Rey
Registered Member
I wrote in an earlier post that I intended to install a Magnaflow exhaust, which I modified. My initial modification was the installation of a Magnaflow X muffler in place of the Magnaflow X crossover pipe. The installation was easy (for my installer). It was a bit quieter than a stock Magnaflow exhaust, but there was still an annoying loud drone upon acceleration at low rpm. At steady-state cruise noise level was quite acceptable.
My research concludes drone is almost universal with any aftermarket exhaust system. The only manufacturer that consistently addresses drone I know of is Corsa, which does not produce an exhaust for the Genesis.
Cruising the web I came across favorable reports of a new muffler from Dynomax. The design is just a year old. It is the "Dynomax VT" muffler. The basic design of the VT muffler is a "straight through" design with a spring loaded flap at the end. The flap stays partially closed at low flow causing exhaust gas/sound to circulate/attenuate within the muffler. At high flow the flap opens with virtually zero back pressure. Google this muffler for more detail.
The VT muffler itself looks like a typical oval design with offset inlet/outlet. I used the 2.5" inlet/outlet model #17156 which fits the 2.5" pipes of the Magnaflow exhaust. Ideally, the muffler would have fitted "flat" with the outlet pipe perfectly centered in the Genesis rear valence. Alas, the VT muffler is too wide to fit horizontally. We canted the muffler at about 60 degrees. The Magnaflow dual outlet pipes just couldn't fit, so we installed a single aftermarket chrome tip. The mufflers hang down a couple of inches more than the Magnaflow/stock combo. We addressed this by painting the VT mufflers flat black with high-temp paint, which cause the mufflers to almost disapear. I do not have photos.
I can say the VT mufflers work fully as advertised. Drone is just gone. There is a little noise increase at former drone levels, but it is far from objectional. The exhaust is louder than the silent OEM exhaust. Sound level is a bit quieter than an OEM Corvette and more like an OEM Cadillac CTS-V. It passed the "wife test" in that she noticed no change from OEM.
The Dynomax 17156 is a direct interchange, according to Dynomax, with Flowmaster 42541 and Magnaflow 11226. Dynomax claims the 17156 at wide open throttle will flow 841 CFM compared with the Flowmaster 42541 at 373 CFM and 588 CFM for hte Magnaflow 11226.
I cannot verify these numbers, but I did do a before/after comparison at idle (600 rpm) when the flap is mostly closed. My gallon per hour consumption rate at idle is about 0.046 GPH to 0.050 GPH, and I noted no change after the VT installation.
I think the OEM exhaust is seriously restricted. I base this on a forum member's dyno report of close to 20 hp horsepower gain with a cat-back system. On most cars one is lucky to get more than 12 hp with a cat-back system.
While Magnaflow and Borla increase exhaust pipe diameter from 2.25" to 2.50", I think this alone is not the big reason for power increases. The stock system is seriously crimped ahead of the central resonator in order to clear a chassis brace. This crimp can be easily removed, and the brace lowered just a bit. The central resonator is actually a fairly efficient design. In my opinion much of the restriction is in the rear mufflers, which can be replaced with the Dynomax VT. In short, I think one can achieve much of the power from an aftermarket exhaust with just these mods.
As for gas mileage increases, I have low expectations. True, pumping losses are reduced with unrestricted intake/exhaust mods, but pumping losses are just a fraction of the gas mileage equation. My guess at this point is an increase in gas mileage of maybe 1 mpg tops.
My research concludes drone is almost universal with any aftermarket exhaust system. The only manufacturer that consistently addresses drone I know of is Corsa, which does not produce an exhaust for the Genesis.
Cruising the web I came across favorable reports of a new muffler from Dynomax. The design is just a year old. It is the "Dynomax VT" muffler. The basic design of the VT muffler is a "straight through" design with a spring loaded flap at the end. The flap stays partially closed at low flow causing exhaust gas/sound to circulate/attenuate within the muffler. At high flow the flap opens with virtually zero back pressure. Google this muffler for more detail.
The VT muffler itself looks like a typical oval design with offset inlet/outlet. I used the 2.5" inlet/outlet model #17156 which fits the 2.5" pipes of the Magnaflow exhaust. Ideally, the muffler would have fitted "flat" with the outlet pipe perfectly centered in the Genesis rear valence. Alas, the VT muffler is too wide to fit horizontally. We canted the muffler at about 60 degrees. The Magnaflow dual outlet pipes just couldn't fit, so we installed a single aftermarket chrome tip. The mufflers hang down a couple of inches more than the Magnaflow/stock combo. We addressed this by painting the VT mufflers flat black with high-temp paint, which cause the mufflers to almost disapear. I do not have photos.
I can say the VT mufflers work fully as advertised. Drone is just gone. There is a little noise increase at former drone levels, but it is far from objectional. The exhaust is louder than the silent OEM exhaust. Sound level is a bit quieter than an OEM Corvette and more like an OEM Cadillac CTS-V. It passed the "wife test" in that she noticed no change from OEM.
The Dynomax 17156 is a direct interchange, according to Dynomax, with Flowmaster 42541 and Magnaflow 11226. Dynomax claims the 17156 at wide open throttle will flow 841 CFM compared with the Flowmaster 42541 at 373 CFM and 588 CFM for hte Magnaflow 11226.
I cannot verify these numbers, but I did do a before/after comparison at idle (600 rpm) when the flap is mostly closed. My gallon per hour consumption rate at idle is about 0.046 GPH to 0.050 GPH, and I noted no change after the VT installation.
I think the OEM exhaust is seriously restricted. I base this on a forum member's dyno report of close to 20 hp horsepower gain with a cat-back system. On most cars one is lucky to get more than 12 hp with a cat-back system.
While Magnaflow and Borla increase exhaust pipe diameter from 2.25" to 2.50", I think this alone is not the big reason for power increases. The stock system is seriously crimped ahead of the central resonator in order to clear a chassis brace. This crimp can be easily removed, and the brace lowered just a bit. The central resonator is actually a fairly efficient design. In my opinion much of the restriction is in the rear mufflers, which can be replaced with the Dynomax VT. In short, I think one can achieve much of the power from an aftermarket exhaust with just these mods.
As for gas mileage increases, I have low expectations. True, pumping losses are reduced with unrestricted intake/exhaust mods, but pumping losses are just a fraction of the gas mileage equation. My guess at this point is an increase in gas mileage of maybe 1 mpg tops.
