danglerb

Couple of the guys that were in the Engine Masters Challenge were talking mufflers and basically tried every legal muffler they could find, and the 2 chamber flowmaster lost something like 40 hp, and the magnaflow almost nothing so virtually everybody in the contest ended up using the Magnaflow. This years contest I think was 434 cubic inch normally aspirated with the winner the highest average HP + torque over about a 3000 rpm power band measured from the best of 3 engine dyno pulls. Winning score was 1080 with 714 peak hp, second place scored 1079 so it was competitive.

I've heard the louder than HP making comment about flowmaster before though. I don't really care for the sound, too braappy.

A few clips from the site, but its easy to find.

MUFFLERS
Only commercially available street-style mufflers are acceptable. Mufflers must remain unmodified from their original as-manufactured design. All engines must utilize two mufflers while running on the dyno. H-pipes, X-pipes, or any such connection between the left and right headers and/or the exhaust system is not allowed. All mufflers must meet the following criteria;

Maximum inlet/outlet tube diameter: 3.5-inches
Minimum overall case length: 10-inches
Maximum overall case length: 18-inches
Minimum diameter (round case): 5-inches
Maximum diameter (round case): 7-inches
Minimum width (oval or square case): 6-inches
Maximum width (oval or square case): 10-inches
Minimum thickness/height (oval or square case): 4-inches
Maximum thickness/height (oval or square case): 6-inches

Exhaust systems must meet the following design specifications in order to properly connect with the exhaust gas ventilation ports in the dyno cell wall (see diagram). Head pipes connecting the header collectors to the mufflers are limited to a maximum length of 6 inches and should be bent or angled in order to properly "aim" the mufflers at the ventilation ports. Head pipes connecting the header collectors to the mufflers are limited to a maximum diameter of 3.5 inches. Exhaust systems may not extend more than 42" from the rear of the engine block. Exhaust systems must provide a minimum of 17-inches of inside clearance; this clearance requirement begins at 25.5 inches behind the back of the engine block in order to clear the dyno tower. However, from the back of the engine block to the 25.5 inch point, there are no clearance issues.

jheis

I replaced the intermediate and rear muffler with a custom cat back system using a single 40 Series Delta Flow feeding into two three inch tail pipes.

This set up was a bit two loud for my taste, so I had them make up a pair of sleeves to reduce the bell of the tail pipes to two inches - which kind of took the edge off the sound. & each sleeve is located by a single SS bolt so I can pop them out in a few seconds if I want to sound like a hooligan.

Otherwise stock '82 dyno'd at 191.4 rwhp - so, don't know if I gained anything - other than a robust V8 burble - but certainly didn't lose anything either.

Total cost was about $200 as opposed the the factory ballast for $1,500 or better (been a few years).

James

Tom Cloutier

I dynoed a Flowmaster a couple years ago and promptly lost 17 hp on my '89 S4 with Scavenger crossover headers. In my most humble opinion they are nothing but hype. Their internal construction consists of sheet metal barriers arranged in various ways to bounce the sound waves around so as to reduce the noise level. The tone produced may be appealing to some, but these little barriers do little but impede the flow of exhaust gases. Straight-through designs like Magnaflow and Borla offer little flow resistance and produce a very sweet sound. Magnaflows are my favorite--the price is reasonable, construction is excellent, they sound great and they are tough. Borlas are way over-priced, they tend to sound tinny and the stainless carcasses are prone to rupturing and there is little or no recourse with the factory.

Tom Cloutier

Malibu310

The Yellow 928 has two small Flowmasters at the end of the pipes - very loud - all the time.

The other installation has the two forward of the transaxle then leading to dual Flowmaster resonators at the exhaust end to keep the car with just a deep but fairly quiet idle... you can get loud on hard accelleration.

Imo000

Danglerb,

Thanks for the info. My concern is that the engines in the challange were over 700hp and that can be a factor when it comes to muffler desing limitations. At that level, you pretty much want straight through flow because they need to get rid of a lot of air. I'm not sure this wouls be the same on a much lower hp motor like the 928. For example, there is an X and a Y brand fuel pump. X can deliver up to 600hp and Y can got up to 800. When both are tested on a 700hp enigne, the Y brand becomes a much better suited pump. I think this is how the Flowmaster got elimminated from this challange.


