AudiOn19s

Talking to my buddy who is a fabricator last night and who will likely be making a mid pipe for me when he's done with the current cage projects he's working on, a question came up that we could not agree on regarding the design of the x-pipe I want for my car.

MOST of the x-pipes I've seen on the market are much like the fabspeed one shown here. Basically two "U" shaped bends with an open, common space where the pipes come together for scavenging / balancing the exhaust. From what I remember the Cargraphic, FVD (M&M), fabspeed units all have this design though some have a larger common area than others.


However the GMG unit is different. It' more of a true "X" design I know from my hot rod days. Difference being on our cars the exhaust gases are not traveling in the same direction as they come into the x like they would in other cars.



My theory on the "U" shaped bends is to best get the exhaust gases traveling in th same direction for a short period prior to the common space where they merge. However in alot of those designs it almost looks like you're forcing most of the exhaust gases to make a 180 degree turn as a result where there previously was not that drastic of a bend in the stock exhaust.

My buddy favors the design of the GMG unit. He says based on the firing order and the resulting pulses in the exhaust system the gas flows won't be hindering each other as they cross in the X.

Looking for additional thoughts on this. I'm leaning towards the "U" design and he's leaning towards the "X" design. He can build either.

To be completely honest about this project it's for sound only. I could care less if it makes 0 hp more, as long as it does not take away hp and gets me the sound I want from the car I will be happy.

Andy

911SLOW

Recently I helped a fellow Rennlister build one.

The X didn't work, the U did. (he has dyno runs for both)


Best,

IPguy

Interested to see how this goes, as I am trying to figure this out as well (also only interested in weight reduction and sound)

I bet Slow will chime in here as he has some good ideas, and he beat me to it.

John, any recommendations on the area of the cross over opening?

911SLOW

What I've sent you via email. Can you please forward it to Andy?

I can't post it in a public forum, I have to respect the fact that it's not my R&D or design.

IPguy

Will do.

Andy, PM with your email.

DHI

Andy,
What are your expectancies in terms of sound?
X-pipe has been trotting in my mind as well, hoping for better sound rather than just plain louder. Recently read that an X pipe would get exhaust note closer to 997GT3s.
Planning to put cats in there?

jlasuncion

I actually just did both (custom made) mated to cargraphic box. I recently went back to the x design because i like the sound of that more. X sounds more refined (similar to 997 gt3) while U is a bit rough (closer to traditional boxer engines).

I have dyno figures for the u type and will do one for the x type soon, using same dyno.

John (911slow), the first dyno with the x design was compromised since my maf was faulty...hence i decided to try again...lets see what happens

Butt dyno says i lost torque around 3.5 to 5k rpm but feels stronger after that...its not accurate and usually Im wrong. Hope i can schedule dyno soon and put an end to my saga

AudiOn19s

I just want it to sound more like a 997 GT3 or 996 cup. Higher in pitch like either of those would be fine in my book. Louder will likely be a by-product as I'm not subjected to emissions testing and will likely go without cats in my setup. Reduced weight is also an additional bonus. I'm trying to determine what mufflers to use in conjunction with the rest of the system to not make it obnoxious. My car is still very much a street car first and as a toy that's not driven on a regular basis I don't mind it being loud(er) but my personal experience is when they get too loud they become no fun on the street as I'm constantly worried about who can hear me having fun before they even see me

onelove

Subscribed, have this on my list of things to do soon as well.

DHI

Andy,
Based on John A's sonorous preference for X design rather than U... Is that what you will end up getting fabbed?

jlasuncion

I will take video when i dyno next week so you guys can hear

X= more high pitched and balanced

U= sounds like a mad/scary modified engine

If you have a bigger exhaust i think you can get away without cats or resonators but with cargraphic R I decided to put resonators to lower volume and minimize the loud backfires I get

AudiOn19s

I'll wait for final judgement until after I see his follow up results after the dyno next week. Interested to see how it plays out before making my final decision.

My fabricator is in the middle of two cage builds right now in his spare time so I don't see this project really happening for me for at least the next month or so. I had to beg him to work my coolant fittings in for me.

KOAN

Andy,

Let me know if your fabricator would consider making 2!

BTW, did you decide about Mid Ohio with NNJR?

woodstock964gt3

Too funny, I'm guessing he could make quite a few of them around here. If he wants to make a few of them I'm in for 1.

Chuck
2004 GT3 Speed Yella
1994 RS America Black (For Sale)
1987 911 long gone (in so many ways)

KOAN

Chuck,

Seems like we have some things in common...GT3, former '87 911...and I was at Woodstock!