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Join Date: Jan 2003
Location: Burlington, Wisconsin
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Quote:
Originally Posted by Craig 930 RS View Post
My 14 years as an engineer in Boeing commercial airplanes (737 & 757) prompted the question.

As you could probably guess, failures in my field are shall we say rather permanent & extensive.

In case we missed it, what gauge 321 is the muffler can?


.050 321 ss with .050 spun end plates and .049 tail pipes remember the major advantage to 321 over 304 is the TI alloy and the added capability to deal with heat and combustion gases thus the reasoning for general avaition to use it in ALL of their exhaust systems when piston powered. when jet powered well thats a different story where inconel and TI are the exclusive products
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Current project 73 914-6 Gt project rusteration 2.4
Reproduction 914-6 oil tanks, 1-5/8" 914-6 heat exchangers source call 2623647426 or email mbconsulting21 @gmail.com

Last edited by mb911; 10-05-2007 at 12:24 PM..
Old 10-05-2007, 12:20 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #21 (permalink)
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Giving this thread a

Anxiously awaiting this little beauty!
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back in the saddle: '95 993 - just another black C2
*SOLD*: '87 930 GP White - heroin would have been a cheaper addiction...
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Old 10-22-2007, 06:22 AM
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Crotchety Old Bastard
 
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That's quite a bump!

The muffler and waste gate are currently being used to make the production fixture. Shouldn't be long before it's ready. I'll do a fitment test on the first production unit and post some pictures. We are also looking into ways of quieting it down a little. Loosing that 180* bend and 3 feet of tailpipe lets out a little more noise.
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 10-22-2007, 07:50 PM
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Brian, lovely work. I already have two holes in my rear valance....

Question: do either you or Ben have a decibel meter? Basic analog ones seem pretty cheap...

For example (no affiliation):

http://cgi.ebay.com/7-Range-Sound-Level-Audio-Noise-Meter-Decibel-DB-New_W0QQitemZ160172994237QQihZ006QQcategoryZ25423Q QssPageNameZWDVWQQrdZ1QQcmdZViewItem

As an "acceptable" volume is so subjective (let's not even get into which sounds "best"), it'd be really helpful to have some metric to compare these exhaust systems against factory stock and each other - you're already doing dyno comparisons, so this would just be more data.

I also figure this would very useful those who have ambitions to meet track noise levels (typically 105 dB @ 4,000 RPM/10 ft here, I think) decide how much sound absorbant material they need to request.

I'm also real curious as to both how much you can affect the sound levels, and how much that affects the power levels? (I'm guessing the effect on power probably stays relatively small until you start cutting back heavily on the noise).

I'm also curious what a Zork or other open pipe measures. I think my old "muffler" was louder than a minimally-silenced Harley, so I figured about 110-115 dB. So much for the "rotary muffler" theory.

I want something light and reasonably free-flowing and don't have a problem with a car that sounds "interesting", but I find a completely open pipe can be very wearing on longer trips and a PITA - especially around LEO - more often than I think "yah! listen to that exhaust sound!"...
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Old 10-27-2007, 01:57 PM
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Crotchety Old Bastard
 
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I have the same opinion when it comes to sound. I like musclecar on the outside and a muffled rumble on the inside. You have to easily have a conversation with the passenger while the car is at idle with the windows down.
You can do that with my mufflers, a bit more difficult with the Zork. Having the engine in the rear and the pipes pointed back helps a lot.

I do have a decibel meter but I don't seem to get accurate readings from it. The background in my quiet neighborhood reads 65db and the exhaust noise reads 82db ???? That seems way off.

The method we plan to use to quiet the mufflers should not affect performance significantly. The current design has the 3"ID turbo outlet pipe going into a 5"ID baffled expansion chamber and then back down to a 3"ID tailpipe. The plan is to pack the expansion chamber walls with carbon fiber mesh so the ID remains at 3" throughout the muffler with very little added weight.

The best news when it comes to exhaust systems on the turbo is that when you are at highway speeds you hear very little exhaust noise at all. Only when you reach boost threshold do you hear the turbo whistle and then at full boost you hear the roar of everything wide open.

The noise that has the most potential to annoy over the long haul is the cackle on decel. You can modulate the throttle and make it as loud as a shotgun or down to a burble. Push in the clutch and all noise stops immediately as if you shut the car off. It's an interesting experience.

I was expecting the first production set to arrive Friday but it didn't happen. So maybe Monday. I'll get them polished up and mounted for a few pix by next weekend and put a few miles on to see how they work out. I'll fish out that noise meter and see what can be done there as well.
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 10-27-2007, 05:43 PM
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Believe it or not my Nokia mobile phone had a sound meter built into it.
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1981 UK 930. G50/01 shortened, 964 3.8RS Fibreglass Body Kit, 18" Alloys 8.5" F & 10" R, 225's F & 285's R, Special Colour Metallic Blue Paint, FIA Sparco Evo's, A/C and Air Pump removed, Electronic Boost Controller, GHL Headers, Tial46 WG.
Fitting - New service kit.
Needs Fitting - Innovate XD-16 Kit, Kokeln IC. Stephen's K27 HFS, EVO Intake Assy & his Modded USA Fuel Head.

1983 UK 911 3.2 Carrera Sport Coupe. Black, Black Leather with Red Piping, Black Alloy Gear Knob, K&N Air Filter Element, Turbo Tie rods.
Needs Fitting - K&N CO Sensor, Round A/F Dial Gauge, Factory Short Shift Kit.

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Old 10-28-2007, 11:54 AM
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