# Custom Pypes/Borla XS '04 system



## svede1212 (Nov 1, 2005)

Well I got it done. It played out pretty much what I thought. Two guys argued with me it wouldn't work until I told them to go ahead and get it done. It went in perfectly. Actually I'm happy things turned out the way it did using a 2½" catlessback. 

I think the biggest improvements besides the fantastic tone was losing a lot of weight and my hyper-sensitive hemorrhoridal butt dyno said I gained low end torque from a better utilization of the X. It's cheaper that the full Borla catback and uses larger muffs than you get with that too. The Pypes X and Pypes collector extensions together eliminate the mid pipes so it goes straight from collectors to X to muffs in one piece. I'll be dyno-ing in a couple of weeks and compare torque curves. 

I have a dB app for my Razr and did a before and after scan of the setups. With a Magnaflow X, two-24" Cobrapacks and two-Spintech Pro Streets I was about 81 dB at 10' behind the exhausts. With the new 2½" Pypes X and the two-Borla XS I am at 80 dB at idle but louder at WOT.

Still don't have a sound clip altho they sound awesome. Here's some pics of the install. The system layed out on the floor, 12" long x 3" Pypes collector extenders, smooth 3">2½" fittings, Pypes X pipe with "drive tunnel" spacing, Borla XS mufflers.










I had 3 bolt flanges welded on my SLP headers a long time ago. It made bolting up the Pypes 12" extenders a breeze to put on. The Pypes pieces are very nice including the X design and notice the extra thick flange on the collector extender. It mic'ed out at .425" thick!










The 14"x9½"x4" Borla XS were a close fit but tucked up pretty nicely.










Getting the system set up to reuse my Borla inter-cooled tips (only one on in this pic). The installer routed the tails the same way SLP does their loud mouth. My old setup had the pass side wrapped around the back of the Harrop cover. With this I got a Borla system for around $650 installed with custom bent tail pipes, no Harrop cover issues, including "mids" and using the larger XS muff. I also ended up getting the X over a foot closer to the collectors and with no muff ahead of it to damp out the pulses a much better scavenging system.


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## danfigg (Sep 27, 2009)

*re*

much more straighter exhaust path nice job I knew it would work. I have my exhaust on as well and it goes in to the shop tomorrow to finish the tails pipes...danfigg


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## svede1212 (Nov 1, 2005)

The shop I use is great. I just pulled in with no appointment and 2½" hours later including wait for the queue I was pulling out. They swore my car was going to be a lot louder than with the 4 mufflers that were on it. I was starting to doubt it but they were wrong. 

Outside of my stock exhaust that wouldn't be able to keep up with my engine now this is my favorite. As I said in another forum this one leaves no doubt I have a serious engine but it sounds adult too. I went to a friends cottage yesterday and one of the guys there said " I thought maybe your car was a Cavalier until you started it. When I heard it I saw it was a GTO". To me that's a perfect compliment. Kind of a John Wayne thing. No need to call attention to yourself but be able to take care of business instead of pose. 

I have to get my kid to hold a camera and take a vid of it. AT WOT is sounds like a smooth running, screaming machine. Hope you get a vid up of yours when it's done.

Here's someone else's picture of what the muffler looks like looking through the 14" of muff. Just amazing the sound and power you get out of it. That's the only thing between the engine and the exit besides the X pipe. BTW I liked the looks of the design of the Pypes X compared to the Magnaflow stamped one I took off.


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## BWinc (Sep 21, 2005)

Very nice, Jerry. Got rid of the slp mids for the better flow and much cleaner look. If I decide I don't like the sound of the stock mufflers when I install my LTs I'll be looking at the Borla XS from the axle on back.


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## svede1212 (Nov 1, 2005)

The Pypes setup worked perfectly for what I was trying to accomplish. On open headers the collector works best about 18" long. That gives the best torque below peak. 

One way to test that is to paint a white stripe on the collector and then do a couple of spirited WOT runs to see where the paint burns off readily. The test shows where the gases are starting to cool and from that exit point on the open headers are tuned for a reflected wave for more scavenging. 

The extenders and transitions give me about 16" of 3" collector. If the gases were starting to cool at 18" then that should be about where they are cooled and shrunk enough to flow close to the same speed in a 2.5" tube. 

That high velocity helps a bunch at the X, more so than lazy gases. From every good technical post I've seen getting the X up as close as you can past the collector allows it to work better. Most have cited to try to get within 24". I went from around mid 46" to about 30" X spacing with this system. I've seen guys say that they got no difference from a X or a H but I wonder how much of that was from placing the X so far back and in a lot of cases behind a cat affecting pulses.

The short distance from the X to the muffs I believe represent the "end" of the system from the engine looking back. When the flow expands into an area at least 2x the original diameter the engine and exhaust system "sees" that as the end of the line. I believe the large packed mufflers should look like a least 2X the pipe diameter and cause things to cool a lot more and easily make their way out the back while maintaining good velocity. . . . At least that was my theory. I think the principles are sound.

PS, I weighed today and the system lost over 25# with the new one


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## danfigg (Sep 27, 2009)

*re*

I have to say your on point here. Start at the collector and work your way back. I have also heard that muffler placement also give a different affect. There are only 3 places that I have seen mufflers at the header collectors. muffler midway usually under the rear seats and at the very end of the exhaust. I sure there is some affect at each of these points. know throw in the X or H pipes and tuning the header with a longer collector and there is alot of science here. Imagine having to tune your exhaust....Danfigg


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## svede1212 (Nov 1, 2005)

I think what's often ignored is reflected waves and their effect. It's hard to imagine a pressure wave traveling fully against a high velocity flowing gas but it does. Sound is a pressure wave with higher and lower pressure areas. If you take off your intake and expose the TB you'll hear a lot of sound coming out when you floor it. That sound is traveling upstream past the intake valve and out the TB. The same thing happens with reflected waves who's timing is determined by the parts traveling against the flow in the exhaust pipe with some frequencies re-enforcing that pressure and some canceling it. 

Another fine point is gas temp. I've been trying to determine what happens to gas velocity in the pipes. The gases exit the engine port at up to 1600* at WOT. At the tail pipe the temp is in the hundreds. The volume of that gas has shrunk a huge amount due to losing heat along the path. That shrinking causes a big slow down in speed as it happens. My plan had always been to have 2.5" tails to keep velocity up. Lazy, slowed down gases "clog" the pipe and the gases ahead of them have to "push" them out of the way.

I don't think all of the "science" improves HP a large amount but you can gain a few and play with the torque curve. Something that has me scratching my head is people that will spend hundreds more on a set of headers to get a 10-15 HP boost over another brand and then just slap on any exhaust, with tone being the primary factor, and then potentially losing 10 HP. 

Some interesting stuff

http://www.superchevy.com/technical/engines_drivetrain/exhaust/0505phr_exh/viewall.html

Exhaust System Technology: Science and Implementation of High Performance Exhaust Systems

A video on collector length






for Harleys but some car examples. The theories are still the same.

RB Racing LSR 2-1 Exhaust Technology

Build Your Own Exhaust - Kemper's Web Page


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## svede1212 (Nov 1, 2005)

I have one tiny clip of idle and rev. I need a cameraman to get a proper one. When I cold started her I measured the dBs from the front and back I got 101 dB from the front! The intake combined with the NW 102 just screams until she warms up a little and the IAC starts closing. The exhaust end was a sane 80 dB at idle. Amazing looking at thru the mufflers and then hearing how much better it was than with the 4 mufflers they replaced.

Borla Idle - YouTube.


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## jpalamar (Jul 22, 2008)

This thread has some really good info in it.


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## Ironmn715 (Nov 30, 2012)

I know this is old but do you have the part number for the Pypes X pipe you used? Is that just their stock off the rack X pipe?

Thanks.

'Moe


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## smitty2919 (Jan 24, 2012)

What were the resulting gains from the re-worked exhaust?


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## Ironmn715 (Nov 30, 2012)

Are the tail pipes just standard aluminized steel tube that you used? Also is that the off the shelf Pypes Universal X pipe kit? Really like the idea of this setup. I am leaning towards using MRT mufflers but otherwise this seems like a very economical way to have a solid custom exhaust.

'Moe


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## svede1212 (Nov 1, 2005)

The system is just Pypes 18" collector extenders and off the shelf "narrow tunnel" X-pipe kit. The tails are just aluminized steel and will probably only last 15-20 years. I gained a lot below 3,000 and at 2,000 it was over 30 RWHP/RWTQ


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## Ironmn715 (Nov 30, 2012)

Thanks for the information Svede. Like I said seems lik a very economical way to get a nice well performing exhaust. 

'Moe


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