So deleted secondary cats....




Sorry no pics but have not been able to get under the car properly yet.
OEM resonator remains in place with oem fittings so I can swap back to cat section if required
.Anyhow it may be complete placebo but car definitely feels more "alert" and feels faster ... I really cant say for sure but that's the sensation and Ill take that.
I've NOT gone for a balance/kiss pipe ... any thoughts on this from a performance perspective ?








Think its decent almost plug and play setup now between test version and "on the road". I was reluctant to delete the mid cats for emissions regs etc but I am really surprised at the but dyno and the change in sound .. was most welcome.
Not necessarily. Flowmaster has performed extensive dyno testing of traditional “H” pipes and various “X” pipe designs and has found that in most typical street applications, there are no clear benefits of one over the other. “X” pipes have become a buzz word in the world of performance exhaust, and are now produced in a wide variety of styles and designs. Some types perform well, and some others can be quite bad due to the excessive turbulence generated in the merge area. Unlike anything else available, Flowmasters Scavenger X-Pipe design features patented D-port technology to maximize the communication surface area between the two banks of cylinders, and maintain the exhaust pulse velocity for peak scavenging. In terms of sound, an X-pipe will generally provide a smoother, higher pitched tone than that of a traditional “H” crossover pipe. In some specialized race applications such as small cubic inch engines and /or restricted (small bore) carburetors, we have found that an “X” pipe can respond well over an “H” pipe. As with all race applications, there is no substitute for time on the dyno, developing the engine package as a system."
here's an H-pipe vs X-pipe chart (from a Mustang site)

hardly any difference but the X-pipe will be quieter vs the h-pipe - either way - it's better than no cross-pipe altogether because it helps even out the pulse in the exhaust and helps with scavenging
I went a different route with primary and secondary removed and replaced with one set of 200 cell cats and an X pipe into OEM Resonator. I had the exhaust checked last week from the cat back and still found over 0.3 bar of back pressure which surprised me as most seem to suggest that the back pressure is mostly in the cats and headers.
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I need to think about the H pipe a bit ... It seems the location of the pipe would be quite important to get the scavanging benefits? I'll keep car like this for a bit and see how I like it ... Spent way too much as it is...

That hp comparison is interesting .. I wonder how no H/X pipe would have fared? The link pipe just merges the gases slightly ahead of the resonator .. So I'm struggling to understand the physics here...
0.3 bar back pressure from resonator back I.e excluding the 200 cell cats? Ufff looks like more gains available then !
Btw I went for 3" tubing for mid section....
Last edited by stevebez; Jul 16, 2012 at 02:10 AM.
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Yep the resonator is effectively a link pipe but seems its main task is to eliminate drone. Seems a link pipe also helps in this regard but from what I have read can also add a bit of power while reducing noise. App it cannot compromise power ...
I quite like the sound now and will stick with it a whole longer and see how it goes ....




They very busy and had the car a week but did a very clean job, although £720 worth
Which is way more than I expected and was quoted.Fair amount of piping + flexi's and app took a days labour to finalise...




I have spoken with Hayward and Scott about a complete system including full length headers, as you say not cheap about 2 terms worth









I think deleting primary and refitting secondaries will make it quieter

I removed the secondarys because i was afraid to get cel of the o2-sensors
but now i think i should remove the primarys and reinstall the secondarys to get the heat away of the enginebay.




If not, I agree I would chop primaries before I got rid of secondaries.
What headers u have?

But do you really think the sound would get quieter?
I have got some vrp-shorties but they are reweld so have to do something that they won't crack again.
Do you have a way of recording a video and posting it by any chance? There are a lot of videos around with those with shorties, keeping their primaries but having gotten rid of their secondaries, but none (that I've come across) that show how the car sounds with the kleemann headers, secondary cat delete, oem resonator and oem muffler.




I got no link pipe so its louder than those with a link pipe. It definitely does not sound like a tractor! Still refined on mild driving, but give it some and wham!
I dont drive the car much (not a DD) so I dont mind the louder pitch as it adds some occasion to the driving experience. Maybe if I used it as a DD I might fit a link pipe to tone it down a touch.
Ill try do a video if I can but not much one can do when car is stationary ...






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