Teach me about exhausts/mufflers

[84porsche]

Here is what I am looking for out of my 911. I want a louder engine sound. I want other cars to hear my car because I am getting tired of getting cut off by motorhomes and trucks not seeing me. So please teach me about mufflers, exhaust and what are the best products to buy and the best products to install that are still legal (pass smog).

I was looking at this:
http://www.pelicanparts.com/techarticles/exhaust_system_upgrades/exhaust_system_upgrades.htm

but I want more of an understanding first. I want to be able to come home at night without waking up the neighborhood so a clean louder sound would be more effective and any performance that would come along with it. Any help is always appreciated.

[Bill Verburg]

I've got one of Joe's header muffler kits like Steve described. It is loud but whether its too, is subjective

[concentric]

I have a B&B that fits your description to a "T" When I have it wound up, it ruins lives, scares children, and bruises fruit, but at idle or a light touch, it's pretty quiet. It came with my new motor.

That being said, I did have to have a crack welded up on the muffler already and they're pretty expensive.

[Bill Verburg]

I had a bunch of B&B mufflers, they all cracked, late ones used under sized(.25") oulets, and they don't stand behing their product.

Never more

[concentric]

Originally posted by Bill Verburg
I had a bunch of B&B mufflers, they all cracked, late ones used under sized(.25") oulets, and they don't stand behing their product.

Never more

Indeed. If I hadn't gotten it thrown in with the motor, I wouldn't have bought it. However, I am pleased with the sound. It will be replaced post-haste with custom header/exhaust system built by jpachard using Coast mufflers. This might be a good option for you as well, but it's not cheap.

[Steve 82SC]

If you're looking for loud and want to save some money, Bursch would satisfy you, although the one's I've heard are a little louder than I would like, although that's strictly a personal issue. If you want to spend more, you might want to go with a system from GHL. I put one on my car and am extremely satisfied. GHL also offers the absolute best customer service. Do a search on GHL......they've stood behind any issue to the customer's total satisfaction. When I had an issue, they sent the part out overnight at their expense.....very nice people.

Steve

[jcc911]

I have a borla dual in quad out, and she screams when you jump on it. It does have some ressonacne between 1900-2800, but when coming up an on ramp or down-shifting, you will know I am there. The only problem is that these mufflers are tough to find.

[mb911]

Guess I need more exposure??????????????????

[Tim Hancock]

FWIW, the 321 Stainless that mb911 makes his mufflers out of is unbelievably expensive and is what nearly all aircraft exhaust systems are made of. Aircraft exhaust systems are made from very thin 321 which renders them very light wieght, yet very strong and more resistant to the corrosive effects of hot exhaust gases over time than plain jane industrial grade 304 stainless.

Here is a description quoted from Mcmaster Carr : "Type 321- Stabilized with minimum .48% titanium for welds subject to severe corrosion and in service from 800 deg to 1600 deg F. For process equipment, flexible couplings, and pressure vessels."

I have looked into buying this raw material to build a custom exhaust for an experimental aircraft I am building and I was shocked by how expensive it is compared to 304.

I do not know what Ben's mufflers sound like, as I have not actually heard one but I can attest that his mufflers are light and very well made out of what I consider to be an almost exotic material.

Do a search on aircraft exhaust systems and I am sure you will find some info on this material. I have been following Ben's threads and it sounds like his mufflers are starting to get installed on numerous cars and I hope someone posts some sound bites soon!

Search mb911 on this forum and you will find some recent info on these mufflers.

[jbrinkley]

mb911's muffler is superior to any muffler constructed. Do some steel research and you'll see. Mine is still sitting here cause I'm lazy, but soon, very soon

['76 911S 3.0]

Is Joe's muffler bulit for B&B headers as it looks like it is mated to on Bill's car? How much does he charge for it? i have a full B&B exhaust, love the headers and sound, but the welds are terrible on the muffler and now I have a whistle coming from the hole they plugged for the dual out side since i only have a single out.

[jtkkz]

check out monty muffler as well

www.**************

[Carrera3.5L]

Hi Chris,

You can listen to this on the next run:



George Narbel's 1 5/8" headers with a Dansk 2-in 2-out muffler with 84mm tips.

Sounds really nice!

Ralph

[mb911]

Jerry,

Did you wire brush the muffler?? If so Make sure you polish it with flitz or something like that as when touching stainless steels(all) with any mild steel as an abrasive little tiny particals break off of the mild steel and lay on the stainless surface which will cause a surface rust like appearance. Just want to save you some clean up.

Let me know how it works out and email if you have any more questions

[unclebilly]

Originally posted by Tim Hancock
FWIW, the 321 Stainless that mb911 makes his mufflers out of is unbelievably expensive and is what nearly all aircraft exhaust systems are made of. Aircraft exhaust systems are made from very thin 321 which renders them very light wieght, yet very strong and more resistant to the corrosive effects of hot exhaust gases over time than plain jane industrial grade 304 stainless.

Here is a description quoted from Mcmaster Carr : "Type 321- Stabilized with minimum .48% titanium for welds subject to severe corrosion and in service from 800 deg to 1600 deg F. For process equipment, flexible couplings, and pressure vessels."

I have looked into buying this raw material to build a custom exhaust for an experimental aircraft I am building and I was shocked by how expensive it is compared to 304.

Sorry to hijack the thread but I've been wanting to discuss exhaust alloys for headers for a while now.

321 and 304 aren't really great for this application, in my opinion. If you're going to go austenitic (300 series alloys), you want 347 for the headers.

Austenitic stainless steel has a relatively high thermal expansion coefficient (that's why the B&B headers and mufflers crack). The hot sections want to expand more than the cooler sections, you get thermal stress, every time you fire up your car, it undergoes another thermal cycle (and resulting cyclic loading), eventually you get a crack.

I think what you want is a ferritic stainless alloy for the exhaust such as 430, 434, or 439. These alloys are desireable because the thermal expansion coefficient is much lower (under 14ppm/°C) than austenitic alloys and soften more at temperature so they shouldn't crack. 400 series alloys are also much less expensive than austenitic alloys because there is no nickel in them.

I think the reason that 300 series alloys are used by many of the header manufacturers is that they're not engineered by engineers - it's a case of material selection by what's available. With regard to the comment about aircraft exhaust being 321, that is entireably possible but I'm surprised it isn't made from Inconel 625 or Haynes 230. I guess it just depends what part of the exhaust system we're talking about and what temperature duty it sees. I know that certain Japanese auto manufacturers use 400 series stainlesses for their headers.

I spec alloys for high temperature applications as part of my occupation so I'm not just a cracker jack on a rant here. I guess my point is that if you're getting custom exhaust made, bear in mind that all stainless alloys are not created equally, and the more expensive the alloy is, doesn't mean that it is better for your application.

[mb911]

All small aircraft have used 321 since the very early days in there mufflers ironically most of there "stacks"(headers to us) were mild steel gas welded. although allot are 321 as well. I have personally repaired mufflers from aircraft (I used to be a FAA repair certified) form 40 years ago and we would be repairing tail pipes and or inlets that were damged once in a while we would repair cracks but not to often. We do however use 347 filler on all the weld joints . The problem with 4 series is that it is not made in many shapes that we want it in. As for larger air craft most of the exhaust are Titanium. I have also used 321 for headers on a 914-6 I did and it worked great no problems ever.

[unclebilly]

You can get 430, 434, & 439 in sheet, roll it and seem weld it. I know for sure that you can get 434 in tube as well but maybe not in small volumes.

[jbrinkley]

yes, I was just going to brush the welds and then, While you're in there happened, I've been trying different polishes to see which one works best, haven't tried flitz yet, just ordered some though'
thanks

[jpahemi]

I've installed Ben's muffler and love the sound; it has a very early 911 sound. The light weight is a tremendous plus. One suggestion would be a tad thicker flanges. Ideally, equal to the SSI flange thickness would be great. One of my flanges wasn't quite square needing a little RTV plus gasket to seal up perfectly. Maybe thicker flanges would've pulled them together a little better. I must add, Ben has offfered to correct the flange issue so it's up to me to send it back. Great customer service.
J.P.

[Tim Hancock]

Unclebilly, I found 430 in a metal catalog and while it looks like it would work, the catalog states that the heat and corrosion resistance less than that of chrome/nickel types (321 is a chrome nickel type). I do not doubt your expertise on materials, but the reason the aircraft exhaust systems have been using 321 is because it has proven to hold up over time against the combination of corrosive and hot gases. This same catalog lists both 321 and 347 as being used for aircraft exhaust systems and also states that both materials are desirable when using in "as welded condition". I am sure some of the materials you mention might work fine and maybe? better, but none the less, 321 has a proven track record in aviation and they tend to worry about failures as one can not just pull off the road when something breaks.

I am not trashing 304 or mild steel or any other material, they all will and have worked. Coming from an aviation background, I just thought it was pretty cool that Ben was marketing a lightweight muffler out of a better than average material.

I myself have built partial auto systems out of galvanized steel (I am somewhat of a cheap SOB sometimes) and it is heavy and it eventually corrodes and it looks like hell but the price was right and it was easy to get locally. To each his own I guess.

Compare Ben's price, material and wieght with the brand that almost always is reported as having cracking issues, then buy whatever trips your trigger.

If anyone cares I could probably scan these metal catalog pages that I referenced.