Stainless Exhaust from Coupe King (Peter Sliskovich)

Jan Gullett

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I recently replaced my Coupe exhaust and thought my experience and observations might be helpful to others.

I decided to go with Peter's stainless system for two reasons. He has always been a pleasure to work with in the past and the quality of the used parts he has supplied have been among the best that I have been able to find short of new OEM. His addition of the "carrot" decibel killer type baffle option was enough to convince me that I could live with the Magnaflow sound level.

The fit and finish of the stainless system parts was outstanding. No bending, forcing or adjusting required for installation. The polished exhaust was beautiful. The easiest exhaust install I have done. There was only one slight crease in the center resonator due to bouncing around in shipment, but this was very minor and not something most people would notice. Peter included all new gaskets, clamps and mounting hardware (save the rubber mount at the end of the tailpipe which I reused), so I had no need to shop for parts.

I upgraded from my stock coupe manifolds to larger B35 manifolds and took advantage of Peter's larger down pipe option. Peter supplied the B35 manifolds in a dull gray ceramic coating and they looked better than new. The manifolds were shipped with the stud bolts inserted and two were bent slightly from bouncing around but I was able to straighten and use them without much effort.

Even with the "carrot" installed, this exhaust added a lot of power and widened the power band about 1000 RPM higher with just a little loss of low end torque. I attribute this to the B35 manifolds, larger down pipes and flow through design.

This exhaust works perfectly with my LJet system using 3.0 bar fuel pressure regulator (from a Saab) on a 3.5 liter engine while the prior exhaust was better fitted with the 2.5 bar OEM 528i & 530i fuel pressure regulator.

The London system I had previously used thicker stainless, a more open design in the muffler exposing more sound deadening material and a three pipe reverse flow resonator resembling the OEM unit. This system used the 3.0 sized downpipes but was over-sized after the resonator. This reflected the "strong, quiet and over-sized" requests on my original London order.

I found the London system was only good for 3-5 years before it started to become noisy (like bolts rattling in a coffee can) due apparently to internal corrosion and loose internal parts. This went away after I replaced the resonator with a glass pack (which sounded great by the way). But the noise problem appeared again in a few years, later in the system. I assume the Magnaflow bits are warranted for longer and I am hopeful it will prove to be more durable (either from better welds or reduced exposure of sound deadening).

Of course nothing is perfect. The London system was quieter with a sound more to my liking when new and later with the glass pack (although real power enthusiasts would probably prefer Peter's system). There is some difference in sound level when you are in the car, but it is more noticeable when you stand in back of the car and hear the Magnaflow direct flow through sound at the end of the tail pipe. Of course the London system did not flow as well and restricted power, but Peter's system is still a little loud for my taste (even with the "carrot") and I may experiment with an additional decibel killer exhaust tip or perhaps add a third can to move more toward OEM levels. But not much adjustment is needed for my tastes so I may just get comfortable with the system as is.

I certainly now have extra power to spare. With the 3.5 liter sport engine, optimized LJet at 3.0 bar, and this exhaust, my coupe feels hot!
 
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Hello Jan, I was doing some research on quieting my Coupeking exhaust system, like yours. Overall, I'm very happy - since 2010 - with the performance and fit. But even with the carrot, I increasingly find the sound slightly too loud and I find myself admiring the more refined/mellow sounds of friends of mine who have E9s but with simply larger diameter steel systems. I've also got B35 manifolds and the full CC stainless all the way back. Did you swap a different rear muffler or try other approaches like a 3rd can? Thanks
 
I used the carrot and coupe king muffler. It is perhaps a little loud but fine to me. But I agree it is not as quiet as OEM set up. Depends on personal preference I guess. I like a little exhaust note. I drive my coupe like a sports car (which it is set up to be).
 
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