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PostPosted: Mon Apr 18, 2016 3:40 pm 
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3 Deuce Weber

Joined: Mon Apr 19, 2004 8:45 pm
Posts: 91
Location: Gaston, OR
Car Model:
What diameter of exhaust pipe should I be running from the turbo to the back of the car if my goal is 3-350HP with an HX35? Is 2.5" adequate or should I go to 3"?

Thanks,

Casey


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PostPosted: Mon Apr 18, 2016 3:47 pm 
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Joined: Mon Oct 21, 2002 11:08 am
Posts: 16447
Location: Blacksburg, VA
Car Model:
I would go 3". Had 2.5" on my car when it was in the 275-300 HP range and the step up to 3" made a significant difference.

Lou

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PostPosted: Mon Apr 18, 2016 5:02 pm 
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3 Deuce Weber

Joined: Mon Apr 19, 2004 8:45 pm
Posts: 91
Location: Gaston, OR
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Lou,

Did you make only the change to 3" and see the improvement? What improvement did it make? More power over all, down low, or up high?

Thanks,

Casey


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PostPosted: Tue Apr 19, 2016 8:30 am 
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Joined: Mon Oct 21, 2002 11:08 am
Posts: 16447
Location: Blacksburg, VA
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Yes, only the change to 3". Boost came up quicker and more power overall. That's about as much detail as I remember. Boost rise was the most noticeable thing on the street and the 1/4 mile times were perhaps 0.2-3 sec faster. Most of that was not gained in the 60 ft.

Lou

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PostPosted: Tue Apr 19, 2016 2:33 pm 
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3 Deuce Weber

Joined: Mon Apr 19, 2004 8:45 pm
Posts: 91
Location: Gaston, OR
Car Model:
Good to know. I'll plan for 3" then. Any trouble areas fitting 3".


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PostPosted: Wed Apr 20, 2016 6:07 am 
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Joined: Mon Oct 21, 2002 11:08 am
Posts: 16447
Location: Blacksburg, VA
Car Model:
Watch up front past the tbar, going under the tbar/trans Xmember, then between gas tank lip and frame rail in back. Good to angle (big oval) muffler upward and I often aim rear of muffler toward the dr side of car. Use muffler with both ends (inlet+outlet) offset. For a turbo car where you don't mind a little noise, I would just forget the muffler. Mine is quite quiet with Hooker Aero Chamber. I have 3" out the back on 64 and 68 Darts. 64 Dart has big Jones muffler and resonator at the very end (headers, NA, big cam, kinda loud).

Best advice - find a good custom exh shop. They are worth driving, paying, and waiting while they do the work (~1/2 day). Most shops are crap, so get a rec from a trusted hot rodder near where you live.

Lou

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PostPosted: Sun May 22, 2016 7:57 am 
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EFI Slant 6
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Joined: Sun Jun 10, 2012 3:54 pm
Posts: 349
Location: Terre Haute IN
Car Model:
Mines a d150 but yes run the 3". Mine is 3" all the way and goes thru a cheap autozone thrush turbo. Offset inlet outlet. Nice and quiet when cruising and even when you step on it, still quiet enough that you hear the hx35 sucking and spooling. :twisted: cant comment on other sizes, just knew I wasnt going any smaller than turbo outlet all the way.

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PostPosted: Sun May 22, 2016 12:34 pm 
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EFI Slant 6

Joined: Thu Jun 04, 2015 6:19 pm
Posts: 317
Location: Florida
Car Model:
What then is the upper HP/turbo suggested limit for a single 2.5" exhaust? Knowing 3" would always be an improvement, fitting and road clearance are still downsides I need to consider.


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PostPosted: Mon May 23, 2016 9:44 am 
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Joined: Mon Oct 21, 2002 11:08 am
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Location: Blacksburg, VA
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Probably about 225-250 HP. I'm sure it will depend on turbo size and engine parameters too. You might make plenty of power with 2.5", but you will just make a little more with 3". There are always tradeoffs.

Lou

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PostPosted: Mon May 23, 2016 3:15 pm 
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EFI Slant 6

Joined: Thu Jun 04, 2015 6:19 pm
Posts: 317
Location: Florida
Car Model:
That was the range I was figuring, thanks.


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PostPosted: Tue Oct 04, 2016 11:14 am 
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Turbo Slant 6
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Joined: Fri Jul 13, 2007 11:11 pm
Posts: 794
Location: clearwater florida
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I had almost identical gains as Lou reported when I changed from 2.5'' to 3''
Mine showed a couple mph gain and lost a couple tenths in the 1/8 mile on 10psi.

Kev

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