Magnaflow Custom muffler made for SSi's and Dual outlets.
 

I've had several mufflers on my 911 with SSI's. The first was a Dansk with a single outlet. The quality of this was very good but I thought the design, weight, and sound quality could be improved. I then when to a Borla that is no longer made. Although the sound is great, the baffles would break loose from the spot welds and then vibrate in the muffler. I had the original replace by Borla (at their expense) only to have the same thing happen again last month. I decided to have my own exhaust made using a free flowing Magnaflow muffler with no restrictions (part # 14386) using 2.5 inch inlets and outlets. I also used two Magnaflow 4" tips (# 35136). These parts cost me $143 from a supplier. I then farmed out the fabrication that does only stainless T304 fabrication. The labor and parts from his end came to $430. So I'm out around $600 for a muffler that I feed confident will hold up. The testing of it has been very promising. Absolutely no buzzing or resonance at any rpm. And the sound is absolutely fantastic. Lower rpms, not problem. Get it higher in the rpm band and it wails, especially on deceleration. Fit and finish are perfect. If you have a decent shop around you it may be cheaper to do this compared to many of the aftermaket one being made.

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What I like most about this setup is how free flowing it is. The SSI's are at their peak with my 3.4 that is putting out around 270hp so I wanted as little restiction as possible. The Magnaflow immediately opens to a 2.5 inlet from the 2.0 collector from the SSI and the exits with a 2.5 outlet. Witn no baffles or obstructions. You can see right through the inlets to the outlets on the other side. Still not overly loud, at least to me.

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Hi there

I got linked to this thread from a more recent topic but my question is about this setup.

Its pretty much what I have on my 3.6 conversion with 993 headers and I seem to get quite a bit of backfiring "89911" do you have the same with your setup?

Jevvy,

I think that it is always present but you don't notice it with the std exhaust systems. Only when you have a shorter system - like the SSI, 993, backdate types - do you notice it.

On one of the very few occasions I sat in the passenger seat of my car with its std exhaust, I noticed with windos down that I could just hear it quietly popping and banging away. Now with SSI/M&K and no sound deadening, its very obvious. It crackles away on a trailing/light throttle at ~1500rpm and then it merrily pops and bangs at ~3500rpm on trailing throttle like a TVR AJP motor.

I know my 3.2 is not the same as your 3.6 but I thought this might be useful.

RB

Actually no. Usually thats a sign of your car running rich. You might want to try a air/fuel reading to check.

Hey 89 -911 how much space is there between the bumper and the muffler body? My stock muff on the SSIs is melting my rear FG bumper! I need to put in a heat shield but I was hoping to get a little more air space as well.

ALso, how was weight compared to the 2 in 1 out stock type?

Well I am running an SW custom chip mapped off the AFRs, so I wouldn't have thought so. Remember its only on the trailing throttle that it pops. My own thought is that the fuel doesn't shut off quite as much as it ought to on trailing throttle. On zero throttle there is no popping as I understand that motronic shuts the fuel off entirely and on full throttle there is no popping, missing etc and the car runs perfectly. My car goes on the dyno next in about 7 weeks but that will only show full throttle AFRs.

As I said above, even when 100% std , my car used to pop a little, I just couldn't here it then.

I have one of these mufflers too - except mine is hooked up to a B & B header system. No pops - it's a little louder at 3,000 rpms than 3,800 so I might need to fine tune the tips a little, It sounds great though - very hearty sound.

Mine also pops on down shifting every once in awhile, usually after I have run it really hard.

It really pretty light. I wanted to go with a MK - but at the time, Ben was only making the dual center outlets and I already have my valance cut for dual outs.

BTW - I had mine custom fitted (out of stainless) at a local exhaust shop for around $180.

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Thanks for the replys guys, nice to hear others are popping and banging a bit but as suggested I will also get my A/F ratio checked.

I'm on a dyno day 16th Sept, might wait till then unless suggested otherwise.....Plugs and tail pipe colour both look good so it cant be too far off.

Can any damage be caused by backfires and how bad do they need to be before this starts to happen?

It really is a fairly small unit and can be placed within the area of the old muffler with plenty of room for adjustment in all directions. I wanted him to hide the muffler as much as possible so it sits higher. He uses 100% T304 stainless, even better then the Magnaflow case, which could explain the price compared to Jeremy's.