Our research led us to the innovative Dynomax VT muffler. Dynomax says this muffler is a true high performance muffler with no drone. The VT accomplishes this feat with a spring-loaded flapper valve. At part throttle the valve is closed which diverts the exhaust flow through the muffler's perforated center tube and into a chamber filled with long strand continuous roving fiberglass packing. This sort of packing is much less likely to blow out than the traditional packing material of choice, short strand chopped fiberglass.
This chamber damps out higher frequency noise. The exhaust then passes through into another chamber, which attenuates lower frequency noise before passing out the end of the muffler into the tailpipe.
At higher throttle positions or a backpressure of around 0.29 psi and a flow of 100 scfm a spring loaded valve in the muffler's main tube starts to open. The valve is simply a swing valve with an offset shaft. The offset is what allows the valve to open passively when pressure is applied to its face. As the valve starts to open, the exhaust flow is allowed to flow straight through the muffler and out the tail pipe much like a straight through racing muffler.
|The VT muffler has a perforated main tube with a fiberglass stuffed first chamber to get rid of high frequency noise with a Helmholtz type rear chamber for lower frequency noise. The continuous fiber fiberglass packing is a lot less likely to blow out than chopped short strand stuff commonly used as muffler stuffing. You can see the spring loaded flapper door in the main tube shown in the open position. At low flows, the flapper closes under spring tension and the exhaust is forced through the perforations though the stuffing, past a baffle into the second chamber and out the tail pipe. This really quiets things down. At higher flows, the valve opens and the front perforated tube acts like a conventional high performance absorption muffler while the rear part still acts like a resonating chamber. You can have both high flow and quiet with the VT muffler!|
|The muffler in place under the tight confines of the G35 undercarriage.|
At about 500 scfm of flow or 0.43 psi of backpressure, the valve is fully open and the muffler works a lot like a straight though racing muffler although it probably has a greater effect on gas velocity more than backpressure as the exhaust gasses still have to exit into the rear resonator and make a short jump to the tail pipe. So a traditional straight though perforated core muffler will still have less of an impact on power but with nowhere near the silencing potential of the VT muffler.
This technology has been around for several years, several Nissan OEM applications have mufflers like this, no surprise because Dynomax’s parent company is Tenneco, Nissan’s OEM muffler supplier of choice. Dynomax is cool for exploiting this bit of OEM technology for the aftermarket.
|Berk Technology modded their exhaust to accept the big VT muffler instead of the small resonator that was here previously.|
The VT Muffler is a high quality piece fabricated from corrosion resistant stainless steel with all welded joints, no crappy swaged stuff here, making the part sweet enough to install on Berk’s stainless exhaust without laming it out. Since we didn’t want to mess around and had to appease Frank, lest he program MotoIQ to self-destruct, we obtained the largest and quietest VT muffler made, part number 17963 with a 3” core.