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DIY Turbo Discussion greddy on a 1.8? homebrew kit?

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Old 09-19-2009, 12:12 PM   #41
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nicely done except those "cheater bends" in and out of the muffler... those kill flow bad.
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Old 09-19-2009, 12:30 PM   #42
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nicely done except those "cheater bends" in and out of the muffler... those kill flow bad.
Do you really think it's worse than a 180*?

All the equivalent length/friction loss homework problems I've done have caused me to think of any way I can avoid the stock double-back setup for the longer bodied mufflers.

I know his is a poor version of a 90* bend, but you have a 90* before the 180* in the other case anyhow. Call his a 135* cheater bend if it's say 2/3rds as efficient as a proper 90*. You've still got 1/2 the relative friction loss as a stock-like setup.

I'm not saying it couldn't have been done better (especially on the exit side where stock there is a simple 90* elbow), but from a packaging standpoint, to reduce bends, it works, and likely better than full bend routing. The crosspipe inside the muffler is at an angle as well, so it's not as bad as it looks.

Besides, I'm about to do the same thing and don't want to hear the comments of the dissenters.
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Old 09-19-2009, 01:03 PM   #43
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Thanx guys. I wanted it as straight/bend free as possible, but the space left around the muffler if I would have angled it would have been way too little. Possible, but I don't want anything to bang/clink around so I had to scratch that idea.
The 180 bend idea I wasn't crazy about either since it would make for much longer exhaust piping, and still the room around muffler would be cramped in the diff area.
This seemed to be the solution.
I am absolutely crazy about how good it sounds and how much power its gained
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Old 09-19-2009, 02:53 PM   #44
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I am absolutely crazy about how good it sounds and how much power its gained
I am envious.

I need to say screw this project and walk back to the maintenance room and get started now...that or take the easy route and PM ARTech back.
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Old 09-19-2009, 02:59 PM   #45
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dew eet
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Old 09-19-2009, 05:23 PM   #46
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Do you really think it's worse than a 180*?

All the equivalent length/friction loss homework problems I've done have caused me to think of any way I can avoid the stock double-back setup for the longer bodied mufflers.

I know his is a poor version of a 90* bend, but you have a 90* before the 180* in the other case anyhow. Call his a 135* cheater bend if it's say 2/3rds as efficient as a proper 90*. You've still got 1/2 the relative friction loss as a stock-like setup.

I'm not saying it couldn't have been done better (especially on the exit side where stock there is a simple 90* elbow), but from a packaging standpoint, to reduce bends, it works, and likely better than full bend routing. The crosspipe inside the muffler is at an angle as well, so it's not as bad as it looks.

Besides, I'm about to do the same thing and don't want to hear the comments of the dissenters.
it's probably fine, but yes, I think it's much worse than a U-bend.

the problem is that the flow will hit that sharp corner and become turbulent at the discontinuity. in the U, it will only lose energy from making the turn.
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Old 09-19-2009, 09:34 PM   #47
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Here is a comparison. I dont think one would have better flow than the other. My exhaust is offset on both sides btw.

I don't know, I think my way is not that bad. I'm no expert, but from the way it looked under there, I would chose my way over the u-bend for flow. It definitely LOOKS better to me anyhow.

Just my .02
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Old 09-19-2009, 11:05 PM   #48
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I think this is more like it



It probably doesn't make a big difference there but a cheater bend in a manifold or dp does kill flow.
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Old 09-20-2009, 12:14 AM   #49
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ART has it right. the muffler doesn't have diagonally angled inlets and outlets, it has straight in/out pipes.
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Old 09-20-2009, 12:19 AM   #50
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OK I give up lol.
I still absolutely love it and don't mind the flow restriction even If I have one. I've gained quite a bit of power and have much better spool going from stock exhaust to this, so I'm definitely happy with what I have.
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Old 09-20-2009, 01:16 AM   #51
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that's all that matters. you obviously did something right if it's spooling so much sooner. I think you know the next step. 3" dp
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Old 09-20-2009, 01:53 AM   #52
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sick..I need to make an exhaust for mine too...
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Old 09-20-2009, 02:28 AM   #53
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I should ride up to sac and have you build me one too. HAHA.

I'm in sacramento every week anyway.
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Old 09-20-2009, 11:25 AM   #54
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Quote:
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OK I give up lol.
I still absolutely love it and don't mind the flow restriction even If I have one. I've gained quite a bit of power and have much better spool going from stock exhaust to this, so I'm definitely happy with what I have.
sorry to bust your nuts about it. it's really not going to affect spool way down at the muffler much anyway. you got audio of the install?
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Old 09-20-2009, 04:46 PM   #55
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Its all good
I'll get audio soon.
I think I blew the headgasket yesterday
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Old 10-02-2009, 06:45 PM   #56
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sorry to dredge up an old thread, but i noticed that you went with 2.5 inch tubing. Do you think that the exact same setup would be able to fit in 3"
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Old 10-02-2009, 09:07 PM   #57
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I don't see why not. I chose to do 2.5 because my downpipe is 2.5.

It might be a little tougher to clear everything with 3" since its already pretty close, but Its possible for sure.
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Old 10-02-2009, 10:58 PM   #58
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i have a 2.5" dp as well, but i wanted to over build for future setups. do you think that i would have any issues, or it is just plain dumb to mix and match like this?
Also, do you think a resonator would quiet things down a bit or would that just be wasted money/ effort?
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Old 10-02-2009, 11:08 PM   #59
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Well I went without a resonator and the car is QUIET. I mean it sounds AWESOME. Super quiet for a straight through exhaust. I am really glad I didn't waste money on a resonator, since its barely louder than stock the way it is.

I don't think there's anything wrong with mixing/matching but if you have a 2.5 dp I don't think making the exhaust .5 bigger will help much. I mean if you were to go full 3" then yeah I'd say run 3" all the way. I don't think you can go wrong either way, I just chose to keep all my piping exactly same size.

Though now that I think about it, it WILL PROBABLY be quite a bit louder with 3".
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Old 10-05-2009, 12:17 AM   #60
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do you offer welding as a side job to help a fellow miata turbo owner

i have a 2.5" downpipe, with a 2.5" crush bend test piping running into i think stock piping midpipe to a greddy muffler that is about 2.5" but neckdown to stock piping size since its a axle back

i would to basically replace with a long *** 2.5" pipe from dp to axle back, could you possible help me out

just wondering

Thanks
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