"!!!
X PIPE....developed to act as a "diffuser".......as the exhaust pulse comes down one of the two Jeep header pipes (which are shorties and uneven lengths as well) it hits the X pipe and "sees" an expansion section. This section acts to slow down the flow and increase pressure. This in turn creates a negative pressure reflection which travel back up the opposite pipe. If the header or header section is tuned correctly then this negative pressure pulse arrives at the exhaust valve of the opposite cylinder in time to help scavenge the last of the exhaust gasses from that cylinder as well as pull on the arriving fresh air charge which is the overlap period of the camshaft.
Again to the "gear heads" that read this it will all make sense and to some non gear heads as well.
Conclusion; What was I thinking????? Why did I have a X Pipe designed and installed in the location I did???? The Jeep has an unequal length factory headers and substantially unequal length cross over center (catalytic) pipe/pipes. Any X Pipe is going to disturb the pressure wave activity. If one now understands the function and where and why it's used and placement are critical to engine performance....then one can now assume that on the Jeep an X pipe designed exhaust will hurt overall performance, and that is why I lost power on the dyno my second time. You just can't put one in because it's suppossed to work IF YOU DONT KNOW HOW AND WHY IT WORKS AND YOU DONT ENGINEER IT AND PROVE IT WORKS!!