Tom Cloutier,

Do you know if the hp loss was due to the cross over design, the muffler or both?

C.F.

All great info this , keep it coming.

I can only contribute by adding a link to a good article

David Visard exhaust science

whall

I mounted it where the cats were located. Then I ran the outlets straight back with a resonator on each side and then straight out the back (not out the side). I used all 2-1/2" mandrel bends. Did the work in my shop so it is not show quality but looks okay and sounds phenomenal.

anonymousagain

FWIW, I took a brief tour of the FlowMaster plant some years back before they exploded into popularity. While FlowMaster was "primarily" a V-8 muffler builder at the time, my Dad was transitioning to Sprint Cars, but still racing Midgets (4cyl), so they agreed to build a one-off unit for the V4 engine, that had (iirc) a 98db restriction at the time.

The FlowMaster worked very well, with increased hp over the previous Magna while remaining near the 98db level. Point is, the unit was tailored to the engine requirements AND sound intentions. Always, they built units designed for intentional apps and nearly always stock engine configurations - that's where the sales are at. Sure, they can build for anything, but their products are intentional and not universal.

General Design (during my 20min tour/discussion): FlowMaster essentially built band-pass subwoofer boxes, such that the exhaust flow was calculated as if it were the sub-driver producing the sound waves. Direction of the waves through the band-pass passages allow tuning of the output sound, but there's a magic combination that produces the best flow as well - agian, think of tuning a band-pass box for the intended subwoofer to get the best matched output. [A Fosgate driver requires a completely different bandpass than a JL, etc.] The output db level is obviously the limiting factor, and sales dependant, so they would play with before/after the optimal design, to get their interpretation of the best sound within reasonable overall output db. But always engine specific.

Band-pass subwoofer boxes as mufflers !!

andreas_thunell

I just finnished building my exhaust and recorded the soundcheck.

Here is the clip. It´s zipped. Just unzip it.... Listen to the resonse at 1.17 , I like it The record is just a simple record it sounds even better in present.

http://forum.porsche.nu/forum/attach...achmentid=2492

Here is the thread I started on the swedish forum. It´s in swedish but with LOTS of pictures of the project!

http://forum.porsche.nu/forum/showth...3&page=1&pp=10

danglerb

A muffler in general is correctly modeled as a flow restrictor, so two mufflers can flow identically at lower rates and just have different max CFM where the pressure drop starts to increase faster. The Flowmaster vs Magnaflow could just be a factor with 434 cubes twisting 7500 rpm, but I will ask about any effects they noted at lower rpm.

Walker got the design essentially right with the turbo mufflers for the Corvair (original Porschev

My 83 5 spd doesn't seem to have much room for cat or muffler options, something about a bigger battery box?

Tom Cloutier

I did back to back comparisons of a Magnaflow and then a Flowmaster. Only the mufflers differed--everything else was the same. Lost 17hp with the Flowmaster. If you look at the typical Flowmaster design, it's pretty clear to me anyway that it will be more restrictive than a straight through design.

Tom Cloutier

Rick Carter

Tom,
Maybe you could post your two part article on exhaust science. I've lost track of how many times I've been told my car, with your exhaust, is the best sounding V8 someone has ever heard. I think Don H. got similar comments; not knocking the also proven X pipes that provide the same power gains, just bragging on the sweet sound.

John Struthers

IMO -anectdotal-:
Anything over 2 1/2 " will set up a a resonance vibe/ring.
Wether it's the pipe itself, the heatshields, or, the hangers you might end up with irritating resonance in the cab. And because it's a vibration it can migrate to other things that vibrate. The engine rpm and gear also affect the resonance spectrum range.
Although, there is a good arguement against adding restrictive elements to the exhaust I kept adding till the exhaust note came down a bit from the Nascar sound.
With my early model single pipe I went to 2 1/2' pipe, a Hi-Flow Cat, back to the 15" long oval Flowmaster -50 series?- that exited thru a 'flat' chrome tailpipe (grows on ya') they didn't have the
dual round tips. Beyond loud! Way to much vibration and resonance. Had them put in a Thrush resonator 1/2 way between the exhaust 'turn' to muffler at the rear and the cat.
This not only reduced decibles to a decent range but stiffened the long section of the 2 1/2 ' pipe.
The stiffening, in turn, pretty much eliminated the resonance induced vibration throughout the car.
Your call in the end.