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Originally Posted by TiAgX5
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Everything I have posted I noted as the general consensus of current information or it might, could, may or may not deliver a particular result of horsepower and/or torque.
The older the articles I found the more likely there were several schools of 'expert' conclusions. There are still anecdotal 'expert' counterpoints or particular applications that don't hold true to the general consensus. I am not going to challenge the findings of Lingenfelter or Hennessey. I have read other similar test findings from reputable organizations.
It is important to note the Lingenfelter article is about conclusions drawn in 1996 derived from a small block Chevy. It could well be that the H-pipe delivered in that particular application. The X-pipe was not a consideration then. This following are their current offerings:
Akrapovic Stainless Evolution Exhaust ZO6 ZR1 Corvette 2006-2012 - Lingenfelter Performance Corsa Camaro SS Stainless Steel Cat Back Exhaust 6 Speed AT 2010-2013 - Lingenfelter Performance While neither look like the X-pipe pictured in this thread, both merge the two sides to equalize the exhaust and contribute to scavenging.
I assume this article was before X-pipes were a factor. Meaning, there is no comparison where Lingenfelter might conclude--don't bother with and H-pipe if performance is the goal.
The phrase you mention read-- additional torque was at or below peak torque. That doesn't mean to you the gain is very near peak torque? If that was the case, per my chevy small block days, the torque peak was at 3500 to 4000 RPMs and wouldn't be usable normal street driving for me.
The majority of current findings are that the H-pipe measured performance benefits are within the range of dyno error or the variables in other conditions that impact torque and horsepower from one dyno run to the other. As I mentioned in previous posts, results vary per the application. Since an H-pipe does equalize the exhaust the Lingenfelter testing base may be one of those applications that the H-pipe is a performance benefit. On the other hand the increase in exhaust velocity or scavenging via a H-pipe is very little to none so my guess any increase was very small.
I have not seen the Hennessey information you reference. Does it say the unequal length was the reason they scrapped the X-pipe? The impact on X-pipe performance with unequal exhaust lengths from the exhaust has been a specific question I have asked. Both performance exhaust makers clearly said it does not. The exhaust is still equalized and the level of scavenging does not change.
The following is the current SRT8 exhaust offering which includes and X-pipe but not the components that would be unequal length:
MagnFlow Stainless Steel Cat-Back System Performance Exhaust | 2006 - 2010 Jeep SRT-8 Parts & Accessories | Hennessey Performance
I think the only conclusions of this discussion that is worthwhile is that either route will change the sound, the X-pipe will very likely result in an improvement of how long it takes from point A to point B and how you get the best performance may be different for a 3.0, 4,4, 4.6 4.8 and also different depending on what engine mods or exhaust system mods one has already done.
IMO,if you want the biggest improvement of A to B performance of a X5--reduce the back pressure rather than a H,Y,X or whatever pipe. That was the first thing we did in the good ol' days. It still holds true for the vast majority of applications, the X5 not being a part of the few where it is detrimental.