Is a flex tube 100% necessary on the DP? - Page 2 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 11-10-2009, 10:16 PM   #21
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Quote:
Originally Posted by wayne_curr View Post
Seriously dude I was just thinking that. This turbotim guy doesn't know his *** from a hole in the ground when it comes to fabrication.

Thanks guys, i'm going to fearlessly procede without a flex pipe and will make sure I have one in place before my first track day next season. This saves me some cash for sure that can go toward some bitchin hardware or something.
That's what I'd do. Use no flex, if it breaks you can fix it now that you have the tools. In a year you'll be making these for everyone here.
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Old 11-10-2009, 10:17 PM   #22
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They will be named "ABSURD MEGA HYPERFLOW"
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Old 11-10-2009, 10:21 PM   #23
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They will be named "ABSURD MEGA HYPERFLOW"
I like it! But the stickers would cost too much
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Old 11-10-2009, 10:28 PM   #24
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Originally Posted by 18psi View Post
Please tell me why not.
The whole deal with not running a flex in my system relies on the length between supports. in my case, it's long--basically the head to the one behind the rear o2 sensor somewhere (I forget and am above the car currently). That's a pretty long lever arm and it doesn't make the rest of the system move much.

Attaching it to the tranny shortens that lever arm. Also if you just do the easy "tack on a hanger rod" method, it focuses a lot of stress at one point. result: a hole ripped in your pipe where the hanger was.
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Old 11-10-2009, 10:31 PM   #25
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Originally Posted by TurboTim View Post
That's what I'd do. Use no flex, if it breaks you can fix it now that you have the tools. In a year you'll be making these for everyone here.
Lol, Wankerflow.
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Old 11-10-2009, 10:32 PM   #26
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Haven't had a flex pipe for months now and I have a hanger attached to the trans tail. No issues so far.
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Old 11-10-2009, 10:32 PM   #27
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Damn. That's the way I have had my dp for basically ever. no cracks or breakage but I'll definitely be on the look out.
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Old 11-11-2009, 12:32 AM   #28
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Originally Posted by 18psi View Post
Damn. That's the way I have had my dp for basically ever. no cracks or breakage but I'll definitely be on the look out.
Did you even get a thousand miles on your setup before your motor broke?
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Old 11-11-2009, 12:42 AM   #29
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Not that it's any scientific proof, but FM does not use flex joints in their downpipes and who knows how many they've shipped and are used. From their website:

"The pipes are cut and bent on a massive CNC (computer numerical control) pipe bender for consistency and accuracy. Due to the accuracy of the process, we were able to remove a heavy, expensive flex joint that was also a potential failure point."
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Old 11-11-2009, 12:44 AM   #30
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Quote:
Originally Posted by wayne_curr View Post
Did you even get a thousand miles on your setup before your motor broke?
I predict a catfight . Lol
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Old 11-11-2009, 12:44 AM   #31
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Quote:
Originally Posted by wayne_curr View Post
Did you even get a thousand miles on your setup before your motor broke?


Actually since I've always had daily drivers I only put about 1k miles on my miata since the day I BOUGHT IT. 95% of those miles are WOT pulls though

I sold my suby though, so as soon as the motor is back in, the miata will be getting daily useage.


My 6 speed showed up today. I want to make love to it.
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Old 11-11-2009, 02:01 AM   #32
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My FM downpipe does not have a flex pipe.
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Old 11-11-2009, 02:16 AM   #33
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I wouldnt feel safe running over a cat without a flex in the downpipe

Seriously, if you do happen to bottom out the exhaust, a lack of flex will most likely mean cracked dp/manifold. Why risk it for $25?
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Old 11-11-2009, 02:27 AM   #34
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Quote:
Originally Posted by TurboTim View Post
none ... have a flex section except for Evan's MSM; everyone else was too cheap
Ha!!!

Here's the aforementioned flexibility that Tim made for my car:

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Old 11-11-2009, 02:58 AM   #35
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Quote:
Originally Posted by curly View Post
I don't have one. Greddy cast manifold, greddy turbo, the used kit came with a custom 2.5" DP, bolted to 2.5" mid pipe that's welded to a 2.5" cat, then VTA. I had more pipe after the cat going to a magnaflow muffler for about a year, and so far about 1.5 year without the muffler, a dozen or more track days, no cracking.
Same here maybe thats the key to the greddy manifold not cracking, no flex pipe ftw
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Old 11-11-2009, 03:33 AM   #36
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Interesting debate.

I seem to want to agree with both sides as with having a car that sits pretty low hitting the exhaust seems to be pretty common and I imagine having that shock being able to be absorbed by a flex tube placed at the right spot in the system seems like it would do the job of saving parts in the long run.

My current downpipe is my exhaust and isnt but the distance from the turbine outlet to in front of the drivers side tire. No flex for me until I get the full 3in out the back. Im just worried about hitting hard things in the road.

Last edited by Tw34k; 11-11-2009 at 05:01 AM.
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Old 11-11-2009, 04:57 AM   #37
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When I got my downpipe fabricated I didnt even consider one. Never ran one and never had a problem. You dont 100% need it.
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Old 11-11-2009, 08:55 AM   #38
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Quote:
Originally Posted by ARTech View Post
Why risk it for $25?
You and your cheap sources. I use a $80 "turbo" flex with the smooth inside.
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Old 11-11-2009, 09:30 AM   #39
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hard-mounting to the transmission is also not a good idea.

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Old 11-11-2009, 02:08 PM   #40
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hard-mounting to the transmission is also not a good idea.

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