Relieving the pressure build up is definitely correlated to the increase in power production, via the use of a crossover pipe, but the reasoning is actually much simpler than that. Picture what's really going on in the exhaust system of a 2-plane V8. The successive firing of 2 cylinders on 1 side, while nothing happens on the other; the opposite bank during that time has a lower net pressure. Adding any type of crossover section simply gives the exhaust another pipe to travel down during the moments of excess pressure.

TK

 

Although it may seem that simple, I'll have to disagree. While the typical American V8 does have cylinders that fire on one bank successively, they are out of phase enough to not hamper each other. The leading pulse will cause an area of low pressure behind it as it moves down the pipe, which is beneficial to the following pulse.

If it was just a straight piece of pipe that opened up soon enough, each pulse would leave at it own time with nothing stopping it. But there are enough physical obstructions in the line that not all the pulse wants to leave of it's own free will. It reflects.

I have an infrared video camera at work, Fluke Ti5x, that I use to locate hot spots on eqipment. We've used it several times on exhaust systems to pin point where the reflected wave collides with the following pulse. With a straight run and no obstructions you can see the smooth heat pattern generated along the tubing. Any change in the tubing, read muffler, will cause a reflected wave. Some mufflers are worse than others.

A long stretch of tubing can cause resonance, you can see where the standing wave occurs with this camera. The camera is such a great tool that you can see temperature changes in the radiator, engine block, headers, anything that you want to look at. If you look at you oil pan you can see the real level. It's one snell of a tool and it works wonders for exhaust systems.

 

so guys what i understand from you that : in our case inline V6 350z an X-Pipe will reduce the time diffrence in pulse`s and that what makes less rasp and deeper sound ? u know by mixing the pulses !!
and how it will effect the power ,,more or less in low-end HP ? (if i`m right)

 

canceled the X-pipe installing on my APS 2.5 TD, some one advise me to keep it as it is for future if i go F/I since it`s great exhaust with F/I setups .
sorry if you wear waiting for the results

 

Actually if you go turbo, the need for an X probably diminishes. Not sure for supercharging as the firing sequence and pulses down each bank are retained. For NA, some type of cross over is recommended. I've posted all article already. Not sure if you read it or not.

 

so i`m allright ,no x-pipe for my exhaust

 

Our X-pipe research included old and new Hot Rod, Car Craft articles on tri-wye headers and no-connector, H-pipe, X-pipe dyno and track comparsions. This, as well as lengthly converations with well know tuners and automotive (engine) engineers, has supported my personal opinion that X-pipes work best on normally aspirated engines.

Why? X-pipes improve exhaust gas scavenging and cylinder charging while decreasing reversion especially with long duration overlap (emissions) camshafts.

How? Basically as one cylinder's exhaust pulse travels through the x-pipe it creates a low pressure zone between it and the next the next pulse. This low pressure zone exists between each exhause pulse staring at the exhaust valves. Therefore each exhaust pulse helps pull the subsequent pulse along.

Supporting Data? Reviewing numerous (well over 100) 350Z/G35 dyno results the x-pipe has provided the best peak and mean average torque and mean average horsepower numbers to date. One example: Two 05 G35 Coupes 6MT Rev-up engines and the same modifications other than the exhaust systems.

Results:

Car 1 - 7,000 miles -- P/Tq = 250.4 -- P/HP = 276.7 -- MAve/Tq = 232.08 -- MAve/HP = 187.1 -- Non-connected Exhaust.

Car 2 - 4,700 miles -- P/Tq = 263.5 -- P/HP = 274.1 -- MAve/Tq = 240.47 -- MAve/HP = 202.5 -- X-Pipe Exhaust.

Same dyno / same day / nearly same atmospheric conditions / both cars dynoed back to backwithin one hour.

Of course there are exceptions, but my observation was also documented in print in my G35 Dyno Marathon article from a few years back.

 

I've got a question for you exhaust gurus. If I cut the resonators off my Injen and weld in a non-resonated x-pipe in it's place what effects will I see in terms of sound (volume, rasp, pitch, etc.)? And how about the Magnaflow resonated x-pipe in the place of the seperate resonators, but adding long tube headers/headers and test pipes?

 

You'll be out a decent amount of money, and won't add that much power.

 

I'm talking purely sound wise. Even at that a non-resonated x-pipe vs. a resonated x-pipe with test pipes?

 

Dave O. What were the specs of the exhaust systems in the test.

 

I think it would be noticeably louder w/o the resonated x-pipe. I remember a while back Fast Intentions made a special order catback exhaust. It was the same as the regular 2.5" intimidator that they offer, just replaced the resonated magnaflow x-pipe with a unresonated x-pipe. It seemed louder from the sound clip.