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Old 11-27-2006, 11:05 PM   #1
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Default How not to make your own Downpipe.

So today I took my downpipe off to weld in a bung for my AEM Wideband. I had no idea how crappy it is. First of all the bends suck, they aren't welded very well though and look like crap. The final bend is crush bent, making my 2.5" DP more like 1.5" so my entire exhaust system is bottlenecked at that point. To top the cake my external wastegate system is also complete crap. I'll post some more pictures of that after a bit when I take them. I also spent 5 minutes today drilling a hole in the pipe and welding the bung in it. I didn't care what the weld looked like so don't let that be a example of my welding ability.
Again:
HOW NOT TO BUILD YOUR DOWNPIPE!
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Old 11-27-2006, 11:13 PM   #2
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Hahaha that's sweet.
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Old 11-27-2006, 11:19 PM   #3
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wow that is one ugly bend but i don't know if it gets any smaller than stock
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Old 11-27-2006, 11:21 PM   #4
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The rest of my exhuast system looks good, all 2.5" going back after that flange. That is definitely the bottleneck of the system for sure. That's what I get for buying a car with the DIY turbo setup already on it. Always better to do it right yourself.
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Old 11-27-2006, 11:21 PM   #5
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WOW!

That has to be the fugliest D/P ive seen! I hope you didnt make that..If you did then think of it as a learning experience!! that thing will be killing so much power from your system. I bet when you get a proper 2.5"DP youll spool at least 300 rpm earlier and make 10-15 more RWHP without any other changes!

Have a look at the bottom of page 6 on my Cardomain site for a real DP!
http://www.cardomain.com/ride/264041/6
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Old 11-27-2006, 11:25 PM   #6
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Yeah i definitely didn't make that downpipe. The sad thing is the guy i bought the car from in Kentucky had the entire kit put together by a performance shop. They must have been smoking rocks to think they were building a good product. Mine would look far better. I might end up rolling out my own product early '07 we'll see.
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Old 11-28-2006, 02:02 AM   #7
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that looks pretty bad, you'll pick up some power if you get a nicer downpipe 3" would be nice.

Check out my old vs. new downpipe, that sure made a huge difference in spoolup/response/power on my car.
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Old 11-28-2006, 02:09 AM   #8
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Man, do you have pics of your manifold as well. because that downpipe is pretty badass.
Who made it up for you?
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Old 11-28-2006, 02:22 AM   #9
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holy **** that thing is beefy
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Old 11-28-2006, 02:28 AM   #10
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Quote:
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Check out my old vs. new downpipe, that sure made a huge difference in spoolup/response/power on my car.

No way...Not possible

Thats a gorgeous piece RusMan.
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Old 11-28-2006, 02:35 AM   #11
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Very quality looking piece. 3"? Gotta love some real craftsmanship.
-Michael-
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Old 11-28-2006, 03:40 AM   #12
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Holy crap rus....
How do you stop your transmission tunnel from melting with a 3" dump pipe?? i have enough trouble with a 2.5"!
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Old 11-28-2006, 03:45 AM   #13
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SS would be better at it than Mild Steel.
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Old 11-28-2006, 09:53 AM   #14
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anybody who has made one can appreciate all those cuts and welds
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Old 11-28-2006, 10:12 AM   #15
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cjernigan, what's up with the wastegate port, it looks like it comes back around the front?


ohhh, wait, were you the dude who bought that used kit off ebay? So your external wastegate was actually a port off the exhaust, not the manifold?
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Old 11-28-2006, 10:21 AM   #16
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Quote:
How do you stop your transmission tunnel from melting with a 3" dump pipe??
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Originally Posted by braineack View Post
SS would be better at it than Mild Steel.
No, SS would be worse.
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Old 11-28-2006, 10:36 AM   #17
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Doesn't stainless steel have greater insulating properities. Mild Steel on the other hand radiates like a champ.
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Old 11-28-2006, 11:19 AM   #18
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No 304 SS will conduct heat better than 409 MS.
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Old 11-28-2006, 11:30 AM   #19
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I'm still sticking with more heat stays inside the stainless tubes and does not get passed into the surrounding air. Mild steel tubes will give off heat rather then insulatling it. It's exactly why SS downpies do better for underhood temps then MS, and why you need to get them thermal coated.
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Old 11-28-2006, 12:28 PM   #20
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Quote:
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No 304 SS will conduct heat better than 409 MS.
matweb says otherwise (16.2 W/m-K vs. 24.9 W/m-K). A mild steel like 1018 is 51.9 W/m-K, chrome-moly 4130 is 42.7. As a reference, 6061-T6 aluminum is 167!

Generally speaking, stainless steels conduct less heat but expand more than mild steels. I think this expansion problem is why you don't want to ceramic coat stainless pipes.
